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LECTURE 


ON    THE 


APPLICATIONS  OF  CHEMISTRY  AND  GEOLOGY 


TO 


AGRICULTURE. 


*The  profit  of  the  earth  is  for  a^l ;  the  king  himself  is  served  by  the  ^elAJ'—Eeclea.  r.  fi 


BY  JAS.  F.  W.  JOHNSTON,  M.A.,  F.R.SS.  L.  &  E., 

FELLOW   OF    THE   GEOLOGICAL  AND   CHEMICAL   SOCIEaTIES, 

Honorary  Member  of  the  Royal  Agricultural  Society,  Foreign  ..lember  of  the  Royal 
Swedish  Academy  of  Agriculture,  &c.  &c  ;  Chemist  to  the  Agricultural 
Chemistry  Association  of  Scotland,  and  Reader  in  Chemistry 
and  Mineralogy  in  the  University  of*Durham. 


NEW  EDITION,  WITH  AN  APPENDIX, 

OONTAININa   SUGGESTIONS  FOR  EXPERIMENTS  IN  PRACTICAl,  AGRICTILTtTaK 


NEW     YORK: 
C.  M.  SAXTON,  AGRICULTURAL  BOOK  PUBLISHER, 

N«.  laa  FULTON  STREET. 

%4t   , 


VENERABLE  CHARLES  THORP,  p.D.    F.R.S.,  &c.,  &c., 
archdeacon  op  durham,  and  warden  op  the  university  op  durham. 

My  dear  Sir, — 
I  cannot  more  appropriately  dedicate  tlie  following  Lectures  than  to  the  head 
of  the  University  with  which  I  am  officially  connected,  and  within  the  walls 
of  which  the  earlier  Lectures  were  first  delivered. 

In  publishing  this  Volume  I  am  only  endeavouring  to  follow  out  the  enlight- 
ened intentions  of  yourself  and  the  other  Founders  of  the  University  of  Dur- 
ham, who  have  contributed  so  largely  of  their  fortune  and  their  influence  for 
the  promotion  and  diffusion  of  sound  and  useful  learning.  That  you  have  so 
long  and  so  successfully  laboured  to  carry  these  intentions  into  effect,  is  ano- 
ther reason  why  I  desire  to  dedicate  my  work  especially  to  you. 

I  need  scarcely  add  how  much  pleasure  it  affords  me  to  embrace  this  public 
opportunity  of  testifying  my  own  personal  regard  and  esteepa. 
BeUeve  me,  my  dear  Sir, 

With  much  respect. 

Your  obedient  humble  servant, 

JAMES  F.  W.  JOHNSTON. 


PREFACE. 


The  First  Part  of  the  following  Lectures  was  addressed 
to  a  Society*  of  practical  agriculturists,  most  of  whom  pos- 
sessed no  knowledge  whatever  of  scientific  Chemistry  or  Ge- 
ology. They  commence,  therefore,  with  the  discussion  of 
those  elementary  principles  which  are  necessary  to  a  proper 
understanding  of  each  branch  of  the  subject.  Every  thing 
in  such  Lectures,  which  is  not — or  may  not  be — easily  un- 
derstood by  those  to  whom  they  are  addressed,  is  worse  than 
useless.  It  has  been  my  wish,  therefore,  to  employ  no  scien- 
tific terms,  and  to  refei  to  no  philosophical  principles,  which 
1  have  not  previously  explained. 

To  many  who  may  take  up  the  latter  portions  cf  the  work, 
some  points  may  appear  obscure  or  difficult  to  be  fully  un- 
derstood ;  such  persons  will,  I  hope,  do  me  the  justice  to  be- 
gin at  the  beginning,  and  to  blame  the  Author  only  when  that 
which  is  necessary  to  the  understanding  of  the  later  is  not 
to  be  found  in  the  earlier  Lectures. 

For  the  sake  of  clearness,  I  have,  in  the  following  pages, 
divided  the  subject  into  four  Parts — the  study  of  each  pre- 
ceding Part  preparing  the  way  for  a  complete  understanding 
of  those  which  follow.  Thus,  Part  I.  is  devoted  to  the  or- 
ganic elements  and  parts  of  plants,  the  nature  and  sources 
of  these  elements,  and  to  an  explanation  of  the  mode  in  which 
they  become  converted  into  the  substance  of  plants  ; — Part 
II.,  to  the  iiiorganic  elements  of  plants,  comprehending  the 
study  of  the  soils  from  which  these  elements  are  derived,  and 

♦  The  Durham  County  Agricultural  Society,  and  the  Members  of  the  Dur- 
ham Farmers'  Club. 

290S-I7  .  • 


VI  PREFACE. 


the  general  relations  of  geology  to  agriculture  ; — Part  III.,  to 
the  various  methods,  mechanical  and  chemical,  by  which 
the  soil  may  be  improved,  and  especially  to  the  nature  of 
manures^  by  which  soils  are  made  more  productive,  and  the 
amount  of  vegetable  produce  increased; — and  Part  IV.,  to 
the  results  of  vegetation^  to  the  kind  and  value  of  the  food 
produced  under  different  circumstances,  and  its  relation  to 
the  growth  and  feeding  of  cattle,  and  to  the  amount  and 
quality  of  dairy  produce. 

By  this  method  I  have  endeavoured  to  ascend  from  the 
easy  to  the  apparently  difficult ;  and  I  trust  that  the  willing 
and  attentive  reader  will  find  no  difficulty  in  keeping  by  my 
side  during  the  entire  ascent. 

The  Author  has  much  pleasure  in  now  presenting  these 
Lectures  to  the  public  in  a  complete  form.  He  has  only  to 
express  a  hope  that  the  delay  which  has  occurred  in  the  pub- 
lication of  the  latter  part  of  the  work  has  enabled  him  to  ren- 
der it  more  useful,  and  therefore  more  worthy  of  the  public 
approbation. 


Note. — The  rapid  sale  of  a  large  impression  having  rendered  a  second 
edition  of  the  first  and  second  Parts  necessary  before  the  entire  comple- 
tion of  the  work,  such  alterations,  corrections,  and  additions  only  have 
been  made  as  could  be  introduced  without  altering  the  original  paging  of 
the  work.  Several  oversights,  however,  have  been  corrected,  and  some 
omissions  supplied,  which  presented  themselves  in  the  earlier  edition. 


CONTENTS. 


FilRT    I. 

0>  THE  ORGANIC  CONSTITUENTS  OF  PLANTS. 


LECTURE  I. 

IMPORTANCE    OP   AGRICULTURE. 


.ntroduction p.  11 

Different  kinds  and  states  of  matter 21 

Carbon,  its  properties  and  relations  to  ve- 
getable life 23 

Oxygen,  its  properties  and  relations  to  ve- 
getable life 24 


Hydrogen,  its  properties  and  relations  to 
vegetable  life p.  25 

Nitrogen,  its  properties  and  relations  to 
vegetable  life  26 

Rewards  of  study 27 


LECTURE  II. 


CHARACTERISTIC    PROPERTIES    OP    ORGANIC    SUBSTANCES. 

On  the  constitution  of  the  atmosphere 31 

The  nature  and  laws  of  chemical  combi- 
nation  32 

Of  water,  and  its  relations  to  vegetable  life..36 
Of  the  co4d  produced  by  the  evaporation 
of  water,  and  its  influence  on  vegetation.  .43 


Characteristic  properties  of  organic  sub- 

staikces 28 

Relative  proportions  of  organic  elements.. 29 
Of  the  form  or  state  of  combination  in 
which  the  organic  elements  enter  into 
and  minister  to  the  growth  of  plants .31 


LECTURE  III. 

CARBONIC  AND  OXALIC  ACIDS,    THEIR  PROPERTIES  AND  RELATIONS. 


Carbonic  acid,  its  properties  and  relations 
to  vegetable  life 45 

Oxalic  acid,  its  properties  and  relations  to 
vegetable  life 47 

Carbonic  oxide,  its  constitution  and  pro- 
perties  48 


Light  carburetted  hydrogen,  the  gas  of 
marshes  and  of  coal  mines 49 

Ammonia,  its  properties  and  relations  to 
vegetable  hfe 50 

Nitric  acid,  its  constitution  and  properties  .  .56 

Q>iestions  to  be  considered 57 


LECTURE  IV. 


SOURCE    OP   THE    ORGANIC    ELEMENTS    OP    PLANTS. 

Form  in  which  the  nitrogen  enters  into 

the  circulation  of  plants 68 

Absorption  of  ammonia  by  plants 70 

Absorption  of  nitric  acid  by  plants 72 

Conclusions 74 


Source  of  the  carbon  of  plants 58 

Form  in  which  carbon  enters  into  the  cir- 
culation of  plants 63 

Source  of  the  hydrogen  of  plants 64 

Source  of  the  oxygen  of  plants 66 

Source  of  the  nitrogen  of  plants .ib. 


LECTURE  V. 

HOW  DOES  THE  FOOD  ENTER  INTO  THE  CIRCULATION  OF  PLANTS  1 


General  structure  of  plants,  and  of  their 

several  parts 4 75 

The  functions  of  the  root 76 

The  course  of  the  sap 86 

Functions  of  the  stem SS 


Functions  of  the  leaves 89 

Functions' of  the  bark 96 

Circumstances  by  which  the  functions  of 

the  various  parts  of  plants  are  modified . .  97 
Effects  of  marling 101 


CONTENTS    OF   PART 


LECTURE  VI. 


SUBSTANCES    OF   "WHICH    PLANTS    CHIJEFLY    CONSIST. 


Woody  fibre  or  lignin— its  constitution 

and  properties p.  103 

Starch — its  constitution  and  properties. . .  .106 

Gum — its  constitution  and  properties 108 

Of  Sugar— its  varieties  and  cliemical  con- 
stitution  109 

Mutual  relations  of  woody  fibre,  starch, 

gum,  and  sugar Ill 

Mutual  transformations  of  woody  fibre, 
starch,  gum,  and  sugar 112 


Of  the  fermentation  of  starch  and  sugar, 
and  of  the  relative  circumstances  under 
which  cane  and  grape  sugars  generally 
occur  in  nature  p.  115 

Of  substances  which  contain  nitrogen. — 
Gluten,  vegetable  albumen,  and  diastase.  116 

Vegetable  Acids. — Acetic  acid,  oxalic  acid, 
tartaric  acid,  citric  acid,  malic  acid 121 

General  :>bservations  nn  the  substances 
of  which  plants  chiefly  consist 126 


LECTURE  VIL 

CHEMICAL    CHANGES   BY   WHICH   THE    SUBSTANCES    OF    WHICH    PLANTS    CHIEFLY 
CONSIST   ARE    FORMED    FROM     THOSE    ON    WHICH    THEY    LIVE. 


Chemical  changes  which  take  place  du- 
ring germination,  and  during  the  devel- 
opement  of  the  first  leaves  and  roots,. . .  130 

Of  the  chemical  changes  from  the  for- 
mation of  the  true  leaf  to  the  expansion 
of  the  flower 134 

On  the  production  of  oxalic  acid  in  the 
leaves  and  stems  of  plants 137 


Of  the  chemical  changes  between  the 
opening  of  the  flower  and  the  ripening 
of  the  fruit  or  seed ^ 13© 

Of  the  chemical  changes  which  take  place 
after  the  ripening  of  the  fruit  and  seed . .  143 

Of  the  rapidity  with  which  these  changes 
take  place,  and  the  circumstances  by 
which  they  are  promoted b. 


LECTURE  VIII. 


HOW  THE  SUPPLY  OF  FOOD  FOR  PLANTS  IS  KEPT  UP  IN  THE  GENERAL 
VEGETATION  OF  THE  GLOBE. 

Of  the  supply  of  ammonia  to  plants 156 

Of  the  supply  of  nitric  acid  to  plants 159 

Theory  of  the  action  of  nitric  acid  and 

ammonia 163 

Comparative  influence  of  nitric  acid  and 

of  ammonia  in  different  climates 166 

Stimulating  influence  of  these  compound*  t). 
Concluding   observations  regarding  the 

c  rganic  constituents  of  pl.-uiia 168 


Of  the  proportion  of  their  carbon  which 
plants  derive  from  the  atmosphere 145 

Of  the  relation  which  the  quantity  of  car- 
bon extracted  by  plants  from  the  air, 
bears  to  the  whole  quantity  contained 
in  the  atmosphere 147 

How  the  supply  of  carbonic  acid  in  the 
atmosphere  is  renewed  and  regulated ..  148 
eneral  conclusions  in  relation  thereto. ..  156 


PiLHT    II. 

ON  THE  INORGANIC  ELEMENTS  OF  PLANTS. 

LECTURE  IX. 

INORGANIC    CONSTITUENTS    OP    VEGBTABLE    SUBSTANCES. 


Of  the  relative  proportions  of  inorganic 

matter  ill  vegetable  substances p.  178 

Kind  of  inorganic  matter  found  in  plants. .  180 
Of  the  several  elementary  bodies  usually 
met  with  in  the  ash  ofi)lanls 182 


Of  those  compounds  of  the  inorganic  ele- 
ments which  enter  directly  into  the 
circulation,  or  exist  in  the  substance 
and  ash  of  plants 183 


LECTURE  X. 

INORGANIC    CONS'I'ITUKNTS    OIV  PLANTS    CONTINUED, 
Inorganic  constituents  of  plants  continued. 200  I  To  what  extent  do  the  crops  most  usual- 
Tabular  view  of  the  constitution  of  tlie         |      ly  cultivated  exhaust  the  soii  of  inor- 

compounds  of  the  inorganic  elements         j      ganic  vegetable  food  7 220 

above  described 214  j  Of  the  alleged  constancy  of  the  inorganic 

On  the  relative  proportions  of  the  differ-  constituents   of  plants,  in    kind   and 

ent  inorganic  compounds  present  in  quantity    225 

the  ash  of  plants 216  | 


LECTURE  XL 

NATURE    AND   ORIGIN    OF    SOILS. 

Of  the  organic  matter  in  the  soil 229  I  On  the  general  structure  of  the  earth's 

General  constitution  of  the  earthy  part  of         |      crust 237 

the  soil , 230  I  Relative  positions  and  peculiar  charac- 

Of  the  classification  of  soils  from  their         |      ters  of  the  several  strata 239 

chemical  constituents 232  j  Classification  of  the  stratified  rocks,  their 

Of  the  distinguishing  characters  of  soils         1      extent,  and  the  agricultural  relations  of 

and  subsoils 235        the  soils  derived  from  them 241 

Of  the  general  origin  of  soils 23tj  | 

LECTURE  XIL 

COMPOSITION  OP  THE  GRANITIC  ROCKS,  AND  OP  THEIR  CONSTITUENT  MINERALS. 

Composition  of  the  granitic  rocks 257  I  Of  the  occurrence  of  such  accumulations 

Of  ihe  degradation  of  the  granitic  rocks,         |      in  Great  Britain,  and  of  their  influence 

and  of  the  soils  formed  from  them  ...260 
Of  the  trap  rocks,  and  the  soils  formed 

from  them 263 

Of  supeificial  accumulations  of  foreign 

materials,  and  of  the  means  by  which 

they  have  been  transported 266 


n  modifying  the  character  of  the  soil.. 270 
llow  far  these  accumulations  of  drift  in- 
terfere with  the  general  deductions  of 

Agricultural  Geology 272 

Of  superficial  accumulations  of  peat 275 


LECTURE  XIII. 

EXACT    CHEMICAL    CONSTITUTION    OP    SOILS. 

Of  the  exact  nature  of  the  organic  con-  I  Of  the  exact  chemical  constitution  of 
stituents  of  soils,  and  of  the  mode  of  |  certain  soils,  and  of  the  results  to  be 
separating  them 277  |      deduced  from  thom 282 

Of  Ihe  exact  chemical  constitution  of  Of  the  physical  properties  of  soils 290 

the  earthy  part  of  the  soil 281  |  Conclusion 297 


FABT  ZIX. 

ON  THE  IMPROVEMENT  OF  THE  SOIL  BY  MECHANICAL  AND 
CHEMICAL  MEANS. 

LECTURE  XIV. 


THE    QUALITIES    OF    THE    SOIL    MAY   BE    CHANGED    BY   ART. 


Connection  between  the  kind  of  soil  and 
the  kind  of  plants  that  grow  ujion  it.  p.  304 

Of  draining,  and  its  effects 300 

Practical  effects  of  draining 311 


Of  the  theory  of  springs p.  312 

Of  ploushinii'and  subsoiling 318 

Of  deep-ploughing  and  trenching 321 

Improvement  of  the  soil  by  mixing 323 


LECTURE  XV. 

IMPROVEMENT    OP   THE    SOIL   BY    CHEMICAL    MEANS. 


Of  saline  manures 327 

Theory  of  the  action  of  potash  and  soda.328 
Sulphates  of  potash,  soda,  magnesia,  and 

lime  (gypsum) 331 

Theory  of  the  action  of  these  sulphaies  .332 

Nitrates  of  potash  and  soda 335 

Effect  of  these  nitrates  on  the  quantity 

of  various  crops 336 

Effect  of  the  nitrates  on  the  quality  of 

the  crop 3.39 

Cases  in  which  they  have  failed .341 

Theory  of  the  action  of  these  nitrates... 343 
Special  effects  of  the  nitrates  of  potash 

and  soda 344 


Use  of  common  salt 345 

Chlorides  of  calcium  and  magnesium.,. 347 
Phosphate  of  Hme  and  earth  of  bones... 348 

Silicates  of  potash  and  soda 349 

Salts  of  ammonia ib. 

Of  mixed  saline  manures 352 

Wood  ashes ib. 

Use  of  kelp 355 

Straw  a.«!hes 356 

Turf-peat  or  Dutch-ashes 350 

Crushed  granites  and  lavas 361 

Results  of  experiments  with  mixed  ma- 
nures  362 


LECTURE  XVI. 

OF   THE    USE    OF    LIME    AS    A    MANURE. 


Of  the  composition  of  common  and 
magnesian  limestones  364 

Of  the  burning  and  slaking  of  lime 366 

Changes  which  the  hydrates  of  lime 
and  magnesia  undergo  by  prolonged 
exposure  to  the  air 367 

States  of  chemical  combination  in  which 
lime  may  be  applied  to  the  land 369 

Of  the  various  natural  forms  in  which 
cor6ona/e  of  lime  is  applied  to  the  land. 370 

Effects  of  marl,  and  of  (he  coral,  shell, 
and  lime-stone  sands  upon  the  soil 374 

Of  the  use  of  chalks,  as  a  manure  375 

Is  lime  indispensable  to  the  fertility  of 
the  soill 377 

States  of  combination  in  which  lime  ex- 
ists in  the  soil 379 

Of  the  quantity  of  lime  which  ought  to 
be  added  to  the  soil 381 


Ought  lime  to  be  applied  In  large  doses 
at  distant  intervals,  or  in  smaller  quan- 
tities more  frequently  repeated! 383 

Form  and  state  of  combination  in  which 

lime  ought  to  be  applied  to  the  land. ,  .386 
Use  and  advantage  of  the  compost  form. 383 

When  ought  lime  to  be  applied  1 389 

Of  the  effects  produced  by  lime  upon 

the  land  and  upon  the  crops 390 

Circumstances  by  which  the  effects  of 

lime  are  modified 393 

Effects  of  an  overdose  of  lime 395 

Length  of  time  during  which  lime  acts.. 396 

Of  the  sinking  of  lime  into  the  soil 397. 

Why  liming  must  be  repeated  398 

Theory  of  the  action  of  lime 400 

Of  lime  as  the  food  of  plants ib. 

The  chemical  action  of  lime  is  exerted 
chiefly  on  the  organic  matter  of  the  soil.401 


CONTENTS    OF   PART    III. 


Of  the  forms  in  which  organic  matter 
usually  exists  in  the  soil,  and  the  cir 
cumstances  under  which  its  decom- 
position may  take  place *..p.  401 

General  action  of  alkaline  substances 
upon  organic  matler 403 

Special  effects  of  caustic  lime  upon  the 
several  varieties  of  organic  matter  in 
the  soil 404 

Action  of  mild  (or  carbonate  of)  lime 
upon  the  vegetable  matter  of  the 
soil 406 


Of  the  comparative  utility  of  burned  and 

unburned  lime p.  409 

Action  of  lime  on  organic  substances 

which  contain  nitrogen 409 

How  these  chemical  changes  directly 

benefit  vegetation 412 

Why  lime  must  be  kept  near  the  surface.ib. 
Action  of  lime  upon  the  inorganic  or 

mineral  matter  of  the  soil 413 

Action  of  lime  on  animal  and  vegetable 

life 415 

Use  of  silicate  of  lime. 416 


LECTURE  XVII. 

OF    ORGANIC    MANURES. 


Of  green  manuring  or  the  application  of 
vegetable  matter  in  a  green  state .417 

Important  practical  results  obtained  by 
green  manuring 418 

Of  the  plants  which  in  different  soils 
and  climates  are  employed  for  green 
manuring 419 

Will  green  manuring  alone  prevent  land 
from  becoming  exhausted  1 421 

Of  the  practice  of  green  manuring 422 

Of  natural  manuring  with  recent  vegeta- 
ble matter Jb. 

Wei-iht  of  roots  left  in  the  soil  by  the 
different  grasses  and  clovers 423 


Improvement  of  the  soil  by  laying  down 
to  grass 424 

Improvement  of  the  soil  by  the  planting 
of  trees 429 

Of  the  use  of  sea- weed  aa  a  manure 431 

Of  manuring  with  dry  vegetable  sub- 
stances  433 

Use  of  rape-dust 434 

Use  of  decayed  vegetable  matter  as  a 
manure 43€ 

Use  of  charred  vegetable  matters— soot, 
&c.,  as  manures 437 

Of  the  theoretical  value  of  different 
vegetable  substances  as  manures 440 


LECTURE  XVIII. 


ANIMAL     MANURES. 


Of  flesh,  blood,  and  skin 443 

Of  wool,  woollen  rags,  hair,  and  horn. .  ,445 

Of  the  composition  of  bones 446 

On  what  does  the  fertilizing  action  of 

bones  depend  1 447 

or  the  application  of  bone-dust  to  pas- 
ture lands 451 

Of  animal  charcoal,  the  refuse  of  the  su- 
gar refineries,  and  animalized  carbon. .4.52 
Of"  fish,  fish  refuse,  whale  blubber,  and 

oil 453 

Relative  fertilizing  value  of  the  animal 

manures  already  described.  454 

Of  the    droppings  of  fowls — pigeons' 

dung  and  guano 456 

Results  of  experiments  with  guano 459 

Of  liquid  animal  manures— the  urine  of 
man,   of  the    cow,    the   horse,    the 

sheep,  and  the  pig 460 

Of  the  waste  of  liquid  manure — of  urate 
and  of  sulphated  urine 463 


Of  solid  animal  manures— night  soil, 
the  dung  of  the  cow,  the  horse,  the 
sheep,  and  the  pig 465 

Of  the  quantity  of  manure  produced 
from  the  same  kind  of  food  by  the 
horse,  the  cow,  and  the  sheep 468 

Of  the  relative  fertilizing  values  of  dif- 
ferent animal  excretions 469 

Influence  of  circumstances  on  the  quali- 
ty of  animal  manures 470 

Of  the  changes  which  the  food  under- 
goes in  passing  through  the  bodies  of 
animals '. 472 

Of  farm-yard  manure,  and  the  loss  it  un- 
dergoes by  fermenting 474 

Of  top-dressing  with  fermenting  ma- 
nures     477 

Of  eating  off  with  sheep 478 

Of  the  improvement  of  the  soil  by  irri- 
gation   479 


ON  THE  PRODUCTS  OF  THE  SOIL,  AND  THEIR  USB  IN  THE  FEEDING 

OF  ANIMALS. 


LECTURE  XIX. 

OF  THE  PRODUCE  OP  THE  SOIL. 


Of  the  maximum  or  greatest  possible  and 
the  average  or  actual  produce  of  the 

land p.  487 

Of  the  circumstances  by  which  the  pro- 
duce of  food  is  affected — climate,  sea- 
son, soil,  &c 488 

Influence  on  the  mode  of  culture  on  the 

produce  of  food 490 

Of  the  theory  of  the  rotation  of  crops. . . .  492 

Why  land  becomes  tired  of  clover 494 

Of  the  theory  of  fallows 495 

Of  wheat  and  wheaten  fl(3ur 498 

Of  the  composition  of  wheaten  flour.. ..  499 
Of  the  influence  of  soil  and  climate  on 

the  composition  of  wheaten  flour 501 

Infltience  of  variety  of  seed,  of  mode  of 
culture,  oflime  of  cutting,  and  of  special 
manures  on  the  composition  of  wheat.  502 
Of  the  effects  of  germination  and  of  bak- 
ing upon  the  flour  of  wlieat 504 

Of  the  supposed  relation  between  the  per- 
centage  of  gluten   in  flour,  and  the 

weight  of  bread  obtained  from  it 507 

Of  the  composition  of  barley,  and  the  in- 
fluence of  different  manures  upon  the 
relative  proportions  of  its  several  con- 
stituents  508 

Effect  of  malting  upon  barley 509 

Of  the  composition  of  oats,  and  effect  of 
manures  in  modifying  that  composition.  510 


Of  the  composition  of  rye,  and  the  effect 
of  different  manures  upon  its  composi- 
tion  p.  510 

Composition  of  rice,  Indian  corn,  and 
buck-wheat. 511 

On  the  alleged  general  effect  of  different 
manures  in  modifying  the  amount  of 
gluten  and  albumen  in  wheat,  barley, 
oats,  and  rye 513 

Composition  of  peas,  beans,  and  vetches.  515 

Effect  of  soils  and  manures  on  the  quality 
of  peas  and  beans 518 

Of  the  composition  o I' potatoes,  and  the 
effect  of  circumstances  in  modifying 
their  composition SQO 

Of  the  composition  of  the  turnip,  the  car- 
rot, tlie  beet,  and  'he  parsnip 523 

Of  the  composition  of  the  green  stems  of 
peas,  vetches,  clover,  spurry,  and 
buck-wheat , 

Of  the  composition  of  the  grasses  when 
made  into  hay  

Of  hemp,  line,  rape,  and  other  oil-bearing 
seeds i 

General  differences  in  composition  among 
the  different  kinds  of  vegetable  food... 

Average  composition  and  produce  of  nu- 
tritive matter  per  acre,  by  each  of  the 
usually  cultivated  crops 530 


525 


529 


LECTURE  XX. 


OP    MILK    AND 

Of  the  properties  and  composition  of 
milk 533 

Of  the  circumstances  by  which  the  com- 
position or  quality  of  milk  is  modified.  534 

Of  the  circumstances  which  affect  the 
quantity  of  the  milk 540 

Of  the  mode  of  separating  and  estimating 
the  several  constituents  of  milk 542 

Of  the  sugar  of  milk,  and  of  the  acid  of 
milk  or  lactic  acid 543 

Of  the  mutual  relations  which  exist  be- 
tween lactic  acid  and  the  cane,  grape, 
and  milk  sugars 544 

Of  the  souring  and  preserving  of  milk. . .  546 


ITS    PRODUCTS. 

Of  the  separation  and  measurement  of 
cream — the  gaJactometer— the  compo- 
sition of  cream,  and  the  prepai'afion  of 
cream  cheese 547 

Of  the  separation  of  butter  by  churning 
or  otherwise 549 

Of  the  composition  of  butter 551 

Of  the  average  quantity  of  butter  yielded 
by  milk  and  cream,  and  of  the  yearly 
produce  of  a  cow 552 

Of  the  circumstances  which  affect  tlie 
quality  of  butter 533 

Of  the  fatty  substances  of  which  butter 
consists,  and  of  the  acid  of  butter  (buty- 


CONTENTS    OF    PART    IV. 


ric  add),  and  the  capric  and  caproic 

acids p.  557 

Of  casein  or  the  curd  of  miltt  and  its  pro- 
perties  561 

Or  the  relations  of  casein  to  the  sugars 

and  fats 562 

Of  the  rancidity  and  preservation  of  butter  563 
Of  the  natural  and  artificial  curdling  of 

milk 566 

Of  the  preparation  of  rennet 567 

Theory  of  the  action  of  rennet 569 

Of  the  circumstances  by  which  the  quali- 
ty of  cheese  isaffected 573 

Circumstances  under  which  cheese  of 
different  qualities  may  be  obtained  from 
the  same  milk 675 


Of  the  average  quantity  of  cheese  yielded 
by  different  varieties  of  milk,  and  of 
the  produce  of  a  single  cow p.  580 

Of  the  fermented  liquor  from  milk,  and  of 
milk  vinegar 581 

Of  the  composition  of  ihe  saline  constitu- 
ents of  milk ib. 

Purposes  served  by  milk  in  the  animal 
economy 582 

On  the  churning  of  milk  in  the  French 
chum ib. 

Quantity  of  milk  zCnd  butter  yielded  by 
Ayrshire  cows 583 

Profit  of  making  butter  and  cheese  com- 
pared with  that  of  selling  the  milk 584 


LECTURE  XXI. 

OF  TUB  FEEDING  OF  ANIMALS,  AND  THE  PURPOSES  SERVED  BY  THE  FOOD. 


Of  the  substances  of  which  the  parts  of        i 
animals  consist 586  I 

Whence  does  the  body  obtain  these  sub- 
stances? are  they  contained  in  the 
foodi 589 

Of  the  respiration  of  animals,  and  of  the 
purposes  sei-ved  by  the  starch,  gum, 
and  sugar  contained  in  vegetable  food..  591 

Of  the  origin  and  purposes  served  by  the 
fat  of  animals 594 

Of  the  natural  waste  of  the  parts  of  the 
body  in  a  fuUgrown  animal 597 

Of  the  kind  and  quantity  of  food  necessa- 
ry to  make  up  for  the  natural  waste  in 
the  body  of  a  full-grown  animal 598 

The  health  of  an  animal  can  be  sustained 
only  by  a  mixed  food 60C 

Of  the  kind  and  quantity  of  additional 
food  required  by  the  fattening  animal..  60 

Kind  and  quantity  of  additional  food  re- 
quired by  a  growing  animal GOi 


Kind  and  quantity  of  additional  food  re- 
quired by  a  pregnant  animal 604 

Kind  EUid  quantity  of  additional  food  re- 
quired by  a  milking  animal 605 

Influence  of  size,  condition,  warmth,  ex- 
ercise, and  light  on  the  (luantity  of  food 
necessary  to  make  up  for  the  natural 
waste 607 

Influence  of  the  form  or  state  in  which 
the  fond  is  given  on  the  quantity  re- 
quired by  an  animal 611 

Influence  of  soil  and  culture  on  the  nutri- 
tive value  of  agricultural  produce 612 

Can  we  correctly  estimate  the  feeding 
properties  of  ditTerent  kinds  of  produce 
under  all  circumstances  1 613 

Effect  of  different  modes  of  feeding  on 
the  manure  and  on  the  soil 615 

Summary  of  the  views  illustrated  in  this 
lecture 617 

Concluding  section 619 


APEXIITDZZ. 


t  Suggestions    for    experiments    in 

practical  agriculture p.  1 

II.  Effect  of  sudden    alternations    of 

temperature 11 

III.  Results  of  experiments  in  practical 
agriculture  made  during  tiie  spring 
and  summer  of  1841 — 

At  Aske  Hall 13 

AtErslcine 16 

At  Barochan — 

1.  On  hay 17 

2.  On  winter  rye 18 

3.  On  wheat 19 

4.  On  potatoes 20 

5.  On  moss  oats . 21 

6.  On  oats,  with  sulphate  and  ni- 

trate of  soda,  as  a  top-dressing.  .22 

7.  On  peas  and  beans,with  sulphate 

of  soda 23 

8.  On  nitrate  of  soda  as  a  top-dress- 

ing for  gooseberry  and  currant 

bushes 23 

IV.  Suggestions  for  comparative  ex- 
periments with  guano  and  other 
manures 24 

V.  Of  the  examination  and  analysis  of 

soils 27 

Determinationof  the  physical  pro- 
perties of  the  soil ib. 

Of  the  organic  matter  present  in 
the  soil 29 

Of  the  soluble  saline  matter  in  the 
soil 31 

Determination  of  the  quantity  of 
the  several  constituents  of  the 
soluble  saline  matter .  ,33 

Of  the  insoluble  earthy  matter  of 
the  soil 37 

VI.  Different  theories  of  the  action  of 

gypsum 39 

VII.  Suggestions  for  experiments  with 

the  silicates  of  potash  and  soda. .  .40 
Vm.  Results  of  experiments  in  practical 

agriculture  made  in  1842 — 
A.  Experiments  on  turnips — 

1.  Made  at  Lennox  Love 42 

2.  Made  at  Barochan 43  to  46 

3.  Made  at  South  bar 46 

4.  Made  at  Muirkirk .  ib. 

5.  Effectofgypsum  on  the  tur- 

nip crop vi 47 


VIII.  Results  of  experiments  in  praeti* 
cal  agriculture  made  in  1842 — 

B.  Experiments  on  potatoes — 

1.  Those  of  Mr.  Campbell,  of 

Craigie p.  47 

2.  Those  of  Mr.  Fleming,  of 

Barochan  47  to  61 

C.  Experiments  upon  barley 51 

D.  Experiments  upon  oats — 

1.  Those  of  Lord  Blantyre 52 

2.  Those  of  Mr.  Fleming 53 

E.  Experiments  upon  wheat — 

1.  Those  of  Lord  Blantyre 53 

2.  Those  of  Mr.  Flemifig 54 

3.  Those  of  Mr.  Burnet,  of  Gad- 

girth Ib 

F.  Experiments  upon  pasture  and 

other  grasses — 

1.  Those  of  Mr.  Alexander 56 

2.  Those  of  Mr.  Fleming 56 

3.  TliosenfMr.Campbeli,ofIsla.ib. 

G.  Experiments  upon  mixed  crops 

by  Mr.  Alexander 57 

H.  Experiments  upon  beans — 

1.  Those  of  Mr.  Alexander ib. 

2.  Those  of  Lord  Blantyre ib. 

I.  Effect  of  the  top-dressings   ap- 

plied in  1841  upon  the  crop 
ofl842 58 

II.  Remarks  upon  the  experiments 

of  1842 ib. 

A.  The  experiments  on  turnips.  ..59 

B.  The  experiments  on  potatoes.  64 

C.  The  experiments  on  barley... 67 

D.  The  experiments  on  oats ib. 

E.  The  experiments  on  wheat 63 

F.  The  experiments  on  grass 71 

G.  The  experiments  on  mixed 

crops 73 

H.  The  experiments  on  beans.. ..ib. 
IX.  Results  of  additional  experiments 

made  in  1842 75 

Remarks  on  these  experiments... 78 
X.  Experiments  in  practical  agricul- 
ture made   in  1843  by  Mr. 
Fleming,  of  Barochan— 

1.  With  guano  upon  potatoes. .  .83 

2.  On  hay 85 

3.  On  oats 86 

4.  On  turnips 87 

Remarks  on  these  experiments... 89 


LECTURES 

ON   THE 

APPLICATIONS  OF  CHEMISTRY  AND  GEOLOGY 

TO 

AGRICULTURE. 


ON  THE  ORGANIC  ELEMENTS  OF  PLANTS. 


LECTURE  I. 


Im 


iportance  of  Agriculture— Relation  of  the  growth  of  food  to  the  population  of  Great  Britain-- 
Recent  progress  and  prospects  of  English  Agriculture— Application  of  Chemical  and  Geo- 
logical Science  to  the  art  of  culture— to  the  improvementof  soils— the  rotation  of  crops— 
the  application  of  manures,  «&c.— Outline  of  the  Course  of  Lectures— Number  and  nature 
■  of  the  elementary  bodies— The  organic  elements  Carbon,  Hydrogen,  Oxygen,  and  Nitro 
gen,  their  properties  and  their  relations  to  vegetable  life. 

Were  I  about  to  address  you  in  a  single  or  detached  Lecture  only,  I 
should  think  it  my  duty  to  select  some  one  branch  of  the  art  of  culture 
for  special  illustration,  and  without  much  introductory  matter  to  pro- 
ceed at  once  to  the  exposition  of  the  principle  or  principles  on  which  it 
depended.  As  the  present,  however,  is  only  the  first  of  a  Series  of  Lec- 
tures I  hope  to  have  the  honor  of  delivering  to  you,  I  may  be  permitted 
to  introduce  my  subject  with  a  few  prefatory  remarks,  which  will  here 
find  their  appropriate  place. 

la  regard  to  the  importance  of  Agriculture  it  may  appear  superfluous 
in  me  to  address  you.  That  art  on  which  a  thousand  millions  of  men 
are  dependent  for  their  very  sustenance — in  the  prosecution  of  which 
nine-tenths  of  the  fixed  capital  of  all  civilized  nations  is  embarked — and 
probably  two  hundred  millions  of  men  expend  their  daily  toil — that  art 
must  confessedly  be  the  most  important  of  all ;  the  parent  and  precursor 
of  all  other  arts.  In  every  country  then,  and  at  every  period,  the  in- 
vestigation of  the  principles  on  which  the  rational  practice  of  this  art  is 
founded,  ought  to  have  commanded  the  principal  attention  of  the  great- 
est minds.  To  what  other  object  could  they  have  been  more  benefi- 
cially directed  ? 

But  there  are  periods  in  the  history  of  every  country  when  the  study 
of  Agriculture  becomes  more  urgent,  and  in  that  country  acquires  a 
vastly  superior  importance.  When  a  tract  of  land  is  thinly  peopled, 
like  the  newly  settled  districts  of  North  America,  New  Holland,  or 
New  Zealand,  a  very  defective  system  of  culture  will  produce  food 
enough  not  only  for  the  wants  of  the  inhabitants,  but  for  the  partial  sup- 
ply of  other  countries  also.  But  when  the  population  becomes  more 
dense,  the  same  imperfect  or  sluggish  system  will  no  longer  suffice. 
The  land  must  be  better  tilled,  its  special  qualities  and  defects  must  be 
studied,  and  means  must  gradually  be  adopted  for  extracting  the  maxi- 
mum produce  from  every  portion  susceptible  of  cultivation. 

The  British  islands  are  in  this  latter  condition.  Agriculture  now  is 
of  vastly  more  importance  to  us  as  a  nation,  than  it  was  towards  the 
close  even  of  the  last  century.  In  1780,  the  island  of  Great  Britain 
contained  about  9  millions  of  inhabitants ;  it  now  contains  nearly  20. 
The  land  has  not  increased  in  quantity,  but  the  consumption  of  food  has 
probably  more  than  doubled.  The  importation  from  abroad  has  not  in- 
creased to  any  important  extent;  by  improved  management,  therefore, 
the  same  area  of  land  has  been  caused  to  yield  a  double  produce. 

But  the  population  will  continue  to  increase ;  can  we  expect  that  the 
food  raised  from  the  land  will  continue  to  increase  in  the  same  ratio? 


£2  ON    IMFROV£M£NTS    IN    AGRICUIiTURE. 

This  is  an  important  question,  to  which  we  can  give  only  an  imperfest 
and  somewhat  unsatisfactory  answer. 

The  superficial  area  of  Great  Britain  comprises  about  57  millions  of 
acres,  of  which  34  millions  are  in  cultivation,  about  13  millions  are  in- 
capable of  culture,  and  the  remaining  10  millions  are  waste  lands  suscep- 
tible of  improvement.  The  present  population,  therefore,  is  supported 
by  the  produce  of  34  millions  of  acres,  or  every  34  acres  raises  food  for 
about  20  people.  Suppose  the  10  millions  of  acres  which  are  suscepti- 
ble of  improvement  to  be  brought  into  such  a  stale  of  culture  as  to 
maintain  an  equal  proportion — the  most  favourable  supposition — they 
would  raise  food  for  an  additional  population  of  about  6  millions,  or 
would  keep  Great  Britain  independent  of  any  large  and  constant  foreign 
supply  till  the  number  of  its  inhabitants  amounted  to  26  millions. 
But  at  the  present  rate  of  increase  this  will  take  place  in  about  20 
years,*  so  that  by  1860,  unless  some  general  improvement  take  place 
in  the  agriculture  of  the  country,  the  demands  of  the  population  will 
have  completely  overtaken  the  productive  powers  of  the  land. 

But  though  we  cannot  say  how  far  the  fertility  of  the  soil  may  be  in- 
creased, or  how  long  it  may  be  able  to  keep  a-head  of  the  growing 
numbers  of  the  people,  we  have  our  own  past  experience,  the  example 
of  other  countries,  and  the  indications  of  theory,  all  concurring  to  per- 
suade us  that  the  limit  of  its  productive  powers  can  neither  be  predicted 
nor  foreseen. 

If  we  glance  at  the  history  of  British  agriculture  during  the  last  half 
century — from  the  introduction  of  the  green  crop  system  or  the  alternate 
iusbandry  from  Flanders  into  Norfolk,  up  to  the  present  time — we  find 
the  results  of  each  successive  improvement  more  remarkable  than  the 
former.  The  use  of  lime,  a  more  general  drainage  of  the  soil,  the  in- 
vention of  improved  ploughs  and  other  agricultural  implements,  as  well 
as  the  introduction  of  better  and  more  economical  modes  of  using  them, 
the  application  of  bone  manure,  and  more  recently  of  thorough  draining 
and  subsoil  ploughing,  have  all  tended  not  only  to  the  raising  of  crops 
at  a  less  cost,  but  in  far  greater  abundance,  and  on  spots  which  our 
forefathers  considered  wholly  unfit  for  the  growth  of  corn. 

The  result  of  each  new  improvement,  I  have  said,  has  seemed  more 
astonishing  than  the  former.  For  after  a  waste  piece  of  land  has  been 
brought  into  an  average  state  of  productiveness,  we  are  not  prepared  for 
any  great  improvement  upon  it  by  new  labours;  nor  could  we  readily 
believe  that,  half  a  century  after  such  land  had  been  in  culture,  its  pro- 
duce or  its  value  should  at  once  be  doubled,  by  a  better  draining,  a 
deeper  ploughing,  or  by  sprinkling  on  its  surface  a  small  quantity  of  a 
saline  substance  imported  from  a  foreign  country. 

Yet  the  example  of  the  Chinese  shows  us  that  the  productive  powers 
of  the  soil  are  not  to  be  easily  estimated.  Nothing  repays  the  labours 
of  the  husbandman  more  fully  than  the  willing  soil — nothing  is  more 
grateful  for  his  attention,  or  offers  surer  rewards  to  patient  industry,  or 
to  renewed  attempts  at  improvement. 

In  China  we  see  a  people  whom  we  call  semi-barbarians,  multiply- 
ing within  their  own  limits  till  their  numbers  are  almost  incredible? 

•  For  more  precise  data  and  calculations  see  Porter't  Progress  of  the  Nation. 


'ROSPECTS   OF    SCIENTIFIC    AGRICULTURE.  13 

practisiug  from  the  most  remote  ages,  and  in  the  most  skilful  manner, 
various  arts  which  the  progress  of  modern  science  has  but  recently  in- 
troduced into  civilized  Europe ;  cultivating  their  soil  with  the  most  assid- 
uous labour,  and  stimulating  its  fertility  by  means  which  we  have  hith- 
erto neglected,  despised,  or  been  wholly  ignorant  of — but  which  the  dis- 
coveries of  the  present  time  are  pointing  out  as  best  fitted  to  secure  the 
amplest  harvests — and  have  thus  been  enabled  to  compel  their  limited 
soil  to  yield  a  sufficient  sustenance  to  its  almost  unlimited  poi)ulation.* 

Experience  and  example,  therefore,  encourage  us  to  look  forward  to 
still  further  improvements  in  the  art  of  culture,  and,  independent  of  such 
as  may  be  derived  from  purely  mechanical  principles,  theoretical 
cnemistry  seems  to  point  out  the  direction  in  which  important  advances 
of  another  kind  may  reasonably  be  anticipated.  The  Chinese  are  said 
to  be  not  only  familiar  with  the  relative  value  and  efficiency  of  the  va- 
rious manures,  but  also  to  understand  how  to  prepare  and  apply  without 
loss  that  which  is  best  fitted  to  stimulate  and  support  each  kind  of  plant. 
How  far  this  statement  is  exaggerated  we  are  unable  at  present  to  de- 
termine, but  it  is  in  this  direction  that  chemistry  appears  likely  to  pro- 
mote the  advance  of  European  agriculture.  The  practical  farmer  al- 
ready rejoices  in  having  in  one  ton  of  bone  dust  the  equivalent  of  14 
tons  of  farm-yard  manure;  some  of  the  most  skilful  living  chemists 
predict  that  methods  will  hereafter  be  discovered  for  compressing  into  a 
still  less  bulky  form  the  substances  required  by  plants,  and  that  we 
shall  live  to  see  extensive  manufactories  established  for  the  preparation 
of  these  condensed  manures. t 

*  An  intelligent  correspondent  reminds  me  that  the  agricultural  skill  of  the  Chinese  is 
questioned  by  recent  writers  on  the  customs  of  that  country.  This  doubt  is  founded  chiefly 
on  the  rudeness  of  their  agricultural  implements  and  the  scarcity  of  cattle,  whether  horses 
or  cows,  among  them.  But  in  this  densely  peopled  country  the  hoe  they  employ  serves 
the  purpose  of  every  other  implement  (^Davis's  China,  ii.  ^),  and  where  the  place  of  cat- 
tle is  supplied  by  an  equivalent  number  of  men,  there  can  be  no  comparative  want  of 
valuable  manure.  The  population  of  China,  however,  is  probably  not  so  dense  in  all  the 
provinces  as  it  has  hitherto  been  supposed.  Many  writers  have  estimated  the  entire 
population  at  300  millions,  while  recent  statists  reduce  it  to  175  millions.  Taking  even  the 
higher  estimate,  the  population  is  not  more  dense  than  in  England  and  Holland— the  area 
of  China  proper  being  1,200,000  square  miles,  or  eight  times  that  of  France.  It  is  considera- 
bly less  dense,  indeed,  if  we  take  into  account  the  number  of  horses  and  cattle  which  in 
Europe  are  reared  and  fed  on  the  produce  of  the  land.  We  may  hereafter  expect  more  ac- 
curate information,  however,  especially  regarding  the  interior  of  this  interesting  country.— 
See  Appendix  A. 

1  Should  the  opinions  above  expressed  appear  too  sanguine  to  some,  or  be  treated  by  any 
of  my  readers  as  merely  theoretical,  1  would  refer  them  to  the  words  of  Mr.  Smith  of  Dean- 
ston,  the  inventor  of  the  subsoil  plough,  and  the  introducer  of  the  greatest  practical  im- " 
1  provement  in  modern  agriculture.  After  stating  that  at  least  threefourth.t  of  the  ichole  ara- 
ble lar>d  in  the  country  is  under  very  indifferent  cvMure,  chiefly  from  the  want  of  complete 
draining  and  deep  working,  and,  adverting  to  the  increased  produce  it  may  be  made  to 
yield,  he  says,  "  it  is  not  at  all  improbable  that  Brilain  may  become  an  exporting  country  in 
grain  in  the  course  of  the  next  twenty  ye&rs."— Remarks  on  Thorough  Draining  and  Deep 
Ploughing,  by  James  Smith,  Esq.,  of  Deanston  Works,  p.  22.  Were  the  population  to 
remain  stationary,  Mr.  Smith  may  be  right ;  at  all  events,  this  opinion  shows  that  even 
practical  men  do  not  despair  of  attaining  to  a  pitch  of  improvement  in  agriculture  which 
theoretical  writers  dare  not  venture  to  predict. 

But  among  all  persons  of  enlarged  information  a  similar  opinion  prevails.  Thus  the 
eloquent  author  of  a  recent  work  on  the  principles  of  population  says,  "  the  single  alteration 
of  substituting  the  kitchen-garden  husbandry  of  Flanders  in  our  plains,  and  the  terraced 
culture  of  Tuscany  in  our  hflis,  for  the  present  system  of  agricultural  management,  would 
at  once  doubl^j  the  produce  of  the  British  islands,  and  procure  ample  subsistence  for  twice 
the  number  of  .ts  present  mha.bit&nts.''— Alison's  Principles  of  Population,  I.  p.  216.  These 
hopes  are  not  to  be  rejected  or  suppressed  ;  for,  though  they  may  never  be  fully  realized, 
yet  they  are,  as  it  were,  the  seeds  of  exertion,  from  which  ample  harvests  of  good  may 
hereafter  be  reaped. 


4  NEGLECT    OF    SCIENTIFIC    AGRICULTURE    IN    SCHOOLS. 

Thus  much  may  be  said  in  regard  to  the  future  hopes  and  prospects 
of  scientific  agriculture.*  But  how  few  practical  men  are  acquainted 
with  what  is  already  known  of  the  principles  of  the  important  art  by 
which  they  live!  Trained  up  in  ancient  methods — -attached  generally 
to  conservative  principles  in  every  shape — the  practical  agriculturists, 
as  a  body,  have  always  been  more  opposed  to  change  than  any  other 
large  class  of  the  community.  They  have  been  slow  to  believe  in  the 
superiority  of  any  methods  of  culture  which  differed  from  their  own, 
from  those  of  their  fathers,  or  of  the  district  in  which  they  live — and, 
even  when  the  superiority  could  nc  longer  be  denied,  they  have  been 
almost  as  slow  to  adopt  them. 

But  the  awakening  spirit  of  the  time  is  making  itself  felt  in  the  re- 
motest agricultural  districts  ;  old  prejudices  are  dying  out,  and  the  cul- 
tivators of  this  most  ancient,  most  important,  and  noblest  of  all  the  arts, 
are  becoming  generally  anxious  for  information,  and  eager  for  improve- 
ment.! 

Two  circumstances  have  contributed  to  retard  the  approach  of  this 
better  state  of  things. 

In  the  first  place,  the  agricultural  interest  in  England  has  hitherto 
expended  its  main  strength  in  attempting  to  secure  or  maintain  impor- 
tant political  advantages  in  the  state.  The  encouragement  of  experi- 
mental agriculture  has  been  in  general  neglected,  while  the  diffusion 
of  practical  knowledge  has  been  either  wholly  overlooked  or  considered 
subordinate  to  other  objects.  No  national  efforts  have  been  made  for 
the  general  improvement  of  the  methods  of  culture.  While  for  the 
other  important  classes  of  the  community  special  schools  have  been  es- 
tablished, in  which  the  elements  of  all  the  branches  of  knowledge  most 
necessary  for  each  class  have  been  more  or  less  completely  taught,  and 
a  more  enhghtened,  because  better  instructed,  race  of  men  gradually 
trained  up,  no  such  schools  have  been  instituted  for  the  benefit  of  the 
agriculturist.  In  our  Universities,  in  which  the  holders  of  land,  those 
most  interested  in  its  improvement,  are  nearly  all  educated,  a  lesson 
upon  agriculture,  the  right  arm  of  the  State,  has  hitherto  scarcely  ever 
been  given 4     With  the  practice  of  the  art,  the  theory  has  also  been 

Those  who  have  access  to  the  Journal  of  the  Royal  English  Agricultural  Society  will 
find  in  the  first  number  a  paper  by  Mr.  Pusey,  "  On  the  present  state  of  the  science  of  Agri- 
culture in  England,"  in  which  much  valuable  information  is  contained,  and  of  a  more  prac- 
tical kind  than  I  have  been  able  to  introduce.  This  paper  ought  to  be  printed  in  a  separate 
•form,  and  circulated  widely  among  those  who  are  not  members  of  the  Royal  English  Agri 
cultural  Society. 

t  This  opinion  has  been  confirmed  by  the  numerous  communications  I  have  received 
from  all  parts  of  the  country  since  the  publication  of  these  Lectures  was  announced,  and  in 
which  I  am  assured  that  the  want  of  knowledge  ;s  generally  felt,  and  a  supply  in  a  sufficient- 
ly elementary  form  desired,  by  all  classes  of  agf  culturists.  I  conclude,  therefore,  that  Lie- 
big  means  the  following  sentence  to  apply  to  hit*  German  countrymen  :  "  What  can  be  ex- 
pected from  the  present  (generation  of)  farmers,  which  recoils  witii  seeming  distrust  and 
aversion  from  all  the  means  of  assistance  offered  it  by  chemistry,  and  which  does  not  un- 
derstand the  art  of  making  a  rational  application  of  chemical  discoveries."  I  do  not  think 
chemists  ought  in  fairness  to  blame  the  practical  agriculturists  for  not  understanding  the 
art  of  applying  chemical  discoveries  to  the  improvement  of  the  culture  of  the  land.  They 
must  first  know  what  the  discoveries  are  ;  and  the  error  has  hitherto  been,  that  no  steps 
have  been  taken  to  diffuse  this  preliminary  knowledge. 

t  However  satisfied  young  men  may  be  to  avoid  the  labor  of  additional  study  while  at 
College,  how  many  in  after- life  regret  that  their  early  attention  had  not  been  directed  to 
some  of  those  branches  of  knowledge  which  are  applicable  to  common  life.  Thus  the  late 
Lord  Dudley,  in  his 'etters  to  the  Bishop  of  Llandaff,  invariably  laments,  "  as  mistakes  in 


ENCOURAGEMENT    OF   AGRICULTURAL    LITERATURE.  15 

neglected.  '  Scientific  men  have  had  no  inducement  lo  devote  their 
time  and  talents  to  a  subject  which  held  out  no  promise  of  reward, 
either  in  the  shape  of  actual  emolument  or  of  honorary  distinction. 
And  thus  has  arisen  the  second  of  those  circumstances,  by  which  I  con- 
sider the  approach  of  a  better  state  of  things  to  have  been  retarded — 
namely,  the  want  of  an  Agricultural  Literature. 

With  the  exception  of  a  small  number  of  periodical  publications, 
none  of  these  even  too  well  supported,  by  which  attempts  have  been 
zealously  made  to  difflise  important  information  among  the  practical 
farmers — it  cannot  be  denied  that  the  press  has  not  been  encouraged  to 
do  its  utmost  on  behalf  of  agricultural  knowledge  in  general — while  the 
single  work  of  Sir  Humphry  Davy  is  nearly  all  that  chemical  science 
has,  in  this  country,  been  induced  to  contribute  to  the  advancement  of 
agricultural  theory  during  the  last  forty  years.* 

Many  of  you  have  probably  read  this  work  of  Sir  Humphry  Davy, 
and  are  prepared  to  acknowledge  its  value.  Yet  how  many  things 
does  he  pass  over  entirely,  how  many  things  leave  unexplained  !  Since 
his  time,  not  only  have  numerous  practical  observations  and  discoveries 
been  made,  but  the  entire  science  of  animal  and  vegetable  chemistry 
has  been  regenerated.  We  are  not,  therefore,  to  expect  in  his  work  a 
view  of  the  present  state,  either  of  our  theoretical  knowledge,  or  of  our 
practical  agriculture.  It  belongs  rather  to  the  history  of  the  progress  oi 
knowledge,  than  to  the  condition  of  existing  information.  Hence  the 
merits  of  the  agricultural  chemistry  of  Davy  are  not  to  be  tried  by  its 
accordance  with  actual  knowledge,  but  with  what  was  known  in  1812, 
when  its  distinguished  author  read  his  course  of  lectures  for  the  last 
time  before  the  Board  of  Agriculture. 

We  may  with  certainty  predict,  hov/ever,  that  neither  the  practice 
nor  the  theory  of  agriculture  will  be  permitted  to  experience  in  future 
that  want  of  general  encouragement  under  which  during  the  last  half 

his  early  life,  his  unacquaintance  with  the  rudiments  of  agriculture — liis  ignorance  of  bota- 
ny and  geology." — (See  also  a  note  to  the  Review  of  these  Letters  in  the  Quarterly  Review 
for  December,  1840.) 

For  this  state  of  things  we  shall  soon  have  at  least  a  partial  remedy.  It  is  a  remarkable 
fact  that  nearly  all  the  new  educational  institutions  of  the  higher  class,  on  the  Continent  of 
Europe,  of  which  so  many  have  been  founded  within  the  present  century,  and  all  those 
which  have  been  established  in  America,  I  believe,  without  exception,  have  incorporated 
into  their  course  of  general  study  one  or  more  of  the  newer  sciences.  Can  we  have  a  more 
consentaneous  and  universal  testimony  to  their  value  and  importance  than  this  7  The  Uni- 
versity of  London  has  been  induced,  by  the  same  public  demand  for  this  species  of  instruc- 
tion, to  include  Chemistry  and  Botany  in  its  course  of  arts ;  and  circumstances  only  have 
caused  Geology  to  be  omitted  for  a  time.  Its  numerous  affiliated  institutions  have  followed 
its  steps;  and  hence  the  Catholic  College  of  St.  Cuthbert,  at  Ushaw,  has  in  this  respect  an- 
ticipated its  Protestant  neighbor  at  Durham. 

But  should  the  agricultural  interest  rest  satisfied  with  this  introduction  of  one  or  two 
branches,  suppose  it  generally  done,  into  the  University  course  of  study?  Many  are  of 
opinion  that  it  ought  not,  and  that  the  general  interests  of  practical  agriculture  would  be 
manifestly  promoted,  among  other  means,  by  the  establishment  of  agricultural  colleges,  in 
which  all  the  branches  necessary  to  be  known  by  enlightened  agriculturists  of  every  class 
should  be  specially  and  distinctly  taught.  Whether  such  Colleges  might  be  beneficially 
annexed  to  the  existing  Universities,  is  a  question  deserving  of  serious  consideration. 

*  The  latest  edition  of  Lord  Dundonald's  "Treatise  on  the  intimate  connection  between 
Chemistry  and  Agriculture,"  which  I  have  seen,  is  dated  London,  1803. 

I  should  be  doing  injustice  to  a  good  chemist  and  a  zealous  agriculturist,  were  1  not  to 
direct  the  attention  of  my  readers  to  a  series  of  excellent  articles  on  chemical  agriculture 
by  Dr.  Madden,  inserted  in  the  numbers  of  the  Quarterly  Journal  of  Agriculture  for  the  last 
two  years. 

Since  the  above  went  to  press.  Three  Lectures  on  Agriculture  have  appeared  from  the 
pen  of  Dr.  Daubeny,  of  Oxford,  whose  name  will  secure''.hem  an  extended  circulation. 


16  GENERAL    SCIENCE   AND    AGRICULTURE. 

century  they  have  in  England  been  permitted  to  languish.  *  The  public 
mind  has  been  awakened,  and  the  establishment  of  Agricultural  Associ- 
ations, provincial  and  local,  are  manifestations  of  the  interest  now  felt 
upon  the  subject  in  all  parts  of  the  country.  It  requires  only  the  general 
exhibition  of  such  an  interest,  and  the  adoption  of  some  general  means  of 
encouragement,  to  stimulate  both  practical  ingenuity  and  scientific  zeal 
to  expend  themselves  on  this  most  valuable  branch  of  national  industry. 

Science  is  never  unwilling  to  lend  her  hand  to  the  practical  arts  ;  on 
the  contrary,  she  is  ever  forward  to  proffer  her  assistance,  and  it  is  not 
till  her  advances  have  been  rejected  or  frequently  repulsed,  that  she  re- 
frains from  aiding  in  their  advancement. 

Need  I  advert,  in  proof  of  this,  to  the  unwearied  labours  of  the  vege- 
table physiologists — or  to  the  many  valuable  observations  and  experi- 
ments recorded  in  the  memoirs  of  scientific  chemists.  In  these  memoirs, 
or  in  professedly  scientific  works,  such  observations  have  not  unfre- 
quently  been  permitted  to  rest; — the  public  mind  being  unprepared 
either  to  appreciate  their  value  or  to  encourage  the  exertions  of  those  wko 
were  willing  to  give  them  a  practical  and  popular  form. 

And  how  numerous  are  the  branches  of  science  connected  with  this 
art  ?  Need  I  speak  of  botany,  which  is,  as  it  were,  the  foundation  on 
which  the  first  elements  of  agriculture  rest ;  or  of  vegetable  physiology, 
to  the  indications  of  which  it  has  hitherto  almost  exclusively  looked  for 
improvement  and  increased  success ;  or  of  zoology,  which  alone  can 
throw  light  on  the  nature  of  the  numerous  insects  that  prey  upon  your 
crops,  and  so  often  ruin  your  hopes, — and  which  can  alone  be  reason- 
ably expected  to  arm  you  against  their  ravages,  and  instruct  you  to  ex- 
tirpate them  ?  Meteorology  among  her  other  labours  tabulates  the  highest, 
the  mean,  and  the  lowest,  temperatures,  as  well  as  the  quantity  of  rain 
which  falls  during  each  day  and  each  month  of  the  year.  Do  you 
doubt  the  importance  of  such  knowledge  to  the  proper  cultivation  of  the 
land  ?  Consider  the  destructive  effects  of  a  late  frost  in  spring,  or  of  a 
continued  heat  in  summer,  and  your  doubts  will  be  shaken.  A  wet  sea- 
son in  our  climate  brings  with  it  many  evils  to  the  practical  agriculturist ; 
but  what  effect  must  the  rain  have  on  the  soil,  in  countries  where  nearly 
as  much  falls  in  a  month,  as  in  England  during  the  course  of  a  whole 
year  ;* — where  every  thing  soluble  is  speedily  washed  from  the  land,  and 
nothing  seems  to  be  left  but  a  mixture  of  sand  and  gravel  ?  It  may 
indeed  be  said  with  truth,  that  no  department  of  natural  science  is  inca- 
pable of  yielding  instruction — that  scarcely  any  knowledge  is  superflu- 
ous— to  the  tiller  of  the  soil. 

It  is  thus  that  all  branches  of  human  knowledge  are  bound  together, 
and  all  the  arts  of  life,  and  all  the  cultivators  of  them,  mutually  de- 
pendent. And  it  is  by  lending  each  a  helping  hand  to  the  others,  that 
the  success  of  all  is  to  be  secured  and  accelerated ;  while  with  the  gene- 
ral progress  of  the  whole  the  advance  of  each  individual  is  made  sure. 
The  recent  contributions  and  suggestions  of  geology  are  the  best  proof 
of  the  readiness  of  the  sciences  of  observation  to  give  their  aid  to  the 
promotion  especially  of  agricultural  knowledge.  The  geologist  can 
best  explain  the  immediate  origin  of  your  several  soils,  the  cause  of  the 

*  At  Canton,  in  the  month  of  May,  the  fall  of  rain  is  often  as  much  as  20  inches. 


GEOLOGY    CONNECTED    WITH    AGRICULTURE.  17 

diversities  which  even  in  the  same  farm,  it  may  be  in  the  same  field, 
they  not  unfrequently  exhibit;*  the  nature  and  differences  among  your 
subsoils,  and  the  advantages  you  may  expect  from  breaking  them  up  or 
bringing  tliem  to  the  surface. 

Geology  is  essentially  a  popular  science,  and  the  talents  of  its  emi- 
nent English  cultivators  are  admirably  fitted  to  make  it  still  more  so. 
Hence,  a  certain  amount  of  knowledge  of  this  science  has  been  of  late 
years  very  generally  diffused,  and  its  relations  to  agriculture  are  be- 
coming every  day  better  understood.  The  Highland  Society  of  Scot- 
land, among  its  many  other  useful  exertions,  has  done  very  much  to 
connect  agriculture  and  geology  with  the  sphere  of  its  own  labours, 
while  the  Journal  of  the  Royal  Agricultural  Society  of  England  mani- 
fests a  similar  desire  on  the  part  of  that  numerous  and  talented  body,  to 
illustrate  the  connection  of  agriculture  with  geology  and  chemistry,  in 
the  southern  division  of  the  island.  That  Dr.  Buckland,  Mr.  Murchi- 
son,  and  Mr.  De  la  Beche  have  each  engaged  to  make  a  gratuitous  sur- 
vey of  the  subsoils  in  several  extensive  agricultural  districts,  at  the  re- 
quest of  the  Council  of  this  Society,f  shows  that,  where  their  services  are 
estimated,  our  most  eminent  scientific  men  will  not  hesitate  to  devote  them 
to  the  development  of  the  most  important  branches  of  national  industry. 

The  time,  therefore,  is  peculiarly  favourable  for  the  increase  and  diffu- 
sion of  agricultural  knowledge.  The  growth  of  our  population  re- 
quires it — practical  men  are  anxious  to  receive  instruction — scientific 
men  are  eager  to  impart  what  they  know,  and  to  make  new  researches 
for  the  purpose  of  clearing  up  what  is  unknown — are  we  not  justified, 
therefore,  in  anticipating  hereafter  a  constant  and  general  diffusion  of 
light,  a  steady  progress  of  agricultural  improvement  ? 

Having  thus  glanced  at  the  state  and  prospects  of  scientific  agricul- 
ture in  general,  and  especially  of  the  art  of  culture  in  England,  permit 
me  to  advert  to  a  few  of  those  questions  of  daily  occurrence  among  you, 
to  which  chemistry  alone  can  give  a  satisfactory  answer.  I  shall  not  in 
this  place  allude  to  the  subject  of  manures — which  form  alone  an  entire 
chapter  of  most  recondite  chemistry,  and  which  I  shall  take  up  in  its 
proper  place,  but  I  shall  select  a  few  isolated  topics,  the  bearing  of 
chemical  knowledge  upon  which  is  sufficiently  striking. 

Some  soils  are  naturally  barren,  but  how  few  of  our  agriculturists  are 
able,  in  regard  to  such  soils  generally,  to  say  why  ;  how  few  who  pos- 
sess the  knowledge  requisite  for  discovering  the  cause  !  Of  these  bar- 
ren lands  some  may  be  improved  so  as  ^mply  to  repay  the  outlay  ;  some, 
from  their  locality  or  from  other  causes,  are  in  the  present  state  of  our 
knowledge  irreclaimable.  How  important  to  be  able  to  distinguish  be- 
tween these  two  cases ! 

*  I  cannot  refer  to  a  plainer,  more  simple,  or  more  beautiful  illustration  of  this  fact  than 
that  which  is  presented  in  a  short  paper  by  Sir  John  Johnstone,  Bart.,  inserted  in  the  Jour- 
nal  of  the  English  Agricultural  Society,  I.  p.  271,  entitled  "On  the  Application  of  Geology  to 
Agriculture."  See  also  an  able  paper  by  the  Rev.  Mr.  Thorpe,  of  which  a  valuable  report  is 
contained  in  the  Doncaster  Chronicle  of  December  5th,  and  which  will  be  published  in  the 
proceedings  of  the  Geological  and  Polytechnic  Society  of  the  West  Riding  of  Yorkshire. 

t  Journal  of  the  Royal  Agricultural  Society,  Report  of  their  Council,  I.  p.  188. 

To  form  a  just  idea  of  the  value  and  importance  of  such  surveys,  it  ia  only  necessary  to 
read  chap,  xv.,  pp.  463  to  480,  of  Mr.  De  la  Beche's  "  Geological  Report  on  Cornwall  and  De- 
von," or  Professor  Hitchcock's  "Rep-rtrt  on  a  re-examination  of  the  Economic  Geology  ot 
Massachusetts." 


18  CHEMISTRY    AND    AGR  CULTURE. 

Some  apparently  good  soils  are  yet  barren  in  a  high  degree.  In  en- 
deavouring to  improve  such  soils,  practical  men  have  no  general  rule — 
they  can  have  none.  They  vi^ork  in  the  dark — like  a  man  who  makes 
experiments  in  a  laboratory,  without  a  teacher  or  without  a  book,  till, 
after  many  blunders  and  much  expense,  he  discovers  some  fact,  to  him- 
self new,  but  to  others  long  known,  and  forming  only  one  of  many  ana- 
logous facts,  flowing  from  a  common,  and  probably  well  understood, 
principle. 

"  The^pplication  of  chemical  tests  to  such  a  soil,"  says  Sir  Humphry 
Davy,  "  is  obvious.  It  must  contain  some  noxious  p'Vinciple,  for  be  de- 
ficient in  some  necessary  element. — J.]  which  may  be  easily  discovered 
and  probably  easily  destroyed.  Are  any  of  the  salts  of  iron  present, 
they  may  be  decomposed  by  lime.  Is  there  an  excess  of  siliceous  sand, 
the  system  of  improvement  must  depend  on  the  application  of  clay  and 
calcareous  matters.  Is  there  a  defect  of  calcareous  matter,  the  remedy 
is  obvious.  Is  an  excess  of  vegetable  matter  indicated,  it  may  be  re- 
moved by  liming,  paring,  and  burning.  Is  there  a  deficiency  of  vege- 
table matter,  it  is  to  be  supplied  by  manure." — [Agricultural  Chemistry, 
Lecture  1.] 

What  was  true  in  regard  to  the  applications  of  chemistry  in  the  time 
of  Sir  Humphry  Davy  is  more  true  in  a  high  degree  of  the  chemistry 
of  our  time.  Not  only  is  the  nature  of  soils  better  understood,  but  we 
know  in  many  cases  what  a  soil  must  contain  before  it  will  produce  a 
given  crop.  Why  do  pine  forests  settle  themselves  on  the  naked  and 
apparently  barren  rocks  of  Scotland  and  of  Northern  Europe,  content  if 
their  young  roots  can  find  but  a  crevice  in  the  mountain  to  shelter  them  1 
Why  does  the  beech  luxuriate  in  the  alluvial  soils  of  Southern  Sweden, 
of  Zealand,  and  Continental  Denmark  ?  Why  does  the  birch  spring 
up  from  the  ashes  of  the  pine  forest — -why  the  rapid  rush  of  delicate 
grass  from  the  burned  prairies  of  India  and  of  Northern  America  ? 
Whence  comes  the  thick  and  tender  sward  of  the  mountain  limestone 
districts — whence  the  gigantic  wheat  stalk  of  a  virgin  soil  ?  Why  do 
the  same  forest  trees  propagate  themselves  for  ages  on  the  same  spots 
without  impoverishing  the  soil — why  do  the  natural  grasses,  the  longer 
they  are  undisturbed,  render  he  land  only  the  more  fertile  ? 

These,  one  would  think,  aie  scarcely  cheiirical  questions,  and  yet  to 
all  of  them,  and  to  a  thousand  such,  chemistry  alone  can  and  will  give 
a  satisfactory  answer. 

The  rotation  of  crops  is  a  practical  rule,  the  benefit  of  which  has 
been  proved  by  experience ;  it  becomes  a  true  philosophical  principle 
of  action,  when  we  discover  the  causes  from  which  this  benefit  springs. 
Botany  has  thrown  considerable  light,  and  of  an  interesting  and  impor- 
tant kind,  upon  this  practice,  but  chemistry  has  fully  cleared  it  up  and 
established  the  principle. 

Sir  Humphry  Davy  speaks  of  the  use  of  lime.  Can  you  explain  the 
mysterious,  and  apparently  fickle  and  diversified,  agency  of  this  sub 
stance  in  reference  to  vegetation  ?  Are  the  advantages  so  frequently 
attendant  upon  its  use  to  be  ascribed  to  the  chemical  character  of  ihe 
soil  to  which  it  is  applied,  to  the  kind  and  quantity  of  the  vegetable 
matter  it  contains,  or  to  the  geological  nature  of  the  rocks  on  whicn  it 
rests?     Are  they  dependent  upon  the  drainage   and  exposure  of  the 


THEORETICAL    KNOWLEDGE    STILL    VERY    DEFECTIVE.    **         .9 

land — on  the  kind  of  crop  to  be  raised — on  the  general  climate  of  the 
district — on  the  maxima  and  minima  of  temperature — or  on  the  quanti- 
ty of  rain  which  falls? 

So  with  gypsum.  Why  are  its  effects  lauded  in  one  district,  doubted 
in  another,  and  decried  in  a  third!  Are  no  rules  or  principles  to  be 
discovered,  by  which  these  diversified  effects  are  to  be  explained,  and 
the  true  purpose  and  fit  use  of  these  and  other  mineral  substances  clear- 
ly pointed  out?  Such  principles  are  yet  1o  be  sought  for;  but  if 
sought  by  the  way  of  well  devised  and  accurately  conducted  experi- 
ment, they  are  sure  to  be  discovered. 

The  land  is  exhausted  by  frequent  cropping.  "What  language  more 
familiar,  what  statement  more  true  than  this?  Yet  how  few  under- 
stand what  exhaustion  implies;  how  few  can  explain  either  how  it 
takes  place,  by  what  means  it  can  be  remedied,  or  how,  if  left  to  her- 
self, nature  at  length  does  apply  a  remedy  ! 

Have  you  any  doubt  in  regard  to  the  prevailing  ignorance  on  this 
subject  ?  To  be  satisfied,  you  have  only  to  look  with  an  experienced 
eye  on  the  agricultural  practice  of  the  county  of  Durham.  Are  there 
not  thousands  of  acres  in  the  centre  of  this  county  which  exhibit  a  de- 
gree of  unproductiveness  not  natural  to  the  soil ; — which  have  been 
overcropped,  and  worn  out,  and  impoverished?  A  soil  comparative- 
ly fertile  by  nature  has  been  rendered  unfertile  by  art.  That  which 
was  naturally  good  has  been  rendered  as  unproductive  and  unprofitable 
as  that  which  was  naturally  bad.  Has  this  state  of  things  arisen  from 
ignorance,  from  design,  or  from  necessity  ?  By  whichever  of  these  it 
ha:s  been  immediately  caused,  it  is  clear  that  the  requisite  degree  of 
knowledge  on  the  part  of  the  owners  of  the  soil  would  have  retarded  if 
not  wholly  prevented  it. 

The  same  knowledge  will  enable  them  to  reclaim  these  lands  again, 
and  gradually  restore  them  to  a  more  fertile  condition  ;  for  the  changes 
which  the  soil  undergoes  in  such  circumstances  are  all  chemical 
changes, — either  in  the  relative  quantities  of  the  substances  it  contains, 
or  in  the  state  of  combination  in  which  they  exist. 

The  art  of  culture  indeed  is  almost  entirely  a  chemical  art,  since 
nearly  all  its  processes  are  to  be  explained  only  on  chemical  principles. 
If  you  add  lime  or  gypsum  to  your  land,  you  introduce  new  chemical 
agents.  If  you  irrigate  your  meadows,  you  must  demand  a  reason 
from  the  chemist  for  the  abundant  growth  of  grass  which  follows.  Do 
you  find  animal  manure  powerful  in  its  action,  is  the  effect  of  some 
permanent,  while  that  of  others  is  speedily  exhausted  ? — does  a  mixture 
of  animal  and  vegetable  manure  prepare  the  land  best  for  certain,  kinds 
of  grain? — do  you  employ  common  salt,  or  gypsum,  or  saltpetre,  or  ni- 
trate of  soda,  with  advantage  ? — in  all  these  cases  you  observe  chemical 
results  which  you  would  be  able  to  control  and  modify  did  you  possess 
the  requisite  chemical  knowledge. 

It  is  not  wonderful  that  even  theoretical  agriculturists  should  be  far 
behind  in  the  knowledge  of  those  principles  on  which  their  most  impor- 
tant operations  depend.  The  greatest  light  has  been  thrown  upon  the 
art  of  culture  by  the  researches  of  organic  chemistry,  a  branch  which 
may  be  said  to  have  started,  if  not  into  existence,  at  least  into  a  new 
life,  within  the  last  ten  j  sars.     Every  day  too  is  adding  to  the  number 


20    *       OUTLINE  OP  THE  COURSE  OF  LECTURES. 

and  ralue  of  its  (Hscoveries,  and  the  agriculturist  may  well  be  pardoned 
for  not  keeping  j)ace  with  the  advances  of  a  department  cf  science, 
which  even  the  professed  and  devoted  chemist  can  scarcely  overtake. 

I  might  advert  also  to  the  mechanical  operations  of  ploughing,  wheth- 
er common  or  subsoil,  of  fallowing,  draining,  weeding,  and  many 
others,  as  being  only  so  many  methods  by  which  chemical  action  is  in- 
duced or  facilitated  ; — to  the  growth  of  plants,  and  even  to  such  ob- 
served differences  as  that  of  the  relative  quantity  of  leaves  and  tubers  in 
the  potatoe,  and  of  grain  and  straw  in  our  corn-fields,  as  interesting 
cases  on  which  scientific  chemistry  throws  a  flood  of  light.  I  might 
shew  how  the  feeding  of  your  cattle  and  the  raising  and  management 
of  dairy  produce  are  not  beyond  the  province  of  chemistry,  but  that  the 
only  approach  to  scientific  principle  yet  made,  even  in  these  branches 
of  husbandry,  is  derived  from  the  results  of  chemical  research. 

But  I  do  not  dwell  on  any  of  these  points:  they  will  all  hereafter 
come  under  our  review  in  their  appropriate  order,  and  will  afford  me  an 
opportunity  of  laying  before  you  many  important  facts,  as  well  as,  I 
hope,  valuable  practical  deductions  and  observations. 

While,  however,  I  feel  justified  in  saying  thus  much  of  the  light 
which  existing  chemical  knowledge  throws  on  the  natural  processes  of 
vegetation,  and  on  the  artificial  methods  of  practical  agriculture,  I 
would  not  lead  you  to  suppose  that  our  knowledge  is  by  any  means 
complete,  that  there  are  not  many  points  over  which  much  darkness 
still  rests — that  some  of  the  theoretical  views  now  entertained  are  not 
crude,  adopted  too  hastily,  and  generalized  too  rapidly.  But  a  similar 
confession  may  be  made  in  reference  to  all  the  modern  sciences  of  ob- 
servation without  diminishing  their  importance  or  detracting  from  the 
value  of  the  facts  they  embody.  Human  science  is  progressive  in  all 
its  branches,  and  to  refuse  to  follow  the  indications  of  existing  know- 
ledge because  it  is  to  some  extent  uncertain,  would  be  as  foolish  as  to 
refuse  to  avail  ourselves  of  the  morning's  light,  because  it  is  not  equal 
to  that  of  the  midday  sun. 


1  advance,  therefore,  to  the  special  object  of  these  lectures,  and  I  shall 
first  present  you  with  a  rapid  outhne  of  the  method  which  I  intend  to 
follow.  It  is  indispensable  that  this  method  should  be  simple,  and  that 
every  consecutive  portion  should  be  so  fitted  to  clear  the  way  for,  and 
thp3w  light  upon,  what  is  to  follow,  that  we  may  be  able  to  advance 
fron?  the  first  rudiments  to  the  most  difficult  and  abstruse  parts  of  our 
subject,  without  any  chance  of  the  illustrations  being  even  difficult  to 
comprehend.  This  end  I  do  not  hope  perfectly  to  attain,  but  it  will  be 
my  constant  aim,  and,  with  due  attention  on  your  part,  I  do  not  fear 
that  we  shall  fail  in  arriving  at  a  perfect  understanding  of  the  various 
points  to  which  I  shall  have  occasion  to  direct  your  attention. 

I  propose,  therefore,  to  bring  before  you — 

I.  The  constitution  of  vegetable  substances  with  the  properties  of  the 
elementary  and  compound  bodies  which  either  enter  into  the  substances 
of  plants  or  contribute  to  their  growth  and  nourishment. 

II.  The  general  structure  and  functions  of  the  several  parts  of  nlflnffl 


ORGANIC    AND    INORGANIC    MATTER.  21 

— their  mode  of  growth — and  the  manner  in  which  their  fooa  is  ab- 
sorbed, changed,  and  converted  into  parts  of  their  substance. 

III.  The  origin,  nature,  and  principal  differences  of  soils — with  the 
circumstances  on  wbich  their  relative  fertility  depends,  or  under  which 
it  is  modified. 

IV.  The  nature  and  differences  of  manures,  and  their  mode  of  action, 
whether  directly  in  supplying  food  to  the  plant,  or  indirectly  in  hasten- 
ing and  increasing  their  growth. 

V.  The  nature  and  diversities  of  the  food  raised  as  the  result  of  cul- 
ture— especially  in  reference  to  their  several  equivalents  or  powers  of 
supporting  animal  life. 

Under  this  head  the  feeding  of  cattle  and  the  variations  in  the  quan- 
tity and  quality  of  dairy  produce,  will  form  subjects  of  consideration. 

These  different  branches,  I  believe,  comprehend  the  whole  subject 
of  chemical  agriculture  ;  in  regard  to  all  of  them  we  shall  derive  either 
from  chemistry  or  geology  much  important  information. 

§  1.  Different  kinds  and  states  of  matter. 

All  the  forms  of  matter  which  present  themselves  to  our  view, 
whether  in  the  solid  crust  of  the  globe  on  which  we  live,  in  the  air 
which  forms  the  atmosphere  by  which  we  are  surrounded,  or  in  the  bo- 
dies of  animals  and  plants — all  are  capable  of  being  divided  into  the  two 
great  groups  of  organic  and  inorganic  matter.  The  solid  rocks  and  soils, " 
the  atmosphere,  tlie  waters  of  the  seas  and  oceans,  every  thing  which 
neither  is  nor  has  been  the  seat  of  life,  may  generally  be  included  under 
the  head  of  inorganic  matter.  The  bodies  of  all  living  animals  and 
plants,  and  their  dead  carcases,  consist  of  organic  or  organized  matter. 
These  generally  exhibit  a  kind  of  structure  readily  visible  by  the  eye, 
as  in  the  pores  of  wood,  and  in  the  fibres  of  hemp,  or  of  the  lean  of 
beef,*  and  are  thus  readily  distinguished  from  inorganic  matter,  in 
which  no  such  structure  is  observable. 

But  in  many  substances  of  organic  origin  also,  no  structure  is  obser- 
vable. Thus,  sugar,  starch,  and  gum,  are  formed  in  plants  in  great 
abundance,  and  yet  do  not  present  any  pores  or  fibres ;  they  have  never 
been  endowed  with  organs,  yet  being  produced  by  the  agency  of  living 
organs,  they  are  included  under  the  general  name  of  organic  matter. 
So  when  animals  and  plants  die,  their  bodies  undergo  decay,  but  the 
matter  of  which  they  are  composed  is  considered  as  of  organic  origin, 
not  only  as  long  as  any  traces  of  structure  are  observable,  but  even  after 
all  such  traces  have  disappeared.  Thus  coal  is  a  substance  of  organic 
origin,  though  almost  all  traces  of  the  vegetable  matter  from  which  it 
lias  been  derived,  have  been  lojig  ago  obliterated. 

Again,  heat  chars  and  destroys  wood,  starch,  and  gum,  forming  black 
substances  totally  unlike  the  original  matter  acted  upon.  By  distillation, 
wood  yields  tar  and  vinegar ;  and  by  fermentation,  sugar  is  converted 
first  into  alcohol,  and  then  into  vine^r.  All  substances  derived  from 
vegetable  or  animal  products  by  these  and  similar  processes  are  included 
under  the  general  designation  of  organic  bodies. 

*  The  pores  of  wood  and  fibres  and  minute  vessels  in  animals  being  the  organt  or  instru. 
meats  of  hfe,  the  substances  themselves  are  called  organized  or  organic. 

2 


22  NUMBER    Of    ELEMENTARY    BODIES 

Now  if  we  take  a  portion  of  almost  any  of  those  numerous  forms 
of  matter  which  we  meet  with  either  in  the  inorganic  or  in  the  organic 
kingdoms,  we  find,  that  on  subjecting  it  to  certain  cliemical  processes,  it 
is  capable  of  being  resolved  or  separated  into  more  than  one  substance. 
Thus  coal  when  put  into  a  gas  retort  is  resolved  into  tar,  coal  gas,  and 
certain  other  substances.  Wood,  when  treated  in  the  same  way,  yields 
pyroligneous  acid,  tar,  and  water,  and  leaves  behind  a  residue  of  char- 
coal. Jf  again  we  subject  charcoal  to  the  action  of  heat  (not  in  the 
open  air),  or  to  any  other  process  we  can  devise,  we  can  never  separate 
any  thing  further  from  it.  After  all  our  operations  we  obtain  only 
charcoal. 

So  a  piece  of  common  lead  ore,  when  heated  in  a  similar  manner, 
will,  if  pure,  give  offsulphuronly,  and  leave  the  lead  behind,  from  which 
nothing  but  lead  can  afterwards  be  extracted. 

Thus  it  is  evident  that  wood  and  the  ore  of  lead  differ  from  charcoal 
and  metallic  lead  in  this  respect,  that  the  former  consist  of  more  than  one 
kind  of  matter,  the  latter  of  one  kind  of  matter  only.  Hence  charcoal 
and  lead  are  called  simple  or  elementary  bodies,  while  wood  and  all  otli- 
er  substances  which  are  capable  of  being  resolved  into  two  or  more 
different  kinds  of  matter  are  called  compound  bodies. 

The  diversified  forms  of  matter  which  present  themselves  to  our  no- 
tice in  the  mineral  crust  of  the  globe,  and  in  the  organs  and  vessels  of 
.plants  and  animals,  are  absolutely  without  number.  We  can  no  more 
reckon  them  than  we  can  the  stars  of  heaven.  Yet  it  is  one  of  those  re- 
sults of  modern  chemistry  which  to  the  mind  not  yet  familiarized 
with  chemical  discoveries  appears  most  wonderful, — that  these  num- 
berless forms  of  matter  are  capable  of  being  resolved  into,  and  there- 
fore are  composed  or  made  up  of,  only  55*  of  those  simple  or  ele- 
mentary substances,  the  nature  of  which  has  been  above  explained. 
Occasionally  these  elementary  substances  occur  in  a  separate  state,  as 
in  native  [so  called  when  found  in  the  malleable  state,]  gold  and  silver, 
but  they  are  generally  found  associated  together,  forming  substances 
from  whioh  several  of  the  55  simple  bodies  may  be  extracted. 

All  the  material  substances  in  nature  consist  of  one  or  more  of  these 
65  elementary  bodies.  This  is  suflSciently  surprising,  yet  it  is,  if  pos- 
sible, still  more  remarkable  that  nearly  the  entire  mass  of  every  vege- 
table substance  may  be  resolved  into  one  or  more  o^  four  only  of  these 
simple  substances. 

When  a  portien  of  animal  or  vegetable  matter  is  burned  it  either  en- 
tirely disappears  or  leaves  behind  it  only  a  small  quantity  of  ash.  Ani- 
mal and  vegetable  oils  and  fats,  gum,  sugar,  and  starch,  when  burned, 
disappear  entirely ;  a  piece  of  wood  or  of  lean  meat  leaves  a  small 
quantity  of  earthy  (inorganic)  matter  behind. 

Now  all  that  disappears  when  any  portion  of  vegetable  matter,  of  any 
kind,  is  burned,  consists  generally  of  three,  and  only  in  some  rare  cases 

•  The  names  of  these  elementary  bodies  are  as  follows :— Oxygen,  hydrogen,  nitrogen, 
sulphur,  selenium,  phosphorus,  chlorine,  bromine,  iodine,  fluorine,  carbon,  boron,  silicon, 
potassium,  sodium,  lithium,  barium,  strontium,  calcium,  magnesium,  aluminium,  glucinium, 
yttrium,  zirconium,  thorium,  cerium,  lanthanium,  manganese,  iron,  cobalt,  nickel,  zinc, 
cadmium,  load,  tin,  bismuth,  copper,  uranium,  mercury  (quicksilver),  silver,  palladium, 
iridium,  platinum,  gold,  osmium,  titanium,  tantalum  (columbium),  fungsten,  molybdenum, 
vaoadiumT  chromium,  antimony,  tellurium,  arsenic. 


»  ROPERTIES    OF    CARBON.  23 

of  more  than  four,  of  tix  elementary  bodies.  These  four  are  carbon, 
oxygen,  hydrogen,  and  nitrogen.  With  the  exception  of  the  matter  ii' 
destructible  by  tire  (the  ash),  chemical  analysis*  has  hitherto  failed  to  detect 
the  presence,  in  any  notable  quantity,  of  more  than  these  four  substances. 
The  same  remarks  apply  with  almost  equal  truth  to  animal  substances. 
The  destructible  part  of  these  also  consists  of  tlie  same  four  elements. 

To  the  agriculturist,  therefore,  an  acquaintance  with  these  four  con- 
stituent parts  of  all  that  lives  and  grows  on  the  face  of  the  globe  is 
indispensable.  It  is  impossible  for  him  to  comprehend  the  laws  by 
which  the  operations  of  nature  in  the  vegetable  kingdom  are  conducted, 
nor  the  reason  of  the  processes  he  himself  adopts  in  order  to  facilitate  or  to 
modify  these  operations,  without  this  previous  knowledge  of  the  nature 
of  the  elements — the  raw  materials  as  it  were — out  of  which  all  the 
products  of  vegetable  growth  are  elaborated. 

I  shall  first,  therefore,  exhibit  to  you  briefly  the  properties  of  these 
organic  constituents  of  plants,  in  order  that  w^e  may  be  prepared  for  the 
further  inquiries — by  what  means  or  in  what  form  they  enter  into  the  cir- 
culation of  plants — and  how,  when  they  have  so  entered,  they  are  con- 
verted into  those  substances  of  which  the  skeleton  of  the  plant  consists 
or  which  are  produced  in  its  several  organs. 

§  2.   Carbon — its  properties  and  relations  to  vegetable  life. 

Carbon  is  the  name  given  by  chemists  to  the  substance  of  wood  char- 
coal in  its  purest  form.  When  wood  is  distilled  in  close  vessels,  or 
burned  in  heaps  covered  over,  so  as  to  prevent  the  free  access  of  air, 
wood  charcoal  is  left  behind.  When  this  process  is  well  performed,  the 
charcoal  consists  of  carbon  with  a  slight  admixture  only  of  earthy  and 
saline  matters,  which  remain  behind  on  burning  the  charcoal  in  the  air. 

Heated  in  the  air,  charcoal  burns  with  little  flame,  and,  with  the  ex- 
ception of  the  ash  which  is  left,  entirely  disappears.  It  is  converted  into 
a  kind  of  air  known  among  chemists  by  the  name  of  carbonic  acid,  which 
ascends  as  it  is  formed  and  mingles  with  the  atmosphere. 

Charcoal  is  light  and  porous,  and  floats  upon  water,  but  plumbago  or 
black  lead  and  the  diamond,  which  are  only  other  forms  of  carbon,  are 
heavy  and  dense.  The  former  is  2i,  and  the  latter  3|,  times  heavier 
than  water.  The  diamond  is  the  purest  form  of  carbon,  and  at  a  high 
temperature  it  burns  in  the  air  or  in  oxygen  gas,  and,  like  charcoal,  dis- 
appears in  the  state  of  carbonic  acid  gas. 

Of  this  carbon  all  vegetable  substances  contain  a  very  large  portion. 
It  forms  from  40  to  50  per  cent.,  by  weight,  of  all  the  parts  of  plants 
which  are  cultivated  for  the  food  of  animals  or  of  man,  [that  is,  of  these 
plants  in  their  dried  state.]  In  the  economy  of  nature,  therefore,  it  per- 
forms a  most  important  part. 

The  light  porous  charcoals  obtained  from  wood  [especially  from  the 
willow,  the  pine,  and  the  box],  and  from  animal  substances,  possess 
several  interesting  properties,  which  are  of  practical  application  in  the 
ar^f  culture.  1°.  They  have  the  power  of  absorbing  in  large  quanti- 
ty into  their  pores,  the  gaseous  substances  and  vapours  which  exist  in 

•  Under  the  general  name  of  chemical  analysis  are  comprehended  the  various  processes 
by  which,  aa  above  explained,  natural  forms  of  matter  may  be  resolved  or  separated  into 
the  several  elentenis  or  simple  substances  of  which  they  consist. 


84  PROPERTIES    or    OXYGEN 

the  atmospiere  ;*  and  on  this  property,  as  I  shall  explain  liereafter,  the 
use  of  charcoal  powder  as  a  manure  probably  in  some  measure  depends. 
2°.  They  also  separate  from  water  any  decayed  animal  matters  or  col- 
ouring substances  which  it  may  hold  in  solution  ;  hence  its  use  in  fillers 
for  purifying  and  sweetening  impure  river  or  spring  waters,  or  for  clari- 
fying syrups  and  oils.  This  action  is  so  powerful  that  port  wine  is 
rendered  perfectly  colourless  by  filtering  through  a  well  prepared  char 
coal. 

In  or  upon  the  soil  charcoal  for  a  time  will  act  in  the  same  manner, 
will  absorb  from  the  air  moisture  and  gaseous  substances,  and  from  the 
rain  and  trom  flowing  waters  organized  matters  of  various  kinds,  any 
of  which  it  will  be  in  a  condition  to  yield  to  the  plants  which  grow 
around  it,  when  they  are  such  as  are  likely  to  contribute  to  their 
growth. 

3°.  They  have  the  property  also  of  absorbing  disagreeable  odours  in 
a  very  remarkable  manner.  Hence  animal  food  keeps  longer  sweet 
when  placed  in  contact  with  charcoal — hence  also  vegetable  substances 
containing  much  water,  such  as  potatoes,  are  more  completely  preserved 
by  the  aid  of  a  quantity  of  charcoal — and  hence  the  refuse  charcoal  of  the 
sugar  refiners  is  found  to  deprive  night-soil  of  its  disagreeable  odour,  and 
to  convert  it  into  a  dry  and  portable  manure.  4°.  They  exhibit  also 
the  still  more  singular  property  of  extracting  from  water  a  portion  of  the 
saline  substances  they  may  happen  to  hold  in  solution,  and  thus  allow- 
ing it  to  escape  in  a  less  impure  form.  The  decayed  (half  carbonized) 
roots  of  grass,  which  have  been  long  subjected  to  irrigation,  may  act  in 
one  or  all  of  these  ways  on  the  more  or  less  impure  water  by  which 
they  are  irrigated — and  thus  gradually  arrest  and  collect  the  materials 
which  are  fitted  to  promote  the  growth  of  the  coming  crop. 

§  3.   Oxygen — its  properties  and  relations  to  vegetable  life. 

Oxygen  is  a  substance  with  which  we  are  acquainted  only  in  the  gas- 
eous or  aeriform  state. f  By  the  unaided  senses  it  cannot  be  distin- 
guished from  common  air,  being  void  of  colour,  taste  and  smell.  But 
if  a  lighted  taper  be  plunged  into  it,  the  flame  is  wonderfully  increased 
both  in  size  and  brilliancy,  and  the  taper  bums  away  with  great 
rapidity. 

The  effect  of  this  gas  upon  animal  life  is  of  a  similar  kind.  When 
a  living  animal  is  introduced  into  a  large  vessel  filled  with  oxygen,  the 
rapidity  of  the  circulation  is  increased,  all  the  vital  functions  are  stimu- 
lated and  excited,  a  state  of  fever  comes  on,  and  after  a  time  the  ani- 
mal dies. 

By  these  two  characters,  oxygen  is  distinguished  from  every  other  ele- 
mentary body.  It  exists  in  the  atmosphere  to  the  amount  of  21  percent, 
of  its  bulk,  and  in  this  state  of  air  is  necessary  to  the  existence  of  ani- 
«ials  and  of  plants,  and  to  the  support  of  combustion  on  the  face  of  the 
globe.  It  exists  also  largely  in  water,  every  nine  pounds  of  this  liquid 
containing  eight  pounds  of  oxygen.  4^ 

•  Thus  of  ammonia  they  absorb  95  times  their  own  bulk,  of  sulphuretted  hydrogen  65  times, 
of  oxygen  9  times,  of  hydrogen  nearly  twice  their  bulk,  and  of  aqueous  vapour  so  much  as  to 
increase  their  weight  from  10  to  20  per  cent. 

t  la  this  state  it  is  readily  obtained  by  heating  in  a  glass  retort  the  red  oxide  of  mercury 
of  the  shops,  or  a  white  salt  known  by  the  name  of  chlorate  of  potash 


PROPERTIES    OF    HYDROGEN.  25 

But  the  quantity  of  tliis  substance  which  is  stored  up  in  the  solid  rocks 
is  still  more  remarkable.  Nearly  one-half  of  the  weight,  of  the  solid 
rocks  which  compose  the  crust  of  our  globe,  of  every  solid  substance  we 
see  around  us — of  the  houses  in  which  we  live,  and  of  the  stones  on 
which  we  tread — of  the  soils  which  you  daily  cultivate,  and  much  more 
than  one-half  by  weight  of  the  bodies  of  all  living  animals  and  plants, 
consist  of  this  elementary  body  oxygen,  known  to  us,  as  I  have  already 
said,  only  in  the  state  of  a  gas.  It  may  not  appear  surprising  that  any 
one  elementary  substance  should  have  been  formed  by  the  Creator  in 
such  abundance  as  to  constitute  nearly  one-half  by  weight  of  the  entire 
crust  of  our  globe,  but  it  must  strike  you  as  remarkable,  that  this  should 
also  be  the  element  on  the  presence  of  which  all  animal  life  depends — 
and  as  nothing  less  than  wonderful,  that  a  substance  which  we  know 
only  in  the  state  of  thin  air,  should,  by  some  wonderful  mechanism,  be 
bound  up  and  imprisoned  in  such  vast  stores  in  the  solid  mountains  of 
the  globe,  be  destined  to  pervade  and  refresh  all  nature  in  the  form  of 
water,  and  to  beautify  and  adorn  the  earth  in  the  solid  parts  of  animals 
and  plants.  But  all  nature  is  full  of  similar  wonders,  and  every  step 
you  advance  in  the  study  of  the  principles  of  the  art  by  which  you  live, 
you  will  not  fail  to  mark  the  united  skill  and  bounty  of  the  same  great 
Contriver. 

Oxygen  gas  is  heavier  than  common  air  in  the  proportion  of  about  11 
to  10  [its  specific  gravity  by  experiment  is  1-1026,  air  being  1]  ;  it  is 
also  capable  of  being  absorbed  by  water  to  a  certain  extent.  One  hun- 
dred measures  of  water  dissolve  6i  of  this  gas.  [De  Saussure.  Ac- 
cording to  Dr.  Henry,  100  volumes  of  water  absorb  only  3^  of  oxygen.] 
Rain,  spring,  and  river  waters,  alwaj-s  contain  a  portion  of  oxygen 
which  they  have  derived  from  the  atmosphere,  and  this  oxygen,  as  they 
trickle  through  the  soil,  ministers  to  the  growth  and  nourishment  of  plants 
in  vaAous  ways.   Some  of  these  will  be  explained  in  a  subsequent  lecture. 

In  an  atmosphere  of  pure  oxygen  gas,  plants  refuse  to  vegetate,  and 
speedily  perish. 

§  4.'  Hydrogen — its  properties  and  relations  to  vegetable  life. 

Hydrogen  is  also  known  to  us  only  in  the  state  of  gas,  and  when  per 
fectly  pure  agrees  wiih  oxygen  and  common  air  in  being  without  colour, 
taste,  or  smell.  It  is  not  known  to  occur  in  nature  in  a  free  or  simple 
state,  nor  does  it  exist  so  abundantly  as  either  carbon  or  oxygen.  It 
forms  a  small  per  centage  of  the  weight  of  all  animal  and  vegetable 
substances,  and  constitutes  one-ninth  of  the  weight  of  water,  but  with 
the  exception  of  coal,  it  does  not  enter  as  a  constituent  into  any  of  the  large 
mineral  masses  that  exist  in  the  crust  of  the  globe. 

When  a  lighted  taper  is  plunged  into  this  gas  it  is  immediately  ex- 
tinguished, but  if  in  contact  with  the  air  the  gas  itself  takes  fire  and  burns 
with  a  pale  yellow  flame.  If  previously  mixed  with  air  or  with  oxygen 
gas,  it  liindles  and  burns  with  a  loud  explosion.  During  this  combus- 
tion water  is  formed.     [See  the  Second  Lecture.] 

It  does  not  support  life,  animals  cease  to  breathe  when  introduced  into 
it,  and  plants  gradually  wither  and  die.  It  is  the  lightest  of  all  known 
substances,  being  about  14^  times  lighter  than  common  air,  so  that  if  the 
stopper  be  removed  from  a  bottle  in  which  it  is  contained  it  almost  irame- 


26  PROPERTIES    OF    NITROGEN. 

diately  escapes,  [its  specific  gravity,  by  experiment,  is  0-0687,  air  be- 
ing 1.]  It  is  the  element  which  is  employed  to  give  buoyancy  to 
balloons  ;  and  by  this  great  levity  and  its  relations  to  flame  it  is  readily 
distinguished  from  all  other  known  substances. 

Water  absorbs  it  only  in  very  small  quantities,  100  gallons  taking  up 
no  more  than  about  1^  gallons  of  hydrogen  gas.  But,  as  already  ob- 
served, this  gas  does  not  exist  in  nature  in  a  free  state — is  not  necessary, 
therefore,  to  the  growth  of  plants  or  animals  in  this  state — and  hence  its 
insolubility  in  water  is  in  unison  with  the  general  adaptation  of  every 
property  of  every  body,  to  the  health  and  growth  of  the  highest  orders 
of  living  beings. 

Hydrogen  gas  is  readily  obtained  from  water  by  putting  into  it  a  few 
pieces  of  metallic  iron  or  zinc,  and  adding  a  little  sulphuric  acid  (oil  of 
vitriol).  •  Bubbles  of  the  gas  are  liberated  from  the  surface  of  the  mcti.1, 
ascend  through  the  water,  and  may  be  collected  on  the  surface. 

§  5.  Nitrogen — its  proimrlies  and  relations  to  vegetable  life. 
Nitrogen  is  also  known  to  us  only  in  the  form  of  gas.  It  exists  in  the 
atmosphere  to  the  amount  of  79  per  cent,  of  its  bulk.  It  is  without 
colour,  taste,  or  smell.  Animals  and  plants  die  in  this  gas,  and  a  taper 
is  instantly  extinguished  when  introduced  into  it ;  the  gas  itself  under- 
going no  change.  It  is  lighter  than  atmospheric  air,  in  the  proportion 
of  97i  to  100,  [its  density  is  0-976,  air  being  1.]  It  is  an  essential 
constituent  of  the  air  we  breathe,  serving  to  temper  the  ardour  with 
which  combustion  would  proceed  and  animals  live  in  iindiiuted  oxygen 
gas.  It  forms  a  part  of  very  many  animal  and  of  some  vegetable  sub- 
stances, but  it  is  not  known  to  enter  into  the  composition  of  any  of  the 
great  mineral  masses  of  which  the  earth's  crust  is  made  up.  In  coal 
alone,  which  is  of  vegetable  origin,  it  has  been  delected  to  the  amount 
of  one  or  two  percent.  It  is  therefore  much  less  abundant  in  nature 
than  any  of  the  other  so  called  organic  elements — and  it  exhibits  much 
less  decided  properties  than  any  of  them  ;  yet  we  shall  hereafter  see 
that  it  performs  certain  most  important  functions  in  reference  both  to  the 
growth  of  plants  and  to  the  nourishment  of  animals. 

One  hundred  volumes  of  water  dissolve  about  li  volumes  of  this 
gas.*  Spring  and  rain  waters  absorb  it  as  they  do  oxygen,  from  the  at- 
mospheric air,  and  bear  it  in  solution  to  the  roots,  by  which  it  is  not  un- 
likely that  it  may  be  conveyed  directly  into  the  circulation  of  plants. 


Such  are  the  several  elementary  bodies  of  which  the  organic  or  de- 
structible part  of  vegetable  substances  is  formed.  With  one  exception 
they  are  known  to  us  only  in  the  form  of  gases  ;  and  yet  out  of  these 
gases  much  of  the  solid  parts  of  animals  and  of  plants  are  made  up. 
When  alone,  at  the  ordinary  temperature  of  the  atmosphere  they  form 
invisible  kinds  of  air;  when  united,  they  constitute  those  various  forms 
of  vegetable  matter  which  it  is  the  aim  and  end  of  the  art  of  culture  to 
raise  with  rapidity,  with  certainty,  and  in  abundance.  How  difficult 
to  understand  the  intricate  processes  by  which  nature  works  up  these 

•  Henry  De  Saussure  says,  that  pure  water  absorbs  4  per  cent,  of  its  bulk  of  this  gas. 


REWARDS    OF    STUDY.  27 

raw  materials  into  her  many  beautiful  productions — ^yet  how  interest- 
ing it  must  be  to  know  her  ways,  how  useful  even  partially  to  find  them 
out! 


Permit  me,  in  conclusioK,  to  submit  to  you  one  reflection.  We  have 
seen  that  oxygen,  hydrogen,  and  nitrogen,  are  alT  gaseous  substances, 
which  when  pure  are  destitute  of  colour,  taste,  and  smell.  They  can- 
not be  distinguished  by  the  aid  of  our  senses.  Man  in  a  state  of  nature 
— uneducated  man — cannot  discern  that  they  are  diflerent.  Yet  so 
simple  an  instrument  as  a  lighted  taper  at  once  shows  them  to  be  totally 
unlike  each  other.  This  simple  instrument,  therefore,  serves  us  in- 
stead of  a  new  sense,  and  makes  us  acquainted  with  properties  the  ex- 
istence of  which,  without  such  aid,  we  should  not  even  have  suspected. 
Has  the  Deity  then  been  unkind  to  man,  or  stinted  in  his  benevolence 
in  withholding  the  gift  of  such  a  sense  ?  On  the  contrary,  he  has  given 
us  an  understanding  which  when  cultivated  is  better  than  twenty  new 
senses.  The  cliemist  in  his  laboratory  is  better  armed  for  the  investi- 
gation of  nature,  than  if  his  organs  of  sense  had  been  many  times  mul-^ 
liplied.  He  has  many  instruments  at  his  command,  each  of  which, 
like  the  taper,  tells  him  of  properties  which  neither  his  senses  nor  any 
otlier  of  his  instruments  can  discover;  and  the  further  his  researches 
are  carried,  the  more  willing  does  nature  seem  to  reveal  her  secrets  to 
him,  and  the  more  rapidly  do  his  chemical  senses  increase.  Do  you 
think  that  the  rewards  of  study  and  patient  experimental  research  are 
confined  to  the  laboratory  of  the  chemist,  and  that  the  Deity  will  prove 
less  kind  to  you,  whose  daily  toil  is  in  the  great  laboratory  of  nature  1 
As  yet  3'ou  see  but  faintly  the  reason  of  many  of  your  commonest  oper- 
ations, and  over  the  results  you  have  comparatively  little  control — but 
tiie  light  is  ready  to  spring  up,  the  means  are  within  your  reach — you 
have  only  to  employ  your  minds  as  Uligently  as  you  labour  with  your 
hands,  and  ultimate  success  is  sure 


^  LECTURE  II. 

Oharactcristic  properties  of  organic  substances— Relative  proportions  of  organic  elements- 
Variable  proportions  of  inorganic  elements  in  plants — Forhi  in  which  the  organic  ele 
ments  are  taken  up  by  plants— The  atmosphere,  its  constitution  and  relations  to  vegetable 
life — Nature  and  laws  of  chemical  combination— Water  and  its  relations  to  vegetable  life 

§  1.  Characteristic  properties  of  organic  substances. 

Of  the  four  elementary  substances  described  in  tbe  former  lecture,  the 
organic  part  of  all  animal  and  vegetable  substances  consists.  What  is 
understood  by  the  term  organic  has  also  been  explained. 

But  organic  substances  possess  certain  characters  by  which  they  are 
distinguished  from  the  inorganic  or  dead  matter  of  tlie  globe,  and  on 
which  their  connection  with  the  principle  of  life,  and  with  the  art  of 
culture,  entirely  depends.  These  characteristic  properties  are  chiefly 
the  following : 

1°.  They  are  all  easily  decomposed  or  destroyed  by  a  moderately 
high  temperature.  If  wood  or  straw  be  heated  in  the  air,  as  over  the 
flame  of  a  candle,  it  becomes  charred,  burns,  and  is  in  a  great  measure 
dissipated.  So  sugar  and  starch  darken  in  colour  when  heated,  black- 
en, and  take  fire.  The  same  is  true  of  all  vegetable  substances.  But 
limestone,  clay,  and  other  earthy  or  stony  matters,  undergo  no  appar- 
ent change  in  such  circumstances — they  are  not  decomposed. 

2°.  When  exposed  to  the  air,  especially  if  it  be  warm  and  moist, 
vegetable  and  animal  substances  putrify  and  decay.*  They  decom- 
pose of  their  own  accord,  and  after  a  time  almost  entirely  disappear. 
Such  is  not  the  case  with  inorganic  matters.  If  the  rocks  and  stones 
crumble,  their  particles  may  be  washed  away  by  the  rains  to  a  lower 
level,  but  they  never  putrify  or  wholly  disappear. 

3°.  They  consist  almost  entirely  of  two  or  more  of  the  four  organic 
elements  only.  The  mineral  substances  we  meet  with  on  the  earth's 
surface,  and  collect  for  our  cabinets,  often  contain  portions  of  many  ele- 
mentary bodies;  but,  with  few  exceptions,  the  organic  part  of  all  plants, 
that  which  lives  and  grows,  contains  only  the  four  simple  substances 
described  in  my  former  lecture. 

4°.  They  are  distinguished  also  by  this  important  character,  that 
ihey  cannot  be  formed  by  human  art.  Many  of  the  inorganic  com- 
pounds which  occur  in  the  mineral  crust  of  the  globe  can  be  produced  by 
the  chemist  in  his  laboratory,  and  were  any  corresponding  benefit  likely 
to  be  derived  from  the  expenditure  of  time  and  labour,  there  is  reason  to 
believe  that,  with  a  few  exceptions,  nature  might  be  imitated  in  the  for- 
mation of  any  of  her  mineral  productions.  But  in  regard  to  organic  sub- 
stances, whether  animal  or  vegetable,  the  chemist  is  perfectly  at  fault. 
He  can  form  neither  woody  fibre,  npr  sugar,  nor  starch,  nor  muscular 
fibre,  nor  any  of  those  substances  which  constitute  the  chief  bulk  of  ani- 
mals and  plants,  and  which  serve  for  the  food  of  animated  beings. 

*  For  an  expleuiation  of  the  exact  nature  and  end  of  this  putrefaction,  see  the  subscquen 
Lecture,  '■^  On  the  decay  ofanimai  and  vegetable  substances,'' 


PROSPECTS    OF   SCIENCE.  29 

This  is  an  important  and  striking,  and  is,  I  believe,  likely  to  remain  a 
permanent  distinction,  between  most  substances  of  organic  and  of  inor- 
ganic origin. 

Looking  back  at  the  vast  strides  which  organic  chemistry  has  made 
witliin  the  last  twenty  years,  and  is  still  continuing  to  make,  and  trust- 
ing to  the  continued  progress  of  human  discovery,  some  sanguine  chem- 
ists venture  to  anticipate  the  time  when  the  art  of  man  shall  not  only 
acquire  a  dominion  over  that  principle  of  life,  by  the  agency  of  which 
plants  now  grow  and  alone  produce  food  for  man  and  beast,  but  shall  be 
able  also,  in  many  cases,  to  imitate  or  dispense  with  the  operations  of  that 
principle:  and  to  predict  that  the  time  will  come  when  man  shall  man- 
ufacture by  art  those  necessaries  and  luxuries  for  which  he  is  now  wholly 
dependent  on  the  vegetable  kingdom. 

And,  having  conquered  the  winds  and  the  waves  by  the  agency 
of  steam,  is  man  really  destined  to  gain  a  victory  over  the  uncertain  sea- 
sons too?  Shall  he  come  at  last  to  tread  the  soil  beneath  his  feet  as  a 
really  useless  thing — to  disregard  the  genial  shower,  to  despise  the  influ- 
ence of  the  balmy  dew — to  be  indifferent  alike  to  rain  and  drought,  to 
cloud  and  to  sunshine — to  laugh  at  the  thousand  cares  of  the  husband- 
man— to  pity  the  useless  toil  and  the  sleepless  anxieties  of  the  ancient 
tillers  of  the  soil  ?  Is  the  order  of  nature,  through  all  past  time,  to  be  re- 
versed— are  the  entire  constitution  of  society,  and  the  habits  and  pur- 
suits of  the  whole  human  race,  to  be  completely  altered  by  the  pro- 
gress of  scientific  knowledge  ? 

By  placing  before  man  so  many  incitements  to  the. pursuit  of  know- 
ledge, the  will  of  the  Deity  is  ,that  out  of  this  increase  of  wisdom  he 
should  extract  the  means  of  increased  happiness  and  enjoyment  also. 
But  set  man  free  from  the  necessity  of  tilling  the  earth  by  the  sweat  of 
his  brow,  and  you  take  from  him  at  the  same  time  the  calm  and  tran- 
quil pleasures  of  a  country  life — the  innocent  enjoyments  of  the  return- 
ing seasons — the  cheerful  health  and  happiness  that  wait  upon  labour 
in  the  free  air  and  beneath  the  bright  sun  of  heaven.  And  for  what? — 
only  to  imprison  him  in  manufactories,  to  condemn  him  to  the  fretful 
and  feverish  life  of  crowded  cities. 

To  such  ends,  I  trust,  science  is  not  destined  to  lead  ;  and  he  is  not 
only  unreasonably,  but  thoughtlessly  sanguine,  who  would  hope  to  de- 
rive from  organic  chemistry  such  power  over  dead  matter  as  to  be  able 
to  fashion  it  into  food  for  living  animals.  With  such  consequences  be- 
fore us  it  seems  almost  sinful  to  wish  for  it. 

Yet,  that  this  branch  of  science  will  lead  to  great  ameliorations  in  the 
art  of  cuhure,  there  is  every  reason  to  believe.  It  will  explain  old  meth- 
ods— it  will  clear  up  anomalies,  reconcile  contradictory  results  by  ex- 
plaining the  principles  from  which  they  flow — and  will  suggest  new  meth- 
ods by  which  better,  speedier,  or  more  certain  harvests  may  be  reaped. 

§  2.  Relative  proportions  of  organic  elements. 
Though  the  substance  of  plants  consists  chiefly  of  the  four  organic  ele- 
ments, yet  these  bodies  enter  into  the  constitution  of  vegetables  in  very 
difTerent  proportions.  This  fact  has  already  been  adverted  to  in  a  gen- 
eral manner:  it  will  appear  more  di&inctly  by  the  following  statement 
of  the  exact  quantities  of  each  element  contained  in  1000  parts  by 
2* 


30         RELATIVE  PROPERTIES  OF  ORGANIC  ELEMENTS. 

weight  of  some  of  the  more  important  lands  of  vegetable  substance  you 
are  in  the  habit  of  cultivating  : — 

Hay  from 


young  Clover 

Clover- . 

^.fter-math 

3  mos.  old. 

Oats. 

Seed. 

Hay. 

Peas. 

Wheat. 

Hay. 

Potatoes. 

Carbon  . 

507 

507 

494 

471 

465 

455 

458 

441 

Hydrogen 

66 

64 

58 

56 

61 

57 

50 

58 

Oxygen 

389 

367 

350 

349 

401 

431 

387 

439 

Nitrogen 

38 

22 

70 

24 

42 

34 

15 

12 

Ash  .     . 

.     not  stated 

40 

28 

100 

31 

23 

90 

50 

1000*  lOOOf  1000*  lOOOf  lOOOt  1000*  lOOOf  lOOOf 

The  numbers  in  the  above  table  represent  the    constitution  of  the 

plants  and  seeds,  taken  in  the  stale  in  which  they  are  given  to  cattle  or 

are  laid  up  for  preservation,  and  then  dried  at  230°  Fahrenheit.     By 

this  drying  they  lost  severally  as  follows  : 

1000  parts  of  Potatoes  .     .     lost     .     .     .     722  parts  of  water 
ditto         of  Wheat     .     .      —     ...     166         ditto 
ditto         of  Hay    ...      —     ...     158         ditto 
ditto         of  Aftermath  Hay  —     .    136  to  140         ditto 
ditto         of  Oats     ...      —     ...     151         ditto 
ditto         ofClover  Seed  .      —     ....    112         ditto 
ditto        of  Peas     ...     —     ...       86         ditto 
In  crops  as  they  are  reaped,  therefore,  and  even  as  they  are  given  for 
food,  much  water  is  present.     When  artificially  dried,  the  carbon  ap- 
proaches to  one-half  of  their  weight — the  oxygen  to  more  than  one- 
third§ — the  hydrogen  to  little  more  than  5  per  cent. — and  the  nitrogen 
rarely  to  more  than  2h  per  cent.     These  proportions  are  variable,  but 
they  represent  very  nearly  the  relative  weights  in  which  these  elements 
enter  into  the  constitution  of  those  forms  of  vegetable  matter  which  are 
raised  in  the  greatest  quantity  for  the  support  of  animal  life. 

Bat,  besides  the  organic  part,  vegetable  substances  contain  an  inor- 
ganic portion,  which  remains  behind  in  the  form  of  ash  when  the  plant  is 
consumed  by  fire,  or  of  dust  when  it  decomposes  and  disappears  in 
consequence  of  natural  decay. 

In  the  dried  hay,  oats,  &c.,  of  which  the  composition  is  represented 
in  the  above  table,  we  see  that  the  quantity  of  ash  is  very  variable,  in 
oats  being  as  small  as  4  per  cent.,  while  of  hay  every  hundred  pounds 
left  10  of  ash.  A  sim'ilar  difference  is  observed  generally  to  prevail 
throughout  the  vegetable  kingdom.  Each  variety  of  plant,  when 
burned,  leaves  a  weight  of  ash,  more  or  less  peculiar  to  itself.  Herba- 
ceous plants  generally  leave  more  than  the  wood  of  trees — and  differ- 
ent parts  of  the  same  plant  yield  unlike  quantities  of  inorganic  matter.JI 

•  Boussingault  Annates  de  Chim.  et  de  Phys.  (1838)  lxvii.  p.  20  to  38. 

t  Ditto  ditto  (1839)  Lxxt.  p.  113  to  136. 

X  Ditto  ditto  (1838)  lxix.  p.  356. 

§  This  will  appear  no  v^ay  inconsistent  with  the  statement  in  the  former  Lecture,  that 
oxygen  constitutes  one-half  by  weight  of  alHjujn^  plants,  when  it  is  recollected  that  of  the 
water  driven  oif  in  drying  these  plants  eight-ninths  by  weight  consist  of  oxygen,  and  that 
600  lbs.  of  grass,  for  example,  yield  only  from  80  to  100  lbs.  of  hay. 

H  Thus  of  the  oak,  the  dried  bark  left  60  of  ash— the  dried  leaves  53 — tlie  dried  albumuin 
4— and  the  dried  wood  only  2  parts  in  a  thousand  of  ash.— X>«  Saicssure. 


ON    THE    CONSTITUTION    OF    THE   ATMOSPHERE.  31 

.These  facts  are  of  great  importance  in  the  theciry  and  in  the  enlightened 
practice  of  agriculture.  They  will  hereafter  come  under  special  and 
detailed  consideration,  when  we  shail  have  examined  the  nature  of  the 
soils  in  which  plants  grow,  and  shall  be  prepared  to  consider  the  chemi- 
cal nature,  the  source,  and  the  functions,  of  the  inorganic  compounds 
which  exist  in  living  animal  and  vegetable  substances. 

§  3.  Of  the  form  or  state  of  combination  in  which  the  organic  elements 
enter  into  and  minister  to  the  growth  of  plants. 

From  ihe  details  already  presented  in  the  preceding  Lecture,  in  re-  ^ 
gard  to  the  properties  of  carbon  and  tit<<rogen,  and  the  circumstances  M^ 
under  which  they  are  met  with  in  nature, — it  will  readily  occur  to  you  C' 
that  neither  of  these  elementary  bodies  is  likely  to  enter  directly,  or  in  a 
simple  state,  into  the  circulation  of  plants.  The  former  (carbon)  being 
a  solid  substance,  and  insoluble  in  water,  cannot  obtain  admission  into 
the  pores  of  the  roots,  the  only  parts  of  the  plants  with  which,  in  nature, 
it  can  come  in  contact.  The  latter  (hydrogen)  does  not  occur  either  in 
the  atmosphere  or  in«the  soil  in  any  appreciable  quantity,  and  hence,  in 
its  simple  state,  forms  no  part  of  the  food  of  plants.  Oxygen  and  nitro- 
gen, again,  both  exist  in  the  atmosphere  in  the  gaseous  state,  and  the 
former  is  known  to  be  inhaled,  under  certain  conditions,  by  the  leaves 
of  plants.  Nitrogen  may  also  in  like  manner  be  absorbed  by  the  leaves 
of  living  plants,  but,  if  so,  it  is  in  a  quantity  so  small  as  to  have  hitherto 
escaped  detection.  The  two  latter  substances  (oxygen  and  nitrogen) 
are  also  slightly  soluble  in  water,  and,  besides  being  inhaled  by  the 
leaves,  may  occasionally  be  absorbed  in  minute  quantity  along  with  the 
water  taken  in  by  the  roots.  But  by  far  the  largest  proportion  of  these 
two  elementary  bodies,  and  the  whole  of  the  carbon  and  hydrogen  • 
which  find  their  way  into  the  interior  of  plants,  have  previously  entered 
into  a  state  of  mutual  combination — forming  what  are  called  distinct 
chemical  compounds.  Before  describing  the  nature  and  constitution  of 
these  compounds,  it  will  be  proper  to  explain,  1°.  the  constitution  of  the 
atmosphere  in  which  plants  live,  and,  2°.  the  nature  of  chemical  com- 
bination and  the  laws  by  which  it  is  regulated. 

§  4.  On  the  constitution  of  the  atmosphere. 

The  air  we  breathe,  and  in  which  plants  live,  is  composed  principal- 
ly of  a  mixture  of  oxygen  and  nitrogen  gases,  in  the  proportion  very 
nearly  of  21  of  the  former  to  79  of  the  latter.  It  contains,  however,  as 
a  constituent  necessary  to  the  very  existence  of  vegetable  life,  a  small 
per  centage  of  carbonic  acid.  On  an  average  this  carbonic  acid 
amounts  to  about  a^^^th  part*  of  the  bulk  of  the  air.  On  the  shores 
of  the  sea,  or  of  great  lakes,  this  quantity  diminishes ;  and  it  becomes 
sensibly  less  as  we  recede  from  the  land.  It  is  also  less  by  day  than 
by  night  (as  3*38  to  4*32),  and  over  a  moist  than  over  a  dry  soil. 

The  air  is  alsO  imbued  with  moisture.  Watery  vapour  is  every 
where  diffused  through  it,  but  the  quantity  varies  with  the  season  of 
the  year,  with  the  climate,  with  the  nature  of  the  locality,  with  its  alti- 

•  0-04  per  cent.  The  mean  of  IM  experiments  made  by  Saussure  at  Geneva  at  all  times 
of  the  year  and  of  the  day  gave  4- .5  volumes  in  10000.  The  maximum  was  574,  and  th« 
minimum  3 15. 


32  NATURE    OF  CHEMICAL   COMBINATIO'. 

tude,  and  with  its  distance  from  the  equator.  In  temperate  climates, 
it  oscillates  on  the  same  spot  between  i  and  li  per  cent,  of  the  weight 
of  the  air  ;  being  least  in  mid-winter  and  greatest  In  the  hot  months  of 
summer.  There  are  also  mingled  with  the  atmosphere,  traces  of  the 
vast  variety  of  substances  which  are  capable  of  rising  from  the  surface 
of  the  earth  in  the  form  of  vapour;  such,  for  example,  as  are  given  off 
by  decaying  animal  or  vegetable  matter — which  are  the  produce  of 
disease  in  either  class  of  bodies — or  which  are  evolved  daring  the  oper- 
ations of  nature  in  the  inorganic  kingdom,  or  by  the  artificial  processes 
of  man.  Among  these  . accidental  vapours  are  to  be  included  those 
miasmata,  which,  in  certain  parts  of  the  world,  render  whole  districts 
unhealthy, — as  well  as  certain  compounds  of  ammonia,  which  are  infer- 
red to  exist  in  the  atmosphere,  because  they  can  be  detected  in  rain 
water,  or  in  snow  which  has  newly  fallen. 

In  this  constitution  of  the  atmosphere  we  can  discover  many  beauti- 
ful adaptations  to  the  wants  and  structure  of  animals  and  plants.  The 
exciting  effect  of  pure  oxygen  on  the  animal  economy  is  diluted  by  the 
large  admixture  with  nitrogen  ; — the  quantity  of  carbonic  acid  present 
is  sufficient  to  supply  food  to  the  plant,  while  it  ts  not  so  great  as  to 
prove  injurious  to  the  animal ; — and  the  watery  vapour  sufficas  to 
maintain  the  requisite  moisture  and  flexibility  of  the  parts  of  both  or- 
ders of  beings,  without  in  general  being  in  such  a  proportion  as  to  prove 
hurtful  to  either. 

The  air  also,  by  its  subtlety,  diffuses  itself  everywhere.  Into  every 
pore  of  the  soil  it  makes  its  way.  When  there,  it  yields  its  oxygen  or 
its  carbonic  acid  to  the  dead  vegetable  matter  or  to  the  living  root.  A 
shower  of  rain  expels  the  half-corrupted  air,  to  be  succeeded  by  a  purer 
portion  as  the  water  retires.  The  heat  of  the  sun  warms  the  soil,  and 
expands  the  imprisoned  gases, — these  partially  escape,  and  are,  as  be- 
fore, replaced  by  other  air  when  the  rays  of  the  sun  are  withdrawn. 

By  the  action  of  these  and  other  causes  a  constant  circulation  is,  to 
a  certain  extent,  kept  up, — between  the  atmosphere  on  the  surface, 
which  plays  among  the  leaves  and  stems  of  plants,  and  the  air  which 
mingles  with  the  soil  and  ministers  to  the  roots.  The  precise  effect  and 
the  importance  of  this  provision  will  demand  our  consideration  in  a  fu- 
ture lecture. 

§  5.   The  nature  and  laws  of  chemical  comhination. 

The  terms  combine  and  comhination  in  chemical  language  have  a 
strict  and  precise  application.  If  sand  and  saw-dust  be  rubbed  togeth- 
er in  a  mortar  they  may  be  intimately  intermingled,  but  by  pouring  wa- 
ter on  the  mass  we  can  separate  the  particles  of  wood  and  leave  the 
sand  unchanged  behind.  So  if  we  stir  oatmeal  and  water  together,  we 
may  cause  them  perfectly  to  mix  together,  but  by  the  aid  of  a  gentle 
heat  we  can  expel  the  water  and  obtain  dry  oatmeal  in  its  original 
condition.  Or,  by  putting  salt  into  water,  it  will  dissolve  and  disappear, 
and  form  what  is  called  a  solution,  but  by  boiling  it  down,  as  is  done 
in  our  salt-pans,  the  water  may  bo  entirely  removed  and  the  salt 
procured  of  the  weight  originally  employed  and  possessed  of  its  original 
properties. 

In  none  of  these  cases  has  any  chemical  action  taken  place,  or  any 


CHEMICAL    DECOMPOSITION.  33 

permanent  change  been  produced,  upon  any  of  the  substances.  The  two 
former  were  merely  mixtures. 

In  all  cases  of  chemical  action  a  permanent  change  iahes  place  in  some 
of  the  substances  employed  ;  and  this  change  is  the  result  either  of  a  chem- 
ical combination^  or  of  a  chemical  decomposition. 

Tlius  when  sulphur  is  burned  in  tiie  air,  it  is  converted  into  white  va- 
pours possessed  of  a  powerful  and  very  un[)leasanl  odOur,  and  which 
continue  to  be  given  off  until  the  whole  of  the  sulphur  is  dissipated. 

Here  a  solid  substance  is  permanently  changed  into  noxious  vapours 
■which  disappear  in  the  air,  and  this  change  is  caused  by  the  combination 
of  the  siilphur  with  the  oxygen  of  the  atmosphere. 

In  like  manner  when  lim^tone  is  put  into  a  kiln  and  strongly  heated 
or  burned,  it  is  changed  or  converted  into  quicklime — a  substance  very 
different  in  its  properties  from  the  natural  limestone  employed.  But 
Jiis  is  a  case  of  chemical  decomposition.  The  limestone  consists  of 
lime  and  carbonic  acid.  By  the  lieat  these  are  separated,  the  latter  is 
driven  off  and  the  former  remains  in  the  kiln. 

Again,  when  a  jet  of  hydrogen  gas  is  kindled  in  the  air  or  in  oxygen 
gas,  it  burns  with  a  pa^e  yellow  flame.  If  a  cold  vessel  be  held  over 
this  flame,  it  speedily  becomes  bedewed  with  moisture,  and  drops  of  wa- 
ter collect  upon  it.  How  remarkable  the  change  which  hydrogen  un- 
dergoes during  this  combustion !  It  unites  with  the  oxygen  of  the 
atmosphere  and  forms  water.  How  different  in  its  properties  is  this 
water  from  either  the  oxygen  or  the  hydrogen  by  the  union  of  which  it  is 
formed!  The  former  a  liquid,  the  latter  gases;  the  former  an  enemy 
to  all  combustion,  while  of  the  latter,  the  one  (hydrogen)  burns  readily, 
the  other  (oxygen)  is  the  very  life  and  support  of  combustion  in  all  oth- 
er bodies. 

1°.  It  appears,  therefore,  that  chemical  combination  or  decomposition 
is  always  attended  by  a  permanent  change. 

2°.  That  when  combination  takes  place,  a  new  substance  is  formed 
differing  in  its  properties  from  any  of  those  from  which  it  was  produced, 
or  of  which  it  consists. 

When  two  or  more  elementary  bodies  thus  unite  together  to  form  a 
new  substance,  this  new  substance  is  called  a  chemical  compound. 
Thus  water  is  a  compound  (not  a  mixture)  of  the  two  elementary  bodies 
oxygen  and  hydrogen.  • 

Now  when  such  combination  takes  place,  it  is  found  to  do  so  always 
in  accordance  with  certain  fixed  laws.     Thus  : 

I.  Bodies  unite  together  only  in  constant  and  defmte proportions.  We 
can  7nix  together  oxygen  and  hydrogen  gases,  for  example,  in  any  pro- 
portion, a  gallon  of  the  one  with  any  number  of  gallons  of  tlie  other,  but 
if  we  burn  two  gallons  of  hydrogen  gas  in  any  greater  number  of  gallons 
of  oxygen,  they  will  only  consume  or  unite  with  one  gallon  of  the  oxy- 
gen, the  rest  of  this  gas  remaining  unchanged.  A  quantity  of  water  will 
be  formed  by  this  union,  in  which  the  whole  of  the  hydrogen  will  be 
contained,  combined  with  all  the  oxygen  that  has  disappeared.  Under 
no  circumstances  caji  we  burn  hydrogen  so  as  to  cause  it  to  consume 
more  oxygen,  or  from  a  given  weight  ot  hydrogen  to  produce  more  than 
a  known  weight  of  water.  And  as  oxygen  is  nearly  sixteen  times 
heavier  than  uitrogen,  it  is  obvious  that  one  gallon  of  the  former  is  about 


34  EQUIVALENT    rfUMBERS — ISOMERIC     BODIES 

eight  times  heavier  than  two  gallons  of  the  latter,  so  that  by  weight  these 
two  gases,  when  thus  burned,  unite  together  nearly  in  the  proportion 
of  1  to  8, — one  pound  of  hydrogen  forming  nine  pounds  of  water. 

Again,  when  pure  carbon  is  burned  in  the  air,  it  unites  with  a  fixed 
and  constant  weight  of  oxygen  to  form  carbonic  acid ;  it  never  unites 
with  more,  and  it  does  not  form  carbonic  acid  when  it  unites  with  less. 

Now  this  law  of  fixed  and  definite  proportions  is  found  to  hold  in  re- 
gard to  all  bodies,  and  in  all  cases  of  chemical  combination.     Thus  we 
have  seen  that — 
By  weight.  By  weight. 

1  of  hydrogen  combines  with  8  of  oxygen  to  form  water. 

So  6  of  carbon  combine .     .     .     8     .     j»   .     .     .     carbonic  oxide, 
and  14  of  nitrogen 8 nitrous  oxide. 

Hence  1  of  hydrogen,  6  of  carbon,  and  14  of  nitrogen  unite  respec- 
tively with  the  weight  (8)'  of  oxygen.  These  several  numbers,  there- 
fore, are  said  to  be  equivalent  to  each  other  (they  are  equivalent  numbers). 
Or  they  represent  the  fixed  and  definite  proportions  in  which  these  seve- 
ral substances  combine  together  (t)iey  are  definite  proportionals).  Some 
chemists  consider  these  numbers  to  represent  the  relative  weights  of  the 
atoms  or  smallest  particles  of  which  the  several  substances  are  made  up, 
and  hence  not  unfrequently  speakof  them  as  the  atomic  weights  of  these 
substances,  or  more  shortly  their  atoms. 

For  the  sake  of  brevity,  it  is  often  useful  to  represent  the  simple  or 
elementary  bodies  shortly  by  the  initial  letter  of  their  names.  Thus 
hydrogen  is  represented  by  H,  carbon  by  C,  and  nitrogen  by  N,  and 
these  letters  are  used  to  denote  not  only  the  substances  themselvgs,  but 
that  quantity  which  is  recognised  as  its  equivalent^  proportional^  or 
atomic  weight.     Thus : 

Equivalent 
Symbol.  or  atomic  Name, 

weights. 

H  denotes  1  by  weight,  of  hydrogen. 

C .     .     .     6 carbon. 

O.     .     .     8 oxygen. 

N .     .     .  14* nitrogen. 

Chemical  combination  is  expressed  shortly  by  placing  these  letters  in 
juxta- position,  or  sometimes  in  brackets,  with  the  sign  plus  (+)  between 
them.  Thus  HO  or  (H  -{-  O)  denotes  the  combination  of  one  atom  or 
equivalent  of  hydrogen  with  one  of  oxygen,  that  is,  water ;  and  at  the 
same  time  a  weight  of  water  (9),  equal  to  the  sum  of  the  atomic  weights 
(1  +  8)  of  hydrogen  and  nitrogen. 

A  number  prefixed  or  appended  to  a  symbol,  denotes  that  so  many 
equivalents  of  the  substance  represented  by  the  symbol  are  meant,  as 
that  number  expresses.  Thus  2  HO,  3  H  O,  or  3  (H  -f  O),  mean  two 
or  three  equivalents  of  water,  3  H,  or  H3  three  equivalents  of  hydrogen, 
and  4C  or  C4,  2  N  or  Ng,  four  of  carbon  and  two  of  nitrogen  respec- 
tively. 

n.  Not  only  are  the  quantities  of  the  substances  which  unite  together 
definite  and  constant,  but  the  'properties  or  qualities  of  the  substances 
formed  are  in  general  equally  so.     The  properties  of  pure  water  or  o*" 

•  More  correctly  1, 613,  8013,  a»i  1419. 


LAW    OF    MULTIPLE    PROPORTIONS.  35 

carbonic  acid  are  constant  and  invariable  under  whatever  circumstances 
they  may  be  formed,  and  the  elements  of  which  they  consist,  when  they 
combine  together  in  the  same  proportions,  are  never  known  to  form  any 
other  compounds  but  water  and  carbonic  acid. 

This  law,  however,  thoi2gh  generally,  is  not  universally  true.  Many 
substances  are  known  which  contain  the  same  elements  united  together 
in  the  same  proportions,  and  which,  nevertheless,  possess  very  different 
properties.  Oil  of  turpentine  and  oil  of  lemons  are  in  this  condition. 
They  both  consist  of  the  same  elements,  carbon  and  hydrogen,  united 
together  in  the  same  proportions,  and  j^et  their  sensible  properties  as  well 
as  their  chemical  relations*  are  very  dissimilar. 

Cane  sugar,  starch,  and  gum,  all  of  them  abundant  products  of  the 
vegetable  kingdom,  consist  also  of  the  same  elements,  carbon,  hydro- 
gen, and  oxygen,  united  together  in  the  same  proportions,  and  may  even 
be  represented  by  the  same  form^da  (C^a  Hio  Oio)it  ^nd  yet  these 
substances  are  as  unlike  to  each  other  in  their  properties,  as  many 
bodies  are  of  which  the  chemical  composition  is  very  different.  To 
compounds  thus  differing  in  their  properties,  and  yet  containing  the 
same  elements,  in  the  same  proportions,  chemists  hajjp  given  the  name 
of  Isomeric  bodies.  I  shall  have  occasion  to  make  you  more  familiar 
with  some  of  them  hereafter. 

3°.  Another  important  law  by  which  chemical  combinations  are 
regulated,  is  known  by  the  name  of  the  law  of  multiple  proportions. 
Some  substances  are  observed  to  be  capable  of  uniting  together  in  more 
than  one  proportion.  Thus  carbon  unites  with  oxygen  in  several  pro- 
portions, forming  carbonic  oxide,  carbonic  acid,  oxalic  acid,  &c.  Now 
when  such  is  the  case,  it  is  found  that  the  quantity  (the  weight)  of  each 
substance  which  enters  into  the  several  compounds,  if  not  actually  re- 
presented by  the  equivalent  number  or  atomic  weight,  is  represented  by 
some  simple  multiple  of  that  number.  Thus  two  equivalents  of  carbon 
unite  with  2,  3,  or  4  equivalents  of  oxygen,  to  form  carbonic  oxide, 
oxalic  acid,  and  carbonic  acid  respectively, — while  one  of  nitrogen  unites 
with  1,  2,  3,  4,  or  5  of  oxygen  to  form  a  series  of  compounds,  of  which 
the  last  (N  O5),  nitric  acid,  is  the  only  one  I  shall  have  frequent  occa- 
sion to  speak  of  in  the  present  lectures. 

This  law  of  multiple  proportions,  though  of  great  importance  ia 
chemical  theory,  I  do  not  further  illustrate,  as  we  shall  have  very  little 
occasion  to  refer  to  it  in  the  discussion  of  the  several  topics  which  will 
hereafter  come  before  us. 


Having  thus  briefly  explained  the  nature  and  laws  of  chemical  coin 
bination,  I  proceed  to  make  you  acquainted  with  those  chemical  com- 
pounds of  the  organic  elements  which  are  known  or  are  supposed  to 
minister  to  the  growth  of  plants. 

The  number  of  compounds  which  the  four  organic  elements  form 
with  each  other  is  almost  endless  ;  but  of  this  number  a  very  few  only 

'  By  the  chemical  relations  of  a  substance  are  meant  tae  eflfects  which  are  producei 
upon  it  by  contact  with  other  chemical  substances. 

t  This  formula  means  that  starch,  gum,  and  sugar,  consist  of  12  equivalents  of  carbon 
united  to  10  of  hydrogen  and  10  of  oxygen. 


36  RELATIO^*S    OF   WATER   TO    VEGETABLE   LIFE. 

are  known  to  minister  directly  to  the  growth  or  nourishment  of  plants. 
Of  these,  water,  carbonic  acid,  ammonia,  and  nitric  acid,  are  the  most 
important ;  but  it  will  be  necessary  shortly  to  advert  to  a  few  others,  of 
the  occurrence  or  production  or  action  of  which  we  may  hereafter  havb 
occasion  to  speak. 

§  6.   Of  water  and  its  relations  to  vegetable  life. 

Water  ia  a  compound  of  oxygen  and  hydrogen  in  the  proportion,  as 
already  stated,  of  8  of  the  former  to  1  of  the  latter  by  weight,  or  of  1 
volume  of  oxygen  to  2  of  hydrogen. 

It  is  more  universally  diffused  throughout  nature  than  any  other 
chemical  compound  with  which  we  are  acquainted,  performs  most  im- 
portant functions  in  reference  to  animal  and  vegetable  life,  and  is  en- 
dowed with  properties  by  which  it  is  wouderfuliy  adapted  to  the  exist- 
ing condition  of  things. 

We  are  familiar  with  this  substance  in  three  several  states  of  cohe- 
sion,-^in  the  solid  form  as  ice,  in  the  fluid  as  water,  and  in  the  gaseous 
as  steam.  At  32°  F.  and  at  lower  temperatures,  it  continues  solid,  at 
higher  temperatu|^s  it  melts  and  forms  a  liquid  (water),  which  a 
212°  F.  begins  to  boil  and  is  converted  into  steam.  By  this  change  its 
bulk  is  increased  1700  times,  and  it  becomes  nearly  two-fifths  lighter 
than  common  air,  [common  air  being  1,  steam  is  0-62. J  It  therefore 
readily  rises  into  and  diffuses  itself  tlirough  the  atmosphere. 

I.  There  are  only  one  or  two  circumstances  in  which  water  in  ttie  solid 
form  materially  aflects  or  interferes  with  the  labours  of  the  agriculturist. 

1°.  During  the  frost  of  a  severe  winter,  the  soil  contracts  and  appears 
to  shrink  in.  But  the  water  contained  in  its  pores  freezes  and  expands, 
and  the  minute  crystals  of  ice  thus  formed  separate  the  particles  of  the 
soil  from  each  other.  This  expansion  of  the  water  in  dry  soils  may  not 
be  equal  to  the  natural  contraction  of  the  soil  itself,  yet  still  it  is  suffi- 
cient to  cause  a  coi.siderable  separation  of  the  earthy  particles  through- 
out the  whole  frozen  mass.  When  a  milder  temperature  returns,  and  a 
thaw  commences,  the  soil  expands  and  gradually  returns  to  its  former 
bulk ;  but  the  outer  layers  thaw  first,  and  the  particles  being  previously 
separated  by  the  crystals  of  ice,  and  now  loosened  by  the  thaw,  fall  off 
or  crumble  down,  and  thus  the  soil  becomes  exposed  to  the  mellowing 
action  of  the  atmosphere,  wliich  is  enabled  everywhere  to  pervade  it. 
On  heavy  clay  land  this  effect  of  the  winter's  frost  not  unffe(|uenlly 
proves  very  beneficial.* 

2°.  In  the  form  of  snow  it  has  been  often  supposed  to  be  beneficial  to 
winter  wheat  and  other  crops.  That  a  heavy  fall  of  snow  will  shelter 
and  protect  the  soil  and  crop  from  the  destructive  effects  of  any  severe 
cold  which  may  follow,  there  can  fee  no  doubt.  It  forms  a  ligiit  porous 
covering,  by  which  the*  escape  of  heat  from  the  soil  is  almost  entirely 
prevented.  It  defends  the  young  shoots  also  from  those  alternations  of 
temperature  to  which  the  periodical  return  of  the  sun's  rays  continually 

'  This  alternate  contraction  and  expansion  is  often  injurious  to  the  practical  farmer  in 
ihrotcing  out  his  winter  wheat.  Some  varieties  are  said  to  be  more  thrown  out  than  others, 
and  this  peculiarity  is  sometimes  ascribed  to  the  longer  and  stronger  roots  which  shoot  from 
one  variety  than  from  another ;  it  may,  however,  be  occasionally  owing  to  the  different  na- 
ture of  the  ^oilsi  11  which  the  trials  have  been  made,  or  when,  in  the  same  soil,  to  the  differ- 
ent states  of  dryness  at  different  times. 


ACTION   AND   PROPERTIES   OF   SNOW.  37 

exposes  them  ;*  and  when  a  thaw  arrives,  by  slowly  melling,  it  allows 
the  tender  herbage  gradually  to  accustom  itself  to  the  milder  atmosphere. 

In  this  manner  there  is  no  doubt  that  a  fall  of  snow  may  often  be  of 
great  service  to  the  practical  farmer.  But  some  believe  that  winter 
wheat  actually  thrives  under  snow.  On  this  point  I  cannot  speak  from 
personal  knowledge,  but  1  will  here  mention  two  facts  concerning  snow, 
which  may  possibly  be  connected  with  its  supposed  nourishing  quahty. 

In  the  first  place,  snow  generally  contains  a  certain  quantity  of  ammo- 
nia, or  of  animal  matter  which  gives  off  ammonia  during  its  decay. 
This  quantity  is  variable,  and  is  occasionally  so  small  as  to  be  very  dif- 
ficult of  detection.  Liebig  found  it  in  the  snow  of  the  neighbourhood  of 
G lessen,  and  I  liave  this  winter  detected  traces  of  it  in  the  snow  which 
fell  in  Durhamf  during  tv.'o  separate  storms.  This  ammonia  is  present 
in  greater  quantity  in  the  first  portions  that  fall  and  lie  nearest  the  plant. 
Hence  if  the  plant  can  grow  beneath  the  snow,  this  ammonia  may  affect 
its  growth  ;  or  when  the  first  thaw  comes  it  may  descend  to  the  root,  and 
may  there  be  imbibed.  Rain  water  also  contains  ammonia,  but  when 
rain  falls  in  large  quantity  it  runs  off  the  land,  and  may  do  less  good  than 
the  snow,  which  lies  and  melts  gradually.  [For  the  properties  of  am- 
monia, see  Lecture  III:] 

Another  singular  property  of  snow  is  the  power  it  possesses  of  ab- 
sorbing oxygen  and  nitrogen  from'  the  atmosphere,  in  proportions  very 
different  from  those  in  which  they  exist  in  the  air.  The  atmosphere,  as 
already  stated,  contains  21  percent,  of  oxygen  by  volume  (or  bulk),  but 
the  air  which  is  present  in  the  pores  of  snow  has  been  found  by  various 
observers  to  contain  a  much  smaller  quantity.  Boussingault  [Annalen 
derPhysick  (Poggendorf),  xxxiv.,  p.  211,]  obtained  from  air  disengaged 
by  melting  snow  17  per  cent,  of  oxygen  only,  and  De  Saussure  found 
still  less.  The  difficulty  of  respiration  experienced  on  very  high  moun- 
tains has  been  attributed  to  the  nature  of  the  air  liberated  from  snow 
when  melted  by  the  sun's  rays.  Whether  the  air  retained  among  the 
pores  of  the  snow,  which  in  severe  winters  covers  our  corn-fields,  be 
equally  deficient  in  oxygen  with  that  examined  by  Boussingault,  and 
whether,  if  it  be,  the  abundance  of  nitrogen  can  at  all  affect  vegetation, 
are  matters  that  still  remain  undetermined. 

II.  In  the  fluid  state,  that  of  water,  the  agency  of  tliis  compound  in 
reference  to  vegetable  life,  though  occasionally  obscure,  is  yet  every- 
where discernible. 

Pure  water  is  a  colourless  transparent  fluid,  destitute  of  either  taste  or 

*  The  effects  of  such  alternations  are  seen  on  the  occurrence  of  a  night's  frost  in  spring. 
If  the  sun's  rays  fall  in  the  early  morning,  on  a  frozen  shoot,  it  droops,  withers,  and  black- 
ens—it is  destroyed  by  the  frost.  If  the  plant  be  in  a  shaded  spot,  where  the  sun  does  not 
reach  it  till  after  the  whole  atmosphere  has  been  gradually  heated,  and  tlie  frozen  tissue 
slowly  thawed,  its  leaves  sustain  little  injury,  and  the  warmth  of  the  sun's  rays,  instead  of 
injuring,  cherish  and  invigorate  it.  This  effect  of  sudden  alternations  of  temperature  on  or- 
ganic matter  explains  many  phenomena,  to  which  it  would  here  be  out  of  place  to  advert. 

A  thick  light  covering  of  porous  earth  not  beaten  down  preserves  the  potatoe  pit  from  the 
effects  of  the  frost  better  than  a  solid  compact  coating  of  clay,  in  the  same  way  as  snow 
protects  the  herbage  better  than  a  sheet  of  ice;  and  it  is  because  of  the  porosity  of  the 
covering,  that  ice  may  be  preserved  more  effectually,  and  for  a  longer  period,  in  a  similar 
pit,  than  in  many  well-constructed  ice-houses. 

t  By  adding  two  drops  of  sulphuric  acid  to  four  pints  of  snow  water,  evaporating  to  dry- 
ness, and  mixing  the  dry  mass  with  quicklime  or  caustic  potash.  The  residual  mass  con- 
tained a  brown  organic  matter,  mixed  with  the  sulphate  of  ammonia. 


S8  WATER   NECESSARY    TO    LIFE — ITS  SOLVENT   POWER. 

smell.  It  enters  largely  into  the  constitution  of  all  living  animals  and 
plants,  and  forms  upwards  of  one  half  of  the  weight  of  all  the  newly 
gathered  vegetable  substances  we  are  in  the  habit  of  cultivating  or  col- 
lecting for  the  use  of  man.     [See  page  30.] 

Not  only  does  it  enter  thus  largely  into  the  constitution  of  all  ani- 
mals and  plants,  but  in  the  existing  economy  of  nature  it«  presence  in 
large  (juantities  is  absolutely  necessary  to  the  persistence  of  animal  and 
vegetable  life.  In  the  midst  of  abundant  springs  and  showers,  plants 
shoot  forth  with  an  amazing  rapidity,  while  they  wither,  droop,  and  die, 
when  water  is  withheld.  How  much  the  manifestation  of  life  is  de- 
pendent upon  its  presence,  is  beautifully  illustrated  by  some  of  the  hum- 
bler tribes  of  plants.  Certain  mosses  can  be  ke[  clong  in  the  herbarium, 
and  yet  will  revive  again  when  the  dried  specimens  are  immersed  in 
water.  At  Manilla  a  species  of  Lycopodium  grows  upon  the  rocks, 
which,  though  kept  for  years  in  a  dried  state,  revives  and  expands  its 
foliage  when  placed  in  ^^ater  [the  Spaniards  call  it  Triste  de  Corazon, 
Sorrow  of  the  Heart. — BurneVs  Wanderings,  p.  72.]  Thus  life  lingers 
as  it  were,  unwilling  to  depart  and  rejoicing  to  display  itself  again,  when 
the  moisture  returns.* 

There  are,  however,  three  s])eeial  properties  of  water,  which  are  in 
a  high  degree  interesting  and  important  to  the  practical  agriculturist, 
and  to  which  I  beg  to  direct  your  particular  attention.     These  are: 

1°.  Its  solvent  power; 

2^.  Its  affinity  for  certain  solid  substances  ;  and, 

3°.  The  degree  of  affinity  by  which  its  own  elements  are  held  to- 
gether. 

1°.  When  pure  boiled  water  is  exposed  to  the  air,  it  gradually  ab- 
sorbs a  quantity  of  the  several  gases  of  which  the  atmosphere  is  com- 
posed, and  acquires  more  or  less  of  a  sparkling  appearance  and  an  agree- 
able taste.  The  air  which  it  thus  absorbs  amounts  to  about  -^\h.  of  its 
own  bulk,  and  is  entirely  expelled  by  boiling.  When  thus  expelled, 
this  air,  like  that  obtained  from  snow,  is  found  on  examination  to  contain 
the  oxygen,  nitrogen,  and  carbonic  acid  in  proportions  very  different  from 
those  in  wiiich  they  exist  in  the  atmosphere.  In  the  latter,  oxygen  is 
present  to  tVie  amount  of  only  21  per  cent,  by  volume,  while  the  air  ab- 
sorbed by  water  contains  30  to  32  per  cent,  of  the  same  gas.  In  like 
manner,  the  mean  quantity  of  carbonic  acid  in  the  air  does  not  exceed 
roooo^^  parts  (0-05  per  cent.)  of  its  bulk,  while  that  expelled  from  water, 
which  has  been  long  exposed  to  the  air,  varies  from  11  to  60  ten  thou- 
sand parts  (0-11  to  0-6f  per  cent.) 

•  In  some  species  of  animals,  life  is  in  like  manner  suspended  by  the  absence  of  water. 
The  inhabitants  of  some  land  and  even  marine  shells  may  be  dried  and  preserved  for  a  long 
time  in  a  siiate  of  torpor,  and  afterwards  revived  by  immersion  in  water.  The  Cerithium 
Armatum  has  been  brought  from  the  Mauritius  in  a  dry  state,  while  snails  are  said  to  have 
been  revived  after  being  dried  for  15  years.  The  vibrio  tritici  (a  species  of  worm),  was  re- 
stored by  Mr.  Bauer,  after  an  apparent  death  of  nearly  six  years,  by  merely  soaking  it  in 
water.  The  Furadaria  Anastobea,  a  small  microscopic  animal,  may  be  made  to  undergo 
apparent  death  and  resuscitation  many  times,  by  alternate  drying  and  moistening.  Accord- 
ing to  Spallanzani,  animalculi  have  been  recovered  by  moisture,  after  a  torpor  of  27  years. 
These  facts  tend  to  lessen  our  surprise  at  the  alleged  longevity  of  the  seeds  of  plants. 

t  Of  these  gases  when  unmixed,  water  absorbs  very  different  quantities.  Thus  100  vo- 
lumes of  water  at  60°  F.,  absorb3-55  of  oxygoi,  153  ol'^  hydrogen,  147  of  nitrogen,  (/ienry,) 
106  of  carboiiic  acid,  or  7800  of  ammonia. 


ITS    AFFINITY    FOR   SOLID    SUBSTANCES.  39 

Thus  when  water  falls  in  rain  or  trickles  along  the  surface  of  the 
land,  it  absorbs  these  gaseous  substances,  carries  them  with  it  wherever 
it  goes,  conveys  them  to  the  roots,  and  into  the  circulation  of  plants,  and 
thus,  as  we  shall  hereafter  see,  makes  them  all  minister  to  the  growth 
and  nourishment  of  living  vegetables. 

Again,  water  possesses  the  power  of  dissolving  many  solid  substances. 
If  sugar  or  salt  be  mixed  with  water  in  certain  quantities,  they 
speedily  disappear.  In  like  manner,  many  other  bodies,  both  simple 
and  compound,  are  taken  up  by  this  liquid  in  greater  or  less  quan- 
tity, and  can  only  be  recovered  by  driving  ofTthe  water,  through  the  aid 
of  heat. 

Thus  it  happens  that  the  water  of  our  springs  and  rivers  is  never 
pure,  but  holds  in  solution  more  or  less  of  certain  solid  substances. 
Even  rain  water,  washing  and  purifying  the  atmosphere  as  it  descends, 
brings  down  portions  of  solid  matter  which  had  previously  risen  into  the 
air  in  the  form  of  vapour,  and  as  it  afterwards  flows  along  or  sinks  into 
the  surface  of  the  soil,  it  meets  with  and  dissolves  other  solid  substances, 
the  greater  portion  of  which  it  carries  with  it  wherever  it  enters.  In 
this  way  solid  substances  are  conveyed  to  the  roots  of  plants  in  a  fluid 
form,  which  enables  them  to  ascend  with  the  sap  ;  and  the  supply  of 
these  naturally  solid  substances  is  constantly  renewed,  by  the  succes- 
sive passage  of  new  portions  of  flowing  water.  We  shall  hereafter  be 
able  to  see  more  clearly  and  to  appreciate  more  justly  this  beautiful  ar- 
rangement of  nature,  as  well  as  to  understand  how  indispensable  it  is  to 
the  continued  fertility  of  the  soil. 

Nor  is  it  merely  earthy  and  saline  substances  which  the  water  dis- 
solves, as  it  thus  percolates  through  the  soil.  It  takes  up  also  sub- 
stances of  organic  origin,  especially  portions  of  decayed  animal  and  ve- 
getable matter, — such  as  are  supposed  to  be  capable  of  ministering  to 
the  growth  of  plants, — and  brings  them  within  reach  of  the  roots. 

This  solvent  power  of  water  over  solid  substances  is  increased  by  an 
elevation  of  temperature.  Warm  water,  for  example,  will  dissolve 
Epsom  salts  or  oxalic  acid  in  much  larger  quantity  than  cold  water 
will,  and  the  same  is  true  of  nearly  all  solid  substances  which  this  fluid 
is  capable  of  holding  in  solution.  To  this  increased  solvent  power  of 
the  water  they  absorb,  is  ascribed,  among  other  causes,  the  peculiar 
character  of  the  vegetable  productions,  as  well  as  their  extraordinary 
luxuriance,  in  many  tropical  countries. 

2°.  But  the  affinity  which  water  exhibits  for  many  solid  substances  is 
little  less  important  and  remarkable. 

When  newly  burned  lime  is  thrown  into  a  limited  quantity  of  water 
the  latter  is  absorbed,  while  the  lime  heats,  cracks,  swells,  and  finally 
falls  to  a  white  powder.  When  thus  perfectly  slaked,  it  is  found  to  be 
one-third  heavier  than  before — every  three  tons  having  absorbed  one 
ton  of  water.  This  water  is  retained  in  a  solid  form,  more  solid  than 
water  is  when  in  the  state  of  ice,  and  it  cannot  be  entirely  separated 
from  the  lime  without  the  application  of  a  red  heat.  When  you  lay 
upon  your  land,  therefore,  four  tons  of  slaked  lime,  you  mix  with  your 
soil  one  ton  of  water,  which  the  lime  afterwards  gradually  gives  up, 
either  in  whole  or  in  part,  as  it  combines  with  other  substances.  To 
this  fact  we  shall  return  when  we  hereafter  consider  the  various  ways 


43  USES    OF   WATERY    VAPOUR   IN    VEGETATION. 

in  which  lime  acts,  when  it  is  employed  by  the  farmer  for  the  purpose 
of  improving  his  land.  [See  the  subsequent  lecture,  "  On  the  action  of 
lime  when  employed  as  a  manure.^^] 

For  clay  also,  water  has  a  considerable  affinity,  though  by  no  means 
equal  to  that  which  it  displays  for  quicklime.  Hence,  even  in  well- 
drained  clay  lands,  the  hottest  summer  does  not  entirely  rob  the  clay  of 
its  water.  It  cracks,  contracts,  and  becomes  hard,  yet  still  retains 
water  enough  to  keep  its  wheat  crops  green  and  flourishing,  when  the 
herbage  on  lighter  soils  is  drooping  or  burned  up. 

A  similar  affinity  for  water  is  one  source  of  the  advantages  which  are 
known  to  follow  from  the  admixture  of  a  certain  amount  of  vegetable 
matter  with  the  soil ;  though,  as  in  the  case  of  charcoal,  its  porosity* 
is  probably  more  influential  in  retaining  moisture  near  the  roots  of 
the  plants. f 

3°.  The  degree  of  affinity  by  which  the  elements  of  water  are  held 
together,  exercises  a  material  influence  on  the  growth  and  production 
of  all  vegetable  substances. 

If  I  burn  a  jet  of  hydrogen  gas  in  the  air,  water  is  formed  by  the 
union  of  the  hydrogen  with  the  oxygen  of  the  atmosphere,  for  which  it 
manifests  on  many  occasions  an  apparently  powerful  affinity.  But  if 
into  a  vessel  of  water  I  put  a  piece  of  iron  or  zinc  and  then  add  sulphuric 
acid,  the  water  is  decomposed'  and  the  hydrogen  set  free,  while  the 
metal  combines  with  the  oxygen. 

So  in  the  interior  of  plants  and  animals,  water  undergoes  continual 
tZecomposition  and  recomposition.  In  its  fluid  state,  it  finds  its  way 
and  exists  in  every  vessel  and  in  every  tissue.  And  so  slight,  it  would 
appear,  in  such  situations,  is  the  hold  which  its  elements  have  upon 
each  other — or  so  strong  their  tendency  to  combine  with  other  substan- 
ces, that  they  are  ready  to  separate  from  each  other  at  every  impulse — 
yielding  now  oxygen  to  one,  and  now  hydrogen  to  another,  as  the  pro- 
duction of  the  several  compounds  which  each  organ  is  destined  to  elab- 
orate respectively  demands.  Yet  with  tlie  same  readiness  do  they 
again  re-attach  themselves  and  cling  together,  wlien  new  metamorphoses 
require  it.  It  is  in  the  form  of  water,  indeed,  that  nature  introduces 
the  greater  portion  of  the  oxygen  and  hydrogen  which  perform  so  im- 
portant a  part  in  the  numerous  and  diversified  changes  which  take  place 
in  the  interior  of  plants  and  animals.  Few  things  are  really  more  won- 
derful in  chemical  physiology,  than  the  vast  variety  of  transmutations 
v.'hich  are  continually  going  on,  through  the  agency  of  the  elements  of 
water. 

III.  In  the  state  of  vapour  water  ministers  most  materially  to  the 
life  and  growth  of  plants.  It  not  only  rises  into  the  air  at  212°  Fahr. 
when  it  begins  to  boil,  but  it  disappears  or  evaporates  from  open  vessels 
at  almost  every  temperature,  with  a  rapidity  proportioned  to  the  previ- 
ous dryness  of  the  air,  and  to  the  velocity  and  temperature  of  the  at- 
mospheric currents  which  pass  over  it.     Even  ice  a^d  snow  are  grad- 

*  Affinity  for  water  causes  vegetable  matter  to  combine  chemically  with  it,  porosity  causes 
it  merely  to  drink  in  the  water  mechanically,  and  to  retain  it,  U7ichanged,  in  its  pores. 

t  For  an  exposition  of  the  intimate  relation  of  water  to  the  chemical  constitution  of  the 
solid  parts  of  living  vegetables,  see  a  subsequent  Lecture,  "  On  the  nature  and  production 
of  the  substances  of  which  plants  chi^jj  sa>Ksist." 


FORMATION    CF    CLOUDS    AJ>ID    RAIN.  41 

ually  dissipated  in  the  coldest  weather,  and  sometimes  with  a  degree 
of  velocity  which  at  first  sight  seems  truly  surprising.* 

It  thus  liappens  that  the  atmosphere  is  constantly  impregnated  with 
watery  vapour,  which  in  this  gaseous  state  accompanies  the  air  where- 
ever  it  penetrates,  permeates  the  soil,  pervades  the  leaves  and  pores  of 
plants,  and  gains  admission  to  the  lungs  and  general  vascular  system  of 
animals.  We  cannot  appreciate  the  influence  which,  in  this  highly 
comminuted  form,  water  exercises  over  the  general  economy  of  organic 
nature. 

But  it  is  chiefly  when  it  assumes  the  form  of  rain  and  dew,  and  re- 
descends  to  the  earth,  that  the  benefits  arising  from  a  previous  conversion 
of  the  water  into  vapour  become  distinctly  appreciable.  The  quantity 
of  vapour  which  the  air  is  capable  of  holding  in  suspension  is  depend- 
ent upon  its  temperature.  At  high  temperatures,  in  warm  climates,  or 
in  warm  weather,  it  can  sustain  more— at  low  temperatures  less. 
Hence  when  a  current  of  comparatively  warm  air  loaded  with  moisture 
ascends  to  or  comes  in  contact  with  a  cold  mountain  top,  i  is  cooled 
down,  is  rendered  incapable  of  holding  the  whole  of  the  vapour  in  sus- 
pension, and  therefore  leaves  behind  in  the  form  of  a  mist  or  cloud,  a 
portion  of  its  watery  burden.  In  rills  subsequently,  or  springs,  the 
aqueous  particles  which  float  in  the  midst,  re-appear  on  the  plains  be- 
neath, bringing  nourishmentf  at  once,  and  agreateful  relief  to  the  thirsty 
soil. 

So  when  two  currents  of  air  charged  with  moisture,  but  of  unequal 
temperature,  meet  in  the  atmosphere,  they  mix,  and  the  mixture  has 
the  mean  temperature  of  the  two  currents.  But  air  of  this  mean  tem- 
perature is  incapable  of  holding  in  suspension  the  mean  quantity  of  wa- 
tery vapour ;  hence,  as  before,  a  cloud  is  formed,  and  the  excess  of 
moisture  falls  to  the  earth  in  the  form  of  rain.  In  descending  to  refresh 
the  earth,  this  rain  discharges  in  its  progress  another  ofUce.  It  washes 
the  air  as  it  passes  through  it,  dissolving  and  carrying  those  accidental 
vapours  which,  though  unwholesome  to  man,  are  yet  fitted  to  minister 
to  the  growth  of  plants. 

The  dew,  celebrated  through  all  times  and  in  every  tongue  for  its  sweet 
influence,  presents  the  most  beautiful  and  striking  illustration  of  the  agen- 
cy of  water  in  the  economy  of  nature,  and  exhibits  one  of  those  wise  and 
bountiful  adaptations,  by  which  the  whole  system  of  things,  animate  and 
inanimate,  is  fitted  and  bound  together. 

All  bodies  on  the  surface  of  the  earth  radiate,  or  throw  out  rays 
of  heat,  in  straight  lines — every  warmer  body  to  every  colder ;  and  the 
entire  surface  is  itself  continually  sending  rays  upwards  through  the 
clear  air  into  free  space.  Thus  on  the  earth's  surface  all  bodies  strive, 
as  it  were,  after  an  equal  temperature  (an  equilibrium  of  heat),  while 

*  Mr.  Howard  states  that  a  circular  patch  of  snow  5  inches  in  diameter  lost  in  the  month 
of  January  150  grains  of  vapour  between  sunset  and  sunrise,  and  56  grains  more  before  tho 
close  of  the  day,  when  exposed  to  a  smart  breeze  on  a  .house-top.  From  an  acre  of  snow 
this  would  be  equal  to  1000  gallons  of  water  during  the  night  only.— Prout'  8  Bridgewater 
Treatise, p.  302;  Encyclopcsd.  Metropolian.  Meteorology. 

In  Von  Wrangell's  account  of  his  visit  to  Siberia  and  the  Polar  sea,  translated  by  Major 
Sabine  (p.  390),  it  is  stated  that,  in  the  intense  cold,  not  only  living  bodies— but  the  very 
gnaw — smokes  and  fills  the  air  with  vapour. 

t  For  the  nature  of  this  nourishment  see  the  subsequent  Lectures,  "  On  the  inorganic  con 
ttitutnta  of  plants." 


42  DESCENT  OF  DEW. — UNIVERSAL  BOUNTY  0¥   NATURE. 

the  surface  as  a  whole  tends  gradually  towards  a  cooler  state.  But 
while  the  sun  shines  this  cooling  will  not  take  place,  for  the  earth  then 
receives  in  general  more  heat  than  it  gives  offi  and  if  the  clear  sky  be 
shut  out  by  a  canopy  of  clouds,  these  will  arrest  and  again  throw  back 
a  portion  of  the  heat,  and  prevent  it  from  being  so  speedily  dissipated. 
At  night,  then,  when  the  sun  is  absent,  the  earth  will  cool  the  most ;  on  , 
clear  nights  also  more  than  when  it  is  cloudy,  and  when  clouds  only 
partially  obscure  the  sky,  those  parts  will  become  coolest  which  look  to- 
wards the  clearest  portions  of  the  heavens. 

Now  when  the  surface  cools,  the  air  in  contact  with  it  must  cool  also ; 
and  like  the  warm  currents  on  the  mountain  side,  must  forsake  a  portion 
of  the  watery  vapour  it  has  hitheito  retained.  This  water,  like  the  float- 
ing mist  on  the  hills,  descends  in  particles  almost  infinitely  minute. 
These  particles  collect  on  every  leaflet,  and  suspend  themselves  from 
every  blade  of  grass,  in  drops  of"  pearly  dew." 

And  mark  here  a  beautiful  adaptation.  Different  substances  are  en- 
dowed with  the  property  of  radiating  their  heat,  and  of  thus  becoming 
cool  with  different  degrees  of  rapidity,  and  those  substances  which  in 
the  air  become  cool  first,  also  attract  first  and  most  abundantly  the  par- 
ticles of  falling  dew.  Thus  in  the  cool  of  a  summer's  evening  the  grass 
plot  is  wet,  while  the  gravel  walk  is  dry ;  and  the  thirsty  pasture  and  ev- 
ery green  leaf  are  drinking  in  the  descending  moisture,  while  the  naked 
land  and  I  he  barren  highway  are  still  unconscious  of  its  fall. 

How  beautiful  is  tlie  contrivance  by  which  water  is  thus  evaporated  or 
distilled  as  it  were  into  the  atmosphere — largely  perhaps  from  some  par- 
ticular spots, — then  diffused  equably  through  the  wide  and  restless  air, — 
and  afterwards  precipitated  again  in  refreshing  showers  or  in  long-mys- 
rerious  dews!*  But  how  much  more  beautiful  the  contrivance,  I  might 
almost  say  the  instinctive  tendency,  by  which  the  dew  selects  the  objects 
on  which  it  delights  to  fall ;  descending  first  on  every  living  plant,  copi- 
ously ministering  to  the  wants  of  each,  and  expending  its  superfluity 
only  on  the  unproductive  waste. 

And  equally  kind  and  bountiful,  yet  provident,  is  nature  in  all  her 
operations,  and  through  all  her  works.  Neither  skill  nor  materials  are 
ever  wasted  ;  and  yet  she  ungrudgingly  dispenses  her  favours,  apparent- 
ly without  measure, — and  has  subjected  dead  matter  to  laws  which 
compel  it  to  minister,  and  yet  with  a  most  ready  willingness,  to  the 
wants  and  comforts  of  every  living  thing. 

And  how -unceasingly  does  she  press  this  her  example  not  only  of  un- 
bounded goodness,  but  of  universal  charity — above  all  other  men— on 
the  attention  of  the  tiller  of  the  soil.  Does  the  corn  spring  more 
freshly  when  scattered  by  a  Protestant  hand — are  the  harvests  more 
abundant  on  a  Catholic  soil, — and  does  not  the  sun  shine  alike,  and  the 
dew  descend,  on  the  domains  of  each  political  party  ? 

•  The  beauty  of  this  arrangement  appears  more  striking  when  we  consider  that  the  whole 
ofthe  watery  vapour  in  the  air,  if  it  fell  at  once  in  the  form  of  rain,  would  not  amount  to 
more  than  5  inches  in  depth  on  the  whole  surface  ofthe  globe.  In  England  the  fall  of  rain 
varies  from  22  inches  (London,  York,  and  Edinburgh)  to  68  (Keswick),  while  in  some  few  parts 
of  the  world  (St.  Domingo)  it  amounts  to  as  much  as  150  inches.  The  mean  fall  of  rain 
over  the  whole  earth  is  estimated  at  32  or  33  inches  ;  but  if  we  suppose  it  to  be  only  10  or  16 
Inches,  the  water  which  thus  falls  will  require  to  be  two  or  three  times  re-distilled  in  the  course 
of  every  year.  This  is  exclusive  of  dew,  which  in  many  countries  amounts  to  a  very 
large  (juantity.— See  Proul's  Bridgewaler  Treatise,  p.  309. 


COLD    PRODUCED    BY    EVAPORATION,    AND    ITS    INFLUENCE.  43 

So  science,  from  her  daily  converse  with  nature,  fails  not  sooner  or 
later  to  take  her  hue  and  colour  from  the  perception  of  this  universal 
love  and  bounty.  Party  and  sectarian  differences  dwindle  away  and 
disappear  from  the  eyes  of  him  who  is  daily  occupied  in  the  contempla- 
tion of  the  boundless  munificence  of  the  great  Impartial;  he  sees  him- 
self standing  in  one  common  relation  to  all  his  fellow-men,  and  feels 
himself  to  be  most  completely  performing  his  part  in  life,  when  he  is 
able  in  any  way  or  in  any  measure  to  contribute  to  the  general  welfare 
of  all. 

It  is  in  this  sense  too  that  science,  humbly  tracing  the  footstep?  of  the 
Deity  in  all  his  works,  and  from  them  deducing  his  inteUigence  and  his 
universal  goodness — it  is  in  this  sense,  that  science  is  of  no  sect,  and  of 
no  party,  but  is  equally  the  province,  and  the  properly,  and  the  friend  of  all. 

§  7.  Of  the  cold  produced  by  the  evaporation  of  water,  and  its 
influence  on  vegetation. 

Beautiful,  however,  and  beneficent  as  are  the  provisions  by  which,  in 
nature,  watery  vapour  is  made  to  serve  so  many  useful  purposes,  there 
are  circumstances  in  which,  and  often  through  the  neglect  of  man,  the 
presence  of  water  becomes  injurious  to  vegetation. 

The  ascent  of  water,  in  the  form  of  vapour,  permits  the  soil  to  dry, 
and  fits  it  for  the  labours  of  the  husbandman ;  while  its  descent  in  dew 
refreshes  the  plant,  exhausted  by  the  heat  and  excitement  of  a  long 
summer's  day.  But  the  same  tendency  to  ascend  in  vapour,  gives  rise 
to  the  cold  unproductive  character  of  lands  in  which  water  is  present  in 
great  excess.  This  character  you  are  familiar  with  in  what  are  called 
cold  clay  soils. 

The  epithet  cold,  applied  to  such  soils,  though  derived  probably  from 
no  theoretical  views,  yet  expresses  very  truly  their  actual  condition. 
The  surface  of  the  fields  in  localities  where  such  lands  exist,  is  in  reality 
less  warm,  throughout  the  year,  than  that  of  fields  of  a  different  quality, 
even  in  their  immediate  neighbourhood.  This  is  readily  proved,  by 
placing  the  bulb  of  a  thermometer  immediately  beneath  the  soil  in  two 
such  fields,  when  in  the  hottest  day  a  marked  difference  of  temperature 
will,  in  general,  be  perceptible.  The  difference  is  dependent  upon  the 
following  principle  : — 

When  an  open  pan  of  water  is  placed  upon  the  fire,  it  continues  to 
acquire  heat  till  it  reaches  the  temperature  of  212°  F.  It  then  begins  to 
boil,  but  ceases  to  become  hotter.  Steam,  however,  passes  off",  and  the 
water  diminishes  in  quantity.  But  while  the  vessel  remains  upon  the 
fire  the  water  continues  to  receive  heat  from  the  burning  fuel  as  it  did 
before  it  began  to  boil.  But  since,  as  already  stated,  it  becomes  no  hot- 
ter, the  heat  received  from  the  fire  must  be  carried  off"  by  the  steam. 

Now  this  is  universally  true.  Whenever  water  is  converted  into 
steam,  the  ascending  vapour  carries  off  much  heat  along  with  it. 

This  heat  is  not  missed,  or  its  loss  perceived,  when  the  vapour  or 
steam  is  formed  over  a  fire  ;  but  let  water  evaporate  in  the  open  air 
from  a  stone,  a  leaf,  or  a  field,  and  it  must  take  heat  with  it  from  these 
objects — and  the  surface  of  the  stone,  the  leaf,  or  the  field,  must  become 
colder.  That  stone  or  leaf  also  must  beconis  coldest  from  which  the 
largest  quantity  of  vapour  rises. 


44  WET   AND    COLD   SOILS    IMPROVED    BY    DRAINING. 

Now,  let  two  adjoining  fields  be  wet  or  moist  in  different  degrees,  that 
which  is  wettest  will  almost  at  aJI  limes  give  off  the  largest  quantity  of 
vapour,  and  will  therefore  be  the  coldest.  Let  spring  arrive,  and  the 
genial  sun  will  gently  warm  the  earth  on  the  surface  of  the  one,  while 
the  water  in  the  other  will  swallow  up  the  heating  rays,  and  cause  them 
te  re-ascend  in  the  watery  vapour.  Let  summer  come,  and  while  the 
soil  of  the  one  field  rises  at  raid-day  to  perhaps  100°  F.  or  upwards,  that 
of  the  other  may,  in  ordinary  seasons,  rarely  reach  80°  or  90° — in  wet 
seasons  may  not  even  attain  to  this  temperature,  and  only  in  long 
droughts  will  derive  the  full  benefit  of  the  solar  rays.  I  shall  hereafter 
more  particularly  advert  to  the  important  influence  which  a  hightempe- 
rature  in  the  soil  exercises  over  the  growth  of  plants,  the  functions  of 
their  several  parts,  and  their  power  of  ripening  seeds — as  well  as  to 
certain  beautiful  adaptations  by  which  nature,  when  left  to  herself,  is 
continually  imparting  to  the  soil,  especially  in  northern  latitudes,  those 
qualities  which  fit  it  for  deriving  the  greatest  possible  benefit  from  the 
presence  of  the  sun's  rays.  In  the  mean  time  you  are  willing  to  con- 
cede that  warmth  in  the  soil  is  favourable  to  the  success  of  your  agricul- 
tural pursuits.  What,  then,  is  the  cause  of  the  coldness  and  poverty, 
the  fickleness  and  uncertainty  of  produce,  in  land  of  the  kind  now  al- 
luded to  ?  It  is  the  presence  of  too  much  water.  What  is  the  remedy  ? 
A  removal  of  the  excess  of  water.     And  how  ?  By  effectual  drainage. 

There  are  other  benefits  to  the  land,  which  follow  from  this  removal 
of  the  excess  of  water  by  draining,  of  which  it  would  here  be  out  of 
place  to  treat;  but  a  knowledge  of  the  above  principle  shows  you  that 
the  first  effect  upon  the  soil  is  the  same  as  if  ^'ou  were  to  place  it  in  a 
warmer  climate,  and  under  a  milder  sky — where  it  could  bring  to  ma- 
turity other  fruits,  and  yield  more  certain  crops. 

The  application  of  this  merely  rudimentary  knowledge  will  enable 
you  to  remove  from  many  improvable  spots  the  stigma  of  being  ^oor  and 
cold ;  an  appellation  hitherto  applied  to  them, — not  because  they  are  by 
nature  unproductive,  but  because  ignorance,  or  indolence,  or  indifference, 
has  hitherto  prevented  their  natural  capabilities  from  being  either  ap- 
preciated or  made  available. 


Note.— In  reference  to  the  supposed  fertilizing  effect  of  snow,  adverted  to  in  tlie  above 
lecture,  I  may  mention  a  fact  observed  by  Heyer,  and  quoted  by  Liebig,  (p.  125),  that  willow 
branches  immersed  in  snow  water  put  forth  roots  three  or  four  times  longer  than  when  put 
into  pure  distilled  water,  and  that  the  latter  remained  clear  while  the  snow  water  became 
coloured.  This  shows  that  snow  contains  something  not  present  in  distilled  water,  which 
is  capable  of  accelerating  the  growth  of  plants.  The  experiment  would  have  been  more 
instructive  in  regard  to  natural  operations,  had  the  effect  of  the  snow  water  been  com- 
pared with  that  of  an  equal  bulk  of  rain  water,  collected  under  similar  circumstances. 


LECTURE  111. 

Carbonic  and  oxalic  acids,  their  properties  and  relations  to  vegetable  life—Carbonic  oxide 
and  iigiit  carburetted  hydrogen,  their  properties  and  production  in  nature— Ammonia,  its 
properties  and  relations  to  vegetable  life. 

§  1.  Carbonic  acid,  its  properties  and  relations  to  vegetable  life. 

When  charcoal  is  burned  in  the  air  it  combines  slowly  with  oxygen, 
and  is  transformed  into  carbonic  acid  gas.  In  oxygen  gas  it  burns  more 
rapidly  and  vividly,  producing  the  same  compound. 

This  gas  is  colourless,  like  oxygen,  hydrogen,  and  nitrogen,  but  is 
readily  distinguished  from  all  these,  by  its  acid  taste  and  smell,  by  its  solu- 
bility in  water,  by  its  great  density,  and  by  its  reddening  vegetable  blues. 
Water  at  60  F.  and  under  the  ordinary  pressure  of  the  atmosphere,  dis- 
solves rather  more  than  its  own  bulk  of  this  gas  (100  dissolve  106),  and, 
however  the  pressure  may  be  increased,  it  still  dissolves  the  same  bulk. 

All  gases  diminish  in  bulk  uniformly  as  the  pressure  to  which  they 
are  subjected  is  increased.  Thus  under  a  pressure  of  two  atmospheres 
they  are  reduced  to  one-half  their  bulk,  of  three  atmospheres  to  one- 
third,  and  so  on.  When  water,  therefore,  is  saturated  with  carbonic 
acid  under  great  pressure,  as  in  the  manufacture  of  soda  water,  though 
it  still  dissolves  only  its  own  bulk,  yet  it  retains  a  weight  of  the  gas 
which  is  proportioned  to  the  pressure  applied.  For  the  same  reason 
also,  when  the  pressure  is  removed,  as  in  drawing  the  cork  from  a  bot- 
tle of  water  so  impregnated,  the  gas  expands  and  escapes,  causing  a 
lively  effervescence,  and  the  water  retains  only  its  own  bulk  at  the  ex- 
isting pressure.  This  solution  in  water  has  a  slightly  sour  taste,  and 
reddens  vegetable  blues.  These  properties  it  owes  to  the  presence  of 
the  gas,  which  is  therefore  what  chemists  call  an  acid  body,  and  hence  its 
name  of  carbonic  acid.  [Acids  have  generally  a  sour  taste,  redden 
vegetable  blues,  or  combine  with  bases,  such  as  lime,  soda,  potash,  &c., 
to  form  salts.] 

This  gas  is  one-half  heavier  than  atmospheric  air,  its  density  being 
1'524,  and  hence  it  may  be  poured  through  the  air  from  one  vessel  to 
another.  Hence  also,  when  it  is  evolved  from  crevices  in  the  earth,  in 
caves,  in  wells,  or  in  the  soil,  this  gas  diffuses  itself  through  the  atmos- 
phere and  ascends  into  the  air,  much  more  slowly  than  ihe  elementary 
gases  described  in  the  previous  lecture.  Where  it  issues  from  the  earth 
in  large  quantity,  as  in  many  volcanic  districts,  it  flows  along  the  surface 
like  water,  enters  into  and  fills  up  cracks  and  hollows,  and  sometimes 
reaches  to  a  considerable  distance  from  its  source,  before  it  is  lost  among 
the  still  air. 

Burning  bodies  are  extinguished  in  carbonic  acid,  and  living  beings, 
plunged  into  it,  instantly  cease  to  breathe.  Mixed  with  one-ninth  of  its 
bulk  of  this  gas  the  atmospheric  air  is  rendered  unfit  for  respiration.  It 
is,  however,  the  principal  food  of  plants,  being  absorbed  by  their  leaves 
and  roots  in  large  quantity.  Hence  the  presence  of  carbonic  acid  in  the 
atmosphere  is  necessary  to  the  growth  of  plants,  and  they  have  beenob- 
3 


46  CARBONIC  ACID. — EVIDENCE  OF  UNITY  Or  DESIGN. 

served  to  thrive  better  when  llie  quantify  of  this  gas  in  the  air  is  con- 
siderably augmented.  Common  air,  as  lias  been  already  stated,  does 
not  contain  more  on  an  average  thangTjjo^h  of  its  bulk  of  carbonic  acid, 
but  De  Saussure  found  that  ])lants  in  the  sunshine  grew  better  when  it 
was  increased  to  y^-th  of  the  bulk  of  the  air,  but  beyond  this  quantity 
they  were  injured  by  its  presence,  even  when  exposed  to  the  sun. 
When  the  carbonic  acid  amounted  to  one-half,  the  plants  died  in  seven 
days ;  when  it  reached  two-thirds  of  the  bulk  of  the  air,  they  ceased  to 
grow  altogether.  In  the  shade  any  increase  of  carbonic  acid  beyond 
that  which  naturally  exists  in  the  atmosphere  of  our  globe,  was  found 
to  be  injurious. 

These  circumstances  it  is  of  importance  to  remember.  Did  the  sun 
always  shine  on  every  part  of  the  earth's  surface,  the  quantity  of  carbo- 
nic acid  in  the  atmosphere  might  probably  have  been  increased  with  ad- 
vantage to  vegetation.  But  every  such  increase  would  have  rendered 
the  air  less  fit  for  the  respiration  of  existing  races  of  animals.  Thus 
we  see  that  not  only  the  nature  of  living  beings,  both  y)lants  and  ani- 
mals, but  also  the  periodical  absence  of  the  sun's  rays,  have  been  taken 
into  account  in  the  present  arrangement  of  things. 

In  perpetual  sunshine  plants  would  flourish  tnore  luxuriantly  in  air 
containing  more  carbonic  acid,  but  they  would  droop  and  die  in  the 
shade.  This  is  one  of  those  proofs  of  unity  of  design  which  occasion- 
ally force  themselves  upon  our  attention  in  every  department  of  nature, 
and  compel  us  to  recognise  the  regulating  superintendence  of  one  mind. 
The  same  hand  which  mingled  the  ingredients  of  the  atmosphere,  also 
set  the  sun  to  rule  the  day  only, — tempering  the  amount  of  carbonic 
acid  to  the  time  of  his  periodical  presence,  as  well  as  to  the  nature  of 
animal  and  vegetable  life. 

Carbonic  acid  consists  of  one  equivalent  of  carbon  and  two  of  oxygen, 
and  is  represented  by  CO3.  It  unites  with  bases  (potash,  soda,  lime, 
&c.),  and  forms  compounds  known  by  the  name  of  carbonate.  Thus 
•pearlash  is  an  impure  carbonates  of  potash, — the  common  soda  of  the 
shops,  corbonate  of  soda, — and  limestone  or  chalk,  carbonates  of  lime. 
From  these  compounds  it  may  be  readily  disengaged  by  pouring  upon 
them  diluted  muriatic  or  sulphuric  acids.  From  limestone  it  is  also 
readily  expelled  by  heat,  as  in  the  common  lime-kilns.  During  this 
process  the  limestone  loses  nearly  44  per  cent,  of  its  weight,  [43-7  when 
pure  and  dry,]  a  loss  which  represerjts  the  quantity  ofcarbonic  acid  dri- 
ven off.  [Hence  by  burning  limestone  on  the  spot  where  it  is  quarried, 
nearly  one-half  of  the  cost  of  transport  is  saved,] 

Common  carbonate  of  lime,  in  its  various  forms  of  chalk,  hard  lime 
stone,  or  marble,  is  nearly  insoluble  in  water,  but  it  dissolves  readily  in 
water  containing  carbonic  acid.  Thus,  if  a  current  of  this  gas  be  pass- 
ed through  lime-water,  the  liquid  speedily  becomes  milky  from  the 
formation  and  precipitation  of  carbonate  of  lime,  but  after  a  short  time 
the  cloudiness  disappears,  and  the  whole  of  the  lime  is  re-dissolved. 
The  application  of  heat  to  this  clear  solution  expels  the  excess  ofcar- 
bonic acid,  and  causes  the  carbonate  of  lime  again  to  fall. 

By  exposure  to  the  air,  we  have  already  seen  that  water  always  ab- 
sorbs a  quantity  of  carbonic  acid  from  the  atmosphere.  As  it  after- 
wards trickles  through  the  rocks  or  through  soil  containing  lime,  it  grad- 


CARBONIC    ACID  RENDERS  LIME    SOLUBLE.  47 

ually  dissolves  a  portion  of  this  earth,  equivalent  to  the  quantity  of  gas 
it  holds  in  solution,  and  thus  reaches  the  surface  impregnated  with  cal- 
careous matter.  Or  it  carries  it  in  its  progress  below  the  surface  to  the 
roots  of  plants,  where  its  earthy  contents  are  made  available,  either  di- 
rectly or  indirectly,  to  the  promotion  of  vegetable  growth.  To  the  lime 
thus  held  in  solution,  spring  and  other  waters  generally  owe  their  hard- 
ness, and  it  is  the  expulsion  of  the  carbonic  acid,  by  heat,  that  causes 
the  deposition  of  the  sediment  so  often  observed  when  such  waters  are 
boiled. 

I  propose  hereafter  to  devote  an  entire  lecture  to  the  consideration  of 
the  action  of  lime  upon  land,  as  it  is  employed  for  agricultural  pur- 
poses, but  I  may  here  remark,  that  this  solvent  action  of  the  carbonic 
acid  in  rain  water  is  one  of  the  principal  agents  in  removing  the  lime 
from  your  soils,  and  in  rendering  a  fresh  application  necessary  after  a 
certain  lapse  of  time.  It  is  the  cause  also  of  that  deposit  of  calcareous 
matter  at  the  mouths  of  drains  which  you  not  unfrequently  see  in  lo- 
calities where  lime  is  laid  abundantly  upon  the  land.  The  greater  the 
quantity  of  rain,  therefore,  which  falls  in  a  district,  the  less  permanent 
will  be  the  effects  of  liming  the  land — the  sooner  will  it  be  robbed  of 
this  important  element  of  a  fertile  soil.  Still  carbonic  acid  is  only  one 
of  several  agents  which  act  almost  unceasingly  in  thus  removing  the 
lime  from  the  land,  a  fact  I  shall  hereafter  have  occasion  more  fully  to 
explain. 

In  nature,  carbonic  acid  is  produced  under  a  great  variety  of  circum- 
stances. It  is  given  off  from  the  lungs  of  all  animals  during  respira- 
tion. It  is  formed  during  the  progress  of  fermentatiort.  Fermented  li- 
quors owe  their  sparkling  qualities  to  the  presence  of  this  gas.  Dur- 
ing the  decay  of  animal  and  vegetable  substances  in  the  air,  in  com- 
post heaps,  or  in  the  soil,  it  is  evolved  in  great  abundance.  In  certain 
volcanic  countries  it  issues  in  large  quantity  from  springs  and  from 
cracks  and  fissures  in  the  surface  of  the  earth ;  while  the  vast  amount 
of  carbon  contained  in  the  wood  and  coal  daily  consumed  by  burning, 
is  carried  up  into  the  atmosphere,  chiefly  in  the  form  of  carbonic  acid. 
We  shall  hereafter  consider  the  relation  which  exists  between  these 
several  sources  of  supply  and  the  proportion  of  carbonic  acid  per- 
manently present  in  the  air  and  so  necessary  to  the  support  of  vegetable 
life. 

§  2.  Oxalic  acidf  its  properties  and  relations  to  vegetable  life. 

Oxalic  acid  is  another  compound  of  Carbon  and  oxygen,  which,  though 
not  known  to  minister  either  to  their  growth  or  nourishment,  is  yet  found 
largely  in  the  interior  of  many  varieties  of  plants.  In  an  uncombined 
state  it  exists  in  the  hairs  of  the  chick  pea.  Ifi  combination  with  potash 
it  is  found  in  the  wood  sorrel  (oxalis  acetosella)j  in  the  common  sorrel, 
and  other  varieties  of  rumex, — in  which  it  is  the  cause  of  the  acidity  of 
the  leaves  and  stems, — in  the  roots  of  these  plants  also,  in  the  leaves  and 
roots  of  rhubarb,  and  in  the  roots  of  torraentilla,  bistort,  gentian,  saponaria, 
and  many  others.  It  is  this  combination  with  potash,  formerly  extracted 
from  wood  sorrel,  which  is  known  in  commerce  by  the  name  of  salt  of 
sorrel.     In  combination  with  lime  it  forms  the  principal  solid  parts  of 


48  PROPERTIES    OF    OXALIC    ACID. 

many  lichens,  especially  of  lheparmeli(S  and  variolariee,*  some  of  which 
contain  as  much  oxalate  of  lime  as  is  equivalent  to  15  or  20  parts  of  pure 
acid  in  100  of  the  dried  plant. 

The  crystallized  oxalic  acid  of  the  shops  forms  transparent  colourless 
crystals,  of  an  intensely  sour  taste.  These  crystals  dissolve  readily  in 
twice  their  weight  of  cold  water,  and  the  solution,  when  sufficiently  di- 
lute, is  agreeably  acid  to  the  taste.  This  acid  is  exceedingly  poisonous. 
Half  an  ounce  of  the  crystals  is  sufficient  to  destroy  life  in  a  very  short 
time,  and  a  quarter  of  an  ounce  after  the  lapse  of  a  few  days.  It  con- 
sists solely  of  carbon  and  oxygen  in  the  proportion  of  two  equivalents 
of  the  former  to  three  of  the  latter.  Its  symbol  is  C2O3.  It  combines 
with  bases,  and  forms  salts  which  are  known  by  the  name  of  oxalates, 
and  it  is  characterised  by  the  readiness  with  which  it  combines  with  lime 
to  form  oxalate  of  lime.  If  a  solution  of  the  acid  be  poured  into  lime  wa- 
ter, the  mixture  immediately  becomes  milky  from  the  formation  of  this 
compound,  which  is  insoluble  in  water.f  It  is  this  oxalate  of  lime  which. 
exists  in  the  lichens,  while  oxalate  of  potash  exists  in  the  sorrels. 

Oxalic  acid  is  one  of  those  compounds  of  organic  origin  which  we  can- 
not form,  as  we  can  form  carbonic  acid  by  the  direct  union  of  its  elements. 
In  all  our  processes  for  preparing  it  artificially,  we  arc  obliged  to  have  re- 
course to  a  substance  previously  organized  in  the  living  plant.  It  may 
be  prepared  from  sugar,  starch,  or  even  from  wood,  by  various  chemical 
processes.  The  usual  method  is  to  digest  potato  starch  with  five  times  its 
weight  of  strong  nitric  acid  (aquafortis),  diluted  with  ten  of  water,  till  red 
fumes  cease  to  be  given  oflti  and  then  to  evaporate  the  solution.  The  ox- 
alic acid  separates  in  crystals,  or,  as  it  is  usually  expressed,  crystallizes  in 
the  solution  thus  concentrated  by  evaporation. 

It  is  not  known  to  exist  in  the  soil  or  in  the  waters  which  reach  the 
roots  of  plants.  Where  it  is  found  in  living  vegetables,  therefore,  it  must, 
like  the  other  substances  they  contain,  have  been  formed  or  elaborated 
in  the  interior  of  the  plant  itself.  By  what  very  simple  changes  the 
production  of  this  acid  is  or  may  be  effected,  we  shall  see  in  a  subse- 
quent lecture. 

§  3.   Carbonic  oxide,  its  constitution  and  properties. 

When  carbonic  acid  (CO2)  is  made  to  pass  through  a  tube  containing 

red-hot  charcoal,  it  undergoes  a  remarkable  change.     Its  gaseous  form 

remains  unaltered,  but  it  combines  with  a  second  equivalent  of  carbon 

(becoming  C2O2),  which  it  carries  off'in  the  aeriform  state.     The  new 

'  The parmelia  cruciataa.nd  variolaria communis  are  mentioned  as  peculiarly  rich  in  this 
acid,  which  used  to  be  extracted  from  them  for  sale.  A  species  of  parmelia,  collected  after 
the  droughts  on  the  sands  of  Persia  and  Georgia,  contains  66  per  cent,  of  oxalate  of  lime, 
with  about  23  per  cent,  of  a  gelatinous  substance  similar  to  that  obtained  from  Iceland  moss. 
This  lichen  is  used  for  food  by  the  Kirghuis.  A  similar  lichen  is  collected  about  Bagdad  for 
a  similar  purpose. 

t  Substances  that  are  insoluble  are  generally  without  action  on  the  animal  economy,  and 
may  be  introduced  into  the  stomach  without  producing  any  injurious  effect.  Hence  tliis  ox- 
alate of  Ume,  though  it  contains  oxalic  acid,  is  not  poisonous.  Hence  also,  if  oxalic  acid  be 
present  in  the  stomach,  its  poisonous  action  may  be  taken  away  by  causing  lime  water  or 
milk  of  lime  to  be  swallowed  in  sufficient  quantity.  The  acid  combines  with  the  lime,  as  in 
the  experiment  described  in  the  text,  and  forms  insoluble  oxalate  of  lime.  The  common 
magnesia  of  the  shops  will  serve  the  sarae  purpose,  forming  an  insoluble  oxalate  of  magnesia. 
It  is  by  performing  experiments  under  circumstances  where  the  results  are  visible — as  in 
glass  vessels — that  we  are  enabled  to  predict  the  results  in  circumstances  where  (he  phe- 
nomena are  not  visible,  and  to  act  wif;h  as  much  confidence  as  if  we  could  really  see  them. 


LIGHT    CARBURETTED    HYDROGEN.  49 

gas  thus  pioduceo  is  known  by  the  name  of  carbonic  oxide.  It  consists 
of  one  equivalent  of  carbon  united  to  one  of  oxygen,  and  is  represented 
by  C2  O2,  or  simply  CO. 

This  gas  is  colourless,  without  taste  or  smell,  lighter  than  common  air, 
nearly  insoluble  in  water,  extinguishes  flame,  does  not  support  life; 
burns  in  the  air  or  in  oxygen  gas  with  a  blue  flame,  and  during  this 
combustion  is  converted  into  carbonic  acid.  It  is  produced  along  with 
carbonic  acid  during  the  imperfect  combustion  of  coals  in  our  fires  and 
furnaces,  but  is  not  known  to  occur  in  nature,  or  to  minister  directly  to 
the  growth  of  plants. 


There  exists  a  general  relation  among  the  three  compounds  of  carbon 
and  oxygen  above  described,  to  which  it  may  be  interesting  to  advert, 
in  connection  with  the  subject  of  vegetable  physiology.  This  relation 
appears  when  we  compare  together  their  chemical  constitution,  as  re- 
presented by  their  chemical  formulae  : — 

Carbonic  acid  consists  of  one  of  carbon  and  two  of  oxygen,  or  CO2  ; 

Carbonic  oxide,  of  one  of  carbon  and  one  of  oxygen,  or  CO  ; 

So  that  if  carbonic  acid  be  present  in  a  plant,  and  be  there  deprived 
of  one  e(juivalent  of  its  oxygen,  by  any  vital  action,  it  will  be  converted 
into  carbonic  oxide. 

Oxalic  acid  consists  of  two  of  carbon  and  three  of  oxygen,  or  C2O3. 

If  wc  add  together  the  formulae  for 

Carbonic  acid       =  COg  and 
Carbonic  oxide     =  CO,  we  have 


Hence  this  acid  may  be  formed  in  the  interior  of  plants,  either  by  the 
direct  union  of  carbonic  oxide  and  carbonic  acid,  or  by  depriving  two  of 
carbonic  acid  (2CO2  or  C2O4)  of  one  equivalent  of  oxygen. 

When  in  a  subsequent  lecture  we  have  studied  the  structure  and  func- 
tions of  the  leaves  of  plants,  we  shall  see  how  very  easy  it  is  to  under- 
stand the  process  by  which  oxalic  acid  is  formed  and  deposited  in  the  in- 
terior of  plants,  and  by  which  carbonic  oxide  also  may  be,  and  probably 
is,  produced.  • 

§  4.  Light  carburetted  hydrogen — the  gas  of  marshes  and  of  coal  mines. 

During  the  decay  of  vegetable  matter  in  moist  places,  or  under  water, 
a  light  inflammable  gas  is  not  unfrequently  given  off,  which  differs  in  its 
properties  from  any  of  those  hitherto  described.  In  summer  it  may  often 
be  seen  rising  up  in  bubbles  from  the  bottom  of  stagnant  pools  and 
from  marshy  places,  and  may  readily  be  collected. 

This  gas  is  colourless,  without  taste  or  smell,  and  is  little  more  than 
half  the  weight  of  common  air,  [its  specific  gravity,  by  experiment,  is 
0-5576.]  A  lighted  taper,  plunged  into  it,  is  immediately  extinguished, 
while  the  gas  takes  fire  and'  burns  with  a  pale  yellow  flame,  yielding 
more  light,  however,  than  pure  hydrogen  gas,  which  it  otherwise  re- 
sembles.    Animals  introduced  into  it,  instantly  cease  to  breathe. 

It  consists  of  one  equivalent  of  carbon  (C)  united  to  two  of  hydrogen 
(2H  or  H2),  and  is  represented  by  CHg.     When  burned  in  the  air  or 


80  PROPERTIES    OF    AMMONIA. 

in  oxygen  gas,  the  carbon  it  contains  is  converted  into  carbonic  acid 
(COo),  and  the  hydrogen  into  water  (HO). 

Like  oxalic  acid  this  gas  cannot,  by  any  known  process,  be  produced 
from  the  direct  union  of  the  carbon  and  hydrogen  of  which  it  consists. 
It- is  readily  obtained,  however,  by  heating  acetate  of  potash  in  a  retort, 
with  an  equivalent  proportion  of  caustic  baryta.  [Acetate  of  potash  is 
])repared  by  pouring  vinegar  (acetic  acid)  on  common  pearlash  and 
evaporating  the  solution.] 

In  nature  it  is  largely  evolved  in  coal  mines,  and  is  the  principal  com- 
bustible ingredient  in  those  explosive  atmospheres  which  so  frequently 
cause  disastrous  accidents  in  mining  districts. 

This  gas  is  also  given  off  along  with  carbonic  acid  during  the  fermcH- 
tation  of  compost  heaps,  or  of  other  large  collections  of  vegetable  mat- 
ter. It  is  said  also  to  be  generally  present  in  well  manured  soils, 
[Persoz,  Chimie  Moleculaire,  p.  547,]  and  is  supposed  by  many  to  con- 
tribute in  such  cases  to  the  nourishment  of  plants.  It  is,  however,  very 
sparingly  soluble  in  water,  so  that  in  a  state  of  solution,  it  cannot  enter 
largely  into  the  pores  of  the  roots,  even  though  it  be  abundantly  present 
in  the  soil.  How  far*  it  can  with  propriety  be  regarded  as  a  general 
source  of  food  to  plants,  will  be  considered  in  the  following  lecture. 

§  5.  Ammonia,  its  properties  and  relations  to  vegetable  life. 

Ammonia  is  a  compound  of  hydrogen  and  nitrogen.  It  is  possessed 
of  many  interesting  properties,  and  is  supposed  to  perform  a  very  im- 
portant part  in  the  process  of  vegetation.  It  will  be  proper,  therefore, 
to  illustrate  its  nature  and  properties  with  considerable  attention. 

Ammonia,  like  the  nitrogen  and  hydrogen  of  which  it  is  composed,  is 
a  colourless  gas,  but,  unlike  its  elements,  is  easily  distinguished  from 
all  other  gaseous  substances  by  its  smell  and  taste. 

It  possesses  a  powerful  penetrating  odour  (familiar  to  you  in  the  sinell 
of  hartshorn  and  of  common  smelling  salts),  has  a  burning  acrid  alka- 
line* taste,  extinguishes  a  lighted  taper  as  hydrogen  and  nitrogen  do,  but 
does  not  itself  take  fire  like  the  former.  It  instantly  suffocates  animals, 
kills  living  vegetables,  and  gradually  destroys  the  texture  of  their  parts. 

It  is  absorbed  in  large  quantities  by  porous  substances,  such  as  char- 
coal— \^ich,  as  already  stated,  absorbs  95  times  its  own  bulk  of  am- 
moniacal  gas.  Porous  vegetable  substances  in  a  decaying  state  likewise 
absorb  it.  Porous  soils  also,  burned  bricks,  burned  clay,  and  even  com- 
mon clay  and  iron  ochre,  which  are  mixed  together  on  the  surface  of 
most  of  our  fertile  lands — all  these  are  capable  of  absorbing  or  drinking 
m,  and  retaining  within  their  pores,  this  gaseous  substance,  when  it  hap- 
pens  to  be  brought  into  contact  with  them. 

But  the  quantity  absorbed  by  water  is  much  greater  and  more  sur- 
prising. If  the  mouth  of  a  bottle  filled  with  this  gas  be  immersed  in 
water,  the  latter  will  rush  up  and  fill  the  bottle  almost  instantaneously; 
and  if  a  sufficient  supply  of  ammonia  be  y)resent,  a  given  quantit}'  of 
water  will  take  up  as  much  as  670  times  its  bulk  of  the  gas. 

This  solution  of  ammonia  in  water  is  the  spirit  of  hartshorn  of  the 
«hops.     When  saturated  [that  is,  when  gas  is  supplied  till  the  water  re- 

•  The  term  alkaline,  as  applied  to  taste,  will  be  best  understood  by  describing  it  as  a  taste 
Imilar  to  that  of  the  common  soda  and  pearlash  of  the  shops. 


ITS    COMBINATION    WITH   ACIDS.  61 

fuses  to  take  up  any  more,]  it  is  lighter  than  pure  water,  [its  specific 
gravity  is  0*875,  water  being  1,]  has  the  pungent  penetrating  odour  of  the 
gas,  and  its  hot,  burning,  alkaline  taste — is  capable  of  blistering  the 
skin,  and  decomposing  or  destroying  the  texture  of  animal  and  vegeta- 
ble substances. 

You  will  remark  here  the  effect  which  combination  has  in  investing 
substances  with  new  characters.  The  two  gases  hydrogen  and  nitrogen, 
themselves  without  taste  or  smell,  and  absorbed  by  water  in  minute 
quantity  only,  form  by  their  union  a  compound  body  remarkable  both 
for  taste  and  smell,  and  for  the  rapidity  with  which  water  absorbs  it. 

Ammonia  possesses  also  alkaline  properties,*  it  restores  the  blue 
colour  of  vegetable  substances  that  have  been  reddened  by  an  acid,  and 
it  combines  with  acid  substances  to  form  salts. 

Among  gaseous  substances,  therefore,  there  are  some  which,  like  car- 
bonic acid,  have  a  sour  taste  and  redden  vegetable  blues  ;  others  which, 
like  ammonia,  have  an  alkaline  taste  and  restore  the  blue  colour ;  an., 
a  third  class  which,  like  oxygen,  hydrogen,  and  nitrogen,  are  destitute  of 
taste  and  do  not  affect  vegetable  colours.  These  last  are  called  neu- 
tral  or  indifferent  substances. 

Ammonia,  as  above  slated,  combines  with  acids  and  forms  salts, 
which  at  the  ordinary  temperature  of  the  atmosphere  are  all  solid  sub- 
stances. Hence  if  carbonic  acid  gas  be  mixed  with  ammoniacal  gas, 
a  white  cloud  is  formed  consisting  of  minute  particles  of  solid  carbonate 
of  ammonia — the  smelling  salts  of  the  shops.  Hence  also  a  feather 
dipped  into  Vinegar  or  dilute  muriatic  acid  (spirit  of  salt),  and  then  in- 
troduced into  ammoniacal  gas,  forms  a  similar  white  cloud,  and  be- 
comes covered  with  a  white  down  of  solid  acetate  or  of  muriate  of  ammonia 
(sal  ammoniac).  The  same  appearance  is  readily  seen  by  holding  the 
feather  to  the  mouth  of  a  bottle  containing  hartshorn  (liquid  ammonia), 
from  which  ammoniacal  gas  continually  escapes,  and  by  its  lightness  rises 
into  the  air,  and  thus  comes  in  contact  with  the  acid  upon  the  feathers. 

The  fact  of  the  production  of  a  solid  body  by  the  union  of  two  gases 
(ammonia  and  carbonic  or  muriatic  acid  gases)  is  one  of  a  very  inter- 
esting nature  to  the  young  chemist,  and  presents  a  further  illustration 
of  the  changes  resulting  from  chemical  combination  as  explained  in 
the  previous  lecture. 

Ammonia  is  little  more  than  half  the  weight  of  common  air,  [more 
nearly  three-fifths,  its  specific  gravity  being  0-59,  that  of  air  being  1,] 
hence  when  liberated  on  the  earth's  surface  it  readily  rises  into  and 
mingles  with  the  atmosphere.  It  consists  of  hydrogen  and  nitrogen 
united  together  in  the  proportion  of  three  equiv^ents  of  hydrogen  (3H 
or  H3)  anil  one  of  nitrogen  (N),  [see  Lecture  II,]  and  hence,  it  is  re- 
presented by  the  symbol  (N  +  3H),  or  more  shortly  by  NH3.  100 
parts  by  weight  contain  82i  of  nitrogen  and  17i  of  hydrogen,  [correct- 
ly 82-545  and  17-455  respectively.] 

In  nature,  ammonia  exists  in  considerable  quantity      It  is  widely, 

•  In  the  previous  lectivre,  the  term  acid  was  explained  as  applying  to  substances  possess- 
ed of  a  sour  taste,  and  capable  of  reddening  vegetable  blues  or  combining  with  boats  (pot- 
ash, soda,  magnesia,  «S:v3.)  to  form  salts ;  alkalies  are  such  as  possess  an  alkaline  taste  (see 
previous  Note),  restore  tlie  blue  colour  to  r&idened  vegetable  substances,  or  combine  with 
acida  to  form  salts.  Of  salts,  nitrate  of  sodi  saltoetrc  (nitrate  of  potash),  and  glauber  salts 
(sulphate  of  soda),  are  examples. 


52  ITS  EXISTENCE  IN  NATURE,  AND  SPECIAL  PROPERTIES. 

almost  universally,  diffused,  but  is  not  known  to  form  large  deposits  on 
any  part  of  the  earth's  surface,  or  to  enter  as  a  constituent  into  any 
of  the  great  mineral  masses  of  which  the  crust  of  the  globe  is  com- 
posed. It  exists  most  abundantly  in  a  state  of  combination — in  the 
forms,  for  example,  of  muriate  (sal  ammoniac),  of  nitrate,  and  of  carbon- 
ate of  ammonia.  It  frequently  escapes  into  the  atmosphere  in  an  un- 
combined  state,  especially  where  animal  matters  are  undergoing  decay, 
but  it  rarely  exists  in  this  free  state  for  any  length  of  time.  It  speedily 
unites  with  the  carbonic  acid  of  the  air,  with  one  or  other  of  the  numer- 
ous acid  vapours  which  are  continually  rising  from  the  earth,  or  with 
the  nitric  acid  which  is  formed  at  the  expense  of  the  nitrogen  and  oxy- 
gen of  which  the  atmosphere  consists. 

The  influence  of  ammonia  on  vegetation  appears  to  be  of  a  very 
powerful  kind.  It  seems  not  only  to  promote  the  rapidity  and  luxu- 
riance of  vegetation,  but  to  exercise  a  powerful  control  over  the  func- 
tions of  vegetable  life.  In  reference  to  the  nature  and  extent  of  this 
action,  into  which  we  shall  hereafter  have  occasion  to  inquire,  there 
are  several  special  properties  of  ammonia  which  it  will  be  of  impor- 
tance for  us  previously  to  understand. 

1°.  It  has  a  powerful  affinity*  for  acid  substances.  Hence  the 
readiness  with  which  it  unites  with  acid  vapours  when  it  rises  into  the 
atmosphere.  Hence  also  when  formed  or  liberated  in  the  soil,  in  the 
fold-yard,  in  the  stable,  or  in  compost  heaps,  it  unites  with  such  acid 
substances  as  may  be  present  in  the  soil,  &c.  and  fornxs  saline  com- 
pounds or  salts.  All  these  salts  appear  to  be  more  or  less  liifluential  in 
the  processes  of  vegetable  life. 

2°.  Yet  this  affinity  is  much  less  strong  than  that  which  is  exhibited 
for  the  same  acids  by  potash,  soda,  lime,  or  magnesia.  Hence  if  any 
of  these  substances  be  mixed  or  brought  into  contact  with  a  salt  of  am- 
monia, the  acid  of  the  latter  is  taken  up  by  the  potash  or  lime,  while 
the  ammonia  is  separated  in  a  gaseous  slate.  Thus  when  sal  ammo- 
niac in  powder  is  mixed  with  twice  its  weight  of  quick-lime,  ammoni- 
acal  gas  is  liberated  in  large  quantity.  This  is  the  method  by  which 
pure  ammonia  is  generally  prepared ;  and  one  of  the  many  functions 
performed  by  lime  when  employed  for  the  improvement  of  land,  espe- 
cially on  soils  rich  in  animal  and  vegetable  matter,  is  that  of  decompo- 
sing the  salts,  especially  the  organic  salts,  of  ammonia, — as  will  be 
more  fully  explained  when  we  come  to  treat  at  length  of  this  important 
part  of  agricultural  practice. f 

3°.  The  salts  which  ammonia  forms  with  the  acids  are  all,  like  am- 
monia itself,  very  solujsle  in  water.  Hence  two  consequences  follow. 
First,  that  which  rises  into  the  air  in  the  form  of  gas,  and  there  com- 
bines with  the  carbonic  or  other  acids,  is  readily  dissolved,  washed  out 

*  By  affinity  is  meant  the  tendency  which  bodies  have  to  unite  and  to  remain  united  or 
combined.  Thus  ammonia  forms  a  solid  substance  with  the  vapour  of  vinegar  the  moment 
the  two  substances  come  into  contact;  they  have,  therefore,  a  strong  tendency  to  unite,  or 
an  affinity  for  each  other. 

t  See  Lecture  XVI.  ^^On  the  use  of  lime."  Owing  to  this  property  the  action  of  lime  upon, 
compost  heaps  is  often  injurious,  by  causing  the  evolution  of  the  ammonia  produced  during 
the  decomposition  of  the  animal  matters  they  contain.  This  escape  of  ammonia,  even 
when  imperceptible  by  the  sense  of  smell,  is  easily  detected  by  holdinfi  over  the  heap  a  fea- 
ther  dipped  in  vinegar  or  in  spirit  o!'  salt  (muriatic  ?.cid),  when  vvliite  fumes  are  immediate- 
ly perceived  if  ammonia  be  prese  j » 


DECOMPOSES    GYPSUM.  53 

and  brought  to  the  earth  again  by  the  rains  and  dews ;  so  that  at  the 
same  time  the  air  is  purified  for  the  use  of  animals,  and  the  ammo- 
nia brought  down  for  the  use  of  plants.  And  second,  whatever  salts  of 
ammonia  are  contained  in  the  soil,  being  dissolved  by  the  rain,  are  in 
a  condition  to  be  taken  up,  when  wholesome,  by  the  roots  of  plants;  or 
to  be  carried  off  by  the  drains  when  injurious  to  vegetation. 

4°.  I  have  already  alluded  to  the  fact  of  this  gas  being  absorbed  by 
porous  substances,  and  to  its  presence,  in  consequence,  in  porous  soils, 
and  in  burned  bricks  and  clay.  With  the  purer  kinds  of  unburned 
clay,  however,  and  with  the  oxide  of  iron  contained  in  red  (or  ferrugi- 
nous)* soils,  ammonia  is  supposed  to  form  a  chemical  compound  of  a 
weak  nature.  In  consequence  of  its  affinity  or  feeble  tendency  to  com- 
bine with  these  substances,  they  attract  it  from  the  air,  and  from  decay- 
ing animal  or  vegetable  matters,  and  retain  it  more  strongly  than  many 
porous  substances  can, — yet  with  a  sufficiently  feeble  hold  to  yield  it 
up,  readily  as  is  supposed,  to  the  roots  of  plants,  when  their  extremities 
are  pushed  forth  in  search  of  food.  In  this  case  the  carbonic,  acetic, 
and  other  acids  given  oflT,  or  supposed  to  be  given  off  by  the  roots,  exer- 
cise an  influence  to  which  more  particular  allusion  will  be  made  here- 
after. 

6°.  In  the  state  of  carbonate  it  decomposes  gypsum,  forming  carbon- 
ate of  lime  (chalk)  and  sulphate  of  ammonia.f  The  action  of  gypsum 
on  grass  lands,  so  undoubtedly  beneficial  in  many  parts  of  the  world, 
lias  been  ascribed  to  this  single  property;  it  being  supposed  that  the 
sulphate  of  ammonia  formed,  is  peculiarly  favourable  to  vegetation. 
This  question  will  come  properly  under  review  hereafter.  I  may  here, 
however,  remark  that  if  this  be  the  sole  reason  for  the  efficiency  of  gyp- 
sum, its  application  ought  to  be  beneficial  on  all  lands  not  already 
abounding  either  in  gypsum  or  in  sulphate  of  ammonia.J     But  if  the 

*  Soils  reddened  by  the  presence  of  oxide  of  iron. 

t  Gypsum  is  sulphate  of  lime— consisting  of  sulphuric  acid  (oil  of  vitriol)  and  quicklime. 
Carbonate  of  ammonia  consists  of  carbonic  acid  and  ammonia.  W^hen  the  two  substances 
act  upon  each  oth^r  in  a  moist  state— the  two  acids  change  places— the  sulphuric  acid,  as  it 
vf ere,  preferring  the  ammonia,  tlie  carbonic  acid  the  lime. 

t  Liebig  says — "tlie  sinking  fertility  of  a  meadow  on  which  gypsum  is  strewed  depends 
only  on  its'fixing  in  the  .soil  the  ammonia  of  the  atmosphere,  which  would  otherwise  be  vola- 
tilized with  the  water  which  evaporates."— O^an/c  Chemistrtj  applied  to  Agriculture,  p.  86. 
[^y  fixing  is  meant  the  formina  ni sulphate  with  the  ammonia.  Rain  water  is  supposed  to 
bring  down  with  it  carbonate  of  ammonia  (common  smelling  salts),  which  acts  upon  the  sul- 
pfiateoflimei'iypimn)  in  such  a  way  that  sulphate  of  ammo7iia  ami  carbonate  of  lime  axe 
jiroduced.  Ttie  carbonate  of  ammonia  readily  volatilizes  or  rises  again  into  the  air,  the  sul- 
phate does  not — hence  the  use  of  the  word  fix.] 

When  we  come  to  consider  the  subject  of  mineral  manures  in  general,  we  shall  study 
more  in  detail  the  specific  action  of  gypsum  in  promoting  vegetation— a  very  simple  calcula- 
tion, however,  will  serve  to  shew  that  the  above  theory  of  Liebig  is  far  from  affording  a  satis- 
factory explanation  of  all  the  phenomena. 

Supposing  the  gypsum  to  meet  with  a  sufficient  supply  of  nmmonia  in  the  soil,  and  that  it 
exercises  its  full  influence,  100  lbs.  of  common  unburned  gypsnm  will  flx  or  form  sulphate 
with  nearly  20  lbs.  of  ammonia  containing  IBJlbs.  of  nitrogen.  One  hundred  weight,  there- 
fore, (112 lbs.)  will  form  as  much  sulphate  as  will  contain  22| lbs.  of  ammonia,  and  if  intro- 
duced without  loss  into  the  interior  of  plants  will  furnish  them  with  \Sh  lbs.  of  nitrogen. 

1°.  In  the  first  volume  of  British  Husbandry,  pp.  322,  323,  the  following  experiment  is 
recorded :  ^     ^  , ,    ,      ,    , 

Mr.  Smith,  of  Tunstal,  near  Sittingbourne,  top-dressed  one  portion  of  a  field  of  red  clover 
with  powdered  gypsum  at  the  rate  of  five  bushels  (or  four  hundred  weight')  per  acre,  and 
compared  the  produce  with  another  portion  of  the  same  field,  to  which  no  manure  had  been 

[•  A  ton  of  pure  gypaum,  when  crushed,  will  yield  25  bushels.  It  should,  however,  al- 
ways be  applied  by  weight.  ] 

3* 


64  MODE    IN    WHICH    GYPSUM   ACTS. 

results  of  experimental  farming  in  this  country  are  to  be  trusted,  this  is 
by  no  means  the  case.  The  action  neither  of  this,  nor  probably  of  any 
other  inorganic  substance  applied  to  the  soil,  is  to  be  explained  by  a 
reference  in  every  case  to  one  and  the  same  property  only. 

7°.  The  presence  or  evolution  of  ammonia  in  a  soil  containing  animal 
and  vegetable  matter  in  a  decaying  state,  induces  or  disposes  this  mat- 
ter to  attract  oxygen  from  the  air  more  rapidly  and  abundantly.  The 
result  of  this  is,  that  organic  acid  compounds  are  formed,  which  combine 

applied.  Tlie  first  crop  was  cul  for  hay,  and  the  second  ripened  for  seed.  TJie  following 
were  the  comparative  results  per  acre : 

HAY  CROP.     SEED.         STRAW. 

cwt.  grs.  Ihs.  cwt.  qrs.  lbs. 

Gypsumed 60  3    21  22    3  12 

Unmanured 20  0    20  5    0    0 

Excess  of  produce     .     .    40  3      1  17    3  12 

The  excess  of  produce  in  all  the  three  crops  upon  the  gypsumed  land  is  very  large  :  let  us 
calculate  how  much  nitrogen  this  excess  would  contain.  In  a  previous  lecture  (II.  p.  30)  it 
was  stated  as  the  result  of  Boussingault's  analyses,  that  dry  clover  seed  contained  7  per 
cerit.  of  nitrogen,  and  the  same  experimenter  found  in  the  hay  of  red  clover  1^  per  cent,  (or 
70  and  15  lbs.  respectively  in  lOCW.) 

The  seed  as  it  was  weighed  by  Mr.  Smith  would  still  contain  one-ninth  of  its  weight  of 
water,  and,  consequently,  only  6>^rd  per  cent,  of  nitrogen,  [.see  Lecture  II.  p.  30.]  Let  it 
be  taken  at  6  per  cent,  and  let  the  straw  be  supposed  to  contain  only  1  per  cent,  of  nitro- 
gen, the  quantity  of  this  element  being  found  to  diminish  in  the  grasses  after  the  seed  has 
ripened,  and  averaging  1  per  cent,  in  the  straw  of  wheat,  oats,  and  barley,  the  weight  of  ni- 
trogen reaped  in  the  whole  crop  will  then  be  as  follows : 

1.  40  cwt.  of  hay  (4480  lbs.)  at  1§  per  cent,  of  nitrogen,  contain  67  lbs. 

2.  85  lbs.  of  seed  at  6  per  cent,  contain 5  lbs. 

3.  17  cwt.  3  qrs.  12  lbs.  or  2000  lbs.  of  straw  at  1  per  cent,  contain  20  lbs. 

Total  nitrogen  in  the  excess  of  crop,  92  lb.=?. 

But,  as  above  shewn,  the  fi%'e  bushels  or  four  cwt.  of  gypsum  could  fix  only  90  lbs.  of  am- 
monia containing  74  lbs.  of  nitrogen,  leaving,  therefore,  18  lbs.  or  one  fifth  of  tlie  whole,  to  be 
derived  from  some  other  source. 

Now  this  result  supposes  that  none  of  tlie  gypsum  or  sulphate  of  ammonia  was  carried 
away  by  the  rains,  but  that  the  whole  remained  in  the  soil,  and  produced  its  greatest  jwssihle 
eff*ect  on  the  clover — and  all  in  one  season. 

But  the  effect  of  the  gypsum  does  not  disappear  with  the  crop  to  which  it  is  actually  ap- 
plied. Its  beneficial  action  is  extended  to  the  succeeding  crop  of  wheat,  and  on  grass  lands 
the  amelioration  is  visible  for  a  succession  of  years.  If,  tiien,  the  increased  produce  of  a 
single  year  may  contain  more  nitrogen  than  the  gypsum  can  be  supposed  to  yield,  this  sub- 
stance must  exercise  some  other  influence  over  vegetation  than  is  involved  in  its  supposed 
action  on  the  indefinite  quantity  of  ammonia  in  the  almospliere. 

2'^.  Again,  Mr.  Barnard,  of  Little  Bordean,  Hants,  applied  2|  cwt.  per  acre  on  two-year 
old  sain  foin,  on  a  clayey  soil.  The  increased  produce  of  the  first  cutting  was  a  ton  per 
acre,  and  in  October  fully  a  ton.  the  undressed  part  yielding  scarcely  any  hay  at  all,  while 
the  dressed  part  gave  \\  tons.  The  second  year  no  gypsum  was  applied,  and  the  diflTerence 
is  said  to  have  bebn  at  least  as  great. 

Supposing  the  increased  produce  in  all  to  have  been  4  tons  of  hay,  and  the  nitrogen  it  con- 
tained to  have  been  only  one  per  cent. — the  4  tons  (8960  lbs.)  would  contain  about  90  lbs.  of 
nitrogen.  But  2§  cwt.  would  fix  only  46  lbs.  of  nitrogen  in  the  form  of  ammonia  ;  and  there- 
fore, supposing  it  to  have  produced  its  maximum  effect,  there  remain  AA  lbs.  or  nearly  one 
half  of  the  whole,  unaccounted  for  by  the  theory. 

I  would  not  be  understood  to  place  absolute  reliance  on  the  results  of  the  above  experi- 
ments ;  but  the  way  in  which  such  results  may  be  easily  applied  for  the  purpose  of  testing 
theoretical  views,  will,  I  hope,  convince  ttie  intelligent  practical  agriculturist  how  important 
it  is,  that  the  results  of  some  of  the  experiments  he  is  every  year  making  should  be  accu- 
rately determined  by  weight  and  measure.  By  this  means  data  would  gradually  be  accu- 
mulated, on  which  we  might  hope  to  found  more  unexceptionable  explanations  of  the  phe- 
nomena of  vegetation,  than  the  results  obtained  in  our  laboratories  liave  hitherto  enabled 
us  to  advance. 

In  a  subsequent  note  it  will  be  shewn  that  the  mode  in  which  the  nitrates  of  soda  and 
potash  act — in  other  words,  the  theory  of  their  action  upon  vegetation — may  be  tested  by  a 
similar  simple  calculation,  and  the  importance  of  precise  experiments  made  on  the  farm 
will  then  still  further  appear.  It  is  in  the  hope  of  inducing  some  of  my  readers  to  make 
comparative  trials  and  publish  accurate  results,  that  I  have  introduced  into  the  Appendix 
(No.  I.)  an  outline  of  the  mode  in  which  such  experimenis  laay  most  usefully  be  performed. 


INFLUENCE    OF    AMMONIA    OVER    PLANTS.  55 

With  (he  ammonia,  and  form  ammoniacal  salts.*  On  the  decomposi- 
tion of  these  sahs  by  lime  or  otherwise — the  organic  acids  which  are  se- 
parated from  them,  are  always  more  advanced  towards  that  state  in 
vhich  they  again  become  fit  to  act  as  food  for  plants. 

8°.  But  the  most  interesting,  and  perhaps  the  most  important  proper- 
ty of  ammonia,  is  one  which  I  have  already  had  occasion  to  bring  under 
your  notice,  as  possessed  by  water  also,  and  as  peculiarly  fitting  that 
fluid  for  the  varied  functions  it  performs  in  reference  to  vegetable  life. 
This  property  is  the  ease  with  which  it  undergoes  decomposition,  either 
in  the  air,  in  the  soil,  or  in  the  interior  of  plants. 

In  the  air  it  is  diflused  through,  and  intimately  mixed  with,  a  largo 
excess  of  oxygen  gas.  In  the  soil,  especially  near  the  surface,  it  is  also 
continually  in  contact  with  oxygen.  By  the  influence  of  electricity  in 
the  air,  and  of  lime  and  other  bases  in  the  soil,  it  undergoes  a  constant 
though  gradual  decomposition  (oxidation),  its  hydrogen  being  chiefly 
converted  into  water,  and  a  portion  of  its  nitrogen  into  nitric  acid.f 

In  the  interior  of  plants  this  and  other  numerous  and  varied  decom- 
positions in  all  probability  take  place. 

The  important  influence  which  ammonia  appears  to  exercise  over  the 
growth  of  plants — the  evidence  for  which  I  shall  presently  lay  before 
you — is  only  to  be  explained  on  the  supposition  that  numerous  transfor- 
mations of  organic  substances  are  eflfected  in  the  interior  of  living  vege- 
tables— which  transformations  all  imply  the  separation  from  each  other, 
or  the  re-arrangement  of  the  elements  of  which  ammonia  consists.  In 
the  interior  of  the  plant  we  have  seen  that  water,  ever  present  in  great 
abundance,  is  also  ever  ready  to  yield  its  hydrogen  or  its  oxygen  as  oc- 
casion may  require,  while  these  same  elements  are  never  unwilling  to 
unite  again  for  the  formation  of  water.  So  it  is,  to  a  certain  degree, 
with  ammonia.  The  hj-drogen  it  contains  in  so  large  a  quantity  is  ready 
to  separate  itself  from  the  nitrogen  in  the  interior  of  the  plant,  and,  in  con- 
cert with  the  other  organic  elements  introduced  by  the  roots  or  the  leaves, 
to  aid  in  producing  the  dilTerent  solid  bodies  of  which  the  several  parts 
of  plants  are  made  up.  The  nitrogen  also  becomes  fixed  in  the  coloured 
petals  of  the  flowers,  in  the  seeds,  and  in  other  parts,  of  which  it  appears 
to  constitute  a  necessary  ingredient — passes  oS'in  the  form  of  new  com- 
pounds, in  the  insensible  perspiration  or  odoriferous  exhalations  of  the 
plant,— or  returning  with  the  downward  circulation,  is  thrown  off  by  the 
root  into  the  soil  from  which  it  was  originally  derived.  Much  obscurity 
still  rests  on  the  actual  transformations  which  take  place  in  the  interior 
of  plants,  yet  we  shall  be  able  in  a  future  lecture,  I  hope,  to  arrive  at  a 
tolerably  clear  understanding  of  the  general  nature  of  many  of  them. 

Such  are  the  more  important  of  those  properties  of  ammonia,  to  which 
we  shall  hereafter  have  occasion  to  advert.  The  sources,  remote  as 
well  as  immediate,  from  which  plants  derive  this,  and  other  compounds 
we  have  described  as  contributing  to  the  nourishment  and  growth  of 
plants,  will  be  detailed  in  a  subsequent  section. 

•  Organic  acids  generally  contain  more  oxygen  in  proportion  to  their  carbon  and  hydro- 
gen, than  those  which  are  alkaline  or  neulral. 

t  It  will  be  remembered  that  ammonia  is  represented  by  Nils,  water  by  HO,  and  nitric 
acid  by  NO5.  It  is  easy  to  see,  therefpre,  how,  by  means  of  oxygen,  ammonia  should  be 
converted  into  water  and  nitric  acid. 


56  PROPERTIES     IF    NITRIC    ACID. 

§  6.  Nitri':  acid,  its  c^'utitution  and  'properties. 

When  the  nitre  or  saltpetre  of  commerce  is  introduced  into  a  retort, 
covered  with  strong  sulphuric  acid  (oil  of  vitriol*)  and  heated  over  a  lamp 
or  a  charcoal  fire,  red  fumes  are  given  off,  and  a  transparent,  often 
brownish  or  reddish  licjuid,  distils  over,  which  may  be  collected  in  a  bot- 
tle or  other  receiver  of  glass.  This  liquid  is  exceedingly  acid  and  cor- 
rosive. In  small  quantity  it  stains  the  skin  and  imparts  a  yellow  colour 
to  animal  and  vegetable  substances.  In  larger  quantity  it  corrodes  the 
skin,  producing  a  painful  sore,  rapidly  destroys  animal  and  vegetable 
life,  and  speedily  decomposes  and  oxidizesf  all  organic  substances. 
Being  obtained  from  nitre,  this  liquid  is  called  nitric  acid.  It  consists  of 
nitrogen  combined  with  oxygen,  one  equivalent  of  the  former  (N)  being 
united  to  5  of  the  latter  (O5),  and  is  represented  by  NO5. 

This  acid  contains  much  oxygen,  as  its  formula  indicates,  and  its  ac- 
tion on  nearly  all  organic  substances  depends  upon  the  ease  with  which 
it  is  decomposed,  and  may  be  made  to  part  with  a  portion  of  this  oxygen. 

In  nature,  it  never  occurs  in  a  free  state  ;  but  it  is  found  in  many  in- 
tertropical (hot)  countries  in  combination  with  potash,  soda,  and  lime — in 
the  state  of  nitrates.  It  is  an  important  character  of  these  nitrates  that,  like 
the  salts  of  ammonia,  they  are  all  very  soluble  in  water.  Those  of  so- 
da, lime,  and  magnesia  attract  moisture  from  the  air,  and  in  a  damp  at- 
mosphere gradually  assume  the  liquid  form. 

Saltpetre  is  a  compound  of  nitric  acid  with  potash  (nitrate  of  potash). 
It  is  met  with  in  the  surface  soil  of  many  districts  in  Upper  India,  and 
is  separated  by  washing  the  soil  and  subsequently  evaporating  (or  boil- 
ing down)  the  clear  li(|uid  thus  obtained.  When  pure,  it  does  not  be- 
come moist  on  exposure  to  the  air.  It  is  chiefly  used  in  the  manufac- 
ture of  gunpowder,  but  has  also  been  recommended  and  frequently  and 
successfully  tried  by  the  practical  husbandman,  as  an  influential  agent 
in  promoting  vegetation. 

In  combination  with  soda,  it  is  found  in  deposits  of  considerable  thick- 
ness in  the  district  of  Arica  in  Northern  Peru,  from  whence  it  is  im- 
ported into  tliis  country,  chiefly  for  the  manufacture  of  nitric  and  sulphu- 
ric acids.  More  recently  its  lower  price  has  caused  it  to  be  extensively 
employed  in  husbandry,  especially  as  a  top-dressing  for  grass  lands. 
Like  the  acid  itself,  these  nitrates  of  potash  and  soda,  when  present  in 
large  quantities,  are  injurious  to  vegetation.  This  is  probably  one  cause 
of  the  barrenness  of  the  district  of  Arica  in  Peru,  and  of  other  countries, 
where  in  consequence  of  the  little  rain  that  falls,  the  nitrous  incrusta- 
tions are  accumulated  upon  the  soil.  In  small  quantity  they  appear  to 
exercise  an  important  and  salutary  influence  on  the  rapidity  of  growth, 
and  on  the  amount  of  produce  of  many  of  the  cultivated  grasses.  This 
salutary  influence  is  to  be  ascribed,  either  in  whole  or  in  part,  to  the 
constitution  and  nature  of  the  nitric  acid  which  these  salts  contain.     It 

*  Sulphuric  acid  is  a  compound  of  oxygen  and  sulphur,  which  is  prepared  by  burning  sul- 
phur with  certain  precautions  in  large  leaden  chambers.  It  is  also  obtained  directly  by  dis- 
tilling ^een  vitriol  (sulphate  of  iron)  at  a  high  temperature  in  an  iron  still — hence  its  name  oU 
ofvitnol.  It  is  a  heavy,  oily,  acid,  and  remarkably  corrosive  liquid.  In  a  concentrated  state 
it  is  exceedingly  destructive  both  to  animal  and  to  vegetable  life. 

t  When  a  substance  combines  with  oxygen^  either  in  consequence  of  exposure  to  the  air 
or  in  any  other  circumstances,  .  .8  said  to  become  oxidized. 


QUESTIONS    TO    BE    CONSIDEIIED.  57 

is  chiefly  with  a  view  to  the  explanation  I  shall  hereafter  attempt  to 
give  of  the  nature  of  this  salutary  action,  that  I  have  thought  it  neces- 
sary here  to  make  you  acquainted  with  this  add  compound  of  nitrogen 
and  oxygen,  in  connection  with  the  alkaline  compound  (ammonia)  of  the 
same  gas  with  hydrogen. 

Having  thu^  shortly  descrihed  both  the  organic  elements  themselves, 
and  such  chemical  compounds  of  these  elements  as  appear  to  be  most 
concerned  in  promoting  the  growth  of  plants,  we  are  prepared  for  enter- 
ing upon  the  consideration  of  several  very  important  questions.  These 
questions  are — 

1°.  From  what  source  do  plants  derive  the  organic  elements  of  which 
they  are  composed  ? 

2°.  In  what  form  do  plants  take  them  up-^or  what  proof  have  we 
that  the  compounds  above  described  really  enter  into  plants? 

3°.  By  what  organs  is  the  food  introduced  into  the  circulation  of 
plants?  In  consequence  of  what  peculiar  structure  of  these  several 
parts  are  plants  enabled  to  take  up  the  compounds  by  which  they  appear 
to  be  fed  ;  and  what  are  the  functions  of  these  parts,  by  the  exercise  of 
which  the  food  is  converted  and  appropriated  to  their  own  sustenance 
and  further  growth  ? 

4*^.  By  what  chemical  changes  is  the  food  assimilated  by  plants,  that 
is — after  being  introduced  into  the  circulation,  through  what  series  of 
chemical  changes  does  it  pass,  before  it  is  converted  by  the  plant  into 
portions  of  its  own  substance  ? 

5°.  By  what  natural  laws  or  adaptations  is  the  supply  of  those  com- 
pounds, which  are  the  food  of  plants,  kept  up  ?  Animals  are  supported 
by  an  unfailing  succession  of  vegetable  crops, — by  the  operation  of  what 
invariable  laws  is  food  continually  provided  for  plants  ? 

These  questions  we  shall  consider  in  succession 


LECTURE  IV. 

Source  of  the  organic  elements  of  plants— Source  of  the  carbon— Fcrm  in  which  it  entcra 
into  the  circulation  of  plants — Source  of  the  hydrogen — Source  of  the  oxygen— Source  of 
the  nitrogen — Form  in  wJiich  nitrogen  enters  into  the  circulation  of  plants — Absorption  of 
ammonia  and  nitric  acid  by  plants. 

The  first  of  the  series  of  questions  stated  at  the  close  of  the  preceding 
lecture,  regards  the  source  from  which  plants  derive  the  organic  ele- 
ments of  which  they  are  composed.  They  are  supported,  it  is  ohvious, 
at  the  conjoined  expense  of  the  earth  and  the  air — how  much  do  they 
owe  to  each,  and  for  which  elements  are  they  chiefly  and  immediately 
indebted  to  the  soil,  and  for  which  to  the  atmosphere  ?  We  must  first 
consider  the  source  of  each  element  separately. 

§  1.  Source  of  the  carbon  of  plants. 

We  have  already  seen  reason  to  believe  that  carbon  is  incapable  of 
entering  directly,  in  its  solid  state,  into  the  circulation  of  plants.  It  is 
generally  considered,  indeed,  that  solid  substances  of  every  kind  are  un- 
fit for  being  taken  up  by  the  organs  of  plants,  and  that  only  such  as  are 
in  the  liquid  or  gaseous  state,  can  be  absorbed  by  the  minute  vessels  of 
which  the  cellular  substances  of  the  roots  and  leaves  of  plants  are  com- 
posed. Carbon,  therefore,  must  enter  either  in  the  gaseous  or  liquid 
form,  but  from  what  source  must  it  be  derived  ?  There  are  but  two 
sources  from  which  it  can  be  obtained, — the  soil  in  which  the  plant 
grows — and  the  air  by  which  its  stems  and  leaves  are  surrounded. 

In  the  soil  much  vegetable  matter  is  often  present,  and  the  farmer 
adds  vegetable  manure  in  large  quantities  with  the  view  of  providing 
food  for  his  intended  crop.  Are  plants  really  fed  by  the  vegetable  mat- 
ter which  exists  in  the  soil,  or  by  the  vegetable  manure  that  is  added  to 
it? 

This  question  has  an  important  practical  bearing.  Let  us,  therefore, 
submit  it  to  a  thorough  exainination. 

1°.  We  know,  from  sacred  history,  what  reason  and  science  concur 
in  confirming,  that  there  was  a  time  wlien  no  vegetable  matter  existed 
in  tlie  soil  which  overspread  the  earth's  surface.  The  first  plants  must 
have  grown  without  the  aid  of  either  animal  or  vegetable  matter — that 
is,  they  must  have  been  nourished  from  the  air. 

2°.  It  is  known  that  certain  marly  soils,  raised  from  a  great  depth 
beneath  the  surface,  and  containing  apparently  no  vegetable  matter, 
will  yet,  without  manure,  yield  luxuriant  crops.  The  carbon  in  such 
cases  must  also  have  been  derived  from  the  air. 

3°.  You  know  that  some  plants  grow  and  increase  in  size  when  sus- 
pended in  the  air,  and  without  being  in  contact  with  the  soil. 

You  know,  also  that  tnany  plants — bulbous  flower  roots  for  example 
— will  grow  and  flourish  in  pure  water  only,  provided  they  are  open  to 
the  access  of  the  atmospheric  air.  Seeds  also  will  germinate,  and, 
when  duly  watered,  w^ill  rise  into  plants,  though  sown  iu  substances 
that  contain  no  trace  of  vegetable  n  alter. 


WHENCE    PLANTS  DERIVE    THEIR    CARBON.  59 

Thus  De  Saussure  found  that  two  beans,  when  caused  to  vegetate  in 
the  open  air  on  pounded  flints,  doubled  the  weight  of  the  carbon  they 
originally  contained. 

Under  similar  circumstances  Boussingault  found  the  seeds  of  trefoil 
increased  in  weight  2i  times,  and  wheat  gave  plants  equal  in  weight, 
when  dry,  to  twice  that  of  the  original  grains,  [Ann.  de  Chim.  etde  Phys. 
Ixvii.,  p.  1.]  The  source  of  the  carbon  in  all  these  cases  cannot  be 
doubted. 

4°.  When  lands 4ire  impoverished,  you  lay  them  down  to  grass,  and 
the  longer  they  lie  undisturbed  the  richer  in  vegetable  matter  does  the 
soil  become.  When  broken  up,  you  find  a  black  fertile  mould  where 
little  trace  of  organic  matter  had  previously  existed. 

The  same  observation  applies  to  lands  long  under  wood.  The  vege- 
table matter  increases,  the  soil  improves,  and  when  cleared  and  plough- 
ed it  yields  abundant  crops  of  corn. 

Do  grasses  and  trees  derive  their  carbon  from  the  soil  ?  Then,  how, 
by  their  growth,  do  they  increase  the  quantity  of  carbonaceous  matter 
which  the  soil  contains  ?  It  is  obvious  that,  taken  as  a  whole,  they 
must  draw  from  the  air  not  only  as  much  as  is  contained  in  their  own 
substance,  but  an  excess  also,  which  they  impart  to  the  soil. 

5°.  But  on  this  point  the  rapid  growth  of  peat  may  be  considered  as 
absolutely  conclusive.  A  tree  falls  across  a  little  running  stream,  dams 
up  the  water,  and  produces  a  marshy  spot.  Rushes  and  reeds  spring 
up,  mosses  take  root  and  grow.  Year  after  year  new  shoots  are  sent 
forth,  and  the  old  plants  die.  Vegetable  matter  accumulates ;  a  bog, 
and  finally  a  thick  bed  of  peat  is  formed. 

Nor  does  this  peat  form  and  accumulate  at  the  expense  of  one  spe- 
cies or  genus  of  plants  only.  Latitude  and  local  situation  are  the  cir- 
cumstances which  chiefly  effect  this  accumulation  of  vegetable  matter 
on  the  soil.  In  our  own  country,  the  lowest  layers  of  peat  are  formed 
of  aquatic  plants,  the  next  of  mosses,  and  the  highest  of  heath.  In 
Terra  del  Fuego,  "  nearly  every  patch  of  level  ground  is  covered  by 
two  species  of  plants  (fl^feZm  pwmzZa  of  Brown,  and  donatia  magellan- 
ica)t  which,  by  their  joint  decay,  compose  a  thick  bed  of  elastic  peat." 
"  In  the  Falkland  Islands,  almost  every  kind  of  plant,  even  the  coarse 
grass  which  covers  the  whole  surface  of  the  island,  becomes  converted 
into  this  substance."* 

Whence  have  all  these  plants  derived  their  carbon  ?  The  quantity 
originally  contained  in  the  soil  is,  after  a  lapse  of  years,  increased  ten 
thousand  fold.  Has  dead  matter  the  power  of  reproducing  itself? 
You  will  answer  at  once,  that  all  these  plants  must  have  grown  at  the 
expense  of  the  air,  must  have  lived  on  the  carbon  it  was  capable  of  af- 
fording them,  and  as  they  died  must  have  left  this  carbon  in  a  state  un 
fit  to  nourish  the  succeediilg  races. 

This  reasoning  appears  unobjectionable,  and,  from  the  entire  group  of 
%cts,  we  seem  justified  in  concluding  that  plants  every  where,  ajid 
under  all  circumstances,  derive  the  whole  of  their  carbon  from  the  at- 
mosphere. 

'  Darwin's  Researches  in  Geology  and  Natural  History^  pp.  349-50.  Dr.  Gerville  informs 
me  that  the  astelia  approaches  more  nearly  te  the  junceae  or  rush  tribe^  and  the  donalia  to  our 
tufted  saxifrages,  than  to  any  other  British  ciiits. 


60  THE    VEGETABLE    MATTER    OF    THE    SOIL. 

In  certain  extreme  cases,  as  in  those  of  plants  growing  in  the  air  and 
in  soils  perfectly  void  of  organic  matter,  this  conclusion  must  be  abso 
lutely  true.  The  phenomena  admit  of  no  other  interpretation.  But  is 
it  as  strictly  true  of  the  more  usual  forms  of  vegetable  life,  or  in  the  or- 
dinary circumstances  in  which  plants  grow  spontaneously  or  are  culti- 
vated by  the  art  of  man  ?  Has  the  vegetable  matter  of  the  soil  no 
connection  with  the  growth  of  the  trees  or  herbage  ? — does  it  yield  them 
no  regular  supplies  of  nourishment  ?  Does  nature  every  where  form  a 
vegetable  mould  on  which  her  wild  flowers  may  blossom  and  her  pri- 
meval forests  raise  their  lofty  heads  ?  Has  the  agricultural  experience 
of  all  ages  and  of  all  countries  led  the  practical  farmer  to  imitate  nature 
in  preparing  such  a  soil  ?  Does  nature  work  in  vain  ? — is  all  this  ex- 
perience to  be  at  once  rejected  ? 

While  we  draw  conclusions,  legitimate  in  kind,  we  must  be  cautious 
how,  in  degree,  we  extend  them  beyond  our  premises. 

The  consideration  of  one  or  two  facts  will  shew  that  our  general  con- 
clusion must  either  be  modified  or  more  cautiously  expressed. 

1°.  It  is  true  that  plants  will,  in  certain  circumstances,  grow  in  a  soil 
containing  no  sensible  quantity  of  organic  matter — but  it  is  also  true, 
generally,  that  they  do  not  luxuriate  or  readily  ripen  their  seed  in  such  a 
soil. 

2°.  It  is  consistent  with  almost  universal  observation,  that  the  same 
soil  is  more  productive  when  organic  matter  is  present,  than  when  it  is 
wholly  absent. 

3°.  That  if  the  crop  be  carried  off  a  field,  less  organic  matter  is  left 
in  the  soil  than  it  contained  when  the  crop  began  to  grow,  and  that  by 
constant  cropping  the  soil  is  gradually  exhausted  of  organic  matter. 

Now  it  must  be  granted  that  tillage  alone,  without  cropping,  would 
gradually  lessen  the  amount  of  organic  matter  in  the  soil,  by  continually 
exposing  it  to  the  air  and  hastening  its  decay  and  resolution  into  gaseous 
substances,  which  escape  into  the  atmosphere.  But  two  years'  open 
fallow,  with  constant  stirring  of  the  land,  will  not  rob  it  of  vegetable 
matter  so  effectually  as  a  year  of  fallow  succeeded  by  a  crop  of  wheat. 
Some  of  the  vegetable  matter,  therefore,  which  the  soil  contained  when 
the  seed  was  sown,  must  be  carried  off  the  field  in  the  crop. 

The  conclusion  therefore  seems  to  be  reasonable  and  legitimate,  that 
the  crop  which  we  remove  from  a  field  has  not  derived  all  its  carbon  di- 
rectly from  the  air — but  has  extracted  a  portion  of  it  immediately  from 
the  soil.  It  is  to  supply  this  supposed  loss,  that  the  practical  farmer 
finds  it  necessary  to  restore  to  the  land  in  the  form  of  manure — among 
other  substances — the  carbon  also  of  which  the  straw  or  hay  had  robbed 
the  soil. 

But  how  is  this  reconcileable  with  our  previous  conclusion,  that  the 
whole  of  the  carbon  is  derived  from  the  air  ?  The  difficulty  Ls  of  easy 
solution. 

A  seed  germinates  in  a  soil  in  which  no  vegetable  matter  exists;  it 
sprouts  vigorously,  increases  then  slowly,  grows  languidly  at  the  expense 
of  the  air,  and. the  plant  dies  stunted  or  immature.  But  in  dying  it  im- 
parts vegetable  matter  to  the  soil,  on  which  the  next  seed  thrives  better 
—drawing  support  not  only  from  the  air,  but  b3^  its  roots  from  the  soU 
also.     The  death  of  this  second  plant  enriches  tk;  soil  further,  and  thus, 


HOW    THE    VEGETABLE    MATTER    INCREASES.  61 

while  each  succeeding  plant  is  partly  nourished  by  food  from  the  earth, 
yet  each,  when  it  ceases  to  live,  imparts  to  the  soil  all  the  carbon  which 
during  its  life  it  has  extracted  from  the  air.  Let  the  quantity  which 
each  plant  thus  returns  to  the  soil,  exceed  what  it  has  drawn  from  it  by 
only  one  ten-thousandth  of  the  whole,  and — unless  other  causes  inter- 
vene— the  vegetable  matter  in  the  soil  must  increase. 

Thus  while  it  is  strictly  true  that  the  carbon  contained  in  all  plants 
has  been  originally  derived  from  the  air,  it  is  not  true  that  the  ivhole  of 
what  is  contained  in  any  one  crop  we  raise,  is  directly  derived  from  the 
atmosphere — the  proportion  it  draws  from  the  soil  is  dependent  upon  nu- 
merous and  varied  circumstances. 

The  history  of  vegetable  growth,  therefore — in  so  far  at  least  as  the 
increase  of  the  carbon  is  concerned — may  be  thus  simply  stated  : 

1°.  A  plant  grows  partly  at  the  expense  of  the  soil,  and  partly  at  that 
of  the  air.  When  it  reaches  maturity,  or  when  winter  arrives,  it  dies. 
The  dead  vegetable  matter  decays,  a  part  of  it  is  resolved  into  gaseous 
matter  and  escapes  into  the  air,  a  part  remains  and  is  incorporated  with 
the  soil.  If  that  which  remains  be  greater  in  quantity  than  that  which 
the  plant  in  growing  derived  from  the  soil,  the  vegetable  matter  will  in- 
crease; if  less,  it  will  diminish. 

2°.  In  warm  climates  the  decay  of  dead  vegetable  matter  is  more 
rapid,  and,  therefore,  the  portion  left  in  the  soil  will  be  less  than  in 
more  temperate  regions — in  other  words,  the  vegetable  matter  in  the 
soil  will  increase  less  rapidly — it  may  not  increase  at  all. 

3°.  As  we  advance  intocolder  countries,  the  decay  and  disappearance 
of  dead  vegetable  matter,  in  the  form  ofgaseous  substances  which  escape 
into  the  atmosphere,  become  more  slow — till  at  length,  between  the  par- 
allels of  40°  and  45°,  it  begins  to  accumulate  in  vast  quantities  in  favour- 
able situations,  forming  peat  bogs  of  greater  or  less  extent.  While  the 
living  plant  here,  as  in  warm  climates,  derives  carbon  both  from  the 
earth  and  from  the  air,  the  dead  plant,  during  its  slow  and  partial  decay, 
restores  little  to  the  atmosphere,  and  therefore  adds  rapidly  to  the  vege- 
table matter  of  the  soil. 

4°.  Again,  in  one  and  the  same  climate,  the  decay  of  vegetable  mat- 
ter, and  its  conversion  into  gaseous  substances,  is  more  rapid  in  propor- 
tion to  the  frecjuency  with  which  it  is  disturbed  or  exposed  to  the  action 
of  the  sun  and  air.  Hence  this  decay  may  be  comparatively  slow  in 
shady  woods  and  in  fields  covered  by  a  thick  sward  of  grass ;  and  in  such 
situations  organic  matter  may  accumulate,  while  it  rapidly  diminishes 
in  an  uncovered  soil,  or  in  fields  repeatedly  ploughed  and  subjected  to 
frequent  cropping.* 

Being  thus  fitted,  by  nature,  to  draw  their  sustenance — now  from  the 
earth,  now  from  the  air,  and  now  from  both,  according  as  they  can  most 
readily  obtain  it — plants  are  capable  of  living, — though  rarely  a  robust 
life, — at  the  expense  of  either.  The  proportion  of  their  food  which  they 
actually  derive  from  each  source,  will  depend  upon  many  circumstan- 
ces— on  the  nature  of  the  plant  itself — on  the  period  of  its  growth — on 
the  soil  in  which  it  is  planted — on  the  abundance  of  food  presented  to 

•  In  removing  a  crop  we  take  away  both  what  the  plants  have  received  from  the  earth  and 
what  they  have  absorbed  from  the  air— the  materials,  in  short,  intended  by  nature  to  restore 
the  loss  of  vegetable  matter  arising  from  the  natural  decay. 


62         PLANTS  PARTLY  SUPPORTED  BY  THE  AIR  Ax\D  BY  THE  SOIL. 

cither  extremity — on  the  warmth  and  moisture  of  the  climate — on  the  du- 
ration and  intensity  of  the  sunshine,  and  other  circumstances  of  a  similar 
kind — so  that  the  only  general  law  seems  to  be,  that,  like  animals,  plants 
have  also  the  power  of  adapting  themselves,  to  a  certain  extent,  to  the 
conditions  in  which  they  are  placed  ;  and  of  supporting  life  by  the  aid  of 
such  sustenance  as  may  be  within  their  reach. 

Such  a  view  of  the  course  of  nature  in  the  vegetable  kingdom,  is  con- 
sistent, I  believe,  with  all  known  facts.  And  that  the  Deity  has  bounti- 
fully fitted  the  various  orders  of  plants — with  which  the  surface  of  the 
earth  is  at  once  beautified  and  rendered  capable  of  supporting  animal 
life — to  draw  their  nourishment,  in  some  spots  more  from  the  air,  in  oth- 
ers more  from  the  soil,  is  only  in  accordance  witli  the  numerous  provisions 
we  everywhere  perceive,  for  the  preservation  and  continuance  of  the 
present  condition  of  things. 

By  taking  a  one-sided  view  of  nature,  we  may  arrive  at  startling 
conclusions — correct,  if  taken  as  partial  truths,  yet  false,  if  advanced  as 
general  propositions — and  fitted  to  lead  into  error,  such  as  have  not  the 
requisite  knowledge  to  enable  them  to  judge  for  themselves — or  such  as, 
doubtful  of  their  own  judgment,  are  willing  to  yield  assent  to  the  author- 
ity of  a  name. 

Of  this  kind  appears,  at  first  sight,  to  be  the  statement  of  Liebig,  that 
"when  a  plant  is  quite  matured,  and  when  the  organs  by  which  it  ob- 
tains food  from  the  atmosphere  are  formed,  the  carbonic  acid  of  the  soil 
is  no  further  required" — and  that,  "during  the  heat  of  summer  it  derives 
its  carbon  exclusively  from  the  atmosphere." — [Organic  Chemistry  ap- 
plied to  Agriculture,  p.  48.] 

A  little  consideration  will  shew  us  that,  while  the  proposition  contained 
in  the  former  quotation  may  be  entertained  and  advanced  as  a  matter  of 
opinion — the  latter  is  obviously  incorrect.  In  summer,  when  the  sun 
shines  the  brightest,  and  for  the  greatest  number  of  hours,  the  evapora- 
tion from  the  leaves  of  all  plants  (their  insensible  perspiration)  is  the 
greatest — the  largest  supply  of  water,  therefore,  must  at  this  season  be 
absorbed  by  the  roots,  and  transmitted  upwards  to  the  leaves. — [Lindley's 
Theory  of  Horticulture,  p.  46.] — Butthis  water,  before  it  enters  the  roots, 
has  derived  carbonic  acid  and  other  soluble  substances  from  the  air  and 
from  the  soil,  in  as  large  quantity  at  this  period  as  at  any  other  during 
the  growth  of  the  plant ;  and  these  substances  it  will  carry  with  it  in  its 
progress  through  the  roots  and  the  stem. 

Are  the  functions  of  tlie  root  changed  at  this  stage  of  the  plants' 
growth  ?  Do  they  now  absorb  pure  water  only,  carefully  separating  and 
refusing  to  admit  even  such  substances  as  are  he\d  m  solution?  Or 
do  the  same  materials  which  minister  to  the  growth  of  the  plant  in  its 
earlier  stages,  now  pass  upwards  to  the  leaf  and  return  again  in  the 
course  of  the  circulation  unchanged  and  unemployed,  to  be  again  re- 
jected at  the  roots  ?  Does  all  this  take  place  in  the  height  of  summer, 
while  tlie  plant  is  still  rapidly  increasing  in  size  ?  The  opinion  is  nei- 
ther supported  by  facts  nor  consistent  with  analogy. 

But  such  an  opinion, — however  the  words  above  quoted  may  mislead 
some, — is  not  intended  to  be  advanced  by  Liebig;  for,  in  the  following 
j)age  he  says,  that  "the  power  which  roots  possess  of  taking  up  nourish- 
ment does  not  cease  so  long  as  nutriment  is  present."     In  summer, 


LEAVES    AND    ROOTS    ABSORB    CARBONIC    ACID.  63 

therefore,  as  well  as  in  spring  or  in  autumn,  the  plant  must  be  ever  ab- 
sorbing nourishment  by  these  roots,  if  the  soil  is  capable  of  affording  it — 
and  thus,  in  the  general  vegetation  of  the  globe,  the  increase  of  carbon 
in  growing  plants  must,  at  every  season  of  the  year,  be  partly  derived 
from  the  vegetable  matter  of  the  soil  in  which  they  grow. 

§  2.  Form  in  which  carbon  enters  into  the  circulation  of  plants. 

Supposing  it  to  be  established  that  the  whole  of  the  carbon  contained 
in  plants  has  originally  been  derived  from  the  air — we  have  only  to  in- 
(juire  in  what  state  .this  element  exists  in  the  atmosphere,  in  order  to 
satisfv  ourselves  as  to  the  form  of  combination  in  which  it  is  and  has 
been  received  into  the  circulation  of  plants.  In  considering  the  consti- 
tution of  the  atmosphere  in  the  jjreceding  lecture,  it  was  stated  that  car- 
bonic acid,  a  compound  of  carbon  and  oxygen,  is  always  present  in  it — 
and  that,  though  this  gas  is  ditFused  through  the  air  in  comparatively 
small  quantity  only,  yet  it  is  everywhere  to  be  detected, — while  no 
other  compound  of  carbon  is  to  be  found  in  it  u)  any  appreciable  quanti- 
ty. We  must  conclude,  therefore,  that  from  this  gaseous  carbonic  acid 
tiie  whole  of  the  carbon  contained  in  j)lants  has  been  primarily  derived. 
This  conclusion  is  confirmed  by  the  observation  so  frequently  made, 
that  the  leaves  of  plants  in  sunshine  absorb  carbonic  acid,  and  that 
plants  die  in  an  atmosphere  from  which  this  gas  is  entirely  excluded. 

But  we  have  seen  reason  to  believe  that,  under  existing  circumstan- 
ces, plants  also  extract  a  portion  of  the  carbon  they  contain  from  the 
soil  in  which  they  grow.  In  what  state  or  form  of  combination  do  the 
roots  absorb  carbon  ? 

The  most  abundant  product  of  the  decay  of  vegetable  matter  in  the 
soil,  is  the  same  carbonic  acid  which  ]ilants  inhale  so  largely  from  the 
atmosphere  by  their  leaves.  In  a  soil  replete  with  vegetable  matter, 
therefore,  the  roots  are  surrounded  by  an  atmosphere  more  or  less 
charged  with  carbonic  acid.  Hence  if  they  are  capable  of  inhaling 
gaseous  substances,  this  gas  will  enter  the  roots  in  the  aeriform  state — if 
not,  it  must  enter  in  solution  in  the  water,  wiiich  the  roots  drink  in  so 
largely,  to  supply  the  constant  waste  caused  by  the  insensible  perspira- 
tion of  the  leaves. 

During  the  early  fermentation  of  artificial  manures  there  is  also  de- 
veloped in  the  soil  a  variable  proportion  of  light  carburetted  hydrogen 
(Lecture  III.,  p.  49),  which  is  supposed  by  some  to  enter  occasionally 
into  the  roots.  That  it  does  enter,  however,  is  doubtful, — and  we  are 
safe,  I  think,  in  considering  this  conipound  not  only  as  an  uncertain 
source  of  the  carbon  of  plants,  but  as  one  from  which,  in  the  most  fa- 
vourable circumstances,  they  can  derive  only  a  small  supply. 

Thus,  from  the  eartli  as  from  the  air,  the  most  unfailing  supply  of  food 
is  the  gaseous  carbonic  acid. 

But  as  the  water  passes  through  the  soil  it  takes  up  inorganic  substan- 
ces— potash,  soda,  lime,  magnesia — and  conveys  them  through  the  roots 
into  the  circulation  of  the  plants.  Can  it  refuse  to  take  up  and  to  perform 
a  similar  office  to  the  soluble  organic  substances  it  meets  with,  as  it  sinks 
through  the  soil  ?  Or  do  the  spongioles  of  the  roots  keep  a  perpetual 
watch  over  the  entering  waters,  to  prevent  the  inJ:^rod action  of  every  so- 
luble form  of  carboa  but  that  of  carbonic  acic!     Or,  supposing  such 

4 


64  ROOTS    ABSORB    ORGANIC    SUBSTANCES    ALSO 

substances  introduced  into  the  interior  of  the  plant,  are  none  of  them 
digested  there  and  converted  to  the  general  purposes  of  food  ?  A  state- 
ment of  two  or  three  facts  will  afford  a  satisfactory  reply  to  these  several 
questions. 

1°.  "When  plants  are  made  to  grow  in  infusions  of  madder  the  radicle 
fibres  are  tinged  of  a  red  colour. 

2^.  The  flower  of  a  white  hyacinth  becomes  red  after  a  few  hours, 
when  the  earth  in  which  it  is  planted  is  sprinkled  with  the  juice  of  the 
jphytolaca  decandra  (Biol). 

Therefore  organic  substances  can  enter  into  the  roots,  and  thence  into 
the  circulation,  of  the  plant. 

3°.  The  colour  of  the  madder  does  not  usually  extend  upwards  to 
the  leaves  and  flowers  of  the  plant. 

4°.  The  colour  imparted  to  the  flower  of  the  white  hyacinth  disap- 
pears in  the  sunshine  in  the  course  of  a  few  days. 

Organic  colouring  mattenrs,  therefore,  undergo  a  chemical  change  either 
in  the  stem,  in  the  leaf,  or  in  the  flower — some  sooner,  some  later — and 
the  same  is  probably  the  case  with  most  other  organic  substances  which 
gain  admission  into  tlie  interior  of  plants. 

5°.  Sir  Humphry  Davy  introduced  plants  of  mint  into  weak  solutions 
of  sugar,  gum,  jelly,  the  tanning  principle,  &c.,  and  found  that  they 
grew  vigorously  in  all  oi^  them.  He  then  watered  separate  spots  of  grass 
with  the  same  several  solutions,  and  with  common  water,  and  found  all 
to  thrive  more  than  that  to  which  common  water  was  applied — while 
those  treated  with  sugar,  gum,  and  gelatine  grew  luxuriantly. — [Davy's 
Agricultural  Chemistry,  Lecture  VI.] 

Therefore  dilTerent  organic  substances — being  introduced  into  the  cir 
culation  and  there  changed — are  converted  by  plants  into  their  own  sub- 
stance, or.  act  as  food,  and  nourish  the  plant. 

We  may  consider  it,  therefore,  to  be  satisfactorily  established  that, 
while  a  plajit  sucks  in  by  its  leaves  and  roots  much  carbon  in  the  form  of 
carbonic  acid,  it  derives  a  variable  portion  of  its  immediate  sustenance 
(of  its  carbon)  from  the  soluble  organic  substances  that  are  within  reach 
of  its  roots. 

This  fact  is  never  doubted  by  the  practical  husbandman.  It  forms 
the  basis  of  many  of  his  daily  and  most  important  operations,  while 
the  results  of  these  operations  are  further  proofs  of  the  fact. 

The  nature  of  the  soluble  substances  which  are  formed  during  the  de- 
cay of  animal  and  vegetable  substances — and  which  the  roots  of  plants 
are  supposed  to  take  up — will  be  considered  in  a  subsequent  lecture.* 

§  3.  Source  of  the  hydrogen  of  plants. 

The  source  of  the  hydrogen  of  plants  is  less  doubtful,  and  will  re- 
quire less  illustration,  than  the  source  of  the  carbon.  This  elementary 
substance  is  not  known  to  exist  in  nature  in  an  uncombined  state,  and, 
therefore,  it  must,  like  carbon,  enter  into  plants  in  union  with  some  other 
element. 

1°.  Water  has  been  already  shewn  to  consist  of  hydrogen  In  combina- 

•  Thia  part  of  the  subject  might  have  been  discussed  here  without  appearing  out  of  place 
—but  it  will  come  in  more  appropriately,  I  think,  when  treating  of  the  nature  and  mode  of 
aiJtion  of  vegetable  manurea. 


SOURCE  OF  THE  HYDROGEN  OF  PLANTS.  65 

tion  with  oxygen.  In  the  form  of  vapour,  this  compound  pervades  the 
atmosphere,  and  plays  among  the  leaves  of  plants,  while  in  the  liquid 
state  it  is  diffused  through  the  soil,  and  is  unceasingly  drunk  in  by  the 
roots  of  all  living  vegetables.  In  the  interior  of  plants — at  least  during 
their  growth — this  water  is  continually  undergoing  decomposition,  and 
it  is  unquestionably  the  chief  source  of  the  hydrogen  which  enters  into 
the  constitution  of  their  several  parts.  In  explaining  the  properties  of 
water  I  have  already  dwelt  upon  the  apparent  facility  with  which  its 
elements  are  capable  either  of  separating  from,  or  of  re-uniting  to,  each 
other,  in  the  vascular  system  of  animals  or  of  plants.  The  reason  and 
precise  results  of  these  transformations  we  shall  hereafter  consider. 

2°.  In  light  carburetted  hydrogen  (CH2),  given  off  as  already  stated 
during  the  decay  of  vegetable  matter,  and  said  to  be  always  present  in 
highly  manured  soils,  this  element,  hydrogen,  exists  to  the  amount  of 
nearly  one-fourth  of  its  weight.  On  the  extent,  therefore,  to  which  this 
gaseous  compound  gains  admission  into  the  roots  of  plants,  will  de- 
pend the  supply  of  hydrogen  which  they  are  capable  of  drawing  from 
this  source.  Had  we  satisfactory  evidence  of  the  actual  absorption  of 
this  (marsh)  gas  by  the  roots  or  leaves  of  plants,  in  any  quantity,  we 
should  have  no  difficulty  in  admitting  that  plants  might,  from  this  source, 
easily  obtain  a  considerable  supply  both  of  carbon  and  of  hydrogen.  It 
would  be  also  easy  to  explain  how  (that  is,  by  what  chemical  changes,) 
it  is  capable  of  being  so  appropriated.  But  the  extent  to  which  it  really 
acts  as  food  to  living  vegetables  is  entirely  unknown. 

3°.  Ammonia  is  another  compound,  containing  much  hydrogen,  [its 
formula  being  NH^,  or  one  equivalent  of  nitrogen  and  three  of  hydro- 
gen,] which,  as  I  have  already  stated,  exercises  a  manifest  influence  on 
the  growth  of  plants.  If  this  substance  enter  into  their  circulation  in 
any  sensible  quantity, — if,  as  some  maintain,  it  be  not  only  universally 
diffused  throughout  nature,  but  is  constantly  affecting,  and  influencing  at 
all  times,  the  universal  functions  of  vegetation — there  can  be  no  doubt 
that  the  hydrogen  it  contains  must,  to  an  equal  extent,  be  concerned  in 
the  production  of  the  various  organic  substances  which  are  formed  or 
elaborated  by  the  agency  of  vegetable  life.  How  far  this  probable  in- 
terference of  the  hydrogen  of  ammonia  with  the  functions  of  the  vegeta- 
ble organs,  will  tend  to  explain  or  illustrate  the  influence  actually  exert- 
ed by  this  compound,  we  shall,  by  and  by,  more  accurately  inquire.  In 
the  mean  time,  the  quantity  of  ammonia,  which  actually  enters  into  the 
circulation  of  plants  in  a  state  of.nature,  is  too  little  known,  and  making 
the  largest  allowance,  probably  too  minute,  to  permit  us  to  consider  it  as 
an  important  source  of  hydrogen  to  the  general  vegetation  of  the  globe. 

4°.  The  soluble  organic  substances,  which  enter  into  the  circulation 
of  plants  through  the  roots,  as  shewn  in  the  preceding  section,  do  not 
consist  of  carbon  and  water  only,  but  of  combinations  of  carbon  with 
hydrogen  and  oxygen  in  various  proportions.  From  these  substances, 
therefore,  plants  derive  an  uncertain  and  indefinite  supply  of  hydrogen 
in  a  state  already  half-organized,  and  probably  still  more  easily  assimi- 
lated or  converted  into  portions  of  their  own  substance,  than  when  this 
element  is  combined  with  oxygen  in  the  form  of  water. 

We  may,  therefore,  conclude  generally  in  regard  to  the  source  of  the 
hydrogen  of  plants — that  though  there  are  undoubtedly  several  other 


66  SOURCE  OF  THE  OXYGEN  AND    NITROGEN. 

forms  of  combination  in  which  this  element  may  enter  into  their  circula- 
tion, in  uncertain  quantity — yet  that  all-pervading  water  is  the  main 
and  constant  source  from  which  the  hydrogen  of  vegetable  substances  is 
derived. 

§  4.  Source  of  the  oxygen  of  plants. 

We  can  at  once  perceive,  and  without  difficulty,  the  various  sources 
of  the  oxygen  of  plants  ;  though  it  is  difficult  in  this  case  also  to  say 
how  much  they  derive  from  each. 

1°.  The  water  which  they  imbibe  so  largely  consists  in  great  part  of 
oxygen,  and  is  easily  decomposed,  [eight-ninths  of  the  weight  of  water 
are  oxygen.]     This  alone  would  yield  an  inexhaustible  supply. 

2°.  The  atmosphere  contains  21  per  cent,  of  its  bulk  of  oxygen,  and 
the  leaves  of  plants  in  certain  circumstances  are  known  to  absorb  this 
oxygen.  The  air  in  which  they  live,  therefore,  might  be  another 
source. 

3°.  Carbonic  acid  contains  72  per  cent,  by  weight  of  oxygen,  and 
this  gas  is  also  known  to  be  absorbed  in  large  quantity  from  the  atmos- 
phere by  the  leaves  of  plants — while  its  solution  in  water  is  admitted 
readily  by  the  roots. 

From  any  one  of  these  sources  an  ample  supply  of  oxygen  might 
readily  be  obtained,  and  it  may  be  considered  as  a  proof  of  the  vast  im- 
portance of  this  element  to  the  maintenance  of  animal  and  vegetable 
life,  that  it  is  everywhere  placed  so  abundantly  within  the  reach  of 
living  beings.  It  is  from  the  first  of  these  sources,  however,  from  the 
water  they  contain,  that  plants  are  believed  to  derive  their  principal 
supply.  The  reasons  on  which  this  opinion  is  founded  will  appear 
when  we  shall  have  considered  the  functions  of  the  several  parts  of 
plants,  and  die  chemical  changes  to  which  the  food  is  subjected  in  the 
course  of  the  vegetable  circulation. 

§  5.  Source  of  the  nitrogen  of  plants. 

The  quantity  of  nitrogen  present  in  plants  is  very  small,  compared 
with  that  of  any  of  the  other  elements  which  enter  into  their  constitu- 
tion. Of  this  you  will  be  reminded,  by  a  reference  to  the  analyses  of 
hay,  oats,  and  potatoes,  exhibited  in  the  second  lecture  (page  30),  which 
shew  that  the  nitrogen  contained  in  these  several  crops,  when  perfectly 
dried  at  240°  F.,  is  respectively  1^,  2^,  and  1^  per  cent.  In  the  state 
in  which  they  are  usually  given  to  cattle  they  contain  a  still  less  per 
centage  of  nitrogen,  in  consequence  of  the  quantity  of  water  still  present 
in  them.  Thus  raw  potatoes  as  they  are  given  to  cattle  contain  only  i 
of  a  per  cent,  of  nitrogen,  hay  1^  per  cent.,  and  oats  ly^,^*  per  cent.,  or  a 
hundred  pounds  of  each  contain  5  ounces,  3  pound  5  ounces,  and  1  pound 
14  ounces  respectively. 

It  would  appear  at  first  sight  as  if  this  small  quantity  of  nitrogen 
could  be  of  little  importance  to  the  plant,  especially  since,  as  we  shall 
hereafter  see,  it  does  not  enter  as  a  constituent  into  those  vegetable  sub- 
stances, such  as  woody  fibre,  starch,  sugar,  and  gum,  which  plants  pro- 
duce in  the  greatest  abundance,  and    of  which  their  own  stems  and 

*  0-33, 1-29,  and  1  87  per  cent,  —the  potatoes  containing  also  72  per  cent,  of  water,  the  hay 
14,  and  the  oats  15  per  cent. 


QUANTITY    OF   NITROGEN       JN    PLANTS.  67 

branches  chiefly  consist.  The  same  remark,  however,  applies  to  this, 
as  to  many  other  cases  which  present  themselves  to  the  chemist,  during 
his  analyses,  especially  of  organized  substances, — that  those  elements 
which  are  present  only  in  small  quantity  are  as  necessary — as  essential 
— to  the  constitution  of  the  particular  substance  in  which  they  occur,  as 
other  elements  are  of  which  they  contain  much  ;  and  that  if  these  small 
(juantities  are  removed  or  absent,  not  only  are  the  physical  and  chemi- 
cal properties  of  the  substance  materially  altered,  but  it  is  found  also  to 
exercise  a  very  different  influence  on  animal  and  vegetable  life.  This 
latter  observation  will  present  itselfto  you  in  a  very  striking  light,  when 
we  come  hereafter  to  study  the  nutritive  properties  of  the  several  kinds 
of  food  by  which  animals  are  chiefly  suj^ported, — and  shall  «ee  on  what 
elementary  body  their  relative  nutritive  properties  depend,  or  by  the 
amount  of  which  their  relative  value  appears  at  least  to  be  indicated. 

But  a  consideration  of  the  absolute  quantity  of  nitrogen  contained  in 
an  entire  crop  will  satisfy  you  that  though  small  in  comparative  amount, 
[that  is,  compared  with  the  carbon  and  oxygen  which  plants  contain,] 
this  element  cannot  he  without  its  due  share  of  importance  in  reference 
to  vegetable  life.  Hay,  as  above  stated,  contains,  as  it  is  stacked,  1^* 
per  cent,  of  nitrogen,  or  a  ton  of  hay  contains  30  lbs.  of  this  element.  A 
good  crop  of  hay,  on  land  which  is  depastured  during  the  winter,  will 
amount  to  2  or  2h  tonsf  per  acre.  Taking  2  tons  as  an  average,  the  hay 
from  one  acre  will  contain  60  lbs.  of  nitrogen,  or  from  100  acres  6000  lbs., 
equal  to  2|  tons  of  nitrogen. 

Allowing,  therefore,  nothing  for  the  aftermath,  and  supposing  the 
other  crops  to  contain  no  more  nitrogen  than  the  hay  does,  the  farmer  of 
five  hundred  acres  will  annually  carry  into  his  stack-yard  at  least  13 
tons  of  nitrogen  in  the  form  of  hay,  straw,  grain,  and  other  produce,  t 

Nature  performs  all  her  operations  on  a  large  scale,  and  the  quantity 
of  materials  she  employs  are  large  in  a  corresponding  degree.  Hence, 
though  comparatively  small,  the  nitrogen  in  vegetable  substances  is  ab- 
solutely large.  You  cannot  suppose,  when  viewed  in  this  light,  that 
nitrogen  is  an  element  of  little  consequence  in  reference  to  vegetable 
life  ;  or  that  in  nature  it  should  be  so  constantly  and  universally  dif- 
fused without  reference  to  some  important  end.  If  I  may  be  allowed  a 
familiar  illustration  of  the  mode  in  which  small  quantities  of  matter  will 
affect  the  sensible  properties  of  large  masses,  I  would  recall  to  your 
minds  the  effects  of  seasoning  upon  food,  in  imparting,  when  added  in 
small  quantity  only,  an  agreeable  relish  to  what  would  otherwise  be 

*  In  different  crops  of  hay  Boussingault  found  in  three  several  years  the  following  pro- 
portions of  nitrogen : — 

Hay,  as  commonly  Hay  dried  at 

stacked.  260°  F. 

In  1836  118  1-04  of  nitrogen  per  cent. 

"  1833  1.3  115  «  " 

"  1839  15  1-3  »  " 

Aftermath  24  2  0  "  " 

1  The  Rev.  Mr.  Ogle,  of  Kirkley,  Northumberland,  informs  me  that  some  of  his  land 
near  the  Hall  has  yielded  annually  at  this  rate  for  100  years,  and  without  other  manure  than 
the  droppings  from  the  cattle  which  have  fed  upon  it. 

X  This  average  estimate  gives  but  an  inaccurate  idea  of  the  quantity  actually  contained 
in  some  species  of  crops.  Thus  red  clover  with  the  aid  of  gypsum  will  yield  3  tons  of  hay 
per  acre.  This  hay  contains  more  than  twice  the  quantity  of  nitrogen  (Boussingault)  that 
common  hay  does,  hence  an  acre  of  such  hay  would  contain  at  least  180  lbs.  of  nitrogen. 
(See  Lecture  II.,  p.  30.) 


68  THE  ATMOSPHERE    THE    PRIMARY    SOURCE  OF  NITROGEN. 

insipid.  But  I  need  not  dwell  on  this  point,  since  I  shall  hereafter  lave 
occasion  to  draw  your  attention  to  certain  facts  in  reference  to  the  con- 
stitution of  the  atmosphere,  which  will  satisfy  you  that,  by  the  agency 
of  comparatively  feeble  causes,  gigantic  effects  are  continually  produced 
in  nature, — and  that  we  can  scarcely  fall  into  a  graver  error  in  reason- 
ing of  natural  processes,  than  by  overlooking  the  agency  of  forms  of  mat- 
ter which  present  themselves  to  our  senses  in  minute  quantity  only.  In 
reference  to  insect  life  this  truth  has  been  long  established.^  In  the  coral 
reefs  you  are  familiar  with  the  wonderful  results  of  the  persevering  la- 
bour of  minute  animals  in  one  element.  When  I  come  to  explain  the 
nature  and  origin  of  soils,  I  shall  have  occasion  to  show  that  even  the 
element  on  which  you  labour — the  earth,  on  the  cultivation  of  which 
your  thoughts  and  hands  are  daily  employed — is  occasionally  indebted 
for  some  of  its  most  valuable  properties  to  a  similar  agency,  often  un- 
seen by  you,  and  though  working  for  your  good,  unheeded  and  un- 
thought  of. 

Whence,  then,  is  this  nitrogen  derived  by  plants  ?  The  primary 
source  it  is  not  ditficult  to  see.  We  can  arrive  at  it  by  a  train  of  reason- 
ing similar  to  that  which  led  us.  to  the  atmosphere  as  the  original  source 
of  the  carbon  of  plants.  Nitrogen  does  not  constitute  an  ingredient  of  any 
of  the  solid  rocks,*  nor  do  we  know  any  other  source  than  the  atmosphere 
from  which  it  can  be  obtained  in  very  large  quantity.  It  exists,  as  we 
have  seen,  in  many  vegetables,  and  it  is  more  largely  present  in  animal 
substances,  but  these  organized  matters  must  themselves  have  drawn 
this  element  from  a  foreign  source,  and  the  atmosphere  is  the  only  one 
from  which  we  can  fairly  assume  it  to  have  been  originally  derived. 

But  though  the  nitrogen,  like  the  carbon  of  plants,  may  thus  be  traced 
to  the  atmosphere — as  its  orginal  source — it  does  not  follow  that  this 
element  is  either  absorbed  directly  from  the  air,  or,  in  an  uncombined 
and  gaseous  state.  Though  the  leaves  of  trees  and  herbs  are  continually 
surrounded  by  nitrogen,  the  constitution  of  plants  may  be  unfitted  for 
absorbing  it  by  their  leaves.  The  nitrogen  may  not  only  require  to  be 
in  a  state  of  combination  before  it  can  enter  into  the  circulation,  but  it 
may  also  be  capable  of  gaining  admission  only  by  the  roots.  These 
points  are  considered  in  the  following  section. 

§  6.  Form  in  which  the  nitrogen  enters  into  the  circulation  of  plants. 

The  question  as  to  the  form  in  which  nitrogen  enters  into  the  circula- 
tion of  plants  is  one  which  at  the  present  moment  engages  much  attention. 
It  will  be  proper,  therefore,  to  discuss  it  with  considerable  care. 

1°.  It  is  considered  an  essential  part  of  good  tillage  to  break  up  and 
loosen  the  soil,  in  order  that  the  air  may  have  access  to  the  dead  vege- 
table matter,  as  well  as  to  the  living  roots  which  descend  to  considerable 
depths  beneath  the  surface.  When  thus  admitted  to  the  roots,  it  is  j*rf. 
possible  that  some  of  the  nitrogen  of  the  atmosphere,  as  well  as  some  of 
its  oxygen,  may  be  directly  absorbed  and  appropriated  by  the  plant. 
To  what  extent  this  absorption  of  nitrogen  may  proceed,  however,  we 

•  Except  coal,  and  coal  itself  is  of  vegetable  origin.  Throughout  all  rocks  in  which  or- 
pinic  remains  are  found,  more  or  less  animal  matter  containing  nitrogott  is  to  be  met  with, 
out  these  remains  are  only  accidentally  present,  and  they  must  have  derived  their  nitrogen 
during  life,  either  directly  or  indirectly,  from  the  atmosphere. 


RAIN  WATER  DISSOLVES   IT.  gg 

have  as  yet  no  experimental  results  from  whicli  we  can  form  any  esti- 
mate. Whether  it  lakes  place  at  all  or  not,  is  wholly  a  matter  of  opinion. 

2°.  The  leaves  ofplants,  as  will  be  more  fully  explained  hereafter,  absorb 
certain  gaseous  substances  from  the  atmosphere,  and  we  might,  therefore, 
expect  that  some  of  the  nitrogen  of  the  air  would,  by  this  channel,  be 
admitted  into  their  circulation.  This  view,  however,  is  not  confirmed 
by  any  of  the  experiments  hitherto  made  with  the  view  of  investigating 
the  action  and  functions  of  the  leaves.*  We  are  not  at  liberty,  there- 
fore, to  assume  that  any  of  the  nitrogen  which  plants  contain  has  in  this 
way  been  derived  directly  from  the  air.  It  may  be  the  case  ;  but  it  is 
not  yet  proved. 

3°.  There  is  little  doubt,  however,  that  nitrogen  enters  the  roots  of 
plants  in  a  state  of  solution.  But  the  quantity  they  thus  absorb  is  un- 
certain— it  is  supposed  to  be  small,  and  must  be  variable. 

When  water  is  exposed  to  the  air  in  an  open  vessel  it  gradually  ab- 
sorbs oxygen  and  nitrogen,  though,  as  has  been  stated  in  a  previous  lec- 
ture, in  proportions  different  from  those  in  which  they  exist  in  the  atmos- 
phere. Tlie  whole  (juantity  of  the  mixed  gases  thus  taken  up  amounts 
to  about  4  per  cent,  of  the  bulk  of  the  water  (Humboldt  and  Gay-Lus- 
sac),  and  in  rain  water  about  |  of  the  whole  consist  of  nitrogen.  One 
hundred  cubic  inches  of  rain  water,  therefore,  will  carry  into  the  soil 
about  2|  inches  of  nitrogen  gas.  But  in  passing  through  the  soil,  the 
water  meets  with  other  soluble  substances  before  it  reaches  the  roots, 
especially  the  deep-seated  roots  of  plants.  It  takes  up  carbonic  acid, 
and  it  dissolves  solid  substances,  and  in  doing  so  it  is  a  property  of  water 
to  give  off  a  portion  of  the  other  gases  which  it  had  previously  absorbed 
from  the  air. 

But  let  us  suppose  that  rain  water  actually  takes  to  the  roots,  and  car- 
ries with  it  into  the  circulation  of  the  plant,  2  per  cent,  of  its  bulk  of 
nitrogen,  and  let  us  calculate  how  much  of  the  nitrogen  it  contains  a 
crop  of  hay  could  in  this  way  derive  from  the  air. 

*  See  subsequent  lecture  "  On  the  structure  and  functions  qftlie  several  parts  of  plants.^' 
Tlie  experiment.s  above  referred  to  were  made  upon  plants  growing  in  close  vessels,  the 
air  contained  in  which  was  measured  and  examineo  (analysed)  both  before  the  plants  were 
introduced  and  after  they  had  been  some  time  in  the  vessel.  In  these  expedments  the 
bulk  of  (he  nitrogen  present  has  sometimes  been  observed  to  increase,  but  never  to  dimin- 
ish^ in  quantity.  The  conclusion  seems  satisfactory,  that  no  nitrogen  is  abstracted  directly 
from  the  atmosphere  by  the  loaves  of  plants.  Yet  Boussingault^  very  justly  remarks,  that 
a  diminution  in  the  bulk  of  the  nitrogen  too  small  to  be  detected  in  the  ordinary  mode  of 
making  these  experiments,  would  be  sufficient  to  account  for  a  considerable  portion  of  tliat 
comparatively  s-raall  quantity  of  nitj"ogen  which  is  present  in  all  living  plants.  While,  there- 
fore, we  accord  their  due  weight  to  these  researches  of  the  vegetable  physiologists,  we  are 
not  to  consider  them  as  by  any  means  decisive  of  tjie  question.  With  this  rational  and  cau- 
tious conclusion,  Liebig  is  not  satisfied  ;  he  says,  "  We  have  not  the  slightest  reason  for  be- 
lieving that  the  nitrogen  of  the  atmosphere  takes  part  in  the  processes  of  assimilation  of  planta 
and  animals ;  on  the  contrary,  we  know  that  many  plants  emit  the  nitrogen  which  is  ab- 
sorbed by  their  roots  either  in  the  gaseous  form  or  in  solution  in  water."  (p.  70.)  But  if 
they  occasionally  expire  nitrogen  by  their  leaves  why  must  this  nitrogen  be  exactly  that 
portion  which  has  previously  been  absorbed  by  the  roots  in  the  uncombined  state,  aiid  the 
quantity  of  which  is  so  unceitain  and  so  indefinite? 

r*  Boussingault  details  a  series  of  experiments  in  the  course  of  which  he  made  peas,  tre- 
foil, wheat,  and  oats,  grow  in  the  same  pure  siliceous  sand  containing  no  organic  matter,  ana 
watered  them  with  the  same  distilled  water.  The  absolute  quantity  of  nitrogen  increased 
sensibly  in  the  peas  and  trefoil  during  their  growth  ;  in  the  wheat  and  oats  no  change  could 
be  detected  by  analysis.  From  these  results  he  is  inclined  to  infer  that  the  green  leaves  oi 
the  former  have  the  power  of  sensibly  absorbing  nitrogen  from  the  atmosphere,  while  those 
of  the  latter  have  not  this  power — at  least  under  the  circumstjuices  in  which  the  experi- 
ments were  made.  This  conclusion,  however,  is  not  certain^  as  will  presently  be  shewn.— 
See  Aim.  de  Chim.  el  de  Pkys.  Ixvii.  p.  1,  and  Ixix.  p.  353.] 
4 


70  ABSORPTION    OF   AMMONIA    BY    PLANTS. 

The  quantity  of  rain  that  falls  at  York  from  the  first  of  March  to  the 
middle  of  June — durin/];  which  time  the  grass  grows  and  generally  ri- 
pens— is  about  five  inches.*  On  a  square  foot,  therefore,  there  fall  720 
cubic  inches  of  water,  containing  2  per  cent,  of  their  bulk,  or  14  cubic 
inches  of  nitrogen,  weighing  4|  grains.  This  gives  28  lbs.  for  the  quan- 
tity of  nitrogen  thus  brought  to  the  soil  over  an  entire  acre.  But  if  we 
consider  how  the  rain  falls  in  our  climate,  we  cannot  suppose  the  grass 
in  a  field  to  absorb  by  its  roots,  and  afterwards  perspire  by  its  leaves, 
more  than  one-third  of  the  whole.  This  quantity  would  carry  with  it  9 
lbs.  of  nitrogen  into  the  circulation  of  the  plants — or  little  more  than  a 
seventh  part  of  the  60  lbs.  which,  as  we  have  seen,  are  taken  off  the 
field  in  a  crop  of  hay. 

Such  a  calculation  as  this  affords  at  the  best  but  a  very  rude  approxi- 
mation to  tlie  truth — it  seems,  however,  to  justify  us  in  concluding  that 
jjlants  can  derive  from  the  air,  and  in  an  uncombined  state,  only  a  small 
portion  of  the  nitrogen  they  are  found  to  contain — and  that  they  proba- 
bly draw  a  larger  supply  from  certain  compounds  of  this  elementary  sub- 
stance with  hydrogen  and  oxygen — which  are  known  to  come  within 
the  reach  of  their  roots  and  leaves. 

The  most  important  of  these  compounds,  and  those  perhaps  the  most 
extensively  concerned  in  influencing  vegetation,  are  ammonia  and  nitric 
acid,  the  properties  of  which  have  been  described  in  the  preceding 
lectuie.f 

§  7.  Absorption  of  ammonia  hy  plants. 

That  ammonia  enters  directly  into  the  circulation  of  plants  is  ren- 
dered probable  by  a  variety  of  considerations. 

1°.  Thus  it  is  found  to  be  actually  present  in  the  juices  of  many 
plants.  In  that  of  the  beet-root,  and  in  those  of  the  birch  and  maple 
trees,  it  is  associated  with  cane  sugar  (Liebig.)  Jn  the  leaves  of  the 
tobacco  plant,  and  of  scurvy  grass,  in  elder  flowers,  and  in  many  fungi, 
it  is  in  combination  with  acid  substances,  and  may  be  delected  by 
mixing  their  juices  with  quick-lime. — [Schiibler  Agricultur  Chemie^ 
II.,  p.  56.] 

2°.  Some  plants  actually  perspire  ammonia.  Among  these  is  the 
Chenopodium  Olidum  (stinking  goosefoot),  which  is  described  by  Sir 
William  Hooker  as  "giving  out  a  most  detestable  odour,  compared  to 
putrid  salt  fish."  In  the  odoriferous  matter  given  off  ammonia  is  con- 
tained, and  may  be  detected  by  putting  a  glass  »shade  over  the  plant, 
and  after  a  time  introducing  a  feather  moistened  with  viaegar  or  dilute 
muriatic  acid. — [Chevalier  Jour,  de  Pharm.  X.,  p.  100.]  It  is  also  pre- 
sent in  the  odoriferous  exhalations  of  many  sweet-smelling  plants  and 
flowers. — [Schiibler,  I.,  p.  152.] 

3°.  Nearly  all  vegetable  substances,  when  distilled  with  water,  yield 
an  appreciable  quantity  of  ammonia.     Thus  the  leaves  of  hyssop,  and 

•  The  result  of  experiments  made  in  1S34  by  Prof.  Phillips  and  Mr.  Edward  Gray.  The 
mean  annual  fall  of  rain  at  York  is  about  22  inches. — (See  fiilh  Report  of  the  British  Associa- 
tion, p.  173.) 

t  It  will  be  recollected  that  ammonia  consists  of  one  equivalent  of  nitrogen  (N)  united  to 
three  of  hydrogen  (Hs),  being  represented  by  NH3;  and  that  nitric  acid  consists  of  one  of  ni- 
trogen (N)  and  five  of  oxygen  (O5),  its  formula  being  NO5.— See  Lecture  III.,  p.  34. 


AMMONIA  OBTAINED  FROM  VEGETABLES.  71 

the  flowers  of  the  lime  tree,  yield  distilled  waters  in  which  ammonia 
can  be  detected  (Schiibler),  the  seeds  of  plants  thus  distilled  yield  it  in 
abundance  (Gay-Lussac),  and  traces  of  it  may  be  found  in  most  vege- 
table extracts  (Liebig). 

4°.  Ammonia  is  also  given  off,  among  other  products,  when  wood  is 
distilled  in  iron  retorts  for  the  manufacture  of  pyroligneous  acid,  and  by 
a  similar  treatment  it  may  be  obtained  from  many  other  vegetable  sub- 
stances. 

The  above  facts,  however,  are  not  to  be  considered  as  proofs  that  am- 
monia enters  directly  into  the  circulation  of  plants  either  by  their  roots 
or  by  their  leaves.  That  which  is  associated  with  sugar  in  the  beet,  may 
have  been  formed  by  the  same  converting  power  which,  in  the  intei-ior 
of  the  plant,  has  produced  the  sugar  from  carbonic  acid  and  water.  So, 
that  exhaled  by  the  leaves  of  the  goosefoot,  which  grows  in  waste  places, 
especially  near  the  sea,  may  have  been  produced  during  the  upward 
flow  of  the  sap  or  during  its  passage  over  the  leaf.  And  we  knoio  that 
the  nitrogen  does  not  exist  in  the  state  of  ammonia  in  the  seeds  of  plants, 
or  in  wood,  or  in  coal — though  from  all  of  them  it  may  be  obtained  by 
the  processes  above  described. 

The  production  of  ammonia,  by  the  agency  of  a  high  temperature, 
may  be  illustrated  by  a  very  familiar  experiment  often  performed, 
though  for  a  very  different  purpose.  The  juice  and  dried  leaf  of  tobac- 
co contain  nitre  (nitrate  of  potash)  and  a  little  ammonia.  But  when 
tobacco  is  burned,  ammonia  in  sensible  quantity  is  given  off'  along  with 
the  smoke,  chiefly  in  the  state  of  carbonate  of  ammonia.  This  may  be 
shown  by  bringing  a  lighted  cigar  near  to  reddened  litmus  paper,  when 
the  blue  colour  will  be  restored  ;  or  to  a  red'rose,  when  the  leaves  will 
become  green  ;  or  to  a  rod  dipped  in  vinegar  or  in  dilute  muriatic  acid, 
when  a  white  cloud  will  appear. — [Runge,  Einleitung  in  die  technische 
Chemie,  p.  375.] 

In  this  case  a  portion  of  the  ammonia  given  off'  by  the  tobacco  has 
most  probably  been  formed  during  the  combustion,  at  the  expense  of  the 
nitrogen  cont'ained  in  the  nitrate  of  potash  which  is  present  in  the  leaf. 

5°.  But  there  are  other  circumstances  which  are  strongly  in  favour  of 
the  opinion,  that  ammonia  not  unfrequently  does  enter,  as  such,  into  the 
circulation  of  plants. 

Thus  it  is  proved,  by  long  experiencB,  that  plants  grow  most  rapidly 
and  most  luxuriantly  when  suppHed  with  manure  containing  substances 
of  animal  origin.  These  substances  are  usually  applied  to  the  roots  or 
leaves  in  a  state  of  fermentation  or  decay,  during  which  they  always 
evolve  ammonia.  Putrid  urine  and  night-soil  are  rich  in  ammonia, 
and  they  are  among  the  most  efficacious  of  manures.  This  ammonia 
is  supposed  to  enter  into  the  circulation  of  plants  along  with  the  water 
absorbed  by  their  roots,  and  sometimes  even  by  the  pores  of  their  leaves. 
We  can  scarcely  be  said  to  have  as  yet  obtained  decisive  proof  that  it 
does  so  enter,  but  probabilities  are  strongly  in  favour  of  this  supposition ; 
and  when  we  come  hereafter  to  consider  minutely  the  mode  in  which  it 
is  likely  to  act,  when  within  the  plant,  we  shall  find  the  probabilities 
derived  from  practical  experience  to  be  strengthened  by  the  deductions 
of  theory. 

But  though  the  facts  so  long  observed  in  reference  to  the  action  Ji  an- 


72  OTHER   IMMEDIATE   SOURCES    OF    NITROGEN. 

imal  manures  upon  vegetation,  justify  us  in  believing  that  ammonia 
actually  enters  into  the  roots,  and  perhaps  into  the  leaves,  of  plants — we 
ought  not  hastily  to  conclude  that  all  the  nitrogen  which  plants  are  ca- 
pable of  deriving  from  decaying  animal  matter  must  enter  into  liieir  cir- 
culation in  the  form  of  ammonia.  Other  soluble  compounds  containing 
nitrogen  arc  formed  during  the  decay  of  animal  substances — they  ac- 
tually exist  largely  in  the  liquid  manures  of  the  stable  and  fold-yard, 
and  they  can  scarcely  fail,  when  applied  to  the  soil,  to  be  to  a  certain 
extent  absorbed  by  the  roots  of  plants.  This  urea  is  a  substance  con- 
taining much  nitrogen,  which  exists  in  the  urine  or  excrements  of  most 
animals,  and  by  its  decomposition  produces  carbonate  of  ammonia. 
But  being  very  soluble,  tliis  substance  may  enter  directly  into  the  roots, 
and  may  be  there  decomposed,  and  made  to  give  up  its  nitrogen  to  the 
living  plant.  To  other  compound  substances  of  animal  origin  the  same 
observation  may  apply,* — so  that  while  the  fact,  that  animal  manure  in 
a  state  of  fermentation  Is  very  beneficial  to  vegetation,  may  be  consid- 
ered as  rendering  it  highly  probable  that  the  ammonia  which  such 
manure  contains,  enters  directly  and  supplies  much  nitrogen  to  the 
growing  plants,  it  must  not  be  entirely  left  out  of  view  that,  in  nature,  a 
portion  of  the  nitrogen,  derived  from  animal  substances,  may  be  ob- 
tained immediately  from  other  compounds  in  which  ammonia  does  not 
exist. 

To  what  amount  ammonia  actually  enters  into  the  circulation  of 
plants,  or  how  much  of  the  nitrogen  they  contain  it  actually  supplies, 
we  have  no  means  of  ascertaining.  Were  it  abundantly  present  in  the 
soil,  its  great  solubility  would  enable  it  to  enter,  with  the  water  absorbed 
by  the  roots,  in  almost  unlimited  quantity.  In  a  subsequent  section  we 
shall  consider  the  conditions  under  which  ammonia  is  produced  in  nature, 
the  comparative  abundance  in  which  it  exists  on  the  earth's  surface, 
and  the  extent  of  the  influence  it  may  be  supposed  to  exercise  on  the 
general  vegetation  of  the  globe. 

§  8.  Absorption  of  nitric  acid  hy  plants. 
1°.  That  ammonia  is  actually  present  in  the  juices  of  many  living 
vegetables  has  been  adduced,  as  a  kind  of  presumptive  evidence,  that 
this  compound  is  directly  absorbed  by  plants.  A  similar  presumption 
is  offered  in  favour  of  the  direct  entrance  of  nitric  acid,  by  its  invariable 
presence  in  combination  with  potash,  soda,  lime,  or  magnesia,  in  the 
juices  of  certain  common  and  well  known  plants.  Thus  it  is  said  to  be 
always  contained  in  the  juices  of  the  tobacco  plant,  of  the  sunflower,  of 
the  goosefoot,f  and  of  common  borage.  The  nettle  is  also  said  to  con- 
tain it,  and  it  has  been  detected  in  the  grain  of  barley. t  It  exists  pro- 
bably in  the  juices  of  many  other  plants  in  which  it  has  not  hitherto 

•  Thus  it  may  be  applied  more  strongly  to  the  hippuric  acid.,  which  exists  in  the  urine  of 
the  horse,  and  other  herbivorous  animals.  This  acid  decomposes  naturally  into  benzoic 
and  and  ammonia.  The  sweet-scented  vernal-grass  (Anthoxanthum  Odoratum)  by  which 
hay  is  perfumed,  owes  its  agreeable  odour  to  the  presence  of  this  benzoic  acid.  It  may, 
therefore,  be  supposed  that,  where  cattle  and  horses  graze,  the  grasses  actually  absorb  the 
hippuric  acid  contained  in  the  urine,  which  reaches  their  roots,  decompose  it  as  it  ascends 
with  the  sap,  appropriate  its  nitrogen,  and  exhale  the  odoriferous  benzoic  acid. 

t  Chenopodium,  probably  in  all  the  species  of  this  genus.— See  Liebig,  p.  82. 

t  Grisenthwaite  (New  Theory  of  Agriadture,  p.  105)  says,  it  is  always  present  in  barley  in 
Ihe  form  of  uilrate  of  soda.— (See  Appendix. 


ABSORPTION  OF  NITRIC  ACID — ITS  EFFECT  ON  VEGETATION.        73 

been  sought  for.  Were  we,  therefore,  entitled,  from  the  mere  presence 
of  this  acid  in  plants,  to  infer  that  it  had  really  entered  by  their  roots  or 
leaves,  we  should  have  no  hesitation  in  drawing  our  conclusion.  But, 
like  ammonia,  it  may  have  been  formed  in  the  interior  of  the  living  ve- 
getable ;*  and  hence  the  fact  of  its  presence  proves  nothing  in  regard  to 
the  state  in  which  the  nitrogen  it  contains  entered  into  the  circulation  of 
the  plant. 

2°.  But  nitric  acid,  like  ammonia,  exerts  a  powerful  influence  on  the 
growing  crop,  whether  of  corn  or  of  grass.  Animal  matters,  as  we  have 
seen,  give  otf  ammonia  during  their  decay,  and  manures  are  rich  and 
efficacious  in  proportion  to  the  quantity  of  animal  manure  they  contain. 
The  crop  produced  also  is  valuable  and  rich  in  nitrogen  in  like  propor- 
tion. Therefore,  as  already  stated,  it  is  inferred  that  ammonia  enters 
directly  into  the  living  plant,  and  supplies  it  with  nitrogen. 

The  effect  of  nitric  acid  is  similar  in  kind,  and  perhaps  equal  in  de- 
gree. Applied  to  the  young  grass  or  sprouting  shoots  of  grain,  it  has- 
tens and  increases  their  growth,  it  occasions  a  larger  produce  of  grain, 
and  this  grain,  as  when  ammonia  is  employed,  is  richer  in  gluten^  and 
more  nutritious  in  its  quality. f  An  equal  breadth  of  the  same  field 
yields  a  heavier  produce,  and  that  produce,  weiglit  for  weight,  contains 
more  when  saltpette  or  nitrate  of  soda  have  been  applied  in  certain 
quantities  to  the  young  plants  which  grow  upon  it.  It  is  reasonable  to 
conclude,  therefore,  that  the  acid  of  the  nitrates,  in  some  form  or  other, 

*  Wlien  the  beet-root  arrives  at  maturity,  the  sugar  begins  to  diminish,  and  saltpetre  or 
other  nitrates  to  be  furmed,  probably  at  the  expense  of  the  ammonia  which  the  juice  pre- 
viously contained.-^Decroizelles,  Jour,  de  Phar.,  X.,  p.  42. 

t  The  analogous  effects  of  ammoiiiacal  manures  and  of  the  nitrates  on  the  relative  quan- 
tities of  gluten  and  starch  in  grain,  are  shown  by  the  following  experiments  : 

Hermbstaedt  sowed  equal  quantities  of  the  same  wheat,  on  equal  plots  of  the  same  ground, 
and  manured  them  with  equal  weights  of  different  manures.  Then  from  100  parts  of  each 
sample  of  grain  produced,  he  obtained  starch  and  gluten  in  the  following  proportions: 

Gluten.  Starch.  Produce. 

Without  manure 9-2  C6-7  3  fold. 

With  vegetable  manure  (rotted 

potatoe  haulm) 9-6  65-94  5    « 

With  cow  dung 120  62-3  7    " 

With  pigeons'  dung 12-2  632  9    " 

Witii  horse  dung 13  7  61-64  10    « 

With  goats' dung 329  424  12    « 

With  sheep  dung 32-9  42-8  12    « 

With  dried  night-soil 33-14  4144  14    « 

With  dried  ox-blood 34-24  413  14    « 

With  dried  human  urine    -    -    -    351  39-3  12    "i 

The  manures  employed  by  Hermbstaedt  are  supposed,  during  lermentation,  to  evolve 
more  ammonia  in  the  order  in  which  they  are  here  placed,  beginning  at  the  top  of  the  list ; 
while  the  amount  and  kind  of  the  produce  obtained  by  the  use  of  each,  afford  the  chief  evi- 
dence in  favour  of  the  opinion  that  this  ammonia  actually  enters  into  and  yields  nitrogen  to 
the  plant. 

Mr.  Ilyett  found  in  flour  raised  on  two  patches  of  the  same  land  in  Gloucestershire,  the 
one  dressed  with  nitrate  of  soda,  the  other  undressed,  the  following  proportions : 

Gluten.  Starch. 

In  the  nitrated     -    -    -    23-25  49-5 

In  the  unnitrated.     -    -    19*  55-5 

And  Mr.  Daubeny,  {Three  Lectures  on  Agriculture,  p.  76,]  in  flour  from  wheat  top-dressed 
with  saltpetre,  found — 

In  the  nitrated 15  per  cent,  of  gluten. 

In  the  unnitrated    -    -    -    -     13        "  " 

These  differences  are  not  so  striking  as  in  the  case  of  ammonia,  but  they  are  precisely 
the  same  in  kind^  and  lead  to  the  same  general  conclusion  in  regard  to  the  nature  of  the  in- 
fluence of  the  nitrates  on  vegetation.  Accurate  and  repeated  experiments  on  the  precise 
effects  of  the  nitrates  are  still  much  to  be  desired. 

['  Schiibler.    Grundsiitze  der  Agricultur  Chemte,  II.  p.  170.] 


* 


/4  GENERAL    TONCLUSIONS. 

is  capable  of  entering  into  the  circulation  of  living  plants — and  of  yield- 
ing to  them,  in  whole  or  in  part,  the  nitrogen  they  contain. 

But  here,  again,  as  in  die  case  of  ammonia,  we  are  at  fault  in  regard 
to  the  quantity  of  nitrogen  which  plants  in  a  state  of  nature  actually 
derive  from  nitric  acid  or  the  nitrates.  The  compounds  of  this  acid  with 
potash,  soda,  lime,  and  magnesia  (the  nitrates  of  th'jse  substances),  are 
all  very  soluble  in  water.  The  quantity  of  this  fluid,  therefore,  which 
enters  by  tlie  roots  of  plants,  could  easily  convey  into  their  circulation 
far  more  of  these  nitrates  than  would  be  alone  sufficient  to  supply  the 
whole  of  the  nitrogen  they  require — for  the  formation  of  all  their  parts 
and  products.  But  so  it  might  of  ammonia  or  its  salts,  as  has  already 
been  shown.  I  shall  hereafter  lay  before  you  certain  considerations 
which  may  probably  lead  us  to  approximate  conclusions  in  regard  to 
the  relative  influence  exercised  by  these  two  compounds  on  the  general 
vegetation  of  the  globe. 


Conclusions. — Respecting  tte  form  in  which  nitrogen  enters  into  the 
circulation  of  plants,  we  have  therefore,  I  think,  fairly  arrived  at  these 
deductions: 

1°.  That  the  nitrogen  of  the  atmosphere  may,  to  a^mall  extent,  enter 
directly  into  the  living  vegetable  either  in  the  form  of  gas  or  in  solution 
in  water,  but  that  supposing  nitrogen  to  be  in  this  way  appropriated*  by 
the  plant,  the  quantity  so  taken  up  could  form  only  a  small  quantity  of 
that  w^hich  vegetables  actually  contain. 

2°.  That  ammonia  is  capable  of  entering  into  plants  in  very  large 
quantity,  and  of  yielding  nitrogen  to  them,  and  that  in  European  agri- 
culture, which  employs  fermenting  animal  manure  as  an  important 
means  of  promoting  vegetable  growth,  it  does  appear  to  yield  to  cultiva- 
ted plants  a  considerable  portion  of  the  nitrogen  they  contain. 

3°.  That  nitric  acid,  in  like  manner,  is  capable  of  entering  into  and 
giving  up  its  nitrogen  to  plants;  and  that  where  this  acid  is  employed  as 
an  instrument  of  culture,  the  crops  obtained  owe  part  of  their  nitrogen 
to  the  quantity  of  this  compound  which  has  been  applied  to  the  grow- 
ing plants.  The  same  inference  may  fairly  be  drawn  in  regard  to  the 
effect  of  nitric  acid — when,  in  the  form  of  nitrates,  it  exists  or  is  pro- 
duced naturally  in  the  soil. 

4°.  That  other  compound  bodies,  such  as  are  contained  in  urine,  or  are 
produced  during  the  decay  of  animal  matter,  niay  also  enter  into  the 
circulation  of  plants,  and  yield  nitrogen  to  promote  their  growth. 

On  the  whole,  however,  there  seem  strong  reasons  for  believing  that 
plants  are  mainly  dependent  on  ammonia  and  nitric  acid  for  the  nitro- 
gen they  contain  ;  and  that  they  obtain  it  most  readily,  and  with  least 
labour,  so  to  speak,  from  these  compounds, — though  nature  has  kindly 
fitted  them  for  deriving  a  stinted  supply  from  other  sources,  when  these 
substances  are  not  present  in  sufficient  abundance. 

How  far  each  of  these  compounds  is  employed  by  nature,  as  an  in- 
Btrutnent  in  promoting  the  general  vegetation  of  the  globe,  will  be  con- 
sidered in  a  subsequent  lecture. 

•  Lieblg  and  others  say  that  plants  are  incapable  of  appropriating  or  assimilating  the  nitro 
gen  which  enters  into  their  circulation  in  the  simple  state.  We  shall  const ler  this  ques- 
tion hereafter.  v 


LECTURE  V. 

How  does  the  food  enter  into  the  circulation  of  plants— Structure  of  the  several  parts  of 
plants— Fun  ;tions  of  the  root— Course  of  the  sap— Cause  of  its  ascent— Functions  of 
tlie  stem— of  the  leaves— and  of  the  bark — Circumstances  by  which  the  exercise  of  these 
functions  is  modified. 

Having  now  taken  a  general  view  of  the  source  from  which  plants 
derive  the  elementary  substances  of  which  their  solid  parts  consist,  and  of 
the  slates  of  combination  in  which  these  elements  enter  into  the  vegeta- 
ble circulation, — the  next  step  in  our  inquiry  is — how  are  these  substan- 
ces admitted  into  the  interior  of  living  plants — and  under  what  condi- 
tions or  regulations?  We  are  thus  led  to  study  the  structure  and  func- 
tions of  the  several  parts  of  plants,  and  the  circumstances  by  which  the 
exercise  of  these  functions  is  observed  to  be  modified. 

§  1.   General  structure  of  plants,  and  of  their  several  parts. 

Plants  consist  essentially  of  three  parts — the  roots,  the  stem,  and  the 
leaves.  The  former  spread  themselves  in  various  directions  through 
the  soil,  as  the  latter  do  through  the  air,  and  the  stem  is  dependent  for  its 
food  and  increase  on  the  rapidity  with  which  the  roots  shoot  out  and  ex- 
tend, and  on  the  number  and  luxuriance  of  the  leaves. 

We  shall  obtain  a  clearer  idea  of  the  relative  structure  of  these  several 
parts  by  first  directing  our  attention  to  that  of  the  stem. 

The  stem  consists  apparently  of  four  parts — the  pith,  the  wood,  the 
bark,  and  the  medullary  rays.  The  pith  and  the  medullary  rays,  how- 
ever, are  similarly  constituted,  and  are  only  prolongations  of  one  and 
the  same  substance.  The  pith  forms  a  solid  cylinder  of  soft  and  spongy 
matter,  which  ascends  through  the  central  part  of  the  stem,  and  varies 
in  thickness  with  the  species  and  with  the  age  of  the  trunk  or  branch. 
The  wood  surrounds  the  pith  in  the  form  of  a  hollow  cylinder,  and  is  itself 
covered  by  another  hollow  cylinder  of  bark.  In  trees  or  branches  of 
considerable  age  the  wood  consists  of  two  parts,  the  oldest  or  heart  woody 
often  of  a  brownish  colour,  and  the  newer  external  wood  or  alburnum^ 
which  is  generally  softer  and  less  dense  than  the  heart  wood.  The  bark 
also  is  easily  separated  into  two  portions,  the  inner  bark  or  liber,  and 
the  epidermis  or  outer  covering  of  the  tree.  The  pith  and  the  bark  are 
connected  together  by  thin  vertical  columns  or  partitions,  which  inter- 
sect the  wood  and  divide  it  into  triangular  segments.  A  cross  section 
of  the  trunk  or  branch  of  a  tree  exhibits  these  thin  columns  extending 
in  the  form  of  rays,  or  like  the  spokes  of  a  wheel,  from  the  centre  to 
the  circumference.  Though  they  form  in  reality  thin  and  continuous 
vertical  plates,  yet  from  the  appearance  they  present  in  the  cross  sec- 
tion of  a  piece  of  wood,  they  are  distinguished  by  the  name  of  medulla- 
ry rays. 

These  several  parts  of  the  stem  are  composed  of  bundles  of  small 
tubes  or  hollow  cylindrical  vessels  of  various  sizes,  and  of  different 
kinds,  the  structure  of  which  it  is  unnecessary  for  us  to  study.     They 


76    STRUCTURE  OF  THE  STEMS,  ROOTS,  AND  LEAVES  OF  PLANTS. 

are  all  intended  to  contain  liquid  and  gaseous  substances,  and  to  convey 
them  in  a  vertical,  and  sometimes  in  a  horizontal,  direction.  The 
tubes  which  compose  the  wood  and  bark  are  arranged  vertically,  as  may 
readily  be  seen  on  examining  a  piece  of  wood  even  wiili  the  naked  eye, 
and  are  intended  to  convey  the  sap  upwards  to  the  leaves  and  down- 
wards to  the  roots.  Those  of  which  the  pith  and  medullary  plates  con- 
sist are  arranged  horizontal!}'-,  and  appear  to  be  intended  to  maintain  a 
lateral  intercourse  between  the  pith  and  the  bark — perhaps  even  to  place 
the  heart  of  the  tree  within  the  influence  of  the  external  air. 

The  root,  though  prior  in  its  origin  to  the  stem,  may  nevertheless  for 
the  purpose  of  illustration  be  considered  as  its  downward  and  lateral 
prolongation  into  the  earth — as  the  branches  are  its  upward  prolonga- 
tion into  the  air.*  When  they  leave  the  lower  part  of  the  trunk  of  the 
tree,  they  differ  little  in  their  internal  structure  from  the  stem  itself. 
As  they  taper  off,  however,  first  the  heart  wood,  then  ihe  i)ith,  gradual- 
ly disappear,  till,  towards  their  extremities,  they  consist  only  of  a  soft 
central  woody  part  and  its  covering  of  soft  bark.  These  are  connected 
with,  or  are  respectively  prolongations  of,  the  new  wood  and  bark  of  the 
trunk  and  branches.  At  the  extreme  points  of  the  roots  the  bark  be- 
comes white,  soft,  spongy,  and  full  of  pores  and  vessels.  It  is  by  these 
spongy  extremities  only,  or  chiefly,  that  liquid  and  gaseous  substances 
are  capable  either  of  entering  into,  or  of  making  their  escape  from,  the 
interior  of  the  root. 

The  branches  and  twigs  are  extensions  of  the  trunk ;  and  of  the 
former,  the  leaves  may  be  considered  as  a  still  further  extension.  The 
fibres  of  the  leaf  are  minute  ramifications  of  the  woody  matter  of  the 
twigs,  are  connected  through  them  with  the  wood  of  the  branches  and 
stems,  and  from  this  wood  receive  the  sap  which  they  contain.  The 
green  part  of  the  leaf  may  be  considered  as  a  special  expansion  of  tlie 
bark,  by  which  it  is  fitted  to  act  upon  the  air,  in  ihe  same  way  as  the 
spongy  mass  into  which  the  bark  is  changed  at  the  extremity  of  the  root, 
is  fitted  to  act  upon  the  water  and  other  substances  it  meets  with  in  the 
soil.  For  as  the  fibres  of  the  leaf  are  connected  with  the  wood  of  the 
stem,  so  the  green  part  of  the  leaf  is  connected  with  its  bark,  and  from 
this  green  part  the  sap  first  begins  to  descend  towards  the  root. 

§  2.   The  functions  of  the  root. 
The  position  in  which  the  roots  of  plants  in  their  natural  state  are  ge- 
nerally placed,  has  hitherto  prevented  their  functions  from  being  so  ac- 
curately investigated  as  those  of  the  leaves  and  of  the  stem.     While, 
therefore,  the  main  purposes  they  are  intended  to  serve  are  universally 

'  The  correctness  of  this  comparison  is  proved  by  the  fact  that,  in  many  trees,  the  branch 
if  planted  will  become  a  root,  and  the  root,  if  exposed  to  the  air,  will  gradually  be  trans- 
formed into  a  branch.  The  banana  in  the  forest,  and  the  cirrant  trpe  in  our  gardens,  are 
familiar  instances  of  trees  spontaneously  plantina  their  branches,  and  cnusing  them  to  per- 
form the  functions  of  roots.  In  like  manner,  "  if  the  stem  of  a  youns  plum  or  cherry-tree, 
or  of  a  willow,  be  bent  in  the  autumn  so  that  one-half  of  the  top  can  be  laid  in  the  earth  and 
one-halfof  the  root  be  at  the  same  time  taken  carefully  up— shelterrd  at  finst  and  after- 
wards gradually  exposed  to  the  cold— and  if  in  tlie  following  year  the  remaining  part  of  the 
top  and  root  be  treated  in  the  same  way,  the  branches  of  tlie  top  will  become  roots,  and  the 
ramifications  of  the  roots  will  become  branches,  producing  leaves,  flowers,  and  fruit  in  due 
BediSoa.— [l-oyiAow's  ETwydopadia  of  Agricult.ure.'\  The  tree  is  thus  reversed  in  position, 
and  the  roots  and  branches  being  thus  mutually  convertible  cannot  be  materially  unlike  in 
general  structure. 


ROOTS  ABSORB  AQUEOUS  SOLUTIONS,  AND  OXYGEN.       77 

Known  and  understood,  the  precise  way  in  which  these  ends  are  accom- 
plished by  the  roots,  and  the  powers  with  which  they  are  invested,  are 
still  to  a  considerable  degree  matters  of  dispute. 

I.  It  appears  certain  that  they  are  possessed  of  the  power  of  absorb- 
ing water  in  large  quantity  from  the  soil,  and  of  transmitting  it  upwards 
to  the  stem.  The  amount  of  water  thus  absorbed  depends  greatly  upon 
the  nature  of  the  soil  and  of  the  climate  in  which  a  plant  grows,  but 
much  also  upon  the  specific  structure  of  its  leaves  and  the  extent  of  its 
foliage. 

II.  The  analogy  of  the  leaves  and  young  twigs  would  lead  uS  to 
suppose  that,  when  in  a  proper  state  of  moisture,  the  roots  should 
also  be  capable  of  absorbing  gaseous  substances  from  the  air  which 
pervades  the  soil.  Experiment,  however,  has  not  yet  shown  this  to  be 
the  case. 

We  know,  however,  that  they  are  capable  of  absorbing  gases  through 
the  medium  of  water.  For  if  the  roots  of  a  plant  are  placed  in  water 
containing  carbonic  acid  in  the  state  of  solution,  this  gas  is  found  gradu- 
ally to  disappear.  It  is  extracted  from  the  water  by  the  roots.  And  if 
the  water  in  which  the  roots  are  immersed  be  contained  in  a  bottle  only 
partially  filled  with  the  liquid,  while  the  remainder  is  occupied  by  at- 
mospheric air,  the  oxygen  in  this  air  will  also  slowly  diminish.  It  will 
be  absorbed  by  the  roots  through  the  medium  of  the  water.* 

Again,  if  in  the  place  of  the  atmospheric  air  in  this  bottle,  carbonic 
acid  be  substituted,  the  plant  will  droop  and  in  a  few  days  will  die.  The 
same  will  take  place,  if  instead  of  common  air  or  carbonic  acid,  nitro- 
gen or  hydrogen  gases  be  introduced  into  the  bottle.  The  plant  will  not 
live  when  its  roots  are  exposed  to  the  sole  action  of  any  of  the  three. 

It  is  obvious,  therefore,  that  the  roots  of  plants  absorb  gaseous  sub- 
stances from  the  air  which  surrounds  their  roots,  at  least  indirectly  and 
through  the  medium  of  water.  It  appears  also  that  from  this  air  they 
have  the  power  of  selecting  a  certain  portion  of  oxygen  when  this  gas  is 
present  in  it.  Thirdly,  that  though  they  can  absorb  carbonic  acid  to  a 
limited  amount  without  injury  to  the  plant,  yet  that  a  copious  supply  of 
this  gas,  unmixed  with  oxygen,  is  fatal  to  vegetable  life.  This  deduction 
is  confirmed  by  the  fact  that,  in  localities  where  carbonic  acid  ascends 
through  fissures  in  the  subjacent  rocks  and  saturates  the  soil,  the  growth, 
of  grass  is  found  to  be  very  much  retarded.  And,  lastly,  since  nitrogen 
is  believed  not  to  be  in  itself  noxious  to  vegetable  life,  the  death  of  the 
plant  in  water  surrounded  by  this  gas,  is  supi)Osed  to  imply  that  the  pre- 
sence of  oxygen  is  necessary  about  the  roots  of  a  growing  and  healthy 
plant,  and  that  one  of  the  special  functions  of  the  roots  is  constantly  to 
absorb  this  oxygen. 

This  supposition  is  in  accordance  witli  the  fact  that,  in  the  dark,  the 
leaves  of  plants  absorb  oxygen  from  the  atmosphere ;  for  we  have  al- 
ready seen  reason  to  expect  that,  from  their  analogous  structure,  the  roots 
and  leaves  in  similar  circumstances  should  perform  also  analogous  func- 
tions.    At  the  same  time,  if  the  roots  do  require  the  access  and  presence 

'  It  will  be  recollected  that  water  absorbs  about  4  per  cent,  of  its  bulk  of  air  from  the  at- 
mosphere, of  which  about  one-third  is  oxygen.  If  the  roots  extract  this  oxygen  from  the 
water,  the  latter  will  again  drink  in  a  fresh  portion  from  the  atmospheric  air  which  floats 
above  it. 

4* 


78  DO    SOLID    SUBSTANCES    ENTER    THE    ROOTS? 

of  oxygen  in  the  soil,  it  would  further  appear  that  those  of  some  plants 
require  it  more  tlian  those  of  others  ;  inasmuch  as  some  genera,  like  the 
grasses,  love  an  open  and  friable  soil,  into  which  the  air  is  more  com- 
pletely excluded. — [Sprengel,  Chemie,  II.,  p.  337.] 

III.  We  have  in  a  former  lecture  (IV.  p.  64)  concluded  from  facts 
there  stated,  that  solid  substances,  which  are  soluble  in  water,  accom- 
pany this  hquid  when  it  enters  into  the  circulation  of  the  plant.  This 
appears  to  be  true  both  of  organic  and  inorganic  substances.  Potash, 
soda,  lime,  and  magnesia  thus  find  their  way  into  the  interior  of  plants, 
as  well  as  those  substances  of  animal  and  vegetable  origin  to  which  the 
observations  made  in  the  fourth  lecture  were  intended  more  especially  to 
apply.  Even  silica,*  considered  to  be  almost  insoluble  in  water,  enters 
by  the  roots,  and  is  found  in  some  cases  in  considerable  quantities  in  the 
stem.  Some  persons  have  hence  been  led  to  conclude  that  solid  sub- 
stances, undissolved,  if  in  a  minute  state  of  division,  may  be  drawn  into 
the  pores  of  the  root  and  may  then  be  carried  by  the  sap  upwards  to  the 
stem. 

Considered  as  a  mere  question  of  vegetable  mechanics,  argued  as  such 
among  physiologists,  it  is  of  little  moment  whether  we  adopt  or  reject 
this  opinion.  One  phj'siologist  may  slate  tliat  the  pores  by  which  the 
food  enters  into  the  roots  are  so  minute  as  to  baffle  the  powers  of  the  best 
constructed  microscope,  and,  therefore,  that  to  no  particles  of  solid  mat- 
ter can  they  by  possibility  give  admission — while  another  may  believe 
solid  matter  to  be  capable  of  a  mechanical  division  eo  minute  as  to  pass 
through  the  pores  of  the  finest  membrane.  As  to  the  mere  fact  itself,  it 
matters  not  which  is  right,  or  which  of  the  two  we  follow.  The  adoption 
of  the  latter  opinion  implies  in  itself  merely  that  foreign  substances, 
unnecessary,  perhaps  injurious  to  vegetable  life,  may  be  carried  forward 
by  the  flowing  juices  until  in  some  still  part  of  the  current,  or  in  some 
narrower  vessel,  they  are  arrested  and  there  permanently  lodged  in  the 
solid  substance  of  the  plant. 

By  inference,  however,  the  adoption  of  this  opinion  implies  also,  that 
the  inorganic  substances  found  in  plants, — those  which  remain  in  the 
form  of  ash  when  the  plant  is  burned, — are  accidental  only,  not  essential 
to  its  constitution.  For  since  they  may  have  been  introduced  in  a  mere 
state  of  minute  mechanical  division  suspended  in  the  sap,  they  ought  to 
consist  of  such  substances  chiefly  as  the  soil  contains  in  the  greatest 
abundance,  and  they  ought  to  vary  in  kind  and  relative  quantity  with 
every  variation  in  the  soil.  In  a  clay  land  the  ash  should  consist  chiefly 
of  alumina, f  in  a  sandy  soil  chiefly  of  silica.  But  if,  as  chemical  in- 
quiry appears  to  indicate,  the  nature  of  the  ash  is  not  accidental,  but  es- 
sential, and  in  some  degree  constant,  even  in  very  diflerent  soils,  this 
latter  inference  is  inadmissible; — and  in  reasoning  backwards  from  this 
fact,  we  find  ourselves  constrained  to  reject  the  opinion  that  substances 
are  capable  of  entering  into  the  roots  of  plants  in  a  solid  state — and  this 
without  reference  at  all  to  the  mechanical  question,  as  to  the  relative  size 
of  the  pores  of  the  spongy  roots  or  of  the  particles  into  which  solid  mat- 
ter may  be  divided. 

*  Silica  is  the  name  given  by  ctiemists  to  the  pure  matter  of  flint  or  of  rock  crystal.   Sand 
and  sandstones  consist  almost  entirely  of  silica, 
t  Alumina  ia  the  pure  earth  of  clay. 


SELECTING    POWER    OF    THE    R007  S  79 

IV.  We  are  thus  brought  to  the  consideration  of  the  alleged  selecting 
power  of  the  roots,  which,  if  rightly  attributed  to  them,  must  be  con- 
sidered as  one  of  the  most  important  functions  of  which  they  are  pos- 
sessed. It  is  a  function,  however,  the  existence  of  which  is  disputed  by 
many  eminent  physiologists.  But  as  the  adoption  or  rejection  of  it  will 
materially  influence  our  reasonings,  as  well  as  our  theoretical  views,  in 
regard  to  some  of  the  most  vital  processes  of  vegetation, — it  will  be  pro- 
per to  weigh  carefully  the  evidence  on  which  this  power  is  assigned  to 
the  roots  of  plants. 

1°.  The  leaves,  as  we  shall  hereafter  see,  possess  in  a  high  degree 
the  power  of  selecting  from  the  atmosphere  one  or  more  gaseous  sub- 
stances, leaving  the  nitrogen,  chiefly,  unchanged  in  bulk.  The  absorp 
tion  of  carbonic  acid  and  the  diminution  of  the  oxygen  in  the  experi 
ments  above  described,  appear  to  be  analogous  effects,  and  would  seem 
to  imply  in  the  roots  the  existence  of  a  similar  power. 

2°.  Dr.  Daubeny  found  that  pelargoniums,  barley  {hordeum  vulgare)^ 
and  the  winged  pea  {lotus  tetragonolohus),  though  made  to  grow  in  a 
soil  containing  much  strontia,*  appeared  to  absorb  none  of  this  earth,  foi 
none  was  found  in  the  ash  left  by  the  stem  and  roots  of  the  plant  when 
burned.  In  like  manner  De  Saussure  observed  that  polygonum  persi- 
caria  refused  to  absorb  acetate  of  lime  from  the  soil,  though  it  freely  took 
up  common  salt. —  [Lindley's  Theory  of  Horticulture,  p.  19.] 

3°.  Plants  of  different  species,  growing  in  the  same  soil,  leave,  when 
burned,  an  ash  which  in  every  case  contains  either  different  substances, 
or  the  same  substances  in  unlike  proportions.  Thus  if  a  bean  and  a 
grain  of  wheat  be  grown  side  by  side,  the  stem  of  the  plant  from  the  lat- 
ter seed  will  be  found  to  contain  silica,  from  the  former  none.f 

4°.  But  the  same  plant  grown  in  soils  unlike  in  character  and  com- 
position, contains  always — if  they  are  present  in  the  soil  at  all— very 
nearly  the  same  kindj  of  earthy  matters  in  nearly  the  same  proportion. 
Thus  the  stalks  of  corn  plants,  of  the  grasses,  of  the  bamboo,  and  of  many 
others,  always  contain  silica,  in  whatever  soil  they  grow,  or  at  least  are 
capable  of  growing  with  any  degree  of  luxuriance. 

With  the  view  of  testing  this  point,  Lampadius  prepared  five  square 
])atches  of  ground,  manured  them  with  equal  quantities  of  a  mixture  of 
horse  and  cow  dung,  sowed  them  with  equal  measures  of  the  same 
wheat,  and  on  four  of  these  patches  strewed  respectively  five  pounds  of 
finely  powdered  quariz  (siliceous  sand),  of  chalk,  of  alumina,  and  of 
carbonate  of  magnesia,  and  left  one  undressed.  The  produce  of  seed 
from  each,  in  the  above  order,  weighed  24i,  28|,  26i,  21i,  and  20  ounces 
respectively.  The  grain,  chaff",  and  straw,  from  each  of  the  patches 
left  nearly  the  same  quantity  of  ash — the  weights  varying  only  from  3-7 
to  4-08  per  cent.,  and  the  roots  and  chaff'being  richest  in  inorganic  mat- 
ter.    The  relative  proportions  of  silica,  alumina,  lime,  and  magnesia, 

*  Watered  with  a  solution  of  nitrate  of  strontia.  Strontia  is  an  earthy  substance  resem 
bling  lime,  which  is  found  in  certain  rocks  and  mineral  veins,  but  which  has  not  hitherto  been 
observed  in  the  ashes  of  plants. 

t  It  is  not  strictly  correct  that  the  bean  will  absorb  no  silica,  but  the  quantity  it  will  take  up 
will  be  only  one-thirteenth  of  that  taken  up  by  the  wheat  plant— the  per  centage  of  silica  in 
the  ash  of  bean  straw  being,  according  to  Sprengei,  only  0  22,  while  in  wheat  straw  it  is  287 
per  cent.    Pea  straw  contains  four  times  as  much  as  that  of  the  bean,  or  0  996  per  cent. 

X  For  more  precise  information  on  this  point,  see  the  subsequent  lectures,  "  On  the  inor- 
ganic constituents  of  plants,"  (Part  II.) 


80  PLANTS    MAY   ABSORB    POISONOUS  SUBSTANCES. 

were  the  same  in  all. — [Meyen  Jdlireshericht,  1839,  p.  1.]  Provided, 
therefore,  the  substances  which  plants  prefer  be  present  in  the  soil,  the 
kind  of  inorganic  matter  they  take  up,  or  of  ash  they  leave,  is  not  mate- 
rially affected  by  the  presence  of  other  substances,  even  in  somewhat 
larger  quantity. 

These  facts  all  point  to  the  same  conclusion,  that  the  roots  have  the 
power  of  selecting  from  the  soil  in  which  they  grow,  those  substances 
which  are  best  fitted  to  promote  the  growth  or  to  maintain  the  healthy 
condition  of  the  plants  they  are  destined  to  feed. 

6°.  It  has  been  stated  above  that  the  roots  of  certain  plants  refuse  to 
absorb  nitrate  of  strontia  and  acetate  of  lime,  though  presented  to  them 
in  a  state  of  solution — the  same  is  true  of  certain  coloured  solutions  which 
have  been  found  incapable  of  finding  their  way  into  the  circulation  of 
plants  whose  roots  have  been  immersed  in  them.  On  the  other  hand, 
it  is  a  matter  of  frequent  observation  that  the  roots  absorb  solutions  con- 
taining substances  which  speedily  cause  the  death  of  the  plant.  Arsenic, 
opium,  salts  of  iron,  of  lead,  and  of  copper,  and  many  other  substances, 
are  capable  of  being  absorbed  in  quantities  which  prove  injurious  to  the 
living  vegetable — and  on  this  ground  chiefly  many  physiologists  refuse  to 
acknowledge  that  the  roots  of  plants  are  by  nature  endowed  with  any 
definite  and  constant  power  of  selection  at  all.  But  this  argument  is  of 
equal  force  against  the  possession  of  such  a  power  by  animals  or  even  by 
man  himself;  since,  with  our  more  perfect  discriminating  powers,  aided 
by  our  reason  too,  we  every  day  swallow  with  our  food  wliat  is  more  or 
less  injurious,  and  occasionally  even  fatal,  to  human  life.* 

On  the  whole,  therefore,  it  appears  most  reasonable  to  conclude  that 
the  roots  are  so  constituted  as  (1°)  to  be  able  generally  to  select  from  the 
soil,  in  preference^  those  substances  which  are  most  suitable  to  the  nature 
of  the'  plant — (2°)  where  these  are  not  to  be  met  with,  to  admit  certain 
others  in  their  steadf — (3°)  to  refuse  admission  also  to  certain  substan- 
ces likely  to  injure  the  plant,  though  unable  to  discriminate  and  reject 
every  thing  hurtful  or  unbeneficial  which  may  be  presented  to  them  in 
a  state  of  solution. 

The  object  of  nature,  indeed,  seems  to  be  to  guard  the  plant  against 
the  more  common  and  usual  dangers  only — not  against  such  as  rarely 
present  themselves  in  the  situations  in  which  it  is  destined  to  grow,  or 
against  substances  which  are  unlikely  even  to  demand  admission  into  its 
roots.  How  useless  a  waste  of  skill,  if  I  may  so  speak,  would  it  have 
been  to  endow  the  roots  of  each  plant  with  the  power  of  distinguishing 
ant?  rejecting  opium  and  arsenic  and  the  thousand  other  poisonous  sub- 
stances which  the  physiologist  can  present  to  them,  but  which  in  a  state 
of  nature — on  its  natural  soil  and  in  its  natural  climate — the  liviaig  vege- 
table is  never  destined  to  encounter  ! 

•  I  may  here  remark  that  it  is  by  no  means  an  extraordinary  power  which  these  circum- 
stances seem  to  show  the  roots  of  plants  to  possess.  In  the  presence  of  oxygen,  nitrogen, 
and  carbonic  acid,  in  equal  quantities,  water  will  prefer  and  will  select  the  latter.  From  a 
mixture  of  lime  and  magnesia,  acetic  or  sulpliuric  acid  will  select  and  separate  the  former. 
Is  it  unreasonable  to  suppose  the  rooisof  plants— the  organs  of  a  living  being— to  be  endowed 
with  powers  of  discrimination  at  least  as  great  as  those  possessed  by  dead  matter? 

t  This  conclusion  is  not  strictly  contained  in  the  premises  above  stated,  but  the  facts  from 
which  it  is  drawn  will  be  fully  explained  in  treating  of  the  inorganic  constituents  of  plants. 
It  is  introduced  here  for  the  purpose  of  giving  a  complete  view  of  what  appears  to  be  the 
true  powers  of  discrimination  possessed  by  the  root. 


EXCRETORY  POWER  OF  THE  ROOTS.  81 

V.  Another  function  of  tlie  roots  of  plants^  in  regard  to  which  physiol- 
ogists are  divided  in  opinion  at  the  present  day,  is  what  is  called  their 
excretory  power. 

1°.  When  barley  or  other  grain  is  caused  to  germinate  in  pure  chalk, 
acetate  of  lime*  is  uniformly  found  to  be  mixed  with  it  after  the  germi- 
nation is  somewhat  advanced  (Becquerel  and  Mateucci,  Ann.  deCliem. 
et  de  Phys.,  1  v.,  p.  310.)  In  this  case  the  acetic  acid  must  have  been  given 
off  (excreted)  by  the  young  roots  during  the  germination  of  the  seed. 

This  fact  raay  be  considered  as  the  foundation  of  the  excretory  theory 
as  it  is  called.  This  theory,  supported  by  the  high  authority  of  Decan- 
doUe,  and  illustrated  by  the  apparently  convincing  experiments  of  Ma- 
caire,  {Ann.  de  Chim.  elde  Phys.,  lii.,  p.  225,)  has  more  recently  been  met 
by  counter-experiments  of  Braconnot,  (Ixxli.  p.  27,)  and  is  now  in  a  great 
measure  rejected  by  many  eminent  vegetable  physiologists.  It  may  in- 
deed be  considered  as  quite  certain  that  the  application  of  this  theory  by 
DecandoUe  and  others  to  the  explanation  of  the  benefits  arising  from  a 
rotation  of  crops,  is  not  confirmed,  or  j)roved  to  be  correct,  by  any  exper- 
iments on  the  subject  tliat  have  hitherto  been  published. f 

According  to  DecandoUe,  plants,  like  animals,  have  the  power  of  se- 
lecting from  their  food,  as  it  passes  through  their  vascular  system,  such 
portions  as  are  likely  to  nourish  them,  and  of  rejecting,  by  their  roots, 

*  Acetate  of  lime  is  a  combination  of  acetic  acid  or  vinegar  with  lime  derived  from  the  chalk. 

1  The  discordant  results  of  Macaire  and  Braconnot  were  as  follow  : 

1°.  Macaire  observed  that  when  pla.nls  o{  Cfio7idrilla  Muralis  were  grown  in  rain  water 
they  imparted  to  it  something  of  the  smell  and  taste  of  opium.  Braconnot  confirmed  this, 
but  attributed  it  to  wounds  in  the  roots  which  allowed  tiie  proper  juice  of  the  plant  to  escape. 
He  says  it  is  almost  impossible  to  free  the  younij  roots  from  the  soil  in  which  tliey  have  grown, 
without  injuring  them  and  causing  the  sap  to  exude. 

2°.  Euphorbia  Pejdiis  (Petty  Spurge)  imparled  to  the  water  in  which  it  grew  a  gummi- 
resinous  substance  of  a  very  acrid  tuste.  In  the  hands  of  Braconnot  it  yielded  to  tlie  water 
scarcely  any  organic  matter,  and  that  only  slightly  bitterish. 

3°.  Braconnot  washed  the  soil  in  which  pianlsof  Eup/ioibia  Br eoni  and  Asdepias  Incnr- 
nata  were  growing  in  pots,  and  obtained  ar  solution  containing  earthy  and  alkaline  salts  with 
only  a  trace  of  organic  matter. 

He  also  washed  the  soil  in  which  the  Poppy  (Papaver  Somniferum)  had  been  grown  ten 
years  successively.  The  solution,  besides  inorganic  earthy  and  alkaline  .salts,  gave  a  consid- 
erable quantity  of  acetic  acid  (in  the  form  of  acetate  of  lime)  and  a  trace  of  brown  organic 
matter.  He  infers  that  these  several  plants  do  not  excrete  any  organic  matter  in  sufficient 
quantity  to  be  injurious  to  themselves. 

4°.  Macaire  obseived  that  when  separate  portions  of  the  roots  of  the  same  plant  of  Mercu- 
rialis  Annua  were  immersed  in  separate  vessels,  the  one  containing  pure  water  and  the 
other  a  solution  of  acetate  of  lead,— the  solution  of  lead  was  absorbed  by  the  plant,— was  to 
be  traced  in  every  part  of  it,  and  afterwards  was  partially  transmitted  to  the  pure  water.  Bra- 
connot observed  the  same  results,  but  he  found  the  entrance  of  the  lead  into  the  second  vessel 
to  be  owing  to  theascerUof  the  fluid  up  the  outer  surface  of  tiie  one  root  and  down  the  exterior 
of  the  other,  and  that,  by  preventing  tlie  possibility  of  this  passage,  no  lead  could  be  detected 
among  the  pure  water. 

Tlie  conclusions  of  Macaire,  tlierefore,  in  favour  of  the  rotation  theory  of  DecandoUe 
must  be  considered  as  at  present  inadmissible,  and  we  shall  hereafter  see  reason  to  coin- 
cide, at  least  to  a  certain  extent,  in  the  conclusion  of  Braconnot,  "tliat  if  these  excretions 
(of  organic  matter)  really  take  place  in  the  natural  state  of  the  plant,  they  are  as  yet  so  ob- 
scure and  so  little  known  as  to  justify  the  presumption  that  some  other  explanation  must 
bo  given  of  the  general  system  of  rotation."  Various  illustrations  have  been  given  by  differ- 
ent observers  of  this  supposed  excreting  power  of  the  roots.  Among  the  most  recent  are 
those  oi  Nietner,  wlio  ascribes  the  luxuriant  rye  crops  obtained  without  manure  after  three 
venrs  of  clover,  to  the  excretions  of  this  plant  in  the  soil,  which,  like  those  of  the  pea  and 
Dean  to  the  wheat,  he  supposes  'o  be  nourishing  food  to  the  rye.  He  also  states  that  the 
beet  or  the  turnip  after  tobacco  has  an  unpleasant  taste,  and  is  scarcely  eatable,  which  he 
attributes  Lo  the  excretions  of  the  tobacco  plant.  Meyen  ascribes  the  effect  of  the  clover  to 
(he  green  manure  supphed  by  its  roots  and  stubble  and  tliat  of  the  tobacco  to  the  undecom- 
posed  organic  subsUnces  contained  in  the  sap  and  substance  of  the  roots  and  stems  of  this 
plant,  of  which  so  large  a  quantity  is  left  behind  in  the  Held.— [Meyen' s  Jahresberickt,  18-39, 
p.  5.]— These  objections  of  Meyen  are  not  without  their  weight,  but  we  shall  hereafter  see 
that  they  embody  only  half  the  truth. 


82  EXPERIMENTS    OF  DE    SAUSSUHE. 

v^hen  the  sap  descends,  such  as  are  unfit  to  contribute  to  their  support, 
or  would  be  liurtful  to  them  if  not  rejected  from  their  system.  He  further 
supposes  that,  after  a  time,  the  soil  in  which  a  certain  kind  of  plant 
"rows  becomes  so  loaded  with  this  rejected  matter,  that  the  same  plant 
refuses  any  longer  to  flourish  in  it.  And,  thirdly,  that  though  injurious 
to  the  plant  from  which  it  has  been  derived,  this  rejected  matter  may  be- 
wholesome  food  to  plants  of  a  different  order,  and  hence  the  advantage  to 
be  derived  from  a  rotation  of  crops. 

There  seems  no  good  reason  to  doubt  that  the  roots  of  plants  do  at 
times — it  may  be  constantly — reject  organic  substances  from  their  roofs. 
The  acetic  acid  given  off  during  germination,  and  the  same  acid  found 
by  Braconnot  in  remarkable  quantity  in  the  soil  in  which  the  poppy 
{papaver  somniferum)  has  grown — may  be  regarded  as  sufficient  evi- 
dence of  the  fact — but  the  quantity  of  such  organic  matter  hitherto  de- 
tected among  what  may  be  safely  viewed  as  the  real  excretions  of  plants, 
seems  by  far  too  small  to  account  for  the  remarkable  natural  results  at- 
tendant upon  a  rotation  of  crops. 

Tlie  consideration  of  these  results,  as  well  as  of  the  general  theory  of 
such  a  rotation,  will  form  a  distinct  topic  of  consideration  in  a  subsequent 
part  of  these  lectures.  I  shall,  therefore,  only  mention  one  or  two  facts 
which  seem  to  me  capable  of  explanation  only  on  the  supposition  that 
the  roots  of  plants  are  endowed  with  the  power  of  rejecting,  and  that 
they  do  constantly  reject,  when  the  sap  returns  from  the  leaf,  some  of 
the  substances  which  they  had  previously  taken  up  from  the  soil. 

1°.  De  Saussure  made  numerous  experiments  on  the  quantity  of  ash 
percent,  left  by  the  same  plant  at  different  periods  of  its  growth.  Among 
other  results  obtained  by  him,  it  appeared — 

A.  That  the  quantity  of  incombustible  or  inorganic  matter  in  the  dif- 
ferent parts  of  the  plant  was  different  at  different  periods  of  the  year. 
Thus  the  dry  leaves  of  the  horse  chestnut,  gathered  in  May,  left  7-2  per 
cent.,  towards  the  end  of  July  8-4  per  cent.,  and  in  the  end  of  Septem- 
ber 8-6  per  cent,  of  ash;  the  dry  leaves  of  the  hazel  in  June  left  6-2, 
and  in  September  7  per  cent. ;  and  those  of  the  poplar  (populus  nigra) 
in  May  6-6,  and  in  September  9-3  per  cent,  of  ash.  These  results  are 
easily  explained  on  the  supposition  that  the  roots  continued  to  absorb 
and  send  up  to  the  leaves  during  the  whole  summer  the  saline  and 
earthy  substances  of  which  the  ash  consisted.     But — 

B.  He  observed  also  that  the  quantity  of  the  inorganic  substances  in 
— or  the  ash  left  by — the  entire  plant,  diminished  as  it  approached  to 
maturity.  Thus  the  dry  plants  of  the  vetch,  of  the  golden  rod  {solida- 
go  vulgaris),  of  the  turnsol  {helianthus  animus),  and  of  wheat,  left  res- 
pectively of  ash,  at  three  different  periods  of  their  growth,  [Davy's 
Agricultural  Chemistry,  Lecture  HI,] — 

Before  flowering. 
per  cent. 

Vetch 15 

Golden  rod     ...       9-2 

Turnsol     ....     14-7 

Wheat       ....       7-9 

This  diminution  in  the  proportion  of  ash,  might  arise  either  from  an 

increase  in  the  absolute  quantity  of  vegetable  matter  in  the  plants  ac- 


In  flower 
per  cent. 

12-2 

Seeds  ripe. 

per  cent. 

6-6 

5-7 

50 

13-7 

9-3 

5-4 

3-3 

PROPORTION    OF    SILICA    IN    THE    ASH    CF    PLANTS.  83 

eompanying  their  increase  in  size — or  from  a  portion  of  the  saline  and 

earthy  matters  they  contained  heing  again  rejected  by  the  roots.     But 

if  the  former  be  the  true  explanation,  the  relative  proportions  of  the 

several  substances  of  which  the  ash  itself  consisted,  in  the  several  cases, 

should  have  been  the  same  at  the  several  periods  w^hen  the  experiments 

were  made.     But  this  was  by  no  means  the  case.     Thus,  to  refer  only 

to  the  quantity  of  silica  contained  in   the  ash  left  by  each  of  the  above 

plants  at  the  several  stages  of  their  growth,  the  ashes  of  the 

Before  flowering.        In  flower.  Seeds  ripe. 

per  cent.  per  cent.  per  cent. 

Vetch  contained    ...       1*5  1-5  1'75 

Golden  rod 1-5  1-5  3-5 

Turnsol 1-5  1-5  3-75 

Wheat 12-5  26-0  51-0 

If,  then,  the  proportion  of  silica  in  the  ash  increased  in  some  cases 
four-fold,  while  the  whole  quantity  of  ash  left  by  the  plant  decreased,  it 
appears  evident  that  some  part  of  that  which  existed  in  the  plant  during 
the  earlier  periods  of  its  growth  must  have  bee.^  excreted  or  rejected  by 
the  roots,  as  it  advanced  towards  maturity. 

2°.  Tills  conclilsion  is  confirmed  and  carried  farther  by  another  con- 
sideration. The  quantity  of  ash  left  by  the  ripe  wheat  plant,  in  the 
above  experiments  of  De  Saussure,  amounted  to  3-3  per  cent. ; — of 
which  ash,  51  per  cent.,  or  rather  more  than  one-half,  was  silica.  This 
silica,  it  is  believed,  could  only  have  entered  into  the  circulation  of  the 
plant  in  a  state  of  solution  in  water,  and  could  only  be  dissolved  by  the 
agency  of  potash  or  soda.  But,  according  to  Sprengel,  the  potash,  soda, 
and  silica,  are  to  each  other  in  the  grain  and  straw  of  wheat,  in  the  pro- 
portions of — 

Potash.  Soda.  Silica. 

Grain     ....     0-225  0-24  0-4 

Straw    ....     0-20  0-29  2-87 

Or,  supposing  the  grain  to  equal  one-half  the  weight  of  the  straw— 
their  relative  proportions  in  the  whole  plant  will  be  nearly  as  21  potash, 
27  soda,  205  sihca,  or  the  weight  of  the  silica  is  upwards  of  four  times 
the  weights  of  the  potash  and  soda  taken  together. 

Now  silica  requires  nearly  half  its  weight  of  potash  to  render  it  solu- 
ble in  water,*  or 'three- fifths  of  its  weight  of  a  mixture  of  nearly  equal 
parts  of  potash  and  soda.  The  quantity  of  these  alkaline  substances 
found  in  the  plant,  therefore,  is  by  no  means  sufficient  to  have  dissolved 
and  brought  into  its  circulation  the  whole  of  the  silica  it  contains.  One 
of  two  things,  therefore,  must  have  taken  j)lace.  Either  a  portion  of 
the  potash  and  soda  present  in  the  plant  in  the  earlier  stages  of  its 
growth  must  have  escaped  from  its  roots  at  a  later  stage, f  leaving  the 
silica  behind  it — or  the  same  quantity  of  alkali  must  have  circulated 
through  the  plant  several  times — bringing  in  its  burden  of  silica,  deposit- 

•  A  soluble  glass  may  be  made  by  melting  together  in  a  crucible  for  six  hours  10  parts  of 
carbonate  of  potash,  15  of  silica,  and  1  of  charcoal  powder. 

t  De  Saussure  does  not  state  the  exact  relative  quantities  of  potash  and  soda  at  the  several 
periods  of  the  growth  of  wheat,  though  they  appear  to  have  gradially  diminished.  It 
seems,  indeed,  to  be  true  of  many  plants,  that  the  potash  and  soda  thej^  contain  diminishes 
in  quantity  as  their  age  increases.  Thus  the  weight  of  potash  in  the  juice  of  the  ripe  or 
Bweet  grape,  is  said  to  be  less  than  in  the  unripe  or  sour  grape— and  the  leaves  of  the  potato 
have  been  found  more  rich  in  potash  before  than  after  blossoming  (Liebig). 


84        CAN  THE  ROOTS  MODIFY  THE  FOOD  OF  PLANTS? 

ing  it  in  the  vascular  system  of  the  plant,  and  again  returning  to  the 
soil  for  a  fresh  supply.  In  either  case  the  roots  must  have  allowed  it 
egress  as  well  as  ingress.  But  the  fact,  that  the  proportion  of  silica  in 
the  plant  goes  on  increasing  as  it  continues  to  grow,  is  in  favour  of  the 
latter  view — and  renders  it  very  probable  that  the  same  quantity  of  al- 
kali returns  again  and  again  into  the  circulation,  bringing  with  it  sup- 
plies of  silica  and  probably  of  other  substances  which  the  plant  requires 
from  the  soil.  And  while  this  view  appears  to  be  the  more  probable^it 
also  presents  an  interesting  illustration  of  what  may  probably  be  the 
kind  of  function  discharged  by  the  potash  and  other  inorganic  substances 
found  in  the  substance  of  plants — a  question  we  shall  hereafter  have  oc- 
casion to  consider  at  some  length. 

The  above  considerations,  therefore,  to  which  I  might  add  others  of  a 
similar  kind,  satisfy  me  that  the  roots  of  plants  do  possess  the  power  of 
excreting  various  substances  which  are  held  in  solution  by  the  sap  on  its 
return  from  the  stem — and  which  having  performed  their  functions  in 
the  interior  of  the  plant  are  no  longer  fitted,  in  their  existing  condition, 
to  minister  to  its  sustenance  or  growth.  Nor  is  it  likely  that  this  excre- 
tory power  is  restricted  solely  to  the  emission  of  inorganic  substances. 
Other  soluble  matters  of  organic  origin  are,  no  doubt,  permitted  to  es- 
cape into  the  soil — though  whether  of  such  a  kind  as  must  necessarily 
be  injurious  to  the  plant  from  which  they  have  been  extruded,  or  to  such 
a  degree  as  alone  to  render  a  rotation  of  crops  necessary,  neither  reason- 
ing nor  experiment  has  hitherto  satisfactorily  shown. 

VI.  The  roots  have  the  power  of  absorbing,  and  in  some  measure  of 
selecting,  food  from  the  soil — can  they  also  modify  or  alter  it  as  it  passes 
through  them?  A  colourless  sap  is  observed  to  ascend  through  the 
roots.  From  the  very  extremity  up  to  the  foot  of  the  stem  a  cross  sec- 
tion exhibits  little  trace  of  colouring  matter,  even  when  the  soil  contains 
animal  and  vegetable  substances  wjiich  are  soluble,  and  which  give  dark 
coloured  solutions,  [such  as  the  liquid  manure  of  the  fold-yard.]  Does 
such  matter  never  enter  the  root  ?  If  it  does,  it  must  be  speedily  changed 
or  transformed  into  new  compounds. 

We  have  as  yet  too  few  experiments  upon  this  subject  to  enable  us  to 
decide  with  any  degree  of  certainty  in  regard  to  this  function  of  the  root. 

It  is  probable,  however,  that  as  the  sap  passes  through  the  plant,  it  is 
constantly,  though  gradually,  undergoing  a  series  of  changes,  from  the 
time  when  it  first  enters  the  root  till  it  again  reaches  it  on  its  return  from 
the  leaf. 

Can  we  conceive  the  existence  of  any  powers  in  the  root,  or  in  the 
whole  plant,  of  a  still  more  refined  kind  ?  The  germinating  seed  gives 
off  acetic  acid  into  the  soil, — does  this  acetic  acid  dissolve  lime  from  the 
soil  and  return  with  it  again,  as  some  siippose  (Liebig),  into  the  circula- 
tion of  the  plant?*  Is  acetic  acid  produced  and  excreted  by  tlie  seed 
for  this  very  refined  purpose?  We  have  concluded  that  in  tlie  wheat 
plant  the  potash  and  soda  probably  go  and  come  several  times  during  its 
growth,  and  the  ripening  of  its  seed.     Is  this  a  contrivance  of  nature  to 

•  Braconnot  found  acetate  of  lime  in  very  small  quantitios  to  be  singularly  hurtful  to  vege- 
tation, and  acetate  of  magnesia  a  little  less  so.  He  only  mentions,  however,  some  experi- 
ments upon  mercurialis  annua,  [Ann.  de  Chim.  et  de  Pliys.  Ixxii.  p.  3G,]  and  as  Saussure 
found  that  some  plants  actually  refused  to  take  it  up  at  all,  these  acetates  may  not  be  equally 
injurious  to  all  plants. 


THE    SAP    ASCENDS    THROUGH    THE    WOOD.  85 

make  up  for  the  scarcity  of  alkaline  substances  in  tlie  soil — or  would  the 
same  mode  of  operation  be  emploj^ed  if  potash  and  soda  were  present 
in  greater  abundance  ?  Or  where  the  alkalies  are  present  in  greater 
abundance,  might  not  more  work  be  done  by  them  in  the  same 
time, — might  not  the  plant  be  built  up  the  faster  and  the  larger,  when 
there  were  more  hands,  so  to  sjjeak,  to  do  the  work  ?  Is  the  action  of 
inorganic  substances  upon  vegetation  to  be  explained  by  the  existence 
of  a  power  resident  in  the  roots  or  other  parts  of  plants,  by  which  such 
operations  as  this  are  directed  or  superintended  ?  There  are  many 
mysteries  connected  with  the  nature  and  phenomena  of  vegetable  life, 
which  we  have  been  unable  as  yet  to  induce  nature  to  reveal  to  us.* 
But  the  morning  light  is  already  kindling  on  the  tops  of  the  mountains, 
and  we  may  hope  that  the  deepest  vallies  will  not  forever  remain  obscure. 

§  3.   The  course  of  the  sap. 

If  the  trunk  of  a  tree  be  cut  off  above  the  roots,  and  the  lower  extrem- 
ity be  immediately  plunged  into  a  solution  of  madder  or  other  colouring 
substances,  the  coloured  liquid  will  ascend  and  will  gradually  tinge  the 
wood.  This  ascent  will  continue  till  the  colour  can  also  be  observed 
in  the  nerves  of  the  leaf.  If  at  this  stage  in  the  experiment  the  trunk 
be  cut  across  at  various  heights,  the  wood  alone  will  appear  coloured, 
the  bark  remaining  entirely  untinged.  But  if  the  process  be  allowed 
still  to  continue  when  the  coloured  matter  has  reached  the  leaf,  and  after 
some  further  time  the  stem  be  cut  across,  the  bark  also  will  appear  dyed, 
and  the  tinge  will  be  perceptible  further  and  further  from  the  leaf  the 
longer  the  experiment  is  carried  on,  till  at  length  both  bark  and  wood 
will  be  coloured  to  the  very  bottom  of  the  stem. 

Or  if  the  root  of  a  living  plant,  as  in  the  experiment  of  Macaire  de- 
tailed in  a  preceding  note,  be  immersed  in  a  metallic  solution — such 
as  a  solution  of  acetate  of  lead, — which  it  is  capable  of  absorbing  with- 
out immediate  injury,  and  different  portions  of  the  jjlant  be  examined 
after  the  lapse  of  different  periods  of  time,— first  the  stem,  afterwards 
the  leaves,  then  the  bark  of  the  upper  part  of  the  stem,  aiid  lastly  that 
of  the  lower  part  of  the  stem,  will  exhibit  traces  of  lead. 

These  experiments  show  that  the  sap  which  enters  by  the  roots  as- 
cends through  the  vessels  of  the  wood,  diffuses  itself  over  the  surface 
of  leaves,  and  then  descends  by  the  bark  to  the  extremities  of  the  root. 

But  what  becomes  of  the  sap  when  it  reaches  the  root?  Is  it  deliver- 
ed into  the  soil,  or  does  it  recommence  the  same  course,  and  again,  re- 
peatedly perhaps,  circulate  through  the  stem,  leaves,  and  bark  ?  This 
question  has  been  partly  answered  by  what  has  been  stated  in  the  pre- 
ceding section.  When  the  sap  reaches  the  extremity  of  the  root,  it  ap- 
])ears  to  give  off  to  the  soil  both  solid  and  fluid  substances  of  a  kind  and 

*  The  roots  ofUrees  will  travel  to  comparatively  great  distances,  and  in  various  directions, 
in  search  of  water:  the  roots  of  sainfoin  (Esjjarsette)  will  penetrate  10  or  12  feet  thronghfhe 
calcareous  rubbly  subsoil,  or  down  the  fissures  of  limestone  rocks  on  which  they  delight  to 
grow.  Is  this  llie  result  of  some  perceptive  power  in  the  plant — or  is  it  merely  by  accident 
that  the  roots  display  these  tendencies'? 

Those  who  are  in  any  degree  acquainted  with  the  speculations  of  the  German  pliysiolo- 
gists  of  the  greatest  name — in  regard  to  the  soul  and  even  the  immortality  of  plants — will  not 
accuse  me  of  going  very  far  in  alluding  to  the  possible  existence  of  some  such  perceptive 
power  in  plants.  Von  Martins  gets  rid  of  objectors  by  speaking  of  them  as  "  scieut^Ac  men 
to  whom  the  power  of  comprehending  the  trenscer-dentc'  has  ts^.n  imparled  in  a  lower  iltf  «'  " 
See  Meyen'sJaliresbericht,  1839,  or  iiilliman's  Journal  fcr  January,  1841,  p.  l??. 


86  CAriLLAUY    ATTRACTIONT. 

to  an  amount  which  probably  diflfer  with  every  species  of  plant.  The 
remainder  of  the  sap  and  of  tiie  substances  it  holds  in  solution  must  be 
diffused  through  the  cellular  spongy  terminations  of  the  roots,  and,  with 
the  new  suj)ply  of  liquid  imbibed  from  the  soil,  returned  again  to  tlie 
stern  with  the  ascending  current. 

But  what  causes  the  sap  thus  to  ascend  and  descend?  By  wliaf 
power  is  it  first  sucked  up  through  the  roots,  and  afterwards  forced  down 
again  from  the  leaves?  Several  answers  have  been  given  to  this  ques- 
tion. 

1°.  When  the  end  of  a  wide  tube,  either  of  metal  or  of  glass,  is 
plunged  into  water,  the  \u\md  will  rise  within  the  tube  sensibly  to  the 
same  level  as  that  at  which  it  stands  in  the  vessel.  But  if  a  capillary* 
tube  be  employed  instead  of  one  with  a  wide  bore,  the  liquid  will  rise, 
and  will  permanently  remain  at  a  considerably  higher  level  within  than 
without  the  tube.  The  cause  of  this  rise  has  been  ascribed  to  an  attrac- 
tion which  the  sides  of  the  tube  have  for  the  liquid,  and  which  is  suffi- 
ciently strong  to  raise  it  and  lo  keep  it  up  above  the  proper  level  of  the 
water.  The  force  itself  is  generally  distinguished  by  the  name  o^  capil- 
lary attraction. 

Now,  the  wood  of  a  tree,  as  we  have  seen,  is  composed  of  a  mass  of 
fine  tubes,  and  through  these  the  sap  has  been  said  to  rise  by  capillary 
attraction.  But  if  the  top  of  a  vine  be  cut  off"  when  it  is  juicy  and  full 
of  sap,  the  liquid  will  exude  from  the  newly  formed  surface,  and  if  the 
air  be  excluded,  will  flow  for  a  length  of  time,  and  may  be  collected  in 
a  considerable  quantity  [Lindley's  T/i'eory  of  Horticulture,  p.  47,  note]. 
Such  a  flow  of  the  sap  is  not  to  be  accounted  for  by  mere  capillary  at- 
traction— the  sides  of  tubes  cannot  draw  up  a  fluid  beyond  their  own 
extremities. 

2°.  To  supply  the  defect  of  this  hypothesis,  De  Saussure  supposed 
that  the  fluid  at  first  introduced  by  capillary  attraction  into  the  extremi- 
ties of  the  root,  was  afterwards  propelled  upwards  by  the  alternate  con- 
traction and  expansion  of  the  tubes  of  which  the  wood  of  the  root  and 
stem  is  cotnposed.  This  alternate  contraction  and  expansion  he  also 
supposed  to  be  caused  by  a  peculiar  irritating  property  of  the  sap  itself, 
which  caused  each  successive  part  of  the  tube  into  which  it  found  ad- 
mission to  contract  for  the  purpose  of  expelling  it.  Mr.  Knight  also  as- 
cribed the  ascent  of  the  sap  to  a  similar  contraction  of  certain  other  parts 
of  the  stem.  Being  once  raised,  he  supposed  it  to  return  again  or  de- 
scend by  its  own  weight — but  in  droo[)ing  branches  it  is  obvious  that  the 
sap  must  be  actually  driven  or  drawn  upwards  from  the  leaves  on  iisre- 
turn  to  the  root.     These  explanations,  therefore,  are  still  unsatisfactory. 

3^.  If  one  end  of  an  open  glass  tube  be  covered  with  a  piece  of  mois- 
tened bladder  or  other  fine  animal  membrane,  tied  tightly  over  it,  and  a 
strong  solution  of  sugar  in  water  be  then  poured  into  the  open  end  of  the 
tube,  so  as  to  cover  the  membrane  to  the  depth  of  several  inches,  and  if 
the  closed  end  be  then  introduced  to  the  depth  of  an  inch  below  the  sur- 
face of  a  vessel  of  pure  water,  the  water  will  after  a  short  time  pass 
through  the  bladder  inwards,  and  the  column  of  liquid  in  the  tube  will 
increase  in  height.     This  ascent  will  continue,  till  in  favourable  circum- 

*  Glass  tubes  perforated  by  a  very  fine  bore,  like  a  human  hair,  are  called  capillart/ tubea. 
Such  are  those  of  which  thermometers  are  usually  made. 


CAUSE    OF    THE    ASCENT    OF    THE    SAP.  87 

Stances  the  fluid  will  reach  the  height  of  several  feet,  and  will  flow  out 
or  run  over  at  the  open  end  of  the  tube.  At  the  same  lime  tlie  water  in 
the  vessel  will  become  sweet,  indicating  that  while  so  much  liquid  has 
passed  through  the  membrane  inwards,  a  quantity  has  also  passed  out- 
wards, carrying  sugar  along  with  it.*  To  these  opposite  effects  Dutro- 
chet,  who  first  drew  attention  to  the  fact,  gave  the  names  of  Endosmose, 
denoting  the  inward  progress,  and  Exosmose,{he  outward  progress  of  the 
fluid.  He  supposed  them  to  be  due  to  the  action  of  two  opposite  cur- 
rents of  electricity,  and  he  likens  the  phenomena  observed  during  the 
circulation  of  the  sap  in  plants,  to  the  appearances  presented  during  the 
above  experiment. 

Without  discussing  the  degree  of  probability  which  exists  as  to  the  in- 
fluence of  electricity  in  producing  the  phenomena  of  endosmose  and  ex- 
osmose,  it  must  be  admitted  that  the  appearances  themselves  bear  a 
strong  resemblance  to  those  presented  in  the  absorption  and  excretion  of 
fluids  by  the  roots  of  ])lanls — and  point  very  distinctly  to  at  least  a 
kindred  cause. 

Thus,  if  the  spongy  termination  of  the  root  represent  the  thin  porous 
membrane  in  the  above  experiment — the  sap  with  which  the  tubes  of 
the  wood  are  filled,  the  artificial  solution  introduced  into  the  experimen- 
tal tube — and  the  water  in  the  soil,  the  water  or  aqueous  solution  into 
which  the  closed  extremity  of  the  tube  is  introduced, — we  have  a  series 
of  conditions  precisely  similar  to  those  in  the  experiment.  Fluids  ought 
consequently  to  enter  from  the  soil  into  the  roots,  and  thence  to  ascend 
into  the  stem,  as  in  nature  they  appear  to  do. 

This  ascent,  we  have  said,  will  continue  till  the  fluid  in  the  tubes  of 
the  wood  (the  sap)  is  reduced  to  a  density  as  low  as  that  of  the  liquid 
entering  the  roots  from  the  soil.  But  in  a  growing  tree,  clothed  with 
foliage,  this  will  never  happen.  The  leaves  are  continually  exhaling 
aqueous  vapour,  as  one  of  their  constant  functions,  and  sometimes  in 
very  large  (juantily.  The  sap,  therefore,  when  it  reaches  the  leaves,  is 
concentrated  or  thickened,  and  rendered  more  dense  by  the  separation 
of  the  water,  so  that  when  it  descends  to  the  root,  and  again  begins  its 
upward  course,  it  will  admit  of  large  dilution  before  its  density  can  be 
so  far  diminished  as  to  a|)proach  that  of  the  comparatively  pure  water 
which  is  absorbed  from  the  soil.  And  this  illustration  of  the  ascent  of 
the  sap  appears  the  more  correct  from  the  obvious  purpose  it  points  out 
— (in  addition  to  others  long  recognised) — as  served  by  the  evaporation 
which  is  constantly  taking  place  from  the  surface  of  the  leaf. 

Still  the  cause  of  the  ascent  of  the  sap  is  not  the  more  clear  that  we 
can  imitate  it  in  some  measure  by  an  artificial  experiment.  But  it  will 
be  conceded  by  the  strictest  reasoners  on  physical  phenomena,  that  to 
have  obtained  the  command,  or  even  a  partial  control,  over  a  natural 

*  Instead  of  sugar,  common  salt,  gum,  or  other  soluble  substances  may  be  dissolved  in 
the  water  introduced  at  first  into  the  tube,  and  tlie  denser  this  solution  the  larger  the  quantity 
of  water  which  will  enter  by  the  membrane,  and  the  greater  the  height  to  which  the  column 
will  rise.  It  ceases  in  all  cases  to  rise  only  when  the  portions  of  liquid  within  and  without 
the  membrane  attain  nearly  to  the  same  density  [i.  e.  contain  nearly  the  same  weight  of  solid 
matter  in  solution.]  Instead  of  pure  water  the  vessel  into  which  the  extremity  of  the  tube 
is  phjnged  may  also  contain  a  weak  solution  of  some  soluble  substance — such  as  lime  or  soda 
— in  which  casa  while  the  sugar,  or  salt,  or  gum,  will  pass  outwards,  in  smaller  quantity,  the 
lime  or  soda  will  pass  inwards,  along  with  the  currents  of  water  in  which  they  are  severally 
dissolved. 


88  DECOMPOSITION  TAKES  PLACE  IN  THE  STEM.  " 

power,  is  a  considerable  step  towards  a  clear  conception  of  tlie  nature  of 
that  power  itself.  If  the  phenomena  of  endosmose  can  hereafter  be 
clearly  and  indubitably  traced  to  the  agency  of  electricity  we  shall  have 
advanced  still  another  step,  and  shall  be  enabled  to  devise  other  means 
by  which-a  more  perfect  imitation  of  nature  may  be  effected,  or  a  more 
complete  control  asserted  over  the  phenomena  of  vegetable  circulation. 

§  4.  Functions  of  the  stem. 

The  functions  of  the  stem  are  probably  as  various  as  tbose  of  the 
root,  though  the  circumstances  under  which  they  are  performed  neces- 
sarily involve  these  functions  in  considerable  obscurity. 

The  pith  which  forms  the  central  part  of  the  stem  consists,  as  I  have 
already  stated,  of  lubes  disposed  horizontally.  When  a  coloured  fluid 
is  permitted  to  enter  the  lower  part  of  the  stem  in  the  experiments 
above  described,  the  pith  remains  untinctured  in  the  centre  of  the  col- 
oured wood.  Jt  does  not,  therefore,  serve  for  the  conveyance  of  the  sap. 
Nor  does  it  seem  to  be  vitally  necessary  to  the  health  and  growth  of  the 
plant,  since  Mr.  Knight  has  shown  that,  from  the  interior  of  many  trees, 
it  may  be  removed  without  apparent  injures  and  in  nature,  as  trees  ad- 
vance in  age,  it  gradually  diminishes  in  bulk,  and  in  some  species  be- 
comes apparently  obliterated. 

The  vessels  of  the  wood,  which  surrounds  the  pith,  perform  proba- 
bly both  a  mechanical  and  a  chemical  function.  They  serve  to  convey 
upwards  to  the  leaf  the  various  substances  which  enter  by  the  roots. 
This  is  their  mechanical  function.  But  during  its  progress  upwards, 
the  sap  appears  to  undergo  a  series  of  changes.  When  it  reaches  the 
leaves  it  is  no  longer  in  the  slate  in  which  it  ascended  from  the  root  into 
the  stem.  The  difficulty  of  extracting  the  sap  from  the  wood,  at  dif- 
ferent heights,  has  prevented  very  rigorous  experiments  from  being 
made  on  its  nature  and  contents  at  the  several  stages  of  its  ascent. 
These  it  is  obvious  must  vary  with  the  species  and  age  of  the  plant,  and 
with  the  season  of  the  year  at  which  the  experiment  is  made.  But  the 
general  result  to  be  drawn  from  such  observations  as  have  hitherto  been 
made,  is,  that  those  substances  which  enter  directly  into  the  root,  when 
mingled  with  such  as  have  already  passed  through  the  circulation  of  the 
plant,  undergo,  during  their  ascent,  a  gradual  jjreparation  for  that  state 
in  which  they  become  fit  to  minister  to  the  growth  of  the  plant.  This 
preparation  is  completed  in  a  great  measure  in  the  leaf,  though  further 
changes  still  go  on  as  the  sap  descends  through  the  bark.  This  deduc- 
tion is  strengthened  by  the  fact  that  gaseous  substances  of  various  kinds 
and  in  varying  quantities  exist  in  the  interior  of  the  wood  of  the  grow- 
ing plant.  These  gaseous  subtances,  according  to  Boucherie,  are  in 
some  cases  equal  in  bulk  to  one-twentieih  part  of  the  entire  trunk  of  the 
tree  in  which  they  exist.  They  probably  move  upwards  along  with 
the  sap,  and  are  more  or  less  completely  discharged  into  the  atmosphere 
through  the  pores  of  the  leaves.  That  these  gaseous  substances  not 
only  differ  in  quantity,  but  in  kind  also,  with  the  age  and  species  of 
the  tree,  and  with  the  season  of  ihe  year,  may,  I  think,  be  considered 
as  almost  amounting  to  a  proof  that  they  have  not  been  inhaled  direct- 
ly by  the  roots,  but  are  the  result  of  chemical  decompositions  which 


FUNCTIONS  OF  THE  STF.M  AND  LEAVES.  89 

have  taken  place  on  the  stem  itself,  as  the  sap  mounted  upwards  to- 
vrards  !he  leaves. 

We  have  seen  that  the  roots  exercise  a  kind  of  discriminating  power 
in  admitting  to  the  circulation  of  the  plant  the  various  substances  whicli 
are  present  in  the  soil.  The  vessels  of  the  stem  exhibit  an  analogous 
power  of  admitting  or  rejecting  the  solutions  of  diflerent  substances  into 
which  they  may  be  immersed.  Thus  Boucherie  states  that,  when  the 
trunks  of  several  trees  of  the  same  species  are  cut  ofF  above  the  roots, 
and  the  lower  extremities  immediately  plunged  into  solutions  of  differ- 
ent substances,  some  of  these  solutions  will  quickly  ascend  into  and  pen- 
etrate the  entire  substance  of  the  tree  immersed  in  them,  while  others 
will  not  be  admitted  at  all,  or  with  extreme  slowness  only,  by  the  ves- 
sels of  the  stems  to  which  they  are  respectively  presented.  On  the 
other  hand,  that  which  is  rejected  by  one  species  will  be  readily  admit- 
ted by  another.  Whether  this  partial  stoppage  of,  or  total  refusal  to  ad- 
mit, certain  substances,  be  a  mere  contractile  effort  on  the  part  of  the 
vessels,  or  be  the  result  of  a  chemical  change  by  which  their  exclusion 
is  eftected  or  resisted,  does  not  as  yet  clearly  appear.  That  it  does  not 
depend  upon  the  lightness  and  porosity  of  the  wood,  as  might  be  sup- 
posed, is  shown  by  the  observation  that  the  poplar  is  less  easily  pene- 
trated in  this  way  than  the  beech,  and  the  willow  than  the  pear  tree, 
the  maple,  or  the  plane. 

These  various  functions  of  the  woody  part  of  the  stem  are  performed 
chiefly  by  the  newer  wood  or  alburnum,  or,  as  it  is  often  called,  the  sap 
wood  of  the  tree.  As  the  heart  wood  becomes  older,  the  tubes  of  which 
it  consists  are  either  gradually  stopped  up  by  the  deposition  of  solid 
substances  which  have  entered  by  the  roots,  or  by  the  formation  of 
chemical  compounds,  which,  like  concretions  in  the  bodies  of  animals, 
slowly  increase  in  size  till  the  vessels  become  entirely  closed — or  they 
are  by  degrees  compressed  laterally  by  the-growth  of  wood  around  them, 
so  as  to  become  incapable  of  transmitting  the  ascending  fluids.  Per- 
haps the  result  is  in  most  cases  due  in  part  to  both  these  causes.  This 
more  or  less  perfect  stoppage  of  the  oldest  vessels  is  one  reason  why  the 
course  of  the  sap  is  chiefly  directed  through  the  newer  tubes.* 

The  functions  of  the  bark,  which  forms  the  exterior  portion  of  the 
stem,  will  be  more  advantageously  described,  after  we  shrill  have  con- 
sidered the  purposes  served  by  the  leaves. 

§  5.  Functions  of  the  leaves. 

The  vessels  of  which  the  sap  w(5od  is  composed  extend  upwards  into 
the  fibres  of  the  leaf.  Through  these  vessels  the  sap  ascends,  and  from 
their  extremities  diffuses  itself  over  the  surface  of  the  leaf.  Here  it  un- 
dergoes important  chemical  changes,  the  extent,  if  not  the  exact  nature, 
of  which  will  appear  from  a  short  description  of  the  functions  which  the 
leaves  are  known  or  are  believed  to  discharge. 

1°.  When  the  roots  of  a  Vtv'mg  plant  are  immersed  in  water,  it  is  a 

•  As  the  newest  roots  are  prolongations  of  the  newest  wood,  it  may  be  supposed  that  the 
fact  of  these  roots  being  the  chief  absorbents  from  the  soil,  is  a  sufficient  reason  why  that 
which  is  absorbed  by  them  should  also  pass  up  through  the  wood  with  which  they  are  most 
closely  connected.  But  that  the  pores  of  the  heart  wood  are  really  incapable  of  transmit- 
ting fluids,  is  shown  by  plunging  the  newly  cut  stem  of  a  tree  into  a  coloured  solution — the 
newer  wood  will  be  dyed,  while  more  or  less  of  the  central  portion  will  remain  unchanged. 


90  ESCAPE    OF   WATERY    VAPOUR    FROM    THE    LEAVES. 

matter  of  familiar  observation  that  the  water  gradually  diminishes  in 
bulk,  and  will  at  length  entirely  disappear,  even  when  evaporation  into 
the  air  is  entirely  prevented.  The  water  which  ihns  disap{)ears  is  taken 
up  by  the  roots  of  tlie  plant,  is  carried  up  to  the  leaves,  is  there  spread 
out  over  a  large  surface  exposed  to  the  sun  and  to  the  air,  and  in  the 
form  of  vapour  escapes  in  considerable  proportion  through  the  pores  of 
the  leaves  and  diffuses  itself  through  the  atmosphere. 

The  quantity  of  water  which  thus  escapes  from  the  surface  of  the 
leaves  varies  with  the  moisture  of  the  soil,  with  the  species  of  plant, 
with  the  temperature  and  moisture  of  the  air,  and  with  the  season  of  the 
year.  According  to  the  experiments  of  Hales,  it  is  also  dependent  on 
the  presence  of  the  sun,  and  is  scarcely  perceptible  during  the  night. 
He  found  that  a  sun-flower,  3i  feet  high,  lost  from  its  leaves  during  12 
hours  of  one  day  30,  and  of  another  day  20  ounces  of  water,  while  during 
a  warm  night,  without  dew,  it  lost  only  three  ounces,  and  in  a  dewy 
night  underwent  no  diminution  in  weight.* 

This  loss  of  warery  vapour  by  the  leaf  is  ascribed  to  two  different 
kinds  of  action.  First,  to  a  natural  perspiration  from  the  pores  of  the 
leaf,  similar  to  the  insensible  perspiration  which  is  contiifually  proceed- 
ing from  the  skins  of  healthy  animals ;  and  second,  to  a  mechanical 
evaporation  like  that  which  gradually  takes  place  from  the  surface  of 
moist  bodies  when  exposed  to  hot  or  dry  air.  The  relative  amount  of 
loss  due  to  each  of  these  two  modes  of  action  respectively,  must  differ 
very  much  in  different  species  of  plants,  being  dependent  in  a  great 
measure  on  the  special  structure  of  the  leaf.  In  all  cases,  however,  the 
natural  perspiration  is  believed  very  greatly  to  exceed  the  mere  mechan- 
ical evaporation — though  the  results  of  Hales,  and  of  other  experimen- 
ters, show  that  both  processes  proceed  with  the  greatest  rapidity  under  the 
influence  of  a  warm  dry  atmosphere,  aided  by  the  direct  rays  of  the  sun. 

Among  the  several  purposes  served  by  this  escape  of  watery  vapour 
from  the  surface  of  the  leaf,  it  is  of  importance  for  us  to  notice  the  direct 

*  When  Ihe  escape  of  vapour  from  the  leaves  is  more  rapid  than  the  supply  of  water  from 
the  roots,  tlie  leaves  droop,  dry,  and  wither.  Such  is  sometimes  the  case  with  growing 
crops  in  very  hot  weather,  and  it  always  happens  when  a  twig  or  flower  is  plucked  and  sep- 
arated from  the  stem  or  root.  When  thus  separated  the  leaves  still  continue  to  give  off  wa- 
tery vapour  into  the  air,  and  consequently  the  sap  ascends  from  the  twig  or  stalk  to  supply 
the  place  of  the  water  thus  exhaled. 

But  as  the  sap  ascends  it  must  leave  the  vessels  empty  of  fluid,  and  air  must  rush  in  to 
fill  the  empty  space.  This  will  continue  till  nearly  all  the  fluid  has  risen  from  the  stem  into 
the  leaf,  and  the  vessels  of  the  wood  are  full  of  air.  But  if  the  stem  of  the  twig  or  flower  be 
placed  in  water  this  liquid  will  rise  into  it,  air  will  be  excluded,  and  the  freshness  and  bloom 
of  the  leaves  and  flowers  will  be  longer  prestjrved.  If  the  water  into  which  they  are  intro- 
duced contain  any  substances  in  solution,  these  will  rise  along  with  the  water,  and  will  grad- 
ually make  their  way  through  all  the  vessels  of  the  wood,  till  they  can  be  detected  in  the 
leaves.  By  this  means  even  large  trees  may  in  a  short  time  be  saturated  with  saline  solu- 
tions, capable  of  preserving  them  from  decay.  It  is  only  jiecessary  to  cut  down  or  saw 
through  Ihe  tree  and  insert  its  lower  extremity  info  the  prepared  solution,  when  the  action 
of  the  sun  and  air  upon  the  leave.s  will  cause  it  spontaneously  to  ascend.  Tims  corrosive 
sublimate  (the  subject  of  Kyan's  Patent)  may  be  injected  with  ease,  or  pyroligni/e  o/iron, 
(iron  dissolved  in  wood  vinegar,)  which  Boucherie  recommends  as  equally  efiicient  and 
much  more  economical,  [Ann.  de  Chim.  et  de  Phys.  Ixxiv.  p.  113.]  The  process  is  finislied 
wlien  the  liquid  is  found  to  have  risen  to  the  leaf.  Coloured  solutions  may  in  the  same  way 
be  injected  and  the  wood  tinged  to  any  required  shade.  One  of  the  chief  benefits  attendant 
upon"  the  cutting  of  wood  in  the  winter,  appears  to  be  that  the  absence  of  leaves  prevents  the 
exhaustion  of  the  sap  and  the  ascent  of  air  into  the  vessels  of  the  wood — the  oxygen  of  this 
air  tending  to  induce  decay.  But  the  sap  may  be  retained,  and  the  air  excluded  almost  as 
effectually,  at  any  other  season  of  the  year,  by  stripping  the  tvze  of  its  leaves  and  branches  a 
few  days  before  it  is  cut  down. 


OTHER   VOLATILE    SUBSTANCES    EXHALED.  91 

chemical  influence  it  exercises  over  the  growth  of  the  plant.  As  the  waler 
disappears  from  the  leaf,  the  roots  must  absorb  from  the  soil  at  least  an 
equal  supply.  ^This  water  brings  with  it  the  soluble  substances,  organ- 
ic and  inorganic,  which  the  soil  contains,  and  thus  in  proportion  to  tlie 
activity  with  which  the  leaves  lose  their  watery  vapour,  will  be  the 
quantity  of  those  substances  which  enter  from  the  soil  into  the  general 
circulation  of  the  plant.  This  enables  us  to  understand  how  substances, 
very  sparingljf  soluble  in  water,  should  yet  be  found  in  the  interior  of 
plants,  and  in  very  considerable  quantity,  at  almost  every  stage  of  their 
growth. 

2°.  Besides  watery  vapour,  however,  the  leaves  of  nearly  all  plants 
exhale  at  the  sameb'me  other  volatile  compounds  in  greater  or  less 
abundance.  In  the  petals  of  flowers,  we  are  familiar  with  such  exha- 
lations— often  of  an  agreeable  and  odoriferous  character.  In  the  case  of 
plants  and  trees  also  which  emit  a  sensible  odour,  we  readily  recognise 
the  fact  of  volatile  substances  being  given  off'  by  the  leaves.  But  even 
when  the  sense  of  smell  gives  us  no  indication  of  their  emission  from  a 
single  leaf  or  a  single  plant,  the  introduction  of  a  number  of  such  in- 
odorous plants  into  the  confined  atmosphere  of  a  small  room  after  a  time 
satisfies  us  that  even  they  part  with  some  volatile  matter  from  their 
leaves,  which  makes  itself  perceptible  to  our  imperfect  organs  only  when 
in  a  concentrated  state.  The  probability  therefore  is,  that  the  leaves  of 
all  plants  emit,  along  with  the  watery  vapour  which  they  evolve,  cer- 
tain other  volatile  substances  also,  though  often  in  quantities  so  minute 
as  to  escape  detection  by  our  unaided  senses.  By  the  emission  of  these 
substances  the  plant  probably  relieves  itself  of  what  would  prove  inju- 
rious if  retained,  though  of  the  chemical  nature  and  composition  of  these 
exhalations  little  or  nothing  has  yet  been  ascertained. 

3°.  If  the  branch  of  a  living  plant  bo  so  bent  that  some  of  its  leaves 
can  be  introduced  beneath  the  edge  of  an  inverted  tumbler  full  of  water, 
and  if  the  leaves  be  then  exposed  to  the  rays  of  tlje  sun,  bubbles  of  gas 
will  be  seen  to  form  on  the  leaf,  and  gradually  to  rise  through  the  water 
and  collect  in  the  bottom  of  the  tumbler.  If  this  gas  be  examined  it 
will  be  found  to  be  pure  oxygen. 

If  the  water  contain  carbonic  acid  gas,  or  if  during  the  experiment  a 
little  carbonic  acid  be  introduced,  this  gas  will  be  found  gradually  to  dis- 
appear, while  the  oxygen  will  continue  to  accumulate. 

Or  if  the  experiment  be  made  by  introducing  a  living  plant  into  a  large 
Dell-glass  full  of  common  atmospheric  air,  allowing  it  to  grow  there  for 
12  hours  in  the  sunshine,  and  tlien  examining  or  analysing  the  air  con- 
tained in  the  glass,  the  result  will  be  of  a  precisely  similar  kind.  The 
per  centage  of  oxygen  in  the  air  will  have  increased.*  And  if  the  ex- 
periment be  varied  by  the  introduction  of  a  small  quantity  of  carbonic 
acid  gas  into  the  jar,  this  gas  will  be  found  as  before  to  diminish  in  quan- 
tity, while  the  oxygen  increases.  The  conclusion  drawn  from  these 
exi)eriments,  therefore,  is,  that  the  leaves  of  plants,  tvhcn  exposed  to  the 
rays  of  the  sun,  absorb  carbonic  acid  from  the  air  and  give  off  pure  oxy- 
gen gas. 

It  has  been  already  stated  that  the  proportion  of  carbonic  acid  present 

•  It  will  be  remembered  that  atmospheric  air  contains  about  21  per  ceat.  of  oxygen  gjir 


92  OXYGEN    IS    EMITTED    DURING    THE    DAY, 

in  the  atmosphere  is  exceedingly  small,  [about  l-2500tli  of  this  bulk- 
see  Lecture  If.,  p.  30  ;1  but  if  for  tlie  purj)ose  of  experiment  we  increase 
this  proportion  in  a  gallon  of  air  to  five  or  ten  per  cent.,  introduce  a  liv- 
ing plant  into  it,  and  expose  it  to  the  sunshine,  the  carbonic  acid  will 
gradually  disappear  as  before,  while  the  oxygen  will  increase.  And  if 
we  analyse  the  air  and  estimate  the  exact  bulk  of  each  of  these  gases 
present  in  it  at  the  closeof  our  experiment,  we  shall  find  iliat  the  oxygen 
has  increased  generally  by  as  much  as  the  carbonic  acid  has  diminished. 
That  is  to  say,  if  five  cubic  inches  of  the  latter  have  disappeared,  five 
cubic  inches  will  have  been  added  to  the  bulk  of  the  oxygen.  The 
above  general  conclusion,  therefore,  is  rendered  more  precise  by  this  ex- 
periment, which  appears  to  show  that  under  the  injluence  of  the  sun's 
rays  the  leaves  of  plants  absorb  carbonic  acid  from  the  air,  and  at  the  same 
time  give  off  ais  equal  bulk  of  oxygen  gas. 

And  as  carbonic  acid  (CO2)  contains  its  own  bulk  of  oxygen  gas* 
combined  with  a  certain  known  weight  of  carbon,  it  is  further  inferred 
that  the  oxygen  given  off  by  the  leaves  is  the  same  which  has  been  pre- 
viously absorbed  in  the  form  of  carbonic  acid,  and  therefore  it  is  usually 
stated  as  a  function  of  the  leaves — that  in  the  sunshine  they  absorb  car- 
bonic acid  from  the  air,  decompose  it  in  the  interior  of  the  leaf  rctainits 
carbon,  and  again  reject  or  emit  the  oxygen  it  contained. 

This  conclusion  presents  a  very  simple  viev7  of  the  relations  of  oxygen 
and  carbonic  acid  respectively  to  the  living  leaf  in  the  presence  of  the 
sun,  and  it  appears  to  be  fairly  deduced  from  the  facts  above  stated. 
It  has  occasionally  been  observed,  however,  that  the  bulk  of  oxygen 
given  off  by  the  leaf  has  not  been  precisely  equal  to  that  of  the  carbonic 
acid  absorbed,  [see  Persoz,  Chimie  Moleculaire,  p.  54,]  and  hence  it  is 
also  fairly  concluded  that  a  portion  of  the  oxygen  of  the  carbonic  acid 
which  enters  the  leaf  is  retained,  and  made  available  in  the  production 
of  the  various  substances  which  are  formed  in  the  vascular  system  of 
different  plants.  On  the  other  hand  it  is  stated  by  Sprengel,  that  if  com- 
pounds containing  much  oxygen  be  presented  to  the  roots  of  plants,  and 
thus  introduced  into  the  circulation,  they  are  also  decomposed,  and  the 
oxygen  they  contain  in  part  or  in  whole  given  off  by  the  leaves,  so  that, 
under  certain  circumstances,  the  bulk  of  the  oxygen  which  escapes  is 
actually  greater  than  that  of  the  carbonic  acid  which  is  absorbed  by  the 
leaves.  Such  is  the  case,  for  example,  when  the  roots  are  moistened 
with  water  containing  carbonic,  sulphuric,  or  nitric  acids. — [Sprengel 
Chemie,  11.,  p.  344.] 

It  is  of  importance  to  note  these  deviations  from  apparent  simplicity 
in  the  relative  bulks  of  the  two  gases  which  are  respectively  given  off 
and  absorbed  by  all  living  vegetables.  There  are  numerous  cases  of  the 
formation  of  substances  in  the  interior  of  plants  which  theory  would  fail 
to  account  for  with  any  degree  of  ease,  were  these  apparent  anomalies 
to  be  neglected.  This  will  more  distinctly  appear  when  in  a  subsequent 
lecture  we  shall  inquire  hoiv  or  by  what  chemical  changes  the  substan- 
ces which  plants  contain,  or  of  which  they  consist,  are  produced  from 
the  food  which  they  draw  from  the  air  and  from  the  soil. 

*  This  the  reader  will  recftUectis  proved  by  burning  charcoal  in  a  bottle  of  oxygen  gas  till 
combustion  ceases,  wlien  neaiiy  the  whole  of  the  oxygen  is  converted  into  carbonic  acid,  but 
without  change  of  bulk.— See  Lecture  III.,  p.  i5. 


AND  CARBONIC  ACID  DURING  THE  NIGHT.  33 

The  most  general  and  probable  expression,  therefore,  for  the  function 
of  the  leaf,  now  under  consideration,  appears  to  be  that  in  the  sunshine 
the  leaves  absorb  from  the  air  carbonic  acid,  and  at  the  same  time 
evolve  oxygen  gas,  the  bulk  of  the  latter  gas  given  off  being  nearly 
equal  to  that  of  the  former  which  is  taken  in — the  relative  bulks  of  the 
two  gases  varying  more  or  less  with  the  species  of  plant,  as  well  as 
with  the  circumstances  under  which  it  is  caused  or  is  fitted  to  grow.* 

4°.  Such  is  the  relation  of  the  leaf  to  the  oxygen  and  carbonic  acid 
of  the  atmosphere  in  the  presence  of  the  sun.  During  the  night  their 
action  is  reversed,  they  emit  carbonic  acid  and  absorb  oxygen.  This  is 
proved  by  experiments  similar  to  those  above  described.  For  if  the 
plant  which  has  remained  under  the  bell-glass  for  12  hours  in  the  sun- 
shine— during  which  time  the  oxygen  has  sensibly  increased,  and  the 
carbonic  acid  diminished  in  bulk — be  allowed  to  remain  in  the  same  air 
through  the  following  night,  the  oxygen  will  be  found  to  have  decreased, 
while  the  carbonic  acid  will  be  present  in  larger  quantity  than  in  the 
evening  of  the  previous  day. 

The  carbonic  acid  thus  given  off  during  the  night  is  supposed  to  be 
partly  derived  from  the  soil  through  the  roots,  and  partly  from  the  sub- 
stance of  the  plant  itself.  The  oxygen  absorbed  either  combines  with 
the  carbon  of  the  plant  to  form  a  portion  of  the  carbonic  acid  which  is 
at  the  same  time  given  off  or  is  employed  in  producing  some  of  the 
other  oxidixed  [containing  oxygen  in  considerable  quantity]  compounds 
that  exist  in  the  sap. 

As  a  general  rule,  the  quantity  of  carbonic  acid  given  off  during  the 
night  is  far  from  being  equal  to  that  which  is  absorbed  during  the  day. 
Siill  it  is  obvious  that  a  plant  loses  carbon  precisely  in  proportion  to  the 
amount  of  this  gas  given  off.  Hence,  when  the  days  are  longest,  the 
plant  will  lose  the  least,  and  where  the  sun  is  brightest  it  v/ill  gain  the 
fastest;  since  other  things  being  equal,  the  decomposition  of  carbonic 
acid  proceeds  most  rapidly  where  the  sky  is  the  clearest,  and  the  rays 
of  the  sun  most  powerful.  Hence  we  see  why  in  Northern  regions, 
where  spring,  summer,  and  autumn  are  all  comprised  in  one  long  day 
— vegetation  should  proceed  with  such  rapidity.  The  decomposition  of 
the  carbonic  acid  goes  on  without  intermission,  the  leaves  have  no  night 
of  rest,  but  nature  has  kindly  provided  that,  where  the  season  of 
warmth  is  so  fleeting,  there  should  be  no  cessation  to  the  necessary- 
growth  of  food  for  man  and  beast. 

This  comparison  of  the  functions  performed  by  the  leaf,  during  the 
day  and  night  respectively,  explains  the  chemical  nature  of  the  blanching 
of  vegetables  practised  by  the  gardener,  as  well  as  the  cause  of  the  pale 
colour  of  plants  that  grow  naturally  in  the  absence  of  light. 

When  exjxtsed  to  the  sun,  the  leaves  of  these  sickly  vegetables  evolve 
oxygen,  and  gradually  become  green  and  healthy.  Woody  matter  is 
formed,  and  the  stems  become  strong  and  fibrous. 

The  light  of  the  sun,  in  the  existing  economy  of  nature,  is  indeed 
equally  necessary  to  the  health  of  plants  and  of  animals.     The  former 

*  As  the  oxygen  given  off  by  the  leaves  is  always  the  result  of  a  chemical  decomposition, 
by  which  the  carbonic  acid  or  other  compound  is  deprived  of  a  portion,  at  least,  of  its  oxy- 
gen or  de-oxidized,  this  function  of  the  leaves  in  the  presence  of  tlie  sun  is  often  spoken  of 
as  their  de-oxidizing  power. 

5 


94  LEAVES  SOMETIMES  EBUT  CHLaRlNE. 

become  pale  and  sickly,  and  refuse  lo  perform  their  thost  important 
chemical  functions  when  excluded  from  the  light.  The  bloom  disap- 
pears from  the  human  cheek,  the  hody  wastes  aw»y,  and  the  spirit 
sinks,  when  the  unhappy  prisoner  is  debarred  from  the  sight  of  the  blessed 
sun.  In  his  system,  too,  the  presence  of  light  is  necessary  to  the  perfor- 
mance of  those  chemical  functions  on  which  the  healthy  condition  of  tlie 
vital  fluids  depends. 

The  processes  by  which  oxygen  and  carbonic  acid  are  respectively 
evolved  in  plants  have  been  likened  by  physiologists  to  the  respiration 
and  digestion  of  animals.  It  is  supposed  that  when  plants  respire  they 
give  off  carbonic  acid  as  animals  do,  and  that  when  they  digest  they 
evolve  oxygen.  Respiration  also,  it  is  said,  proceeds  at  all  times,  diges- 
tion only  in  the  light  of  the  sun.  Though  these  views  are  confessedly 
conjectural,  they  are  founded  upon  striking  analogies,  and  may  reason- 
ably be  entertained  as  matters  of  opinion. 

6°.  Other  species  of  decomposition  also,  besides  that  o^  de-oxidization^ 
go  on  in  the  leaf,  or  are  there  made  manifest.  Thus  when  plants  grow 
in  a  soil  containing  much  common  salt  (chloride  of  sodium)  or  other 
chlorides,  they  have  been  observed  by  Sprengel  and  Meyen  to  evolve 
chloride*  gas  from  their  leaves.  This  takes  place,  however,  more  dur- 
ing the  night  than  during  the  day.  Some  plants  also  give  offamn^ionia, 
(Lecture  IV.,  p.  70,)  while  others  (crucifera)),  according  to  Dr.  Daube- 
ny,  [in  his  Three  Lectures  on  Agriculture,  p.  59,]  emit  from  their  leaves 
pure  nitrogen  gas. 

The  evolution  of  chlorine  implies  the  previous  decomposition  of  the 
chlorides,  which  have  been  absorbed  from  the  soil;  while  that  of  nitro- 
gen may  be  due  to  the  decomposition  of  ammonia,  of  nitric  acid,  or 
of  some  other  compound  containing  nitrogen,  which  has  entered  into  the 
circulation  by  the  roots.  The  exact  mode  and  nature  of  the  decompo- 
sition of  these  substances,  and  the  purposes  served  by  them  in  the  vegeta- 
ble economy,  will  come  under  our  consideration  in  a  subsetjuent  lecture. 

The  leaf  has  been  described  (p.  76)  as  an  expansion  of  tlie  bark. 
It  consists  internally  of  twi  layers  of  veins  or  vascular  fibres  laid  one 
over  the  other,  the  upper  connected  with  the  wood — the  lower  with  the 
inner  bark.  It  is  covered  on  both  sides  by  a  thin  membrane  (epider- 
mis), the  expansion  of  the  outer  bark.  This  ihin  inembane  is  studded 
with  numerous  small  pores  or  mouths  (stomata),  which  vary  in  size  and 
in  number  with  the  nature  of  the  plant,  and  with  the  circumstances  in 
which  it  is  intended  to  grow.  It  is  from  the  pores  in  the  upper  part  of 
the  leaf  that  substances  are  supposed  to  be  exhaled,  while  every  thing 
that  is  inhaled  enters  by  those  whica  are  observed  in  the  under  side  of 
the  leaf.f  This  opinion,  however,  is  not  universally  received,  it  being 
admitted  by  some  that  the  power  both  of  absorbing  and  of  emitting 
may  be  possessed  by  the  under  surface  of  the  leaf. 

7°.  We  have  seen  that  the  chief  su])ply  of  the  fluids  which  constitute 

*  Chlorine  is  a  gas  of  a  greenish  yellow  colour,  having  an  unpleasant  taste  and  a  suffocating 
odour.  Wiien  it  combines  with  other  substances  it  forms  chlorides.  It  exists  in,  and  im- 
parts its  smell  to,  chloride  of  lime,  which  is  employed  for  disinlecting  purposes,  and  it 
forms  upwards  of  half  the  weight  of  common  salt. 

t  This  is  illustrated  by  the  action  of  a  cabbage  leaf  on  a  wound.  If  the  upper  side  be  ap- 
plied, the  sore  is  protected  and  quickly  heals,  while  the  under  side  draws  it  and  produces  ■ 
constant  discharge. 


FUNCTIONS    OF    THE    FLOWER-LEAVES.  95 

the  sap  of  plants,  is  derived  from  the  soil.  The  under  side  of  the 
leaves  of  plants  is  also  sui)posed  by  some  to  be  capable  of  absorbing 
moisture  from  the  air,  either  in  the  form  of  watery  vapour,  or  when  it 
falls  upon  the  leaves  in  the  state  of  dew.  Like  the  roots  also  they  may 
absorb  with  the  dew  any  substances  the  latter  happens  to  hold  in  solu- 
tion. And  thus  plants  may,  in  some  degree,  be  nourished  by  the  vola- 
tile organic  substances  which  ascend  from  the  earth  during  the  heat  of 
the  day,  and  which  are  again  in  a  great  measure  precipitated  with  tlie 
evening  dew. 

Whether  the  leaves  ever  absorb  nitrogen  gas  from  the  air  has  not  as 
yet  been  determined  with  sufficient  accuracy.  If  they  do,  it  must  in  gene- 
ral be  in  very  small  quantity  only,  since  it  has  hitherto  escaped  detec- 
tion. In  like  manner  it  is  doubtful  how  far  they  regularly  absorb  any 
other  substances  which  the  air  is  supposed  to  contain.  Thus  it  is  known 
that  nitric  acid  exists  in  the  air  in  very  minute  quantity.  Some  chem- 
ists also  believe  that  ammonia  is  extensively  diffused  through  the  atmos- 
phere in  an  exceedingly  diluted  slate.  Do  the  leaves  of  plants  absorb 
these  substances?  Is  the  absorption  of  them  one  of  the  constant  and  ne- 
cessary functions  of  the  leaves  ?  The  reply  to  these  questions  must  be 
very  uncertain,  and  any  principle  which  professes- to  be  based  upon  such 
a  reply  must  be  regarded  only  as  a  matter  of  opinion. 

8°.  The  petals  of  flower-leaves  perform  a  somewhat  different  function 
from  those  of  the  ordinary  leaves  of  a  plant.  They  absorb  oxygen  at 
all  times — though  more  by  day  than  by  night — and  they  constantly  emit 
carbonic  acid.  The  bulk  of  the  latter  gas  evolved,  however,  is  less  than 
that  of  the  oxygen  taken  in.  The  absorption  of  oxygen  gas,  and  the 
constant  production  of  carbonic  acid,  is,  in  some  flowers,  so  great  as  to 
cause  a  perceptible  'ncrease  of  temperature — and  to  this  slow  combus- 
tion, so  to  speak,  the  proper  heat  observed  in  the  flowers  of  many  plants 
has  been  attributed. 

According  to  some  authors,  the  flower-leaves  also  emit  pure  nitrogen  , 
gas. — [Sprengel,  Cheinie,  II.,  p.  347.]  This  fact  has  not  yet  been  deter- 
mined by  a  sufficient  number  of  accurate  experiments;  it  is  in  accord- 
ance, however,  with  the  results  of  Boussingault,  that,  when  a  plant 
flowers  and  approaches  to  maturity,  the  nitrogen  it  contains  becomes 
less.  If  confirmed,  this  evolution  of  nitrogen  would  throw  an  interest- 
ing light  on  the  most  advantageous  employment  of  green  crops,  both  for 
the  purposes  of  manure  and  for  the  feeding  of  cattle. 

9°.  When  the  leaves  of  a  plant  begin  to  decay,  either  naturally  as  in 
autumn,  or  from  artificial  or  accidental  causes,  they  no  longer  absorb 
and  decompose  carbonic  acid,  even  under  the  influence  of  the  sun's  rays. 
On  the  contrary,  they  absorb  oxygen,  like  the  petals  cf  the  flower,  new 
compounds  are  formed  within  their  substance — their  green  colour  disap- 
pears— they  become  yellow — they  wither,  die,  and  drop  from  the  tree — 
their  final  function,  as  the  organs  of  a  living  being,  is  discharged.  They 
then  undergo  new  changes,  are  subjected  to  a  new  series  of  influences, 
and  are  made  to  serve  new  purposes  in  the  economy  of  nature.  These 
we  shall  hereafter  find  to  be  no  less  interesting  and  important  in  refer- 
ence to  a  further  end,  than  are  the  functions  of  the  living  leaf  to  the 
growth  and  nourishment  of  the  plant. — [See' subsequent  lectu^  *'  On  the 
law  of  the  decay  of  organic  substances.^ ^]  ^ 


96  CUKMIVAL    FUNtTJO.NS  CF    THE  BARK. 

§  6.  Functions  of  the  bark. 

The  inner  bark  being  connected  with  the  under  layer  of  vessels  in  the 
leaf,  receives  from  tliem  the  sap  after  it  has  been  changed  by  the  action 
of  the  air  and  light,  and  transmits  it  downwards  to  the  root. 

The  outer  bark,  especially  in  young  twigs  and  in  the  stalks  of  the 
grasses,  so  closely  resembles  the  leaves  in  its  appearance,  that  we  can 
have  no  difficulty  in  admitting  that  it  must,  not  unfrequently,  perform 
similar  functions.  In  the  Cactus,  the  Stapelia,  and  other  plants  which 
produce  no  true  leaves,  this  outer  bark  seems  to  perform  all  the  functions 
which  in  other  vegetable  tribes  are  specially  assigned  to  the  abundant 
foliage.  During  its  descent  through  the  inner  bark,  therefore,  the  sap 
must  in  very  many  cases  undergo  chemical  changes,  more  or  less  analo- 
gous to  those  which  usually  take  place  in  the  leaf. 

It  is  by  means  of  the  inner  bark  that  the  stems  of  trees,  such  as 
our  forest  and  fruit  trees,  are  enlarged  by  the  deposition  of  annual 
layers  of  new  wood.  The  woody  fibre  is  formed  or  prepared  in 
the  leaf,  and  as  the  sap  descends  it  is  deposited  beneath  the  inner  sur- 
face of  the  inner  bark.  It  thus  happens  that,  as  the  sap  descends,  it  is 
gradually  deprived  of  the  substances  it  held  in  solution  when  it  left  the 
leaf,  and  in  consequence  it  becomes  difficult  to  say  how  much  of  the 
change,  which  the  sap  is  found  to  have  undergone  when  it  reaches  the 
root,  is  due  to  chemical  transformations  produced  during  its  descent,  and 
how  much  to  the  deposition  of  the  woody  fibre  and  other  matters  it  has 
parted  with  by  the  way. 

Among  other  evidences  of  such  changes  really  taking  place  during 
the  descent  of  the  sap,  I  may  mention  an  observation  of  Meyen  [Jahres- 
bericht,  1839,  p.  27],  made  in  the  course  of  his  experiments  on  the  re- 
production of  the  bark  of  trees.  In  these  experiments  he  enclosed  the 
naked  wood  in  strong  glass  tubes,  and  in  three  cases  out  of  eight  the 
tubes  were  burst  and  shattered  in  pieces.  This  could  only  have  arisen 
from  the  disengagement  of  gaseous  substances,  the  result  of  decomposi- 
tion. While,  therefore,  such  gases  as  enter  by  the  roots  or  are  evolved 
in  the  vessels  of  the  wood  during  the  ascent  of  the  sap,  escape  by  the 
leaf  along  with  those  which  are  disengaged  in  the  leaf  itself,  it  is  proba- 
ble that  those  which  are  produced  as  the  result  of  changes  in  the  bark, 
descend  with  the  downward  sap,  and  are  discharged  by  the  root.* 

In  the  bark  of  the  root  it  is  probable  that  still  further  changes  take 
place — and  of  a  kind  which  can  only  be  eflecled  during  the  absence  of 
light.  This  is  rendered  probable  by  the  fact  that  the  bark  of  the  root 
frequently  contains  substances  which  are  not  to  be  met  with  in  any 
other  part  of  the  plant.  Thus  from  the  bark^of  the  fresh  root  of  the  ap- 
ple tree  a  substance  named  phloridzine,  possessed  of  considerable  medi- 
cal virtues,  may  be  readily  extracted,  though  it  does  not  exist  in  the 
bark  either  of  the  stem  or  of  the  branches. 

In  fine,  as  the  food  which  is  introduced  into  the  stomachs  of  animals, 
undergoes  continual  and  successive  chemical  changes  during  its  pro- 
gress through  the  entire  alimentary  canal — so,  numerous  phenomena 
indicate  that  the  sap  of  plants  is  also  subjected  to  unceasing  transforma- 

*  SproDg||teays  that  the  steins  and  twigs,  and  the  stalks  of  the  grasses,  all  absorb  oxygen 
and  give  offCarbonic  acid.— CAemte,  II.,  p.  341. 


FUNCTIONS  OF  THE  HOOT  MODIFIED  BY  THE  SOIL.  97 

tions, — in  the  root  and  in  ihe  stem  as  well  as  in  the  leaves, — atone  time 
in  the  dark,  at  another  under  the  influence  of  the  sun's  rays, — exposed 
when  in  the  leaf  to  the  full  action  of  the  air, — and  when  in  the  root  al- 
most wholly  secluded  from  its  presence  ; — the  new  compounds  pro- 
duced in  every  instance  being  suited  either  to  the  nature  of  the  plant  or 
the  wants  and  functions  of  that  part  of  it  in  which  each  transformation 
takes  place. 

To  some  of  these  transformations  it  will  be  necessary  to  advert  more 
particularly,  when  we  come  to  consider  the  special  changes  by  which 
those  substances  of  which  plants  chiefly  consist,  are  formed  out  of  these 
compounds  on  which  they  chiefly  live. 

§  7.  Circumstances  by  which  the  functions  of  the  various  parts  of  plants 
are  modified. 
Plants  grow  more  or  less  luxuriantly,  and  Their  several  parts  are 
more  or  less  largely  developed,  in  obedience  to  numerous  and  varied 
circumstances. 

I.  In  regard  to  the  special  functions  of  the  ropt,  we  have  already  seen 
that  the  access  of  atmospheric  air  is  in  some  cases  indispensable,  while 
in  others,  by  shooting  vertically  downwards,  the  roots  appear  to  shun 
the  approach  of  either  air  or  light.  It  is  obvious  also  that  a  certain  de- 
gree of  moisture  in  the  soil,  and  a  certain  temperature,  are  necessary 
to  the  most  healthy  discharge  of  the  functions  of  the  root.  In  hot  wea- 
ther the  plant  droops,  because  the  roots  do  not  absorb  water  from  the 
soil  with  sufficient  rapidity.  And  though  it  is  probable  that,  at  every 
temperature  above  that  of  absolute  freezing,  the  food  contained  in  the 
soil  is  absorbed  and  transmitted  more  or  less  slowly  to  the  stem,  yet  it  is 
well  known  that  a  genial  warmth  in  the  soil  stimulates  the  roots  to  in- 
creased activity.  The  practice  of  gardeners  in  applying  bottom  heat  in 
the  artificial  climate  of  the  green-hoase  and  conservatory  is  founded  on 
this  well-known  principle. 

But  the  nature  of  the  soil  in  which  plants  grow  has  also  much  influ- 
ence on  the  way  in  which  the  functions  of  the  root  are  discharged.  As 
a  general  fact  this  also  is  well  known,  though  the  special  qualities  of  the 
soil  on  which  the  greater  or  less  activity  of  vegetation  depends,  are  far 
from  being  generally  understood.  If  the  soil  contain  a  sensible  quantity 
of  any  substance  which  is  noxious  to  plants,  it  is  plain  that  their  roots 
will  be  to  a  certain  degree  enfeebled,  and  their  functions  in  consequence 
ofily  imperfectly  discharged.  Or  if  the  soil  be  deficient  either  in  organic 
food,  or  in  one  or  other  of  those  inorganic  substances  which  the  plants 
necessarily  require  for  the  production  of  their  several  parts,  the  roots 
cannot  perform  their  office  with  any  degree  of  efficiency.  Where  the 
necessary  materials  are  wanting  the  builder  must  cease  to  work.  So  in 
a  soil  which  contains  no  silica,  the  grain  of  wheat  may  germinate,  but 
he  stalk  cannot  be  produced  in  a  natural  or  healthy  state,  since  silica  is 
indispensable  to  its  healthy  construction*. 

II.  The  ascent  of  the  sap  is  modified  chiefly  by  the  season  of  the 
year,  by  the  heat  of  the  day,  and  by  the  genus  and  age  of  the  plant  or 
tree. 

There  seems  reason  to  believe  that  the  plant  never  sleeps,  that  even 
during  the  winter  the  circulation  slowly   proceeds,   though  the  first 


98  ALSO  THE  RAPIDITY  OF  THE  CIRCULATION^. 

genial  sunshine  of  the  early  spring  stimulates  it  to  increased  activity. 
The  general  increased  temperature  of  the  air  does  not  produce  this  ac- 
celeration in  so  remarkable  a  manner  as  the  direct  rays  of  the  sun.  The 
sap  will  flow  and  circulate  on  the  side  of  a  tree  on  which  the  sunshine 
falls,  while  it  remains  sensibly  stagnant  on  the  other.  This  is  shown  by 
the  cutting  down  similar  trees  at  more  and  more  advanced  periods  of 
the  spring,  and  immersing  their  lower  extremities  in  coloured  solutions. 
The  wood  and  bark  on  one  side  of  the  tree  will  be  coloured,  while,  on 
the  other,  both  will  remain  unstained.  If  a  similar  difference  in  the 
comparative  rapidity  of  the  circulation  on  opposite  sides  of  a  trunk  or 
branch  be  supposed  to  prevail  more  or  less  throughout  the  year,  we  can 
readily  account  for  the  annual  layers  of  wood  being  often  thicker  on 
the  one  half  of  the  circumference  of  the  stem  than  on  the  other. 

The  sap  is  generally  supposed  to  flow  most  rapidly  during  the  spring, 
but  if  trees  be  cut  dow^  at  different  seasons,  and  immersed  as  above 
described,  the  coloured  solution,  according  to  Boucherie,  reaches  the 
leaves  most  rapidly  in  the  autumn.* 

The  heat  of  the  day,  other  circumstances  being  the  same,  materially 
affects,  for  the  time,  the  rapidity  of  the  circulation.  The  more  rapidly 
watery  and  other  vapours  are  exhaled  from  the  leaves,  the  more  quick- 
ly must  the  sap  flow  upwards  to  supply  the  waste.  If  on  two  succes- 
sive days  the  loss  by  the  leaves  be,  as  in  the  experiment  of  Hales,  above 
described,  (p.  90,)  as  2  to  3,  the  ascent  of  the  sap  must  be  accelerated 
or  retarded  in  a  similar  proportion.  Hence,  every  sensible  variation  in 
the  temperature  and  moisture  of  the  air,  must  also,  to  a  certain  extent, 
modify  the  flow  of  the  sap  ;  must  cause  a  greater  or  less  transport  of  that 
food  which  the  earth  supplies,  to  be  carried  to  every  part  of  the  plant, 
and  must  thus  sensibly  affect  the  luxuriance  and  growth  of  the  whole. 

But  the  persistance  of  the  leaves  is  a  generic  character,  which  has 
considerable  influence  upon  the  circulation  in  the  evergreens.  In  the 
pine  and  the  holly,  from  which  the  leaves  do  not  fall  in  the  autumn,  the 
sap  ascends  and  descends  during  all  the  colder  months, — at  a  slower 
rate,  it  is  true,  than  in  the  hot  days  of  summer,  yet  much  more  sensibly 
than  in  the  oak  and  ash,  which  spread  their  naked  arms  through  the 
wintery  air.  This  is  illustrated  by  the  experiments  of  Boucherie,  who 
has  observed  that  in  December  and  January  the  entire  wood  of  resinous 
trees  may  be  readily  and  thoroughly  penetrated  by  the  spontaneous  as- 
cent of  saline  and  other  solutions,  into  which  their  stems  may  be  im- 
mersed. 

III.  From  what  has  just  been  stated,  it  will  appear  that  the  mechani- 
cal functions  of  the  stem  are  subject  to  precisely  the  same  influences  as 
the  ascent  of  the  sap.  As  the  tree  advances  in  age,  the  vessels  of  the 
interior  will  become  more  or  less  obliterated,  and  the  general  course  of 
the  sap  will  be  gradually  transferred  to  annual  layers,  more  and  more 

*  Boucherie  makes  a  distinction,  not  hitherto  insisted  upon  by  physiologists,  between  the 
circulation  on  the  surface  of"the  tree  by  wflich  the  buds  and  youns;  twigs  are  supported,  and 
the  interior  circulation,  which  is  not  perfect  until  a  latter  period  of  the  year.  Hence  in  the 
spring,  though  the  sap  is  flowing  rapidly  through  the  bark  and  tiie  newest  wood,  coloured 
solutions  will  not  penetrate  the  interior  of  the  tree  with  any  degree  of  rapidity.  In  autumn, 
on  the  other  hand — when  the  fear  of  approaching  winter  has  already  descended  upon  the 
bark — the  time  of  most  active  circulation  has  only  arrived  for  the  interior  layers  of  the  older 
wood.  It  is  this  season  consequently  that  he  finds  most  favourable  for  impregnating  the 
trunks  of  trees  with  those  soluiions  which  are  likely  to  preserve  them  from  decay.— il^in.  de 
CJiim.  et  de  Phys.^  Ixxiv.,  p.  135. 


CHEMICAL   R.VY3    IN    TIIE    SUN-BEAM.  99 

removed  from  the  centre.  It  is  this  transference  of  the  vital  circula- 
tion to  newer  and  more  perfect  vessels  that  enables  the  tree  to  grow  and 
blossom  and  bear  fruit  through  so  long  a  life.  In  animals  the  vessels 
are  gradually  worn  out  by  incessant  action.  None  of  them,  through 
old  age,  are  permitted  to  retire  from  the  service  of  the  body — and  the 
whole  system  must  stop  when  one  of  them  is  incapacitated  for  the 
further  performance  of  its  appointed  duties. 

In  regard  to  the  chemical  functions  of  the  stem,  it  is  obvious  that  they 
are  not  assigned  to  the  mere  woody  matter  of  the  vessels  and  cells. 
They  take  place  in  these  vessels,  but  the  nature  and  extent  of  the  chemi- 
cal changes  themselves  must  be  dependent  upon  the  quantity  and  kinds 
of  matter  which  ascend  or  descend  in  the  sap.  The  entire  chemical 
functions  of  the  plant,  therefore,  must  be  dependent  upon  and  must  be 
moditied  by  the  nature  of  the  substances  which  the  soil  and  the  air  re- 
spectively present  to  the  roots  and  to  the  leaves. 

•  IV.  In  describing  the  functions  of  the  leaf,  I  have  already  had  occa- 
sion to  advert  to  the  greater  number  of  the  circumstances  by  which  the 
discharge  of  those  functions  is  most  materially  affected.  We  have  seen 
that  the  purposes  served  by  the  leaf  are  entirely  different  according  as 
the  sun  is  above  or  below  the  horizon  ;  that  the  temperature  and  mois- 
ture of  the  air  may  indeed  materially  influence  the  rapidity  with  which 
its  functions  are  discharged — but  that  the  light  of  the  sun  actually  deter- 
mines their  nature.  Thus  the  leaf  becomes  green  and  oxygen  is  given 
off*  in  the  presence  of  the  sun,  while  in  his  absence  carbonic  acid  is  dis- 
engaged, and  the  whole  plant  is  blanched. 

How  necessary  light  is  to  the  health  of  plants  may  be  inferred  from 
the  eagerness  with  which  they  appear  to  long  for  it.  How  intensely* 
docs  the  sun-flower  watch  the  daily  course  of  the  sun, — how  do  the 
countless  blossoms  nightly  droop  when  he  retires, — and  the  blanched 
plant  strive  to  reach  an  open  chink  through  which  his  light  may  reach 
it!* 

That  the  warmth  of  the  sun  has  comparatively  little  to  do  with  this 
specific  action  of  his  rays  on  the  chemical  functions  of  the  leaf,  is  illus- 
trated by  some  interesting  experiments  of  Mr.  Hunt,  on  the  effect  of 
rays  of  light  of  different  colours  on  the  growing  plant.  He  sowed  cress 
seed,  and  exposed  different  portions  of  the  soil  in  which  the  seeds  were 
germinating,  to  the  action  of  the  red,  yellow,  green,  and  blue  rays, 
which  were  transmitted  by  equal  thicknesses  of  solutions  of  these  seve- 
ral colours.  "  After  ten  days,  there  was  under  the  blue  fluid,  a  crop  of 
cress  of  as  bright  a  green  as  any  which  grew  in  full  light  and  far  more 
abundant.  The  crop  was  scanty  under  the  green  fluid,  and  of  a  pale 
yellow,  unhealthy  colour.  Under  the  yellow  solution,  only  two  or  three 
plants  appeared,  but  less  pale  than  those  under  the  green, — while  be- 
neath the  red,  a  few  more  plants  came  up  than  under  the  yellow,  though 
they  also  were  of  an  unhealthy  colour.  The  red  and  blue  bottles  being 
now  mutually  transferred,  the  crop  formerly  beneath  the  blue  in  a  few 

*  A  potato  has  been  observed  to  grow  up  in  quest  of  light  from  the  bottom  of  a  well 
twelve  feet  deep— and  in  a  dark  cellar  a  shoot  of  20  feet  in  length  has  been  met  with,  the 
extremity  of  which  had  reached  and  rested  at  an  open  window.  In  the  leaves  of  blanched 
vegeiables  peculiar  chemical  compounds  are  formed.  Thua  in  the  stalk  of  the  potato  a 
poisOTioq^  substance  called  aolanin  is  producsd,  which  disappears  again  when  the  stalk  is  ex- 
posed to  the  light  and  becomes  green. 


loo  FUNCTIONS    OF    THE    GREEN    TWIGS. 

days  appeared  blighted,  while  on  the  patch  previously  exposed  to  the 
red,  some  additional  plants  sprung  up.''* 

Besides  the  rays  of  heat  and  of  light,  the  sun-beam  contains  what 
have  been  called  chemical  rays,  not  distinguishable  by  our  senses,  but 
capable  of  being  recognized  by  the  chemical  effects  they  produce. 
These  rays  appear  to  differ  in  kind,  as  the  rays  of  different  coloured 
light  do.  It  is  to  the  action  of  these  chemical  rays  on  the  leaf,  and 
especially  to  those  which  are  associated  with  the  blue  light  in  the  solar 
beam,  that  the  chemical  influence  of  the  sun  on  the  functions  of  the  leaf 
is  principally  to  be  ascribed. 

It  cannot  be  doubted  that  the  warmth  and  moisture  of  a  tropical  cli- 
mate act  as  powerful  stimulants — assistants  it  may  be — to  the  leaH  in 
the  absorption  of  carbonic  acid  from  the  air,  and  in  that  rapid  appropria- 
tion (assimilation)  of  its  carbon  by  which  the  growth  of  the  plant  is  has- 
tened and  promoted.  But  the  bright  sun,  and  especially  the  chemical  in- 
fluence of  his  beams,  must  be  regarded  as  the  main  agent  in  the  wonderful 
development  of  a  tropical  vegetation.  Under  this  influence  the  growth 
by  the  leaves  at  the  expense  of  the  air  must  be  materially  increased, 
and  the  plant  be  rendered  less  dependent  upon  tiie  root  and  the  soil  for 
the  food  on  which  it  lives,  f 

V.  Tlie  rapidity  with  which  a  plant  grows  has  an  important  influence 
upon  the  share  which  the  hark  is  permitted  to  take  in  the  general 
nourishment  of  the  whole.  The  green  shoot  performs  in  some  degree 
the  functions  of  the  leaf.  In  vascular  plants,  therefore,  which  in  a  con- 
genial climate  may  almost  be  seen  to  grow,  the  entire  rind  of  a  tall  tree 
may  more  or  less  effectually  absorb  carbonic  acid  from  the  atmosphere, 
during  the  presence  of  the  sun.  The  broad  leaves  of  the  palm  tree, 
when  fully  developed,  render  the  plant  in  a  great  degree  independent  of 
the  soil  for  organic  food — and  the  large  amount  of  absorbing  surface  in 
the  long  green  tender  stalks  of  the  grasses,  and  of  their  tropical  ana- 
logues, must  malerially  contribute  to  the  same  end.  Hence  the  pro- 
portion of  organic  matter  derived  from  the  air,  in  any  crop  we  reap, 
must  always  be  the  greater  the  more  rapid  its  general  vegetation  has 
been. 


It  is  a  fact  familiarly  known  to  all  of  you,  that,  besides  those  circum- 
stances by  which  we  can  perceive  the  special  functions  of  any  one  or- 
gan to  be  modified,  there  are  many  by  which  the  entire  economy  of  the 
plant  is  materially  and  simultaneously  affected.  On  this  fact  the  prac- 
tice of  agriculture  is  founded,  and  the  various  processes  adopted  by  the 
practical  farmer  are  only  so  many  modes  by  which  he  hopes  to  influ- 

*  London  and  Edinburgh  Journal  of  Science,  February,  1840. 

Might  not  our  cheap  blue  glass  be  used  with  advantage  in  glazing  hot-houses,  conserva- 
tories, &c.  ? 

t  The  effect  of  continued  sunshine  may  be  olten  seen  in  our  cornfields  in  May,  when, 
under  the  influence  of  propitious  weather,  the  young  plants  are  shooting  rapidly  up.  When 
such  a  field  is  bounded  by  a  lofty  hedge  running  nearly  north  and  south,  the  ri  lijes  nearest 
the  hedge  on  either  side  will  be  in  the  shade  for  nearly  one-half  of  the  day,  and  will  iuviuiit- 
bly  appear  of  a  paler  green  and  less  healthy  colour.  If  the  hedge  be  studded  with  occasion;  1 
large  trees,  the  spots  on  which  the  shadows  of  those  trees  rest  will  be  indiciiod  hy  disiinct 
pale  green  patches  stretching  further  into  the  field  than  the  first,  and  someiinies  Lvcn^lun 
the  second  ridges. 


EFFECT    OF    MARLING. — REWARDS    OF    NATURE.  101 

ence  and  promote  the  growth  of  the  whole  plant,  and  the  discharge  of 
the  functions  of  all  its  parts. 

Though  manures  in  the  soil  act  immediately  through  the  roots,  they 
stimulate  the  growth  of  the  entire  plant;  and  though  the  application  of 
a  top-dressing  may  be  supposed  first  to  affect  the  leaf,  yet  the  beneficial 
result  of  the  experiment  depends  upon  the  influence  which  the  dressing 
may  exercise  on  every  part  of  the  vegetable  tissue. 

In  connection  with  this  part  of  the  subject,  therefore,  I  shall  only 
further  advert  to  a  very  remarkable  fact  mentioned  by  Sprengel,  which 
seems,  if  correct,  to  be  susceptible  of  important  practical  applications. 
He  states  that  it  has  very  frequently  been  observed  in  Holstein,  that  if, 
on  an  extent  of  level  ground  sown  with  corn,  some  fields  be  marled,  and 
others  left  unmarled,  the  corn  on  the  latter  portions  will  grow  less  luxuri- 
antly and  will  yield  a  poorer  crop  than  if  the  whole  had  been  unmarled. 
Hence  he  adds,  if  the  occupier  of  the  unmarled  field  would  not  have  a 
succession  of  poor  crops,  he  must  marl  his  land  also.* 

Can  it  really  be  that  nature  thus  rewards  the  diligent  and  the  impro- 
ver? Do  the  plants  which  grow  on  a  soil  in  higher  condition  take  from 
the  air  more  than  their  due  share  of  the  carbonic  acid  or  other  vegetable 
food  it  may  contain,  and  leave  to  the  tenants  of  the  poorer  soil  a  less  pro- 
portion than  they  might  otherwise  draw  from  it  ?  How  many  interest- 
ing reflections  does  such  a  fact  as  this  suggest !  What  new  views  does 
it  disclose  of  the  fostering  care  of  the  great  Contriver — of  his  kind  encour- 
agement of  every  species  of  virtuous  labour  !  Can  it  fail  to  read  to  us  a 
new  and  special  lesson  on  the  benefits  to  be  derived  from  the  application 
of  skill  and  knowledge  to  the  cultivation  of  the  soil  ? 

'  Wenn  namlich  aiif  einer  Feldflur  Stiick  um  Sliick  gemergelt  worden  isl,  so  wachsen 
die  Friichte  auf  den  nicht  gemergelten  Feldern,  auch  wenn  hier  alle  friiheren  verhaltnisse 
ganz  dicselben  bleiben,  nicht  mehrsogut,  als  eliedem;  wodurch  die  Besitzer  jener  Felder, 
wenn  sie  nicht  fortwahrend  geringe  Erndten  haben  wollen,  geniithigt  sind,  gleichfalls  zu 
mergein.  Aus  dieser  hochst  vichtigen  Erscheinung,  die  man  sehr  hdujig  in  Holsteinschen 
bemerkt,  &c. — Sprengel, Chemie fur  iMndwirt/ixchqft,  I.,  p.  303. 

5* 


LECTURE   VI. 

abstances  of  which  plants  chiefly  consist— Woody  fibre,  Starch,  Gum,  Sugars— Their  mu- 
tual relations  and  transformations- Gluten,Vegetable  Albumen,  Diastase— Acetic,  Tartaric, 
Malic,  Citric,  and  Oxalic  Acids — General  observations. 

From  what  has  been  stated  regarding  the  structure  of  plants,  it  will  be 
u.nderstood  in  what  way  the  food  is  introduced  into  their  circulation.  The 
rext  inquiry  appears  to  be  how — by  what  chemical  changes — is  the  food, 
when  introduced,  converted  into  those  substances  of  which  plants  chiefly 
consist.  But  in  order  that  we  may  clearly  understand  this  point,  it  is 
necessary  that  we  know  first  the  nature  and  chemical  constitution  of  the 
substances  which  are  most  largely  formed  from  the  food  in  the  interior 
of  the  plant.  To  this  point,  therefore,  I  must  previously  direct  your 
attention. 

If  you  were  to  collect  all  tfie  varieties  of  plants  which  are  within  your 
reach — whether  such  as  are  cultivated  and  used  for  food — or  such  as 
grow  more  or  less  abundantly  in  a  wild  state — and  were  to  extract  their 
several  juices,  and  to  separate  from  each  of  these  juices  the  chemical 
compounds  it  contains — you  would  gradually  gather  together  so  many 
different  substances,  all  possessed  of  different  properties,  that  you  would 
scarcely  be  able  to  number  them. 

But  if  at  the  same  time  you  compared  the  weight  of  each  substance 
thus  collected  with  that  of  the  entire  plant  from  which  it  is  derived,  you 
would  find  also  that  the  quantity  of  many  of  them  is  comparatively  so 
minute  that  only  a  very  small  portion  of  the  vital  energies  of  the  plant 
can  be  expended  in  producing  them, — that  they  may  be  entirely  neglect- 
ed in  a  general  consideration  of  the  great  products  of  vegetation.  Thus 
though  quinine  and  morphine,  the  active  ingredients  in.  Peruvian  bark 
and  in  opium,  are  most  interesting  substances,  from  their  effect  upon  the 
human  constitution,  and  their  use  in  medicine,  yet  they  form  so  small  a 
fraction  of  the  mass  of  the  entire  trees  or  plants  from  which  they  are  ex- 
tracted, that  it  would  be  idle  to  attempt  to  convey  to  you  any  notion  of 
the  way  in  which  plants  grow  and  are  fed,  by  showing  you  how  such 
substances  as  these  are  produced  from  the  food  on  which  plants  live. 

While,  however,  the  examination  would  satisfy  you  that  almost 
every  species  of  plant  produced  in  small  quantity  one  or  more  sub- 
stances peculiar  to  itself,  you  would  observe,  at  the  same  tiine,  that 
every  plant  yielded  a  certain  quantity  of  two  or  three  substances  com- 
mon to  and  produced  by  all,  and  in  most  cases  constituting  the  greater 
portion  of  their  bulk.  Thus  all  trees  and  herbs  produce  wood  or  woody 
fibre,  and  of  this  substance  you  know  that  their  chief  bulk  consists. 
Again,  all  the  grains  and  roots  you  cultivate  contain  starch  in  large 
quantity,  and  the  production  of  this  starch  is  one  of  the  great  objects  of 
the  art  of  culture.  The  juices  of  trees,  and  of  grasses,  and  of  cultivated 
roots,  contain  sugar  and  gum,  and  sometimes  in  such  quantity  as  to 
make  their  extraction  a  source  of  profit  both  to  the  grower  and  to  the 


CONSTITUTION    OF    WOODY    FIBRE.  103 

manufacturer.  The  flour  of  grain  contains  sugar  also,  and  along  with  it 
two  other  substances,  in  small  quantity,  gluten  and  vegetable  albumen^ 
which  are  of  much  importance  in  reference  to  the  nutritive  qualities  of 
the  different  varieties  of  flour.  Sugar  is  also  present  in  the  juices  of 
fruits,  but  it  is  there  associated  with  various  acid  (sour)  substances 
which  disappear  to  a  certain  extent  or  change  into  sugar  as  the  fruit 
ripens. 

Of  these  few  substances  the  great  bulk  of  vegetables  of  all  kinds  con- 
sists. They  constitute  nearly  the  whole  mass  of  those  various  crops 
which  the  art  of  culture  studies  to  raise  for  the  use  of  man  and  beast. 
To  the  study  of^lhese  substances,  therefore,  I  shall  at  present  confine 
your  attention,  and  if  I  shall  afterwards  be  able  to  make  you  under- 
stand how  these  few  compound  bodies  are  produced  in  the  interior  of  a 
plant  from  the  food  it  takes  up,  I  shall  succeed  in  conveying  to  you  as 
much  information  in  regard  to  this  most  interesting  branch  of  our  subject 
as  will  be  necessary  to  a  general  explanation  not  only  of  the  natural 
growth  and  increase  of  plants,  but  of  the  nature  and  efficacy  of  those 
artificial  means  which  the  practical  farmer  employs,  in  order  to  hasten 
their  growth  or  enlarge  their  increase. 

§  1.  Woody  fibre  or  lignin — its  constitution  and  properties. 
1°.  When  a  portion  of  the  stem  of  a  herbaceous  plant,  or  of  the  new 
ly  cut  wood  of  the  trunk  or  branch  of  a  tree,  is  reduced  to  small  pieces, 
and  boiled  in  successive  portions  of  water  an^i  alcohol,  as  long  as  any 
thing  is  taken  up,  a  white  fibrous  mass  remains,  to  which  the  name  of 
woody  fibre  or  lignin  has  been  given.  This  substance  has  no  taste  oi 
smell,  and  is  perfectly  insoluble  in  water.  It  is  nearly  identical  in  its 
chemical  constitution  and  properties,  whether  it  be  obtained  from  the 
porous  willow,  or  from  the  solid  box  tree,  and  the  fibres  of  linen  and  of 
cotton  consist  essentially  of  the  same  substances. 

According  to  the  analysis  of  Dr.  Prout,  this  woody  fibre  when  dried 
at  350°  F.,  consists  of 

From  Box  Woocl.  From  the  Willow. 

Carbon 60-0  49-8 

Hydrogen  ....       5*55  5'58 

Oxygen      ....     44-45  44-62 

100  100 

It  will  be  recollected  that  water  consists  of  oxygen  and  hydrogen, 
combined  in  the  proportion,  by  weight,  of  8  of  the  former  to  1  of  the  lat- 
ter. (See  Lecture  II.,  p.  36.)  Now  if  the  hydrogen  above  given  be 
multiplied  by  8,  the  product  will  be  found  to  be  almost  exactly  the 
weight  of  the  oxygen  given — since 

5-55  X  8  =  44-40,  and 
5-58  X  8  =  44-64. 
In  woody  fibre,  therefore,  the  hydrogen  and  oxygen  exist  in  the  same 
proportion  as  in  water,  and  its  composition,  therefore,  might  be  reprC' 
sented  by 

Carbon 50-0 

Water .     .     50-0 

100 


104  COMPOSITION    OF    WOOD. 

did  we  not  know  that  woody  fibre,  when  heated  or  distilled,  cannot  be 
resolved  into  carbon  (charcoal)  and  water  alone^  and,  therefore,  cannot 
be  supposed  to  consist  of  these  alone. 

It  is  a  remarkable  character  of  this  substance,  however,  that  these  two 
elements,  hydrogen  and  oxygen,  exist  in  it  in  the  proportions  to  form 
water,  and  we  shall  find  the  knowledge  of  this  fact  of  great  importance 
to  us,  when  we  come  to  inquire  how  this  constituent  of  vegetables  is 
formed — from  the  food  on  which  they  live. 

2°.  If  a  portion  of  the  wood  of  a  tree  be  dried  and  analyzed  without 

being  previously  digested  in  water,  alcohol,  and  ether,  as  long  as  any 

thing  is  taken  up,  the  proportion  of  the  constituents  is  found  to  vary 

slightly  with  the  species  of  tree,  but  in  all  cases  the  hydrogen  is  in  larger 

quantity  than  is  necessary  to  form  water  with  the  oxygen  they  contain. 

Thus,  according  to  Payen,  the  dry  wood  of  the  following  trees  consists  of 

Ebony.  Walnut.  Oak.  Beech. 

Carbon      .     .     .     52-85  51-92  60-00  49-25 

Hydrogen      .     .       6-00  5  96  6-20  6-10 

Oxygen     .     .     .     41-15  42-12  43'80  44-65 


100  100  100  100 

The  carbon  in  these  several  kinds  of  wood  differs  as  much  as  three 
per  cent.,  but  in  each  of  them  the  product  of  the  hydrogen,  when  multi 
plied  by  8,  is  considerably  greater  than  the  per  centage  of  oxygen. 

3°.  When  the  solid  substance  of  wood  is  examined  under  the  micro- 
scope it  is  observed  to  consist  of  two  portions  or  kinds  of  matter,  that  of 
which  ihe  original  sides  of  the  cells  and  tubes  is  composed,  called  the 
cellular  matter — the  true  woody  fibre — and  of  a  solid  substance  by  which 
the  cells  are  internally  coated  and  strengthened,  called  the  incrusting 
matter.  It  is  in  this  latter  substance  that  the  excess  of  hydrogen,  exhi- 
bited by  the  preceding  analysis,  is  suf)posed  to  exist,  the  true  woody 
fibre  containing  always  the  hydrogen  arid  oxygen  in  the  proportions  ne- 
cessary to  form  water.* 

•  Payen  at  first  considered  this  incrusting  matter  as  a  peculiar  substance,  for  which  he 
proposed  the  name  of  sclerogene.  His  first  mode  of  separating  it  from  the  cellular  matter 
was  by  treating  the  finely  rasped  wood  (of  the  oak  and  beech)  with  nitric  acid,  which  dis- 
solved out  the  incrusting  matter  and  left  the  cellular  matter  behind.  His  second  mode  was 
to  digest  the  wood  with  dilute  sulphuric  acid,  by  which  the  cellular  matter  was  dissolved 
out,  and  the  incrusting  matter  left.  It  is  obvious,  however,  that  no  reliance  whatever  can  be 
placed  on  the  analyses  of  substances  so  treated,  since  they  cannot  fail  to  have  undergone  a 
chemical  change  by  being  exposed  to  the  action  of  these  strong  acids.  Further  examination 
has  satisfied  Payen  that  the  incrusting  matter  consists  of  at  least  three  substances,  of  which 
one  is  soluble  in  water,  alcohol,  and  ether,  another  in  alcohol  only,  while  the  third  is  insolu- 
ble  in  any  of  these  liquids.    They  are  composed,  according  to  his  analyses,  of 

Soluble  in  Soluble  in 

Insoluble.  alcohol  only.         water  and  alcohol. 

Carbon       ...       48  628  6853 

Hydrogen   ...         6  59  704 

Oxygen       ...        46  31-3  2443»- 

100  100  100 

It  is  impossible  to  say  how  far  the  substances  analysed  by  Payen  are  to  be  considered  as 
pure,  or  as  actually  existing  in  the  pores,  or  in  the  incrusting  matter  of  the  woody  fibre,  but 
it  is  obvious  that  the  presence  of  a  variable  quantity  of  such  substances  will  necessarily 
cause  that  excess  of  hydrogen,  in  the  entire  wood,  which  appears  in  the  analysis  of  the  ebo- 
ny, walnut,  oak,  and  beech  woods,  given  in  the  text.  That  such  an  excess  of  hydrogen 
above  what  is  necessary  to  form  water  with  the  oxygen,  does  exist  in  the  wood  of  most  trees 

[^  Meyen's  Jahresbericht,  1839,  p.  10.] 


COMPOSITION  OF  CELLULAR  MATTER.  105 

It  is  exceedingly  difficult  in  any  case  to  separate  the  cellular  from  the 
incrusting  matter  of  wood,  so  as  to  obtain  the  means  of  determining  by 
analysis  the  exact  difference  in  their  elementary  constitution.  Under 
the  impression  that  in  very  light  and  porous  substances  he  sliould  ob- 
tain the  cellular  matter  in  a  purer  form,  Payen  analysed  the  fibre  of 
cotton — the  pith  of  the  elder,  the  cellular  substance  of  the  cucumber,  of 
the  mushroom,  and  of  other  fungi,  the  spongy  matter  which  forms  the 
extremities  of  the  roots  of  plants,  and  various  other  similar  substances, 
and  in  all  these  varieties  he  found  the  hydrogen  and  oxygen  to  exist  in 
the  proportions  to  form  water.  The  mean  of  his  analyses  was  very 
nearly  as  follows — which  for  the  purpose  of  comparison  I  shall  contrast 
with  that  of  Dr.  Prout : 


Woody  fibre  of  box  and 

Cellular  matter  of  vascu- 

willow—Dr.  Prout. 

lar  plants— Payen. 

Carbon     . 

.      .      50-00 

44-80 

Hydrogen 

.     .       5-55 

6-20 

Oxygen    . 

.     .     44-45 

49-0 

100  100* 

In  both  these  analyses  the  hydrogen  is  very  nearly  8  times  that  of 
the  oxygen.  All  these  substances,  therefore,  may  be  represented  by 
carbon  and  water,  though  the  woody  fibre  of  Dr.  Prout  contains  5  per 
cent,  more  carbon  than  the  cellular  matter  of  Payen. 

If  we  calculate  the  number  of  equivalents  of  each  element  contained 
in  these  two  varietiesf  of  vegetable  fibre  composed  as  above  exhibited, 
we  find  in  the  one  12  of  carbon,  8  of  hydrogen,  and  8  of  oxygen  ;  in 
the  other,  12  of  carbon,  10  of  hydrogen,  and  10  of  oxygen.  They  may 
therefore,  be  conveniently  represented  by  the  following  formulae  : 

WooDT  Fibre by  Cj2    Hg     Cj 

Cellular  Fibre.  .  .  .  by  C12  H,o  C^q 
It  is  not  unlikely  that  both  of  these  forms  of  matter  may  exist,  as 
well  in  the  perfect  wood  of  trees  as  in  the  less  consolidated  pith  of  the 
elder,  or  in  the  fibres  of  cotton — and  that  they  may  occur  intermingled 
also  in  varying  proportions  with  other  substances,  containing  hydrogen 
in  excess.J 

m  its  natural  state,  is  a  fact  to  which  it  will  be  important  to  advert  when  we  consider  here- 
after the  chemical  changes  which  the  food  undergoes  in  the  interior  of  the  plant. 

•  Meyen's  JaJiresbericht,  1839,  p.  10. 

t  This  is  done  very  simply  by  dividing  the  carbon  by  6,  and  the  oxygen  by  8  (see  page 
36),  thus- 
Carbon    ...      50  -h  6  =  8-33  C  which  numbers  )  12 
Hydrogen    •    •  555         =  5-55  }      are  to  each      /   8 
Oxygen   -    •    .  4445 -^  8  =  555  (         other  as         )   8 

X  The  existence  of  a  variety  of  cellular  fibre  identical  in  constitution  with  common  starch, 
as  this  of  Payen  is,  (see  subsequent  section,  p.  106,)  was  previously  rendered  probable  by 
the  observations  of  Dr.  Schleiden,  that  the  embryo  of  the  Scholia  latifolia,  consisting  of 
pores  and  vessels,  the  sides  of  which  exhibit  listinct  concentric  layers,  is  entirely  soluble 
in  water,  with  the  exception  of  the  outer  rind ;  and  that  its  solution  becomes  blue  on  the 
addition  of  iodine.  It  would  appear  as  if  the  cellular  substance  were  in  this  case  wholly 
composed  of  Starch.  iPoggeTidorfs  AnncUen,  xliii.,  p.  398.)  It  may,  however,  be  in  such  a 
state  of  tenuity  in  the  embryo  of  this  plant,  as  to  be  easily  changed  into  starch  by  the  action 
of  hot  water;  and  it  is  still  by  no  means  certain  that  the  cellular  fibre  analyzed  by  Payen 
may  not  also  have  undergone  a  change  by  the  treatment  to  which  it  was  previously  subject- 
ed. I  am  unable,  however,  to  speak  decidedly  on  this  subject,  as  I  have  not  seen  the  de- 
tails of  M.  Pay  en's  several  papers.  (See  subsequent  section,  on  the  mutual  transformationa 
of  tcoody  fibre,  star ch,  gum,  and  sugar,  p.  112.) 


106  PER    CENTAGE  OF  AVOODY  FIBRE  IN  PLANTS. 

I  have  spoken  of  these  varieties  of  woody  fibre  as  constituting  a  largo 
portion  of  the  entire  mass  of  vegetable  matter  produced  during  tlm 
growth  of  plants.  That  such  is  the  case  in  the  more  gigantic  vegetable 
productions,  of  Avhich  the  great  forests  consist,  is  sufficiently  evident 
and  so  far  the  general  statement  is  easily  seen  to  be  correct.  It  is  alsc 
true  of  the  dried  stalks  of  the  grasses  and  the  corn-growing  plants,  of 
which  it  forms  nearly  one-half  the  weight, — but  in  roots  and  some 
plants  which  are  raised  for  food,  the  quantity  of  woody  fibre,  especially 
in  the  earlier  stages  of  their  growth,  is  comparatively  small.*  Thus  in 
the  beet  root  it  forms  only  3  per  cent,  of  the  whole  weight  when  taken 
from  the  ground.  If  suffered  to  remain  in  the  soil  till  it  becomes  old, 
or  if  the  growth  be  very  slow,  the  beet  becomes  more  woody,  as  many 
other  roots  do,  and  the  quantity  of  ligneous  fibre  increases. 

§  2.  Starch — its  constitution  and  properties. 

Next  to  woody  fibre,  starch  is  probably  the  most  abundant  product  of 
vegetation.  To  the  agriculturist  it  is  a  substance  of  much  more  interest 
and  importance  than  the  woody  or  cellular  fibre,  from  the  value  it  pos- 
sesses as  one  of  the  staple  ingredients  in  the  food  of  man  and  animals — 
and  from  its  forming  a  large  portion  of  the  weight  of  the  various  grains 
and  roots  which  are  the  principal  objects  of  the  art  of  culture. 

1°.  "When  the  flour  of  wheat,  barley,  oats,  Indian  corn,  &c.,  is  mixed 
up  into  a  dough  with  water,  and  this  dough  washed  on  a  linen  cloth 
with  pure  water,  a  milky  liquid  passes  through,  from  which,  when  set 
aside,  a  white  ])owder  gradually  falls.  This  white  powder  is  the  starch 
of  wheaten  or  other  flour. 

2^.  When  the  pith  of  the  sago  palm  is  washed,  in  a  similar  manner, 
with  water  upon  a  fine  sieve,  a  white  powder  is  deposited  by  the  milky 
liquid  which  passes  through.  This,  when  collected,  forced  through  a 
metal  sieve  to  granulate  (or  corn)  it,  and  dried  by  agitation  over  the 
fire,  is  the  sago  of  commerce- 

*  The  following  table  shows  the  per  centage  of  woody  fibre  contained  in  some  cotmnop 
«*ants  in  the  green  state,  and  when  dried  in  the  air,  and  at  212°  : 

IN  XHE  GREEN  STATE. 

Dried  in  the  air.    Dried  at  212°.    Woody  fibre.    Water, 
percent.  percent.  percent,      percent. 

Barley  straw,  ripe 50  —  —  — 

Oat  straw,        do, —  47  —  — 

Maize  straw,   do. 24  —  —  .— 

Stalks  oflhe  field  pea  -    ...  —  —  10)^  80 

Field  bean  straw 51  —  —  — 

White  turnip —  —  3  92 

Common  beet  (beta  vulgaris)    -  —  —  3  86 

Young  twigs  of  common  furze  -  —  —  24  50 

Rape  straw,  ripe —  55  12)^  77 

Tare  straw,  do. 37  —  —  — 

Vetch  plant  (v.  sativa)      •    -    ■  42  —  10 j^  77>i 

Do.        (V.  cracca)  in  flower  —  —  5X  68 

Do.        (V.  narbonensis)  do.  —  —  11>^  80 

White  lupin,  in  flower,    -    -    -  —  —  7  86 

Lucerne,  in  flower,      ....  —  —  9  73 

Rye  grass,        do. —  —  11  68 

Red  clover,      do. —  —  7  79 

White  clover,  do. —  —  4>^  81 

Trefoil  (medium)  do.      -    -    •  —  —  8^  73 

Sainfoin  (esparsette)  ....  —  —  7  75 

Trefoil  (agrarium)  in  flower     -  —  —  12  68 

Do,     (rubens)        do.       •    -  —  —  15  60 


? REPARATION    AND    DECOMPOSITION    OF    STARCH.  10''' 

3°.  When  the  raw  potato  is  peeled  and  grated  on  a  fine  grater,  aiid 
the  pulp  thus  produced  well  washed  with  water,  potato  starch  is  ob- 
tained in  the  form  of  a  fine  white  powder,  consisting  of  rounded,  glossy 
and  shining  particles. 

4°.  When  the  roots  of  the  Maranta  Arundinacea  of  the  West  India 
Islands  are  grated  and  washed  like  the  potatoe,  they  yield  the  arrow 
root  of  commerce.  From  the  root  of  the  Manioc,  the  cassava  is  pro- 
cured by  a  similar  process,  and  this,  when  dried  by  agitation  on  a  hot 
plate,  is  the  tapioca  of  the  shops.  By  this  method  of  drying,  both  sago 
and  tapioca  undergo  a  partial  change,  which  will  be  explained  in  a  sub- 
sequent section  (see  p.  113.) 

The  substances  to  which  these  several  names  are  given  are,  when 
pure,  similar  in  their  properties,  and  identical  in  their  chemical  consti- 
tution. They  are  all  colourless,  tasteless,  without  smell,  when  dry 
and  in  a  dry  place  may  be  kept  for  any  length  of  time  without  under- 
going alteration,  are  insoluble  in  cold  water  or  alcohol,  dissolve  readily 
in  boiling  water,  giving  a  solution  which  gelatinizes  (becomes  a  jelly) 
on  cooling — and  in  a  cold  solution  of  iodine*  they  all  become  blue. 

When  dried  at  212°,  they  consist,  according  to  Dr.  Prout,  with  wliose 
analysis  those  of  other  chemists  agree,  of 

Carbon 44-0  per  cent.,  or  12  atoms. 

Hydrogen      ....       6-2  per  cent.,  or  10  atoms.  • 

Oxygen     .....     49-8  per  cent.,  or  10  atoms. 

100 
Starch,  therefore,  may  be  represented  by  the  formula  C^a  Hjo  Oio» 
which  is  identical  with  that  deduced  in  the  preceding  section  for  the 
cellular  fibre  of  Payen.  Both  substances,  therefore,  contain  the  same 
elements  (carbon,  hydrogen  and  oxygen),  united  in  the  ^ame  propor- 
tions, and  in  both,  as  well  as  in  the  common  fibre  of  wood,  the  hydrogen 
and  oxygen  exists  in  the  proportion  to  form  water. 

That  starch  constitutes  a  large  portion  of  the  weight  of  grains  and  roots, 
usually  grown  for  food,  will  appear  from  the  following  table,  which  ex- 
hibits the  quantity  present  in  100  lbs.  of  each  substance  named  : 

Starch  per  cent. 

Wheat  flour 39  to  77 

Rye        ♦* 50  to  61 

Barley    " 67  to  70 

Oatmeal 70  to  80 

Rice  flour 84  to  85 

Maize   •♦ 77  to  80 

Buckwheat 52 

Pea  and  Bean  meal 42  to  43 

Potatoes,  containing  73  to  78  of  water,        .     13  to  15 
It  thus  exists  most  largely  in  the  seeds  of  plants,  and  in  some  roots. 
It  is  frequently  deposited,  however,  among  the  woody  fibre  of  certain 
trees,  as  in  that  of  the  willow,  and  in  the  inner  bark  of  others,  as  in 

•  Iodine  is  a  solid  substance,  of  a  lead-grey  colour,  possessed  of  a  peculiar  powerftil 
odour,  and  forming  when  heated  a  beautiful  violet  vapour.  It  exists  in  small  quantity  in  sea 
water,  and  in  some  marine  plants.  Its  solution  in  water  readily  shows  the  presence  of 
starch,  hy  the  blue  colour  it  imparts  to  i;. 


108  VARIETIES    OF   GUM. 

those  of  the  beech  and  the  pine.*  Hence  the  readiness  with  which  a 
branch  of  the  willow  takes  root  and  spiouts,  and  hence  also  the  occa- 
sional use  of  the  inner  bark  of  trees  for  food,  especially  in  northern  coun- 
tries, and  in  times  of  scarcity.  In  some  roots  which  abound  in  sugar, 
as  in  those  of  the  beet,  the  turnip,  and  the  carrot,  only  2  or  3  per  cent, 
of  starch  can  be  detected. 

§3.   Gum — its  constitution  and  properties. 

The  variety  of  gum  with  which  we  are  most  familiar  is  gum  arabicj 
or  Senegal,  the  produce  of  various  species  of  acacia,  which  grow  in  the 
warmer  regions  of  Asia,  Africa,  and  America.  It  exudes  from  the 
twigs,  and  stems  of  these  trees,  and  collects  in  rounded  more  or  less 
transparent  drops  or  tears.  It  is  also  produced  in  smaller  quantities  in 
many  of  our  fruit  trees,  as  the  apple,  the  plum,  and  the  cherry  ;  it  is 
present  in  some  herbaceous  plants,  as  in  the  althaea  and  malva  officinalis 
(common  and  marsh  mallow] ;  and  it  exists  in  lint,  rape,  and  many 
other  seeds.  When  treated  with  boiling  water  these  plants  and  seeds 
give  mucilaginous  solutions. 

Many  varieties  of  gum  occur  in  nature,  but  they  are  all  characterised 
by  being  insoluble  in  alcohol,  by  dissolving  or  becoming  gelatinous  in 
hot  or  cold  water,  and  by  giving  mucilaginous — viscid  and  glutinous — 
solutions,  which  may  be  employed  as  a  paste. 

Three  distinct  species  of  gum  have  been  recognised  by  chemists : 

1°.  Arahin—o^  which  gum  arable  and  gum  Senegal  almost  entirely 
consisL  It  is  readily  soluble  in  cold  ivater,  giving  a  viscid  solution,  usu- 
ally known  by  the  name  of  the  mucilage  of  gum  arable. 

2°.   Cerasin — which  exists  in  the  gum  of  the  cherry-tree.     It  is  inso 
luble  in  cold  water,  but  dissolves  readily  in  boiling  water.     When  thus 
dissolved  it  may  be  dried  without  losing  its  solubility,  and  is  therefore  by 
boiling  supposed  to  be  changed  into  arabin. 

3°.  Bassorin — existing  in  what  is  called  bassora  gum — and  forming 
a  large  portion  of  gum  tragacanth.f  It  swells  and  becomes  gelatinous  in 
cold  water,  but  does  not  dissolve  in  water  either  cold  or  hot. 

By  these  characters,  the  three  kinds  of  gum  are  not  only  readily  dis- 
tinguished, but  may  be  easily  separated  from  each  other.  Thus  if  a 
native  gum  or  an  artificial  mixture  contain  all  the  three,  simple  steeping 
in  and  subsequent  washing  with  mid  water,  will  separate  the  arabin — 
boiling  water  will  then  take  up  the  cerasin,  and  the  bassorin  will  remain 
behind. 

These  different  kinds  of  gum  all  possess  the  same  chemical  constitu- 
tion.    According  to  the  analyses  of  Mulder,  they  consist  of 
Carbon     .     .     .     45*10  per  cent.,  or  12  atoms. 
Hydrogen      .     .       6-10        "  or  10      ♦' 

Oxygen    .     .     .     48-80t      "  or  10      " 

100 

*  Its  presence  is  readily  detected  in  such  wood  by  a  drop  of  the  solution  of  iodine — which 
^ives  a  permanent  blue  to  starch,  but  tc  the  woody  fibre  only  a  brownish  stain. 

♦  This  gum  exists  along  with  starch  in  the  roots  of  the  various  species  of  orchia,  especially 
of  those  which  are  used  for  making  scdep  (Meyen). 

Berzelius  Arsberdttclse,  1839,  p.  443. 


VARIETIES    AND    CONSTITUTION    OF    SUGAR.  109 

In  these  analyses,  as  in  those  of  starch  and  woody  fihre,  we  see  lliat 
the  per  centage  of  oxygen  is  equal  to  that  of  the  hydrogen  multiplied  by 
8,  and  consequently  that  these  two  elements  are,  as  already  stated,  in 
the  proportion  to  form  water.  But  we  see  also  that  the  carbon  is  in  tlie 
proportion  of  12  atoms  or  equivalents  to  10  of  each  of  the  other  con- 
stituents, and  therefore  gum  may  be  represented  by  Cj2  Hj  g  Oj  „ — a 
formula  which  is  identical  with  that  already  given  for  starch  and  cellu- 
lar fibre. 

It  appears,  therefore,  that  not  only  may  gum,  starch,  and  cellular  Jibre  be 
represented  by  carbon  and  water,  but  that  they  all  consist  of  carbon  and 
the  elements  of  water,  united  together  in  the  sarne  jtroportions. 

Gum  not  only  exists  in  many  seeds,  and  exudes  as  a  natural  product 
from  the  stems  and  twigs  of  many  trees,  but  is  also  contained  in  the 
juices  of  many  other  trees,  from  which  it  is  not  known  to  exude  ;  and  in 
the  sap  of  most  plants  it  may  be  detected  in  greater  or  less  quantity.  It 
may  be  considered,  indeed,  as  one  of  those  substances  which  are  pro- 
duced most  largely  and  most  abundantly  in  the  vegetable  kingdom, 
since,  as  will  hereafter  appear,  it  is  one  of  those  forms  of  combination 
through  which  organic  matter  passes  in  the  interesting  series  of  changes 
it  undergoes  during  the  development  and  growth  of  the  plant. 

§  4.   Of  Sugar — its  varieties  and  chemical  constitution. 

1°.  Cane  Sugar. — Sugar,  identical  in  constitution  and  properties  with 
that  obtained  from  the  sugar-cane,  and  generally  known  by  the  name  of 
cane-sugar,  exists  in  the  juices  of  many  trees,  plants,  and  roots.  In  the 
United  States  of  North  America  the  juice  of  the  maple  tree  is  extensive- 
ly collected  in  spring,  and  when  boiled  down  yields  an  abundant  supply 
of  sugar.  In  the  Caucasus  that  of  the  walnut  is  extracted  for  the  same 
purpose.  The  juice  of  the  birch  also  contains  sugar,  and  it  may  be  ob- 
tained, in  lesser  quantity,  from  the  sap  of  many  other  trees.  In  the 
juice  of  the  turnip,  carrot,  and  beet,  it  is  also  present,  and  in  France  and 
Germany  the  latter  root  is  extensively  cultivated  for  the  manufacture  of 
beet  sugar.  In  the  unripe  grains  of  corn,  at  the  base  of  the  flowers  of 
many  grasses  and  clovers  when  in  blossom,  and  even  in  many  small 
roots,  as  in  that  of  the  quicken  or  couch-grass  (triticum  repens),  the  pre- 
sence of  sugar  may  likewise  be  readily  detected. 

Sugar  is  principally  distinguished  by  its  agreeable  sweet  taste. 
When  pure,  it  is  colourless  and  free  from  smell.  It  dissolves  readily 
in  alcohol  and  in  large  quantity  in  water.  The  solution  in  water,  when 
much  sugar  is  present,  has  an  oily  consistence,  and  is  known  by  the  name 
of  syrup.  From  this  syrup  the  sugar  gradually  deposits  itself  in  the 
form  of  sugar  candy.  If  the  syrup  be  boiled  on  too  hot  a  fire,  it  chars 
slightly,  becomes  discoloured,  and  a  quantity  of  molasses  is  formed. 
Pure  cane-sugar,  free  from  water,  consists  of 

Carbon     .     .     .     44-92  per  cent.,  or  12  atoms. 
Hydrogen     .     .       6-11  "         or  10      " 

Oxygen    .     .     .     48-97  "         or  10      " 

100 
If  we  compare  these  numbers  with  those  given  for  starch  and  gum  in 
the  preceding  sections,  we  see  that  they  are  almost  identical — so  that 


110  CANE,  GRAIE,  MANNA,  AND  LIQUORICE  SUGARS. 

cane-sugar  also  contains  oxygen  and  hydrogen  in  the  proportions  to  form 
water,  and  may  likewise  be  represented  by  the  formula  C,2  H^,,  Ojo* 

2°.  Grape  sugar. — In  the  juice  of  the  grape  a  peculiar  species  of  su- 
gar exists,  which,  in  the  dried  raisin,  j)resents  itself  in  the  form  of  little 
rounded  grains.  The  same  kind  of  sugar  gives  their  sweetness  to  the 
gooseberry,  the  currant,  tlie  apple,  pear,  plum,  apricot,  and  most  other 
fruits.  It  is  also  the  sweet  substance  of  the  chesnut,  of  the  brewers' 
wort,  and  of  all  fermented  liquors,  and  it  is  the  solid  sugar  which  floats 
in  rounded  grains  in  liquid  honey,  and  which  increases  in  apparent 
quantity  as  tlie  honey,  by  keeping,  becomes  more  and  more  sohd. 

Grape  sugar  has  nearly  all  the  sensible  characters  of  cane  sugar,  with 
the  exception  of  being  less  soluble  in  wafer  and  also  less  sweet, — 2  parts- 
of  the  latter  imparting  an  equal  sweetness  with  5  of  the  former. 

In  chemical  constitution  they  differ  considerably.  Thus  grape  sugai 
dried  at  250°  F.,  consists  of 

Carbon     .     .     .     40-47  per  cent.,  or  12  atoms. 
Hydrogen     .     .       6-59         "  or  12      " 

Oxygen   .     .     .     52-94         "  or  12      " 

100 

The  oxygen  here  is  still  eight  times  greater  than  the  hydrogen,  and^ 
therefore,  in  this  variety  of  sugar  also,  these  elements  exist  in  the  pro- 
portioru",  to  form  water.  But  for  every  12  equivalents  of  carbon,  dry 
grape  sugar  contains  12  of  hydrogen  and  12  of  oxygen.  It  is  conse- 
quently represented  by  C12  Hjg  Ojo,  and  contains  the  elements  of  two 
atoms  of  water  (Hg  Oo)  more  than  cane  sugar.* 

3°.  Manna  sugar,  sugar  of  liquorice,  Sfc. — Besides  the  cane  and  grape 
sugars  which  occur  in  large  quantity  in  the  juices  of  plants,  there  are 
other  varieties  which  occur  less  abundantly,  and  are  therefore  of  less  in- 
terest in  the  study  of  the  general  vegetation  of  the  globe.  Among  these 
is  manna,  which  partly  exudes  and  is  partly  obtained  by  incisions  from 
certain  species  of  the  ash  tree  which  grow  in  the  warmer  countries  of 
Southern  Europe  (Sicily  and  Italy),  and  in  Syria  and  Arabia.  It  also 
exists,  it  is  said,  in  the  juice  of  the  larch  tree,  of  common  celery,  and  of 
certain  trees  which  are  met  with  in  New  South  Wales.  Liquorice  root 
also  contains  a  species  of  hiack  sugar,  which  is  known  in  this  country 
under  the  names  of  Spanish  and  Italian  juice,  from  the  countries  where 
it  is  grown.  In  the  mushroom  and  oi\\er  fungi  a  colourless  variety,  ap- 
parently peculiar,  has  also  been  met  with,— and  milk  owes  its  sweet- 
ness to  a  species  of  sugar  formed  in  the  interior  of  the  animal  along  with 
the  other  substances  which  the  milk  contains. 

These  several  kinds  of  sugar  differ  more  or  less,  not  only  in  sensible 
and  chemical  properties,  but  also  in  chemical  constitution,  from  llie  more 
abundant  cane  and  grape  sugars — but  they  form  too  smalJ  a  part  of  the 
general  products  of  vegetation,  and  are  of  too  little  consequence  in  practi- 

*  Solutions  of  cane  and  grape  sugar  are  readily  distinguished  from  each  other  by  the  fol- 
lowing chemical  characters :— 1.  If  the  solution  be  heated  and  a  few  drops  of  sulphuric  acid 
then  added,  cane  sugar  will  be  decomposed,  blackened,  and  made  to  fall  as  a  black  or  brown 
powder— while  a  solution  of  grape  sugar  will  at  tlie  most  be  only  slightly  discoloured.  2.  If, 
instead  of  sulphuric  acid,  caustic  potash  be  employed,  the  cane  sugar  will  be  unchanged, 
wliile  the  grape  sugar  will  be  blackened  and  thrown  down. 


MUTUAL  RELATIONS  OF  WOODY  FJURK,  STARCH,  GUM,  ETC.         Ill 

cal  agriculture  to  render  it  necessary  to  do  more  than  thus  shortly  ad- 
vert to  their  existence.* 

§  5.  Mutual  relations  of  wood t/  fibre,  starchy  gum,  and  sugar. 
It  may  be  interesting  now  to  consider  for  a  moment  the  mutual  rela- 
tions of  the  several  substances,  woody  fibre,  starch,  gum,  and  sugar — 
above  described — which  occur  so  largely  in  the  vegetable  kingdom,  and 
are  serviceable  to  man  for  so  many  ditferent  purposes.  These  relations 
will  be  best  seen  on  comparing  the  formulas  by  which  they  are  respec- 
tively representecL     Thus — 

Woody  Fibre     (lignin)    is  represented  by     C12    Hg      O^ 
Cellular  Fibre  (according  to  Payen)     by     C^a   ^\q  Oio   * 
Starch  (dried  at  212°  F.)  by     Cia    H,oOio 

Gum  (any  of  the  3  varieties)  by     C12    Hio   Oi  0 

Cane  Sugar         (free  from  water)  by     C12    Hio  Oio* 

Grape  Sugar       (dried at  130°  F.)  by     C12    H12   Oi2f 

In  these  forraul<E  we  observe — 

1°.  That  the  e(]ivalents  of  the  oxygen  are  equal  to  those  of  the  hydro- 
gen in  all  the  formulne,  and,  therefore,  that  all  these  substances  may  be 
supposed  to  consist  of  carbon  and  water. 

2°.  The  formulae  for  cellular  fibre,  starcli,  gum,  and  cane  sugar,  are 
identical.  They  consist  of  the  same  elements  united  together  in  the  same 
proportions. 

This  is  one  of  tliose  facts  which  not  only  appear  very  remarkable  to 
the  unlearned,  but  are  scarcely  capable  of  being  clearly  comprehended 
and  explained,  even  by  those  who  have  most  profoundly  studied  this 
branch  of  natural  science.  Starch  and  sugar — how  different  their 
properties  !  how  unlike  their  uses  !  how  unequal  their  iinporlance  to  the 
human  race!  yet  they  consist  of  the  same  weights  of  the  same  substances, 
differently  conjoined.  The  skilful  architect  can  put  together  tlie  same 
proportions  of  the  same  stone  and  cement — and  the  painter  can  combine 
the  same  colours  so  as  to  produce  a  thousand  varied  impressions  on  the 
sense  of  sight.  In  the  hand  of  Deity  matter  is  infinitely  more  plastic. 
At  His  bidding  the  same  particles  can  unite  in  the  same  quantity  so  as 
to  produce  the  most  unlike  impressions — and  on  all  our  senses  at  once. 

3°.  A  knowledge  of  the  above  close  relations  in  composition,  among 
a  class  of  substances  occurring  so  abundantly  in  the  vegetable  kingdom, 
imparts  a  degree  of  simplicity  to  our  ideas  of  this  otherwise  complicated 
subject.  It  does  not  appear  so  mysterious  that  we  should  have  woody 
fibre,  and  starch,  and  gum,  and  sugar,  occurring  together  in  variable 
quantities,  when  we  know  '.hat  they  are  all  made  up  of  tJie  same  ma- 
terials, in  the  same  or  nearly  the  same  proportions — or  that  one  of  these 
should  occasionally  disappear  from  a  plant,  to  be  replaced  in  whole  or 
in  part  by  another. 

*  For  a  list  of  plants  from  which  sugar  has  been  extracted,  seej^'homeon's  OrganitChemiS' 
try  (1838),  p.  647.  ^ 

t  Crystallized  cane  sugar  (sugar  candy)  loses  53  per  cent,  of  water  in  favourable  circum- 
stances. This  is  equal  to  one  equivalent  (HO),  so  that  if  dry  sugar  be  Ci'^Hio  Oio,  crystallized 
sugar  is  C18  Hu  Oil— or  C12  Hio  Oio+HO,  since  there  is  no  doubt  that  this  one  equivalent  of 
the  hydrogen  and  oxygen  exists  in  crystallized  sugar  in  the  state  of  water.  Tn  lilce  manner, 
crystallized  lioney  or  grape  sugar— as  it  occurs  in  honey  or  in  the  dried  grape— loses  9  per 
cent,  of  water  when  heated  to  250°  F.  This  is  equal  to  two  equivalents  (2HO),  so  that  crys- 
tallized grape  sugar  is  represented  by  C12  Hu  O14  or  C12  Hi2  C''4+2nO. 


112  MUTUAL  TRANSrORMATIONS  OF  STARCH,  :.UM,  ETC. 

A  further  question,  however,  arises  in  our  minds.  We  naturally  ask, 
— does  nature,  in  thus  removing  one  of  these  compounds,  and  supplying 
its  place  by  another,  actually  form  from  its  elements  the  new  substance 
introduced,  or  does  she  produce  it  by  a  mere  change  or  transformation 
of  those  previously  existing.  A  satisfactory  reply  to  this  question  may 
be  derived  from  the  facts  detailed  in  the  following  section. 

§.6.  Mutual  transformations  of  zvoody fibre,  starch,  gum,  and  sugar. 

I. WOODY  FIBRE. 

• 

1°.  Action  of  heat. — If  wood  be  reduced  to  the  state  of  fine  saw-dust,  be 
ihert  boiled  in  water  to  separate  everything  soluble,  afterwards  dried  by 
a  gentle  heat,  and  then  heated  several  limes  in  a  baker's  oven,  it  will  be- 
come hard  and  crisp,  and  may  be  ground  in  the  mill  into  a  fine  meal.  The 
powder  thus  obtained  is  slightly  yellow  in  colour,  but  has  a  taste  and 
smell  similar  to  the  flour  of  wheat;  it  ferments  when  made  info  a  paste 
with  yeast  or  leaven,  and  when  baked  gives  a  light  homogeneous  bread. 
Boiled  with  water,  it  yields  a  stiff  tremulous  jelly,  like  that  from 
starch  (Autenrieth. — Schiibler,  Agricultur  Chemie,  i.,  p.  224.)  By  the 
agency  of  heat,  therefore,  it  appears  that  the  woody  fibre  may  be  changed 
into  starch. 

2°.  Action  of  sulphuric  acid. — If  to  tliree  parts  of  the  sulphuric  acid 
of  the  shops  (oil  of  vitriol)  one  part  of  water  be  added,  and  a  portion  of 
delicate  woody  fibre  be  immersed  in  it  for  half  a  minute,  and  the  whole 
then  rubbed  in  a  mortar  with  a  few  dro{)s  of  a  solution  of  iodine — the 
woody  fibre  will  assume  a  blue  colour,  showing  that  it  is  in  part  at  least 
changed  into  starch*  (Schleiden). 

Again,  if  three  parts  of  fine  saw-dust  or  of  fragments  of  old  linen  be 
rubbed  in  a  mortar  with  four  of  the  sulphuric  acid  of  the  shops  added 
by  degrees — it  will,  in  a  quarter  of  an  hotir,  be  rendered  completely  so- 
luble in  water.  If  the  solution  in  water  be  freed  from  acid  by  chalk,  and 
then  evaporated,  a  substance  resembling  gum  arable  is  obtained  (Bra- 
connot).  According  to  Schleiden,  the  fibre  may  be  seen  under  the  mi- 
croscope gradually  to  change  from  without  inwards,  first  into  starch  and 
then  into  gum. 

Further,  if  this  gum  be  digested  with  a  second  portion  of  sulphuric 
acid  diluted  with  8  or  10  times  its  weight  of  water,  it  will  be  gradually 
converted  into  grape  sugar ;  or  the  fibre  of  wood  or  linen  may  be  changed 
directly  into  sugar  by  the  prolonged  action  of  dilute  sulphuric  acid. 

3°.  Action  of  potash. — If  aaw-dust  be  mixed  with  from  two  to  eight 
times  its  weight  of  hydratef  of  potash  and  as  much  water,  and  boiled 
till  a  crust  forms  on  the  surface,  and  if  dilute  sulphuric  acid  be  then  added 
till  the  whole  is  slightly  sour,  the  undestroyed  woody  fibre  will  give  an 

'  It  will  be  recollected  that  starch  is  characterized  by  giving  a  blue  colour  with  a  solution  of 
iodine  (see  p.  107).  ^ 

The  simplest  way  of  trying  this  experiment  is,  to  take  a  quantity  of  clean  cotton — to  wet 
it  with  water,  squeezhig  out  again  as  much  as  possible — then  to  spread  it  out  upon  a  flat  dish 
and  moisten  it  quickly  and  thoroughly  with  the  acid  dihited  as  above.  After  half  a  minute, 
»dd  the  solution  of  iodine,  stir  quickly  with  a  glass  rod,  and  immediately  add  water,  when 
the  blue  compound  of  iodine  and  starch  will  speedily  deposit  itself  —{Schleiden,  Pog.  AnnaL, 
xllii.,  p.  39C.) 

t  Hydrate  of  potash  is  the  caustic  substance  which  is  obtained  by  boiling  common  pearl- 
»sh  wiUi  quick- lime. 


ACTION  OF  HEAT  ON  STARCH.  TIS 

instantaneous  deep  blue  on  the  addition  of  iodine,  showing  that  starch 
has  been  formed. 

Woody  fibre,  therefore,  may  be  changed  into  starch,  either  by  the  un- 
aided action  of  heat,  by  that  of  sulphuric  acid,  or  by  boiling  with  caustic 
potash, — and  the  starch  thus  produeed  may  be  further  transformed,  first 
into  gum  and  then  into  grape  sugar,  by  the  prolonged  action  of  dilute 
sulphuric  acid,  assisted  by  a  moderate  heat. 

II.    STARCH. 

1°.  Action  of  heat. — When  flour,  potato,  or  arrow-root  starch  is 
epread  out  upon  a  tray,  then  introduced  into  an  oven  and  gradually 
heated  to  a  temperature  not  exceeding  300^  F.,  it  slowly  changes,  ac- 
quires a  yellow  or  brownish  tint  according  to  the  temperature  employed, 
and  becomes  entirely  soluble  in  cold  water.  It  is  changed  into  gum. 
Under  the  names  of  starch-gum,  or  British-gum,  this  substance  is  large- 
ly manufactured  in  this  country,  and  is  successfully  substituted  for  gum 
arabic  by  the  calico-printers  in  thickening  many  of  their  colours.* 

The  gum  thus  prepared  not  unfrequently  also  possesses  a  sweet  taste, 
from  the  further  change  of  a  portion  of -the  gum  into  sugar. 

2°.  Action  of  water. —  When  starch  is  dissolved  in  boiling  water,  and 
is  then  allowed  to  stand  in  the  cold  either  in  a  close  vessel  or  exposed  to 
the  air,  it  gradually  changes  into  gum  or  sugar.  The  process,  however, 
is  slow,  and  months  must  elapse  before  the  whole  of  the  starch  is  thus 
spontaneously  transformed  in  the  presence  of  water  (De  Saussure).  It 
takes  place  more  rapidly  when  starch  and  water  are  boiled  together  for 
a  length  of  tim&. 

3°.  Action  of  sulphuric  acid. — From  what  has  been  already  stated  in 
regard  to  the  action  of  this  acid  on  woody  fibre  it  will  readily  be  supposed 
that  native  starch,  of  any  variety,  is  likely  to  undergo  transformation 
when  subjected  to  its  influence. 

In  reality,  if  50  parts  of  starch,  12  of  sulphuric  acid,  and  139  of  water 
be  taken,  and  if  the  starch  be  thoroughly  moistened  with  a  portion  of  the 
water,  and  then  poured  into  the  mixture  of  the  acid  with  the  remainder 
of  the  water,  and  heated  to  190°  F.,  the  starch  will  be  entirely  convert- 
ed into  gum.  By  further  and  more  prolonged  heating  this  gum  is 
changed  into  grape  sugar.  The  gum  or  sugar  may  be  obtained  in  a 
separate  state  by  adding  to  the  solution  either  chalk  or  lime,  which  will 
combine  with  and  carry  down  the  acid.f  One  hundred  pounds  of  starch 
treated  in  this  way  will  yield  from  105  to  122  lbs.  of  dry  grape  sugar. 

The  rapidity  with  which  this  transformation  takes  place  depends 
partly  upon  the  temperature  and  partly  upon  the  proportion  of  acid  em- 
ployed. Thus  100  lbs.  of  starch  mixed  with  600  of  water  and  10  of 
sulphuric  acid,  will  be  converted  into  grape  sugar  by  boiling  for  seven 
hours.  If  by  increasing  the  pressure  the  temperature  be  raised  to  250° 
F.,  the  transformation  will  be  eflfected  in  a  few  minutes.     With  only  one 

•  During  the  baking  of  bread  this  conversion  of  starch  info  gum  takes  place  to  a  consider- 
able extent.  Thus  Vogel  found  that  flour  which  contained  no  gum  gave,  when  baked,  a 
bread  of  which  18  per  cent.,  or  nearly  one-fifth  of  the  whole  weight,  consisted  of  gum. 
Thus  one  of  the  effects  of  baking  is  to  render  the  flour-starch  more  soluble,  and  therefore  (?) 
more  easily  digestible. 

t  It  forms  gypaum  with  it  (sulphate  of  lime)  whic}i  is  a  compound  of  lime  and  sulphuric 
acid. 


114  CHANGE  OF  CANE  INTO  GRAPE  SUGAR. 

pound  of  acid  and  the  same  quantity  of  starch  and  water,  the  change 
will  be  efTecled  in  three  hours  by  a  temperature  of  230°  F.  This  mode 
of  converting  potato  starch  into  grape  sugar  is  said  to  be  extensively 
practised  in  France,  for  the  purpose  of  subsequently  fermenting  the 
sugar  and  converting  it  into  brandy. 

III.    GUM. 

Action  of  sulphuric  acid. — Tf  powdered  gum  arabic  be  rubbed  in  a 
mortar  with  the  sulphuric  acid  of  the  shops,  a  brownish  solution  is  ob- 
tained, which,  when  diluted  with  water  and  treated  with  chalk,  yields  a 
gummy  substance  similar  to  that  obtained  in  the  same  way  from  starch 
and  woody  fibre.  Prolonged  digestion  with  diluted  acid  converts  a  por- 
tion of  this  gum  into  sugar. — [Berzelius,  Traite  de  Chemie,  (1831),  v., 
p.  217.] 

IV. — CANE  SUGAR. 

1°.  Action  of  heat. — When  crystallized  cane  sugar  is  heated  to  320° 
F.  it  melts,  and  if  the  temperature  be  raised  to  360°  F.  it  gives  oflftwo 
atoms  of  water  and  is  changed  into  caramel.  This  caramel  is  an  un- 
crystallizable  sugar,  which  is  generally  present  in  artificial  syrups,  and 
is  often  of  a  brownish  colour.  It  contains  the  elements  of  an  atom  of 
water  less  than  cane  sugar,  and  is  represented  by  Cjjj  Hg  Og.  It  is 
not  known  to  occur  in  the  natural  juices  of  plants. 

2°.  Action  of  sulphuric  acid. — When  cane  sugar  is  digested  with  di- 
lute sulphuric  acid,  aided  by  a  gentle  heat,  it  is  rapidly  converted  into 
grape  sugar.  The  acid  of  grapes  (tartaric  acid)  and  many  other  vege- 
table acids  produce  a  similar  change. 

It  is  obvious  that  this  conversion  of  cane  into  grape  sugar  can  only 
take  place  in  the  presence  of  water,  inasmuch,  as  has  already  been 
shown  (p.  110),  grape  sugar  contains  the  elements  of  two  atoms  of  water 
more  than  cane  sugar,  or 

Cane  sugar.  Water.         Dry  grape  sugar. 


We  may  revert  now  to  the  question  with  which  we  concluded  the 
preceding  section.  Since  these  different  substances  are  so  closely  allied 
in  chemical  consliiution,  and  occur  so  often  in  connection  with  each 
other  in  the  vegetable  kingdom,  does  nature,  when  her  purposes  demand 
the  change,  actually  transform  them,  the  one  into  the  other,  in  the  inte- 
rior of  the  plant?  The  answer  may  now  be  safely  given,  that  she  cer- 
tainly does.  What  we  can  so  readily  perform  by  our  rude  art  may  be 
still  more  easily  effected  in  the  living  vegetable.  That  which  is  starch 
or  gum  in  one  part  of  the  plant,  may  become  cane  or  grape  sugar  in 
another,  and  woody  fibre  in  a  third.  Thus  by  re-arranging  the  same 
kind  and  quantity  of  the  several  elements,  may  the  various  and  unlike 
forms  of  matter  which  constitute  the  main  products  of  vegetation  be 
readily  produced. 

Still  the  facility  is  only  apparent.  We  can  assure  ourselves  of  the 
fact  of  such  conversions,  because  we  can  at  will  induce  them.  But  who 
operates  upon  these  substances  in  the  interior  of  the  plant?  Whose 
mind  and  will  directs  these  changes — prescribing  when,  where,  and  in 


GRAPE    SUGAR   AIOJ^E    FERMEIfTS.  113 

rvhat  onier  they  shall  take  place  ?  How  much  depends  upon  the  re- 
fined and  little  understood  mechanism  of  the  vegetable  structure — how 
much  on  the  living  principle  itself!  What  is  this  living  principle — 
how  can  it  direct  !* 

§  7.  Of  the  fermentation  of  starch  and  sugar — and  of  the  relative  circum- 
stances under  ivhich  cane  and  grape  sugars  generally  occur  in  nature. 
It  will  be  of  use  to  us,  in  connection  with  the  above  transformations, 
to  advert  to  the  property  possessed  by  starch  and  nearly  all  the  known 
varielies  of  sugar  of  entering  into  fermentation  under  favourable  cir- 
cumstances. When  flour  is  made  into  a  paste  with  leaven  or  yeast  it 
begins  to  rise  and  ferment, — sooner  or  later,  according  to  the  kind  of 
flour  and  the  quantity  of  ferment  added.  When  to  a  decoction  of  malt 
or  to  a  solution  of  starch  or  of  cane  or  grape  sugar  in  water,  a  portion  of 
yeast  is  added,  fermentation  is  speedily  induced  ;  and  if  not  arrested  by 
unfavourable  circumstances  it  will  continue  until  the  whole  of  the 
starch  or  sugar  disappears. 

In  all  these  cases  it  is  grape  sugar  alone  that  undergoes  fermentation. 
[Rose,  Poggen.  Annal.,  lii.,  p.  297.]  The  starch  of  the  moist  dough  or 
of  the  solution  is  partially  transformed  into  grape  sugar  before  fermenta- 
tion commences.  Such  is  the  case  also  with  the  decoction  of  malt  and 
with  cane  sugar.  The  fermentation  commences  soon  after  the  first  por- 
tion of  grape  sugar  is  formed,  and  proceeds  more  or  less  rapidly  accord- 
ing as  this  transformation  is  more  or  less  speedily  effected.  Hence,  in* 
the  art  of  brewing,  the  necessity  of  cautiously  regulating  the  tempera- 
ture by  which  this  change  of  the  starch  and  sugar  is  promoted  and  hast- 
ened. 

The  fermentation  itself  is  the  result  not  of  a  mere  transformation  of 
one  form  of  matter  into  another  having  the  same  elementary  constitu- 
tion, but  of  a  decomposition  of  one  substance  into  two  others  unlike  itself 
either  in  properties  or  in  chemical  composition.  The  grape  sugar  is  re- 
solved into  alcohol  (spirits  of  wine),  which  remains  in  the  liquid,  and  info 
carbonic  acid,  which  escapes  in  the  form  of  gas  and  causes  the  fermen- 
tation. Thus  alcohol  being  represented  by  C4  Hg  O2,  and  carbonic  acid 
by  CO,, 

2  of  alcohol  r=  Cg  H,2  O4  and 

4  of  carbonic  acid  =  C4  O3  make  up 


1  of  grape  sugar  =C),2H,20,2. 

It  is  an  interesting  fact  that  the  cane  and  grape  sugars  occur  in  na- 
ture in  circumstances  which  are  entirely  consistent  with  the  statement 
in  the  preceding  section,  regarding  the  action  of  acids  on  the  former 
variety  of  this  natural  product.  Fruits  contain  grape  sugar,  which  in- 
creases in  quantity  as  they  ripen  or  become  less  sour.  In  the  sugar 
cane,  the  beet  root,  and  the  maple  and  birch  trees,  cane  sugar  exists, 
but  in  their  juices  no  acid  is  associated  with  the  sugar.  On  the  contra- 
ry, ammonia  is  known  to  be  present  in  most  of  them  along  with  the 
cane  sugar.  Hence  it  is  inferred,  that  as  in  our  hands  and  in  our  exper- 
iments cane  sugar  is  changed  by  the  agency  of  acids  into  grape  sugar,  and 

•  »*  Oanst  thou  by  searching  find  out  God— Canst  thou  find  out  the  AJmighty  unto  perfection  1" 


116  SUBSTANCES  CONTAINING  NITROGEN. 

with  remarkable  ease  by  that  acid  which  exists  in  the  ripe  grape,  so  it  is 
in  the  interior  of  plants.  Where  sugar  occurs  in  connection  with  an  acid 
in  the  juice  of  a  plant,  it  is  grape  sugar  in  whole  or  in  great  part,  be- 
cause in  the  presence  of  an  acid  body  cane  sugar  cannot  permanently  ex- 
ist, but  is  gradually  transformed  into  the  sugar  of  grapes.  It  thus  ap- 
pears also  why  fruits  so  readily  enter  into  fermentation,  and  why,  even 
when  preserved  with  cane  sugar,  they  will,  in  consetiuence  of  the  acid 
they  retain,  slowly  change  the  latter  into  grape  sugar,  and  thus  induce 
fermentation.* 

§  8.   O/"  substances  which  contain  Nitrogen. — Gluten,  Vegetable 
Albumen^  and  Diastase. 

The  substances  described  in  the  preceding  sections  consist  of  carbon, 
hydrogen,  and  oxygen  only,  and  of  them  the  great  bulk  of  the  vegeta- 
ble productions  of  the  globe  consists.  But  there  are  certain  other  sub- 
stances occurring  along  with  starch  and  sugar,  into  which  nitrogen  enters 
as  a  constituent,  and  which,  though  not  formed  in  the  vegetable  king- 
dom in  very  large  quantity,  are  yet  of  such  interest  and  importance  in 
other  respects,  as  to  make  it  necessary  shortly  to  advert  to  them. 

1^.  Gluten. — When  the  flour  of  wheat  is  made  into  a  dough,  and  this 
dough  is  washed  with  water  upon  a  fine  sieve,  a  milky  liquid  passes 
through,  from  which  starch  gradually  subsides.  Tliis  has  been  already 
slated.  But  on  the  sieve,  when  the  water  ceases  to  go  through  milky, 
there  remains  a  soft  adherent,  tenacious,  and  elastic  substance,  which 
can  be  drawn  out  into  long  strings,  has  scarcely  any  colour,  taste,  or 
smell,  and  is  scarcely  diminished  by  washing  either  with  hot  or  with 
cold  water.  This  substance  is  the  gluten  o(  wheat.  The  flour  of  other 
kinds  of  grain  also  yield  it  by  a  similar  treatment,  though  generally  in 
much  smaller  quantity.     This  appears  from  the  following  table  : — 

The  grain  of 

Wheat  contains  8  to  35  per  cent,  of  gluten. 
Rye  ....  9  to  13         "  " 

Barley    ...  3  to     6        "  " 

Oats  ....  2  to     5         "  " 

When  the  moist  gluten  is  dried  in  the  air  or  at  the  temperature  of 
boiling  water,  it  diminishes  much  in  bulk,  and  hardens  into  a  brittle 
semi-transparent  yellow  substance  resembling  horn  or  glue.  In  this  state 
it  is  insoluble  in  water,  but  dissolves  readily  in  vinegar,  in  alcohol  either 
cold  or  hot,  and  in  solutions  containing  caustic  potash,  or  soda,  [the 
common  pearl-ash  or  soda  of  the  shops  boiled  with  quick-lime.] 

2°.  Vegetable  Albumen. — To  the  white  of  egg  the  name  of  albumen 
(albus,  white)  has  been  given  by  chemists.  It  jwssesses  the  well  known 
property  of  coagulating  or  of  forming  a  white  solid  insoluble  substance, 
when  it  is  heated  either  alone  or  after  being  mixed  with  water. 

When  the  starch  has  subsided  from  the  milky  liquid  which  passes 

*  Milk  also,  in  favourable  circumstances,  as  when  kept  at  a  temperature  of  100°  F.,  tfn- 
dergoes  fermentation,  and  in  some  countries  of  Asia  a  spirituous  liquor  is  prepared  from 
mares'  and  asses'  milk^  In  this  case  the  milk  first  becomes  sour,  then  the  acid  thus  form- 
ed converts  the  milk  sugar  into  grape  sugar,  and  finally  this  sugar  enters  into  fermenta- 
tion. This  takes  place  more  readily  in  consequence  of  the  presence  of  the  decomposing 
cheesy  matter  (casein)  of  the  milk — as  is  shown  by  the  fact  that  the  introduction  of  a  small 
quantity  of  the  curd  of  milk  into  a  solution  of  grape  sugax  will  cause  it  to  ferment. 


GLUTEN,  VEGETABLE   ALBUMEN,    AND    DIASTASE.  117 

through  the  sieve  in  preparing  the  gluten  of  wheat,  the  water  rests  trans- 
parent and  colourless  above  the  white  sediment.  If  this  water  be  heated, 
it  will  become  more  or  less  troubled,  and  white  films  or  particles  will 
separate,  which  may  be  easily  collected,  and  which  possess  all  the  pro- 
perties of  coagulated  albumen,  or  boiled  white  of  egg.  To  this  sub- 
stance the  name  o[  vegetable  albumen  has  been  given.  When  the  fresh 
prepared  gluten  of  wheat  is  boiled  in  alcohol  a  portion  of  albumen  gene- 
rally remains  undissolved,  showing  that  water  does  not  completely  wash 
it  out  from  the  gluten. 

Vegetable  albumen,  when  fresh  and  moist,  has  neither  colour,  taste, 
nor  smell,  is  insoluble  in  water  or  alcohol,  but  dissolves  in  vinegar  and 
in  caustic  potash  or  soda.  When  dry  it  is  brittle,  more  or  less  coloured, 
and  opacjue.  In  the  seeds  of  plants,  it  exists  only  in  small  quantity — 
thus  the  grain  of 

Wheat  contains  |  to  1^  per  cent. 
Rye       ...     2  to  3| 
Barley  •     •  ,  •  iV  to    i 
Oats       .     .     .    ^  to    i         '♦ 
It  occurs  more  largely  however  in  the  fresh  juices  of  plants,  in  those 
of  cabbage  leaves,  turnip  roots,  and  many  others.     When  these  juices 
are  heated  the  albumen  coagulates  and  is  readily  separated. 

Gluten  and  vegetable  albumen  appear  to  be  as  closely  related  as  sugar 
and  starch  are  to  each  other.     Like  these  two  substances,  they  consist 
of  the  same  elements,  united  together  in  the  same  proportions,  and  are 
capable  of  similar  mutual  transformations.     According  to  the  most  re- 
cent analyses,  those  of  Dr.  Scheerer,  they  consist  of 
Carbon  ^  =  54-76 
Hydrogefr  =     7-06 
Oxygen         =  20-06 
Nitrogen       =  18-12 

100 

When  exposed  to  the  air  in  a  moist  state  these  subftances  undergo  de- 
composition. They  ferment,  emit  a  most  disagreeable  odour,  and  pro- 
duce, among  other  compounds,  vinegar  and  ammonia. 

The  important  influence  which  gluten  and  vegetable  albumen  are 
supposed  to  exercise  over  the  nourishing  properties  of  the  different  kinds 
of  food  in  which  they  occur,  will  be  considered  in  a  subsequent  part  of 
these  lectures.* 

3°.  Diastase. — When  cold  water  is  poured  upon  barley  newly  malted 
and  crushed,  is  permitted  to  remain  over  it  for  a  quarter  of  an  hour,  is 
then  poured  off,  filtered,  evaporated  to  a  small  bulk  over  boiling  water, 
again  filtered  if  necessary,  and  then  mixed  with  much  alcohol,  a  white 
tasteless  powder  falls — to  which  the  name  of  diastase  has  been  given. 

*  There  occur  in  the  animal  kingdom— in  the  bodiesof  animals— three  other  forms  of  the 
substance  above  described  under  the  names  of  gluten  and  vegetable  albumen.  These  are 
albumen  or  white  of  egg,  already  mentioned, — casein,  the  curd  of  cheese,— and  fibrin^  the 
substance  of  the  muscular  fibre  of  animals. 

1^.  Casern.— When  the  curd  of  cheese  is  well  washed  with  water,  and  then  boiled  la 
alcohol  to  free  it  from  oily  matter,  it  foraxs  the  casein  of  chemists.  While  moist  it  is  soft 
and  colourless,  but  as  it  dries  it  hardens,  assumes  a  yellow  colour,  and  becomes  semitrans- 
parent.    Even  when  moist  it  is  perfectly  insoluble  either  in  cold  or  in  hot  water.    It  is  solu- 

6 


118  PRODUCTION  OF  DIASTASE. 

If  unmalted  barley  be  so  treated  no  diastase  is  obtained.  This  sub- 
stance, therefore,  is  formed  during  the  process  of  malting. 

If  wheat,  or  barley,  or  potatoes,  which  by  steeping  in  water  yield  no  di- 
astase, be  made  to  germinate  (or  sprout),  and  be  afterwards  bruised  and 
treated  as  above,  diastase  will  be  obtained.  It  is  therefore  produced 
during  germination. 

If  the  shoot  of  a  potato  be  cut  off  within  half  an  inch  of  its  base,  this 
lower  portion,  with  the  part  of  the  potato  to  which  it  is  immediately  at- 
tached, separated  from  the  rest — and  the  three  parts  (the  upper  portion 
of  the  shoot — the  lower  portion  with  its  attached  fragment  of  potato— 
and  the  remaining  mass  of  the  potato)  treated  with  water, — only  that 
portion  will  yield  diastase  in  which  the  base  of  the  shoot  is  situated. 
When  a  seed  sprouts,  therefore,  this  substance  is  formed  at  the  base  of 
the  germ,  and  there  remains  during  its  growth. 

If  the  same  portion  of  the  potato,  or  if  the  grain  of  barley  or  wheat  is 

ble,  however,  in  water  containing  vinegar,  or  to  which  a  little  carbonate  of  potash  or  soda 
has  been  added.  It  may  be  kept  for  any  length  %i  time  in  a  dry  place,  without  undergoing 
decay.  The  changes  undergone  by  old  cheese  are  chiefly  due  to  the  oily  and  other  sub- 
stances with  which  the  curd  is  mixed.  It  has  been  remarked,  that  when  the  gluten  of  wheat 
is  left  for  a  length  of  time  in  a  moist  state  it  undergoes  a  kind  of  fermentation  and  gradually 
acquires  the  smell  and  taste  of  cheese  (Rouelle.) 

2°.  Fibrin. — When  lean  beef  or  mutton  is  long  washed  in  water  till  it  becomes  colourless, 
and  is  then  boiled  in  alcohol  to  separate  the  fat,  a  colourless,  elastic,  fibrous  mass  is  obtained, 
which  is  the  fibrin  of  chemists.  In  recently  drawn  blood  it  exists  in  the  liquid  state,  but  coa- 
gulates spontaneously  when  exposed  to  the  air,  and  forms  the  greater  part  of  the  clot  of 
blood.     It  dissolves  in  a  solution  of  caustic  potash  or  of  nitre,  and  in  vinegar. 

3°.  Albumen. — This  substance  in  the  liquid  state  exists  in  the  while  of  eg^.,  and  in  the 
serum  of  the  blood.  It  coagulates  by  heating  to  160°  F  ,  or  if  previously  mixed  with  water 
by  raising  to  212°  F. 

These  three  substances,  in  addition  to  their  well  Known  sensible  properties,  are  distin- 
jfuished  as  follows :  ^^ 

1°.  Liquid  casein  in  milk,  is  not  coagulatec^^  heating  alone — the  addition  of  rennet  orof 
a  little  acid  (vinegar  or  spirit  of  salt)  is  necessary,  when  it  curdles  readily. 

2°.  Liquid  albumen  in  white  of  egg,  coagulates  by  heat  alone,  as  when  an  egg  is  put  into 
hot  water. 

3°.  Liquid  fibrin  in  the  blood  coagulates  by  mere  exposure  to  the  air,  or  more  rapidly  by 
agitation  in  contact  with  the  air. 

Like  starch  and  sugar  these  three  substances  are  mutually  convertible  by  known  means. 
th\is  fibrin,  if  unboiled^  dissolves  by  digestion  at  80°  F.  in  a  saturated  solution  of  nitre,  and 
acquires  the  properties  of  liquid  albumen;  and  if  to  liquid  albumen  a  little  caustic  potash  be 
added,  and  afterwards  much  alcohol,  it  will  be  thrown  4own  in  the  form  and  with  the  pro- 
perties of  casein. 

All  these  substances  appear  to  contain  the  same  orgaij.j  constituents  in  the  same  propor- 
tions. 

Boussingault  first  showed  the  identity  in  chemical  constitution  of  gluten  and  vegetable  al- 
bumen.— [Pog.  An.,  xl,  p.  2.53.]  Mulder  afterwards  proved  a  similar  identity  between  vege- 
table albumen  and  the  white  of  egg,  fibrin,  and  casein. — [Ann.  de  Chim.  et.  de  Phys.,  Ixv.,  p. 
301.]  Mulder  supposes  them  to  differ  from  each  other  by  the  presence  in  unlike  quantities 
of  a  small  admixture  of  sulphur,  phosphorus  or  phosphate  of  lime. 

Those  who  are  not  familiar  with  the  history  and  with  he  nature  of  chemical  research,  can 
form  no  idea  of  the  time  and  labour  which  has  by  diffeient  chemists  been  expended  on  this 
one  branch.  The  persevering  industry  of  Dr.  Mulder,  of  Rotterdam,  appeared  to  have 
cleared  up  the  entire  subject  by  a  long  series  of  investigations  and  analyses. — [for  an  out- 
line of  his  results,  see  Berzelius  Arsberattlese,  1839,  p.  611,]— when  first  Vogel.  then  Prosper 
Denis,  and  latest  Liebig  and  Dr.  Scheerer,  have  arrived  at  different  results.  Our  ideas  are 
thus  again  unfixed,  and  our  partial  generalizations  set  aside  for  future  emendation. 

The  analysis  inserted  in  the  text,  as  representing  the  composiiion  of  gluten  and  vegetable 
albumen,  is  that  given  by  Dr.  Scheerer  for  the  purest  form  oi  fibrin.  I  have  selected  it  in 
preference  to  the  results  either  of  Boussingault  orof  Mulder,  because  it  is  the  most  recent, 
and  has  been  obtained  with  a  knowledge  of  all  the  previous  researches, — and  assuming  the 
chemical  identity  of  this  entire  group  of  substances,  is  the  most  likely  to  represent  their 
constitution  with  accuracy.  It  differs  from  the  analysis  of  Mulder  only  in  stating  the  nitro- 
gen at  2  per  cent,  higher  than  was  done  by  that  chemist.  The  recent  improvements  in  the 
mode  of  determining  the  true  quantity  of  nitrogen  in  organic  substances,  appear  to  justify 
us  in  expecting  the  result  of  Scheerer  to  be  in  this  respect  the  more  correct. 


DIASTASE  CHANGES  STARCH  INTO  SUGAR.  il9 

examined,  when  the  first  true  leaves  of  the  plant  have  been  fully 
formed  and  expanded,  the  diastase  will  be  found  to  have  in  great  part, 
if  not  entirely,  disappeared.  This  substance,  therefore,  is  first  formed 
when  the  seed  begins  to  sprout,  performs  a  functior  which  makes  its 
presence  necessary  at  the  base  of  the  germ,  and  which  function  being 
discharged  when  the  true  leaves  are  formed,  it  then  disappears.  What 
is  the  nature  of  this  temporary  function,  why  the  diastase  must  reside  at 
the  base  of  the  sprout  in  order  to  discharge  it,  and  why  it  should  so  early 
cease,  will  appear  from  a  detail  of  the  properties  of  this  singular  sub- 
stance. 

Properties  of  diastase. — If  the  solution  obtained  from  malt  be  digested 
with  potato,  flour,  or  other  starch,  at  a  temperature  between  120°  and 
140°  F.,  the  latter  will  gradually  dissolve  and  will  form  a  colourless 
transparent  solution.  "When  this  solution  is  carefully  evaporated  a  yel- 
lowish white  powder  is  obtained,  perfectly  soluble  in  water,  to  which 
the  name  of  dextrine  has  been  given,  [because  its  solution  turns  to  the 
right  a  ray  of  polarized  light  when  passed  through  it.]  This  dextrine 
has  the  same  composition  as  starch.  It  is  merely  starch  changed  or 
transformed  in  such  a  way  as  to  become  soluble  in  cold  water, — a 
change  analogous  to  that  which  it  undergoes  by  simply  boiling  in  water. 
'  But  if  the  digestion  be  continued  after  the  starch  is  dissolved,  the  so- 
lution will  gradually  acquire  a  sweet  taste,  and  if  it  be  now  evaporated 
it  will  yield,  instead  of  dextrine,  a  mixture  of  gum  and  grape  sugar. 
And  if  the  digestion  be  still  further  prolonged,  the  whole  of  the  starch 
will  be  converted  into  grape  sugar  only. — [See  above,  §  6,  p.  113.] 

Thus  diastase  (like  sulphuric  acid)  possesses  the  property  of  trans- 
forming starch  entirely — first  into  gum,  and  then  into  grape  sugar.  The 
intermediate  stage  of  dextrine  has  not  been  recognized  in  the  action  of 
sulphuric  acid,  nor  is  it  easy  to  arre^r.  the  action  of  diastase  exactly  at 
this  point — the  most  carefully  prepared  dextrine  always  containing  a 
mixture  of  gum  and  sugar.  One  part  of  diastase  will  convert  into  sugar 
2000  parts  of  starch. 

A  solution  of  diastase,  when  allowed  to  stand,  soon  undergoes  decom 
position,  and  after  being  boiled,  it  has  no  further  effect  upon  starch.     It 
has  not  been  analysed,  because  it  is  diflScult  to  obtain  it  In  a  pure  state. 
It  contains  nitrogen,  however,  for,  when  moistened  and  exposed  to  the 
air,  it  decomposes,  and,  among  other  products',  yields  ammonia.* 

The  functions  of  diastase — one  of  the  purposes  at  least  for  which  it  is 
produced  in  the  living  seed,  and  situated  at  the  base  of  the  germ — will 
now  be  in  some  measure  understood.  The  starch  in  the  seed  is  the  food 
of  the  future  germ,  prepared  and  ready  to  minister  to  its  wants  when- 
ever heat  and  moisture  concur  in  awakening  it  to  life.  But  starch  is  it- 
self insoluble  in  water,  and  could  not,  therefore,  accompany  the  fluid  sap 
when  it  begins  to  move  and  circulate.  For  this  reason  diastase  is 
formed  at  the  point  where  the  germ  first  issues  from  the  mass  of  food. 
There  it  transforms  the  starch,  and  renders  it  soluble,  so  that  the  young 
vessels  can  take  it  up  and  convey  it  to  the  point  of  growth.  When  the 
starch  is  exhausted  its  functions  cease.     It  is  then  itself  transformed  and 

•  It  will  be  recollected  that  ammonia  contains  nitrogen,  bslng  represented  by  NHs.—See 
Lecture  III.,  p,  51. 


120  ADAPTATIONS  IN  THE  PRODUCTIONS  OF  DIASTASE. 

carried  into  the  general  circulation.  Or  when,  as  in  the  potato,  much 
more  starch  is  present  than  is  in  many  cases  requisite,  its  function  ceases 
long  before  the  whole  of  the  starch  disappears.  Its  presence  is  necessa- 
ry only  until  the  leaves  and  roots  are  fully  formed — when  the  plant  is 
enabled  to  provide  for  itself,  and  becomes  independent  of  the  starch  of 
the  seed.  When  this  period  arrives,  therefore,  the  production  of  dias- 
tase is  no  longer  perceived. 

This  I  have  said  is  one  of  the  purposes  which  appears  to  be  served  by 
diastase  in  the  vegetable  economy.  That  it  is  the  only  one  we  have  no 
reason  to  believe.  There  may  be  others  quite  as  interesting  which  we 
do  not  as  yet  understand.  This  is  rendered  more  probable  by  the  fact 
that  the  diastase  contained  in  one  pound  of  malted  barley  is  capable  of 
converting  into  sugar  five  pounds  of  starch.*  (Liebig.)  And  though 
at  the  temperature  at  which  the  seed  germinates,  more  of  this  substance 
may  be  necessary  to  transform  the  same  weight  of  starch  than  is  re- 
quired in  our  hands,  when  aided  by  artificial  heat, — yet  as  we  never  in 
the  ordinary  course  of  nature  find  any  thing  superfluous  or  going  to 
waste,  there  is  reason  to  believe  that  the  diastase  may  be  intended  also 
to  contribute  directly  to  the  nourishment  and  growth  of  the  plant.  As 
it  contains  nitrogen,  it  must  be  derived  from  the  gluten  or  vegetable  al- 
bumen of  the  seed  ;  and  as  a  young  plant  of  wheat,  when  already  many 
inches  from  the  ground,  contains  no  more  nitrogen  than  was  originally 
present  in  the  seed  itself  (Boussingaull),  this  diastase  may  only  be  the 
result  of  one  of  those  transformations  of  which  glutenf  is  susceptible, 
and  by  which  it  is  rendered  soluble,  and  capable  of  aiding  in  the  pro- 
duction of  those  parts  of  the  substance  of  the  growing  plant  into  which 
nitrogen  enters  as  a  necessary  constituent. 

It  may  not  be  uninstructive  if  we  pause  here  for  a  moment  and  con- 
sider the  beauty  of  the  arrangements  we  have  just  been  describing.  In 
passing  through  a  new  and  interesting  country  we  do  not  hesitate,  at 
times,  to  stop  and  gaze,  and  leisurely  admire.  We  cannot  otherwise 
fully  realize  and  appreciate  its  beauty.  So  in  the  domains  of  science, 
we  cannot  be  ever  hurrying  on — we  must  linger  occasionally,  not  only 
that  we  may  more  carefully  observe,  but  that  we  may  meditate  and 
feel. 

You  see  how  bountifully  nature  has  provided  in  the  seed  for  the  nour- 
ishment of  the  young  plant,  how  carefully  the  food  is  stored  up  for  i;, 
and  in  how  imperishable  a  form — how  safely  covered  also  and  protected 
from  causes  of  decay  !  For  hundreds  of  years  the  principle  of  life  will 
lie  dormant,  and  for  as  many  the  food  will  remain  sound  and  undimin- 
ished till  the  time  of  awakening  comes.  Though  buried  deep  in  the 
earth,  the  seed  defies  the  exertions  of  cold  or  rain,  for  the  food  it  contains 
is  unaffected  by  cold  and  absolutely  insoluble  in  water.     But  no  sooner 

*  It  is  the  diastase  in  malt  which  dissolves  the  starch  of  the  barley  in  the  process  of  brew- 
ing, but  as  the  diastase  contained  in  malt  is  sufficient  to  dissolve  so  large  a  quantity  of  starch, 
it  is  obviously  a  waste  of  labour  to  malt  the  whole  of  the  barley  employed.  One  of  malt  to 
three  of  barley  would  probably  be  sufficient  in  most  cases  to  obtain  a  wort  containing  the 
whole  of  the  starch  in  solution.  Advantage  is  taken  of  this  property  in  the  manufacture  of 
the  white  beer  of  Louvaio,  and  of  other  places  ki  Flanders,  and  in  Germany,  where  the  light 
colour  is  secured  by  adding  a  large  quantity  of  flour  to  a  decoction  of  a  small  quantity  of 
barley. 

t  That  diastase  is  merely  transformed  gluten  we  cannot  say,  because  the  exact  chemical 
constitution  of  diastase  is  as  yet  unknown. 


VEGETABLE    ACIDS.  121 

is  the  sleeping  germ  recalled  to  life,  by  the  access  of  air  and  warmth 
and  duly  tempered  moisture,  than  a  new  agent  is  summoned  to  its  aid, 
and  the  food  is  so  changed  as  to  be  rendered  capable  of  ministering  to  its 
early  wants.  The  first  movement  of  the  nascent  germ — (and  how  it 
moves,  by  what  inherent  or  impartial  force,  who  shall  discover  to  us  ?) 
— is  the  signal  for  the  appearance  of  this  agent — diastase — of  which, 
previous  to  germination,  no  trace  could  be  discovered  in  the  seed.  At 
the  root  of  tlie  germ,  where  the  vessels  terminate  in  the  farinaceous 
matter,  exactly  where  it  is  wanted,  this  substance  is  to  be  found; — there, 
and  there  only,  resolving  and  transforming  the  otherwise  unavailable 
store  of  food,  and  preparing  it  for  being  conveyed  either  to  the  ascending 
sprout  or  to  the  descending  root.  And  when  the  necessity  for  its  yjre- 
sence  ceases — when  the  green  leaf  becomes  developed,  and  the  root  has 
fairly  entered  the  soil — when  the  plant  is  fitted  to  seek  food  for  itself — 
then  this  diastase  disappears,  it  undergoes  itself  a  ne\^  conversion,  and  is 
prepared  in  another  form  to  contribute  to  the  further  increase  of  the  plant. 
How  beautiful  and  provident  are  all  these  arrangements ! — how  plas- 
tic the  various  forms  of  organic  matter  in  the  hands  of  the  All-Intelli- 
gent!— how  nicely  adjusted  in  time  and  place  its  diversified  changes! 
What  an  apparently  lavish  expenditure  of  forethought  and  kind  previ- 
sion, in  behalf  even  of  the  meanest  plant  that  grows  ! 

§  9.    Vegetable  Acids. — Acetic  acid,  Oxalic  acid.  Tartaric  acid, 
Citric  acid,  Malic  acid. 
Another  class  of  compound  substances  remains  to  be  shortly  consid 
ered, — those,  namely,  which  possess  sour  or  acid  properties,  and  which 
are  known  to  be  present  in  large  quantity  in  many  plants,  and  more 
especially  in  the  greater  number  of  unripe  fruits.     They  do  not,  taken 
as  a  whole,  form   any  large  portion  of  the  entire  produce,  either  of  the 
general  vegetation  of  the  globe  or  of  those  plants  which  are  cultivated 
for  food ;  yet  the  growth  of  fruit — as  in  the  grape,  orange,  and  apple 
countries — is  sufficiently  extensive,  and  the  general  interest  in  the  cul- 
tivation of  fruit  trees  sufficiently  great,  to  require  that  the  nature  of  the 
substances  contained  in  fruits,  and  the  peculiar  changes  by  which  they 
are  formed,  should  be  in  some  measure  considered  and  explained. 

I. ACETIC    ACID. 

Acetic  acid  or  vinegar  is  the  most  extensively  diffijsed,  and  the  most 
largely  produced,  of  all  the  organic  acids.  It  is  formed  during  the  ger- 
mination of  seeds,  and  it  exists  in  the  juices  of  many  plants,  but  it  is 
most  abundantly  evolved  during  the  fermentation,  whether  namral  or 
artificial,  of  nearly  all  vegetable  substances.  When  pure  it  is  a  colour- 
less liquid,  having  a  well  known  agreeably  acid  taste.  ^  It  may  be 
boiled  and  distilled  over  without  being  decomposed.  The  vinegar  of  the 
shops  is  generally  very  much  diluted,  but  it  can  be  prepared  of  such  a 
strength  as  to  freeze  and  become  solid  at  45°  F.,  and  to  blister  the  skin 
and  produce  a  sore  when  applied  to  any  part  of  the  body.  When 
mixed  with  water  it  readily  dissolves  lime,  magnesia,  alumina,  &c., 
forming  salts  called  acetates,  which  are  all  soluble  in  water,  and  may, 
therefore,  be  readily  washed  out  of  the  soil  or  of  compost  heaps  by 
heavy  falls  of  rain. 


122  PREPARATION  OF  ACETIC  ACID. 

When  perfectly  free  from  water,  acetic  acid  consists  of — 
Carbon  .     .     .     47-5  per  cent.,  or  4  atoms 
Hydrogen   .     .       5-8         "         or  3      " 
Oxygen.     .     .     46-7         "  or  3      " 


'4 


100 

It  is  therefore  represented  by  the  formula  C, 
those  given  in  the  preceding  sections  for  starch,  sugar,  dec,  tlie  numbers 
representing  the  atoms  of  hydrogen  and  oxygen  are  equal,  and  conse- 
quently these  elements  are  in  the  proportion  to  form  water.  Hence, 
vinegar,  like  sugar,  may  be  represented  by  carbon  and  water. 

Let  us  consider  for  a  moment  the  several  processes  by  which  this  acid 
IS  usually  formed. 

1°.  By  the  distillation  of  wood. — This  a  method  by  which  wood 
vinegar — often  caW^d  pyroligneous  acid — is  prepared  in  large  quantity. 
"Wood  which  has  been  dried  in  the  air  is  put  into  an  iron  retort  and  distil- 
led. The  principal  products  are  vinegar,  water,  and  tarry  matter. 
The  decomposition  is  of  a  complicated  description,  but  by  comparing 
the  constitution  of  woody  fibre  with  that  of  vinegar,  we  can  readily  see 
the  nature  of  the  changes  by  which  the  latter  is  produced. 
Woody  Fibre  is  =  C^a  Hg  Og 
3  of  Vinegar  are  =0,2  Hg  Og 


Difference  =  H^  O^  ;  or  the  elements 

of  one  atom  of  water.  One  portion  of  the  woody  fibre,  therefore,  com- 
bines with  the  elements  of  an  atom  of  water,  obtained  by  the  decompo- 
sition of  another  portion,  and  thus  vinegar  is  produced.  *" 

2°.  Manufacture  of  Vinegar  from  Cane  Sugar. — It  is  a  well  known 
fact  in  domestic  economy,  that  if  cane  sugar  be  dissolved  in  water,  a 
little  vinegar  added  to  it,  and  the  solution  kept  for  a  length  of  time  at  a 
moderate  temperature,  the  whole  will  be  converted  into  vinegar  without 
any  sensible  fermentation.  This  process  is  frequently  followed  in  the 
preparation  of  household  vinegar,  and  was  formerly  adopted  to  some  ex- 
tent in  our  chemical  manufactories.  It  will  be  recollected  that  we  re- 
presented Cane  Sugar  by  C12  ^\o  Oio,  while 
3  of  Vinegar  =    C12  Hg    O3 


Difference  Hi      O^  ;  or  the  elements 

of  an  atom  of  water,  which  cane  sugar  must  lose  in  order  to  be  convert- 
ed into  vinegar.  Whether  the  change  in  this  instance  takes  place  by 
the  direct  conversion  of  cane  sugar  into  vinegar,  or  whetlier  the  former 
is  previously  transformed  into  grape  sugar,  has  not  been  satisfactorily  de- 
termined. 

3°.  Manufacture  of  Vinegar  from  Alcohol. — In  Germany,  where 
common  brandy  is  cheaper  than  vinegar,  it  is  found  profitable  to  manu- 
facture this  acid  from  weak  spirit.  For  this  purpose  it  is  mixed  with  a 
little  yeast,  and  then  allowed  to  trickle  over  wood  shavings  moistened 
with  vinegar,  and  contained  in  a  cask,  the  sides  of  which  are  perforated 
with  holes  for  the  admission  of  a  current  of  air.  By  this  method  oxy- 
gen is  absorbed  from  the  air,  and  in  24  hours  the  alcohol  in  the  spirit  is 
converted  into  vinegar  and  -.^-ster. 


TARTARIC  ACID  IN  THE  GRAPE.  123 

The  explanation  of  this  process  is  also  simple,  alcohol  being  repre- 
sented by  C4  Hg  Og.     Thus — 

Alcohol  =  C4  H(5  O2   ")        f  Vinegar  =  C4  H3  O3 

4  of  Oxygen  =  O4    l_J    3  of  Water    ==       Ho  O, 


Sum  C4H6O0J        I  Sum      =  C4  Ho  Oe 

4°.  Production  of  Vinegar  hy  fermentation. — When  vegetable  mat- 
ters are  allowed  to  ferment,  carbonic  acid  is  given  off  and  vinegar  is 
formed.  In  such  cases  this  acid  is  the  result  of  a  series  of  changes,  du- 
ring which  that  portion  of  the  vegetable  matter  which  has  at  length 
reached  the  state  of  vinegar  has  most  probably  passed  through  the  seve- 
ral previous  stages  of  grape,  sugar,  and  alcohol.  The  carbonic  acid,  as 
has  already  been  explained  (p.  115),  is  given  off  during  the  fermentation 
of  the  grape  sugar,  and  the  consequent  formation  of  alcohol. 

To  simple  transformations,  similar  to  those  above  described,  we  can 
trace  the  origin  of  the  vinegar  which  is  met  with  in  the  living  juices  of 
plants,  and  among  the  products  of  their  decay. 

II. TARTARIC  ACID. 

The  grape  and  the  tamarind  owe  their  sourness  to  a  peculiar  acid  to 
which  the  name  o[ tartaric  acid  has  been  given.  It  is  also  present,  along 
with  other  acids,  in  the  mulberry,  in  the  berries  of  the  sumach  {rhus  co- 
riarii),  and  in  the  sorrels,  and  has  been  extracted  from  the  roots  of  the 
couch-grass  and  the  dandelion. 

When  new  wine  is  decanted  from  the  lees,  and  set  aside  in  vats  or 
casks,  it  gradually  deposits  a  hard  crust  or  tartar  on  the  sides  of  the  ves- 
sels. This  substance  is  known  in  commerce  by  the  name  of  argol,  and 
when  purified  is  familiar  to  you  as  the  cream  of  tartar  of  the  shops.  It 
is  a  compound  of  tartaric  acid  with  potash,  and  from  it  tartaric  acid  is 
extracted  for  use  in  medicina  and  in  the  arts.  The  principal  use  of  the 
acid  is  in  certain  processes  of  the  calico  printers. 

The  pure  acid  is  sold  either  in  the  form  of  a  white  powder  or  of  trans- 
parent crystals,  which  are  colourless,  and  have  an  agreeable  acid  taste. 
It  dissolves  readily  in  water,  and  causes  a  violent  effervescence  when 
mixed  with  a  solution  of  the  carbonate  of  potash  or  of  soda.  As  it  has 
no  injurious  action  upon  the  system,  it  is  extensively  used  in  artificial 
soda  powders  and  effervescing  draughts.  When  added  in  sufficient 
quantity  to  a  solution  containing  potash,  it  causes  a  white  crystalline 
powder  to  fall,  which  is  cream  of  tartar  (or  hitartrate  ofpotash)^  and  from 
lime  water  it  throws  down  a  white  chalky  precipitate  o^  tartrate  of  lime. 
J3oth  of  these  compounds  are  present  in  the  grape. 

When  perfectly  free  from  water  this  acid  consists  of — 
Carbon  .  .  .  =  36*81  or  4  atoms. 
Hydrogen  .  .  =  3-00  or  2  atoms. 
Oxygen    .     .     .  =  60'19  or  5  atoms. 


100 
It  is  therefore  represented  by  the  formula  C4  Hg  O5. 

If  we  compare  the  numbers  by  which  the  atoms  of  hydrogen  and  ox- 
ygen in  this  acid  are  expressed,  we  see  that  these  elements  are  not  in  the 
proportion  to  form  water,  and  that  this  substance,  therefore,  cannot,  like 


124  CONSTITUTION    OF    TARTARIC    AND    CITRIC    ACIDS. 

SO  many  of  those  we  have  hitherto  had  occasion  to  notice,  be  represented 
by  carbon  and  the  elements  of  water  alone. 
It  may  be  represented  by 

4  of  Carbon  .     .  =  C4  ) 

2  of  Water  .     .  =         H2  O^    V    or,  4C+2H4-30 
and  3  of  Oxygen  .     .  =  O3    5 


Tartaric  Acid  =  C4  H2  O5 

And,  though  this  mode  of  representation  does  not  truly  exhibit  the  con- 
stitution of  the  acid,  inasmuch  as  we  have  no  reason  to  believe  that  it 
really  contains  water  as  such — yet  it  serves  to  show  very  clearly  that  in 
the  living  plant  this  acid  cannot  be  formed  directly  from  carbon  and  the 
elements  of  water,  as  starch  ant!  sugar  may,  but  that  it  requires  also 
three  atoms  of  oxygen  in  excess  to  every  five  of  carbon  and  two  of  water. 
We  shall,  in  the  following  lecture,  see  how  nicely  the  functions  of  the 
several  parts  of  the  plant  are  adjusted, — at  one  period  to  the  formation  of 
this  acid,  and  at  another  to  its  conversion  into  sugar  during  the  ripening 
of  the  fruit. 

HI. citric    ACID,    OR    ACID    OF    LEMONS. 

This  acid  gives  their  sourness  to  the  lemon,  the  lime,  the  orange,  the 
cranberry,  the  red  whortleberry,  the  bird-cherry,  and  the  fruits  of  the 
dog-rose  and  the  woody  night-shade.  It  is  also  found  in  some  roots,  as 
in  those  of  the  dahlia  pinnata,  and  the  asarum  europa3um  {asarrabacca), 
and  mixed  with  much  malic  acid,  in  the  currant,  cherry,  gooseberry, 
raspberry,  strawberry,  common  whortleberry,  and  the  fruit  of  the  haw- 
thorn. 

When  extracted  from  the  juice  of  the  lemon  or  lime,  and  afterwards 
purified,  it  forms  transparent  colourless  crystals,  possessed  of  an  agreea- 
ble acid  taste  ;  effervesces  like  tartaric  acid  with  carbonate  of  soda,  and 
like  it,  therefore,  is  much  employed  for  effervescing  draughts.  With 
potash  it  forms  a  soluble  salt,  which  is  a  citrate  of  potash,  and  from  lime 
water  it  throws  down  a  white,  nearly  insoluble,  sediment  of  ci^ra^e  q/" 
lime,  which  re-dissolves  when  the  acid  is  added  in  excess.  In  combi- 
nation with  lime  it  exists  in  the  tubers,  and  with  potash  in  the  roots,  of 
the  Jerusalem  artichoke. 

When  free  from  water,  citric  acid  consists  of 

Carbon     ....     41-49  —  4  atoms. 

Hydrogen     .     .     .       3-43  =  2  atoms. 

Oxygen  .     .     .     .     55*08  =  4  atoms. 

100 
and  is  therefore  represented  by  C4  Hg  O4. 

This  formula  differs  from  that  assigned  to  the  tartaric  acid  only  in 
containing  one  atom  of  oxygen  less,  O4  instead  of  O5.  In  the  citric 
acid,  therefore,  there  are  2  atoms  of  oxygen  in  excess,  above  what  is 
necessary  to  form  water  with  the  2  of  hydrogen  it  contains. 

IV. — malic  acid. 
The  malic  and  oxalic  acids  are  more  extensively  diffused  in  living 
plants  than  any  other  vegetable  acids.     If  acetic  acid  be  more  largely 


CONSTITUTION    OF    MALIC    AND    OXALIC    ACIDS.  125 

foimed  in  nature,  it  is  chiefly  as  a  product  of  the  decomposition  of  or- 
ganic matter,  when  it  has  already  ceased  to  exist  in,  or  to  form  part  of, 
a  living  plant. 

Along  with  the  citric  acid,  it  has  been  already  stated  that  the  malic 
occurs  in  many  fruits.  It  is  found  more  abundantly,  however,  and  is  the 
chief  cause  of  the  sour  taste,  in  the  unripe  apple,  [hence  its  name  malic 
acid,]  the  plum,  the  sloe,  the  elderberry,  the  barberry,  the  fruit  of  the 
mountain  ash,  and  many  others.  It  is  associated  with  the  tartaric  acid 
in  the  grape  and  in  the  Agave  americana. 

This  acid  is  not  used  in  the  arts  or  in  medicine,  and  therefore  is  not 
usually  sold  in  the  shops.  It  is  obtained  most  readily,  in  a  pure  stale, 
from  the  berries  of  the  mountain  ash.  It  forms  colourless  crystals, 
which  have  an  agreeable  acid  taste.  It  combines  with  potash,  soda, 
lime,  and  magnesia,  and  forms  malates,  and,  in  combination  with  one  or 
more  of  these  bases,  it  usually  occurs  in  the  fruits  and  juices  of  plants. 
The  malate  of  lime  is  soluble,  while  the  citrate,  as  already  stated,  is 
nearly  insoluble,  in  water.  This  malate  exists  in  large  quantity  in  the 
juice  of  the  house-leek  {sempervivum  tectorum),m\he  Sedum  telephium, 
the  Arum  maculatum,  and  many  other  juicy  and  fleshy-leaved  plants. 

When  perfectly  free  from  water,  the  malic  acid  has  exactly  the  same 
chemical  constitution  as  the  citric,  and  is  represented  by  the  same  for- 
mula C4  H2  O4.  These  two  acids,  therefore,  bear  the  same  relation 
to  each  other  as  we  have  seen  that  starch,  gum,  and  sugar  do.  They 
are  what  chemists  call  isomeric,  or  are  isomeric  bodies.  We  cannot 
transform  them,  however,  the  one  into  the  other,  by  any  known  means, 
though  there  is  every  reason  to  believe  that  tltey  may  undergo  such 
transformations  in  the  interior  of  living  plants.  Hence  probably  one 
reason  also  why  the  malic  and  citric  acids  occur  associated  together  in 
so  many  different  fruits. 

V. OXALIC    ACID. 

This  acid  has  already  been  treated  of,  and  its  properties  and  cojnposi- 
tion  detailed,  in  a  preceding  lecture  (Lecture  III.,  p.  47).  It  forms  co- 
lourless transparent  crystals,  iiaving  an  agreeably  acid  taste,  and  it 
effervesces  with  the  carbonates  of  potash  and  soda,  but  on  account  of  its 
poisonous  qualities,  it  is  unsafe  to  administer  it  as  a  medicine.  It  oc- 
curs in  combination  with  potash  in  the  sorrels,  in  rhubarb,  and  in  the 
juices  of  many  lichens.  Those  lichens  which  incrust  the  sides  of  rocks 
and  trees,  not  unfrequently  contain  half  their  weight  of  this  acid  in  com- 
bination with  lime.  It  can  be  formed  artificially  by  the  action  of  nitric 
acid  on  starch,  sugar,  gum,  and  many  other  organic  substances. 

When  perfectly  free  from  water,  oxalic  acid  contains  no  hydrogen ; 
but  consists  of — 

Carbon     .     .     .     33-75  =  2  atoms 
Oxygen    .     .     .     66-25  =  3      " 

100 
and  it  is  represented  by  C2  O3.     When  heated  with  strong  sulphuric 
acid,  it  is  decomposed  and  resolved  into  gaseous  carbonic  acid  (CO2)  and 
carbonic  oxide  (CO)  in  equal  volumes.     This  change  is  easily  under- 


126  STARCH  CONVERTED  INTO  WOODY    FIBRE. 

§  10.   General  observations  on  the  substances  of  which  plants  chiefly  consist. 

It  may  be  useful  here  shortly  to  review  the  most  important  facts  and 
conclusions  which  have  been  adverted  to  in  the  present  lecture. 

1°.  The  great  bulk  of  plants  consists  of  a  series  of  substances  capable 
of  being  represented  by,  and  consequently  of  being  formed  in  nature 
from,  carbon  and  the  elements  of  water  only.  Such  are  woody  fibre, 
starch,  gum,  and  the  several  varieties  of  sugar  (p.  111). 

2°.  Yet  the  crude  mass  of  wood,  as  it  exists  in  a  full-grown 
tree,  containing  various  substances  in  its  pores,  cannot  be  represented 
by  carbon  and  the  elements  of  water  alone.  It  appears  always  to 
contain  a  small  excess  of  hydrogen,  which  is  greater  in  some  trees  than 
in  others.  Thus  in  the  chesnut  and  the  lime,  this  excess  is  greater  than 
in  the  pines,  while  in  the  latter  it  is  greater  than  in  the  oak  and  the  ash. 
[For  a  series  of  analyses  of  different  kinds  of  wood  by  Peterson  and 
Schodler,  see  Thomson's  Organic  Chemistry,  p.  849.] 

3°.  These  substances  are,  in  many  cases,  mutually  convertible  even 
in  our  hands.     They  are  probably,  therefore,  still  more  so  in  nature. 

It  is  to  be  observed,  however,  that  all  the  transformations  we  can  as 
yet  effect  are  in  one  direction  only.  We  can  produce  the  above  com- 
pounds from  each  other  in  the  order  of  lignin  or  starch,  gum,  cane  sugar, 
grape  sugar — that  is,  we  can  convert  starch  into  gum,  and  gum  into 
sugar,  but  we  cannot  reverse  the  process,  so  as  to  form  cane  from  grape 
sugar,  or  starch  from  gum. 

The  only  apparent  exception  to  this  statement  with  which  we  are  at 
present  acquainted,  occurs  in  the  case  of  starch.  When  this  substance 
is  dissolved  in  cold  concentrated  nitric  acid,  and  then  mixed  largely  with 
water,  a  substance  [the  Xyloidin  of  Braconnot]  falls  to  the  bottom, 
which  is  a  compound  of  the  nitric  acid  with  woody  fibre  (C,2  Hg  Og.) 
[Pelouze,  see  Berzelius  Arsberdttelse,  1839,  p.  416.]  In  this  instance, 
if  the  above  observation  is  correct,  there  appears  to  be  an  actual  con- 
version.of  starch  into  woody  fibre. 

But  what  we  are  as  yet  unable  to  perform  may,  nevertheless,  be  easily 
and  constantly  effected  in  the  living  plant.  Not  only  may  what  is  starch 
in  one  part  of  the  tree  be  transformed  and  conveyed  to  another  part  in 
the  form  of  sugar, — but  that  which,  in  the  form  of  sugar  or  gum,  passes 
upwards  or  downwards  with  the  circulating  sap,  may,  by  the  instrumen- 
tality of  the  vital  processes,  be  deposited  in  the  stem  in  the  form  of 
wood,  or  in  the  ear  in  that  of  starch.  Indeed  we  know  that  such  actu- 
ally does  take  place,  and  that  we  are  still,  therefore,  very  far  from  being 
able  to  imitate  nature  in  her  power  of  transforming  even  this  one  group 
of  substances  only. 

4°.  Among,  or  in  connection  with,  the  great  masses  of  vegetable  mat- 
ter which  consist  mainly  of  the  above  substances,  we  have  had  occasion 
to  notice  a  few  which  contain  nitrogen  as  one  of  their  constituents — and 
which,  though  forming  only  a  small  fraction  of  the  products  of  vegetable 
growth,  yet  appear  to  exercise  a  most  important  influence  in  the  general 
economy  of  animal  as  well  as  vegetable  life.  The  functions  performed 
by  diastase  in  reference  to  vegetable  growth,  and  to  the  transformations 
of  organized  vegetable  substances,  have  already  been  in  some  measure 
illustrated, — we  shall  hereafter  have  an  opportunity  of  considering  more 


IMPORTANCE  OF  THE  VEGETABLE  ACID.  127 

fully  tiie  influence  which  gluten  and  vegetable  albumen  exercise  ovei 
the  general  efficiency  of  the  products  of  vegetation  in  the  support  of  ani- 
mal life,  and  over  the  changes  which  these  products  must  undergo,  be- 
fore they  can  be  converted  into  the  substance  of  animal  bodies.  In  a 
former  lecture  (Lecture  IV.,  p.  66),  I  have  had  occasion  to  draw  your 
attention  to  the  comparatively  small  proportion  in  which  nitrogen  exists 
in  the  vegetable  kingdom,  and  to  show  that  it  must  nevertheless  be  con- 
sidered as  much  a  necessary  and  constituent  element  in  their  composi- 
tion as  the  carbon  itself;  the  very  remarkable  properties  we  have  al- 
ready discovered  in  the  compounds  above  mentioned  strongly  confirm 
this  fact,  and  illustrate  in  a  striking  manner  the  influence  of  apparently 
feeble  and  inadequate  causes  in  producing  important  natural  results. 

5°.  With  the  exception  of  acetic  acid,  which  in  constitution  is  closely 
related  to  sugar*  and  gum,  all  the  acid  substances  to  which  it  has  been 
necessary  to  advert,  contain  an  excess  of  oxygen  above  what  is  neces- 
sary to  form  water  with  the  hydrogen  they  contain.     Thus 

Vinegar  =  C4  H3  O3  contains  no  excess  of  oxygen. 

Tartaric  Acid  =  C4  Hg  Og     .     .      3  of  oxygen  iL  excess. 

Malic  Acid  )    n    tt    n  o 

Citric  Acid  ^    —^Atlz'^A     -     -      ^ 

Oxalic  Acid  =  Cg  O3  .  .  3 
It  requires  a  little  consideration  to  enable  us  to  appreciate  the  true  im- 
portance of  these  and  other  organic  acids,  in  the  vegetable  economy.  At 
first  sight  they  appear  to  form  a  much  smaller  part  of  the  general  pro- 
ducts of  vegetation  than  is  really  the  case.  We  must  endeavour  to 
conceive  the  quantity  actually  produced  by  a  single  tree  loaded  Vith 
thousands  of  lemons,  oranges,  or  apples, — or  again,  how  much  is  formed 
during  the  growth  of  a  single  comparatively  small  plant  of  garden  rhu- 
barb in  spring,  if  we  would  obtain  an  adequate  idea  of  the  extent  to 
which  these  acids  are  constantly  formed  in  nature.  On  the  other  hand, 
we  must  recollect  also  that  the  greater  portion  of  the  acid  of  fruits  disap- 
pears as  they  ripen,  if  we  would  understand  the  true  nature  of  the  in- 
terest which  really  attaches  to  the  study  of  these  substances,  of  the 
changes  to  which  they  are  liable,  and  of  the  circumstances  under  which 
in  nature  these  changes  take  place. 

6°.  I  will  venture  here  to  draw  your  attention  for  a  moment  to  the  na- 
ture and  extent  of  that  remarkable  power  over  matter,  which  the  chem- 
ist, as  above  explained,  appears  to  possess.  Such  a  consideration  will 
be  of  value  not  only  in  illustrating  how  far  we  really  can  now,  or  may 
hereafter,  expect  to  be  able  to  influence  or  control  natural  operations, 
[see  Lecture  II. ,  p.  32,]  but  what  is  probably  of  more  value  still,  exhibit- 
ing the  true  relation  which  man  bears  to  the  other  parts  of  creation  ;  and, 
in  some  measure,  the  true  position  he  is  intended  to  occupy  among  them. 
1°.  We  have  seen  that  the  chemist  can  transform  certain  substances 
one  into  the  other,  in  a  known  order ;  but  that  as  yet  he  cannot  reverse 
that  order.  Thus  far  his  power  over  matter  is  at  present  limited ;  but 
this  limit  he  may  at  some  future  period  be  able  to  overpass,  and  we 

•  It  is  identical  in  constitution  with  caramel  (p.  114)~the  uncrystalliiable  sugar  of  syrups. 
For 

Vinegar.  Carsimel. 

C3X 


(C4  H3  C3  X  3)  =  Cl2  H9  O9. 


128  POWER  OF  THE  CHEMIST  OVER  MATTER. 

know  not  how  far.  The  discovery  of  a  new  agent,  or  of  a  new  mode 
of  treatment,  may  enable  him  to  accomplish  what  he  has  not  as  yet  the 
means  or  the  skill  to  perform. 

2°.  He  has  it  in  his  power  to  form,  actually  to  produce,  some  of  the 
organic  or  organized  substances  which  occu  in  living  plants.  He  can 
form  gum,  and  grape  sugar,  in  any  quantiry.  Thus  far  he  can  imitate 
and  take  the  place  of  the  living  'principle  it  ^elf 

Numerous  other  cases  are  known,  in  'vhichhe  displays  a  similar 
power.  By  the  action  of  nitric  acid  upon  starch  or  sugar,  [see  Lecture 
III.,  p.  47,]  he  can  form  oxalic  acid,  which,  as  has  already  been  shown, 
occurs  very  largely  in  the  vegetable  kingd  )m.  By  the  action  of  heat 
upon  citric  acid,  he  can  decompose  it  an  3  produce  an  acid  which  is 
met  with  in  the  Wolfsbane  (Aconitum  napellus),  and  hence  is  called 
aconitic  acid.*  Also  by  the  action  of  sul  phuric  acid  he  can  change 
salicine  and  phlorizine — substances  extracted  respectively  from  the  bark 
of  the  willow  and  from  that  of  the  root  of  the  apple  tree — into  a  resinous 
matter  and  grape  sugar.  So,  of  the  compounds  which  are  found  in  the 
solids  and  fluids  of  animal  bodies,  there  are  some  which  he  has  also 
succeeded  in  forming  by  the  aid  of  his  chemical  art.  • 

Elated  by  such  achievements,  some  chemists  appear  willing  to  hope 
that  all  nature  is  to  be  subjected  to  their  dominion,  and  that  they  may 
hereafter  be  able  to  rival  the  living  principle  in  all  its  operations.  It  is 
true  that  what  we  now  know,  and  can  accomplish,  are  but  the  begin- 
nings of  what  we  may  fairly  expect  hereafter  to  effect.  But  it  is  of  con- 
sequence to  bear  in  mind  the  true  position  in  which  we  now  stand,  and 
the  tBue  direction  in  which  all  we  at  present  know  seems  to  indicate  that 
our  future  advances  in  knowledge,  and  in  control  over  nature,  are  likely 
to  proceed.     And  this  leads  me  to  observe — 

3°.  That  our  dominion  is  at  present  limited  solely  to  transforming 
and  decomposing.  We  can  transform  woody  fibre  into  gum  or  sugar— 
we  cannot  form  either  gum  or  sugar  by  the  direct  union  of  their  elements. 
We  can  resolve  salicine  by  the  acid  of  sulphuric  acid  into  resin  and 
grape  sugar  ;  but  we  cannot  cause  the  elements  of  which  they  consist  to 
unite  together  in  our  hands,  so  as  to  form  any  one  of  the  three.  We 
cannot  even  cause  the  resin  and  the  sugar  to  re-unite  and  rebuild  the  sali- 
cine from  which  they  were  derived. 

So  we  can  by  heat  drive  off  the  elements  of  water  from  the  citric  and 
cause  the  aconitic  acid  to  appear ;  but  we  cannot  persuade  the  unwilling 
compounds,  when  thus  separated,  to  return  to  their  former  condition  of 
citric  acid  ;  and,  if  we  could,  we  should  still  be  as  far  removed  from  the 
power  of  commanding  or  compelling  the  direct  union  of  carbon,  hydro- 
gen, and  oxygen,  in  such  proportions,  and  in  such  a  way,  as  to  build  up 
either  of  the  two  acids  in  question. 

Again,  we  can  actually  form  oxalic  acid  by  the  action  of  nitric  acid 

'These  two  acids  differ  from  each  other  only  iiy  the  elements  of  an  atom  of  water.    Thus 
Citric  Acid    .     .    =  C4  'i     04 
Aconitic  A;id    .    =  C4  Hj  O3 


Difference      .    .    =        Hi  O     or  HO,  one  of  water. 
It  is  easy  to  see,  therefore,  how,  by  the  evolution  of  the  elements  of  an  atom  of  water,  the 
one  acid  m::''  >>e  changed  into  the  other.    The  scientific  reader  will  excuse  me  (if  on  the 
grounds  of  simplicity  alone)  for  representing,  both  here  and  in  the  text,  the  citric  acid  by 
C    Ha  O4,  instead  of  by  Cia  Hs  On  +  3HO,  whic:  Liebig  and  his  pupils  prefer. 


TRUE    rnOSPECTS  OF  CHEMICAL  SCIENCE.  129 

upon  starch,  or  wood,  or  sugar,  or  any  other  of  a  great  variety  of  vegeta- 
ble substances — but  we  cannot  prepare  it  by  the  direct  union  of  its  ele- 
ments. We  can  only  as  yet  procure  it  from  substances  which  have 
already  been  organized — which  have  been  themselves  produced  by  the 
agency  of  the  living  principle. 

The  same  remarks  apply  with  slight  alteration  to  those  substances  of 
animal  origin  to  which  I  have  above  alluded  as  being  within  the  power 
of  the  chemist  to  produce  at  will.  There  is  hardly  an  exception  to  the 
rule,  that  in  producing  organic  substances,  as  they  are  called,  the  chem- 
ist must  employ  other  organic  substances  which  are  as  yet  beyond  his 
art — which,  so  far  as  we  know,  can  only  be  formed  under  the  direction 
of  the  living  principle.  Thus  the  sum  of  the  chemist's  power  in  imita- 
ting organic  nature  consists,  at  present,  in  his  ability — 

1°.  To  transform  one  substance  found  only  in  the  organic  kingdom 
into  some  other  substances,  produced  more  or  less  abundantly  in  the 
same  kingdom  of  nature.  This  power  he  exercises  when  he  converts 
starch  into  sugar,  or  fibrin  into  albumen  or  casein. 

2°.  To  resolve  a  more  complex  or  compound  substance  into  two  or 
more  which  are  less  so,  and  of  which  less  complex  substances  some  may 
be  known  to  occur  in  vegetable  or  animal  bodies. 

3°.  To  decompose  organic  compounds  by  means  of  his  chemical  agents, 
and  as  the  result  of  such  decompositions  to  arrive  at  one  or  more  com- 
pounds, such  as  are  formed  under  the  direction  of  the  living  principle. 

In  no  one  case  can  he  form  the  substances  of  which  animals  and  plants 
chiefly  consist,  out  of  those  on  which  animals  and  plants  chiefly  live. 

But  this  is  the  common  and  every-day  result  of  the  agency  of  the  liv- 
ing principle.  Is  there  as  yet,  then,  any  hope  that  the  chemical  labo- 
ratory shall  supersede  the  vascular  system  of  animals  and  plants ;  or 
that  the  skill  of  the  chemist  who  guides  tlie  operations  within  it,  shall 
ever  rival  that  of  the  principle  of  life  which  presides  over  the  chemical 
changes  that  take  place  in  animal  and  vegetable  bodies  ? 

The  true  place,  therefore,  of  human  skill — the  true  prospects  of  chem- 
ical science — are  pointed  out  by  these  considerations.  No  science  has 
accumulated  so  many  and  such  various  treasures  as  chemistry  has  done 
during  the  last  20  years — none  is  at  present  so  widely  extending  the 
bounds  of  our  knowledge  at  this  moment  as  the  branch  of  organic  chem- 
istry— men  may  therefore  be  excused  for  entertaining  more  sanguine 
expectations  from  the  progress  of  a  favourite  science  than  sober  reason- 
ing would  warrant.  Yet  it  is  of  importance,  I  think,  and  especially  in 
a  moral  point  of  view,  that  amid  all  our  ardour,  we  should  entertain 
clear  and  just  notions  of  the  kind  and  extent  of  knowledge  to  which  we 
are  likely  to  attain,  and — as  knowledge  in  chemistry  is  really  power 
over  matter — to  what  extent  this  power  is  likely  ever  to  be  carried. 

At  present,  if  we  judge  from  our  actual  knowledge,  and  not  from  our 
hopes — there  is  no  prospect  of  our  ever  being  able  to  imitate  or  rival 
living  nature  in  actually  compounding  from  their  elements  her  nume- 
rous and  varied  productions.  That  we  may  clearly  understand,  and  be 
able  to  explain  many  of  her  operations,  and  even  to  aid  her  in  effecting 
them,  is  no  way  inconsistent  with  an  inability  to  imitate  her  by  the  re- 
sources of  art.  This  will,  I  trust,  appear  more  distinctly  in  the  sQbse- 
quent  lecture. 


LECTURE  VII. 

Chemical  changes  by  which  the  substances  of  which  plants  chiefly  consist  are  formed  from 
those  on  which  they  live.— Changes  during  germination— during  the  growth  of  the  plant— 
during  the  ripening  of  fruit. — Autumnal  changes. 

Having  thus  considered  the  nature  and  chemical  constitution  of  those 
substances  which  constitute  by  far  the  largest  part  of  the  solids  and 
fluids  of  living  vegetables,  we  are  now  prepared  for  the  further  question 
— hy  what  chemical  changes  these  substances  of  which  plants  consist,  are 
formed  out  of  those  on  which  they  live  ? 

The  growth  of  a  plant  from  the  germination  of  the  seed  in  spring  till 
the  fall  of  the  leaf  in  autumn,  or  the  return  of  the  succeeding  spring- 
lime,  may  in  perennial  plants  be  divided  into  four  periods — during  which 
they  either  live  on  different  food,  or  expend  their  main  strength  in  the 
production  of  different  substances.  These  periods  may  be  distinguished 
as  follows : — 

1°.  The  period  of  germination — from  the  sprouting  of  the  seed  to  the 
formation  of  the  perfect  leaf  and  root. 

2°.  From  the  expansion  of  the  first  true  leaves  to  the  period  of  flow- 
ering. 

3°.  From  the  opening  of  the  flower  to  the  ripening  of  the  fruit  and 
seed. 

4°.  From  the  ripening  of  the  seed  or  fruit,  till  the  fall  of  the  leaf  and 
the  subsequent  return  of  spring.  On  the  ripening  of  the  fruit  the  func- 
tions of  annual  plants  are  in  general  discharged,  and  they  die ;  but  per- 
ennial plants  have  still  important  duties  to  perform  in  order  to  pr€^are 
them  for  the  growth  of  the  following  spring. 

The  explanation  of  the  chemical  changes  to  which  our  attention  is  to 
be  directed  will  be  more  clear,  and  perhaps  more  simple,  if  we  consider 
them  in  relation  to  these  several  periods  of  growth. 

§  1 .  Chemical  changes  which  take  j>laee  during  germination  and  during 
the  development  of  the  first  leaves  and  roots. 

The  general  nature  of  the  chemical  changes  which  take  place  during 
germination  is  simple  and  easy  to  be  comprehended. 

Let  us  first  consider  shortly  the  phenomena  which  have  been  observed 
to  accompany  germination,  and  the  circumstances  wliich  are  most  fa- 
vourable to  its  rapid  and  healthy  progress. 

1°.  Before  a  seed  will  begin  to  sprout,  it  must  be  placed  for  a  time  in 
a  sufficiently  moist  situation.  We  have  already  seen  how  numerous 
and  important  are  the  functions  which  water  performs  in  reference  to 
vegetable  life  (Lecture  IL,  p.  36,)  in  every  stage  of  a  plant's  growth. 
In  the  seed  no  circulation  can  take  place — no  motion  among  tlie  parti- 
cles of  matter — until  water  has  beer  largely  imbibed  ;  nor  can  the  food 
be  conveyed  through  the  growing  vessels,  unless  a  constant  supply  of 
fluid  be  afforded  to  the  seed  and  its  infant  roots. 

2°.'  A  certain  degree  of  warmth — a  slight  elevation  of  temperature- 
is  also  favourable,  and  in  most  cases  necessary,  to  germination.  • 


EFFECT    OF    AIR   AND    LIGHT    ON    GERMINATION.       •  131 

The  degree  of  warmth  which  is  required  in  order  that  seeds  may  be- 
gin to  grow,  varies  with  the  nature  of  tlie  seed  itself.  In  Northern  Si- 
beria and  other  icy  countries,  plants  are  observed  to  spring  up  at  a  tem- 
perature but  slightly  raised  above  the  freezing  point  (32°  F.,)  but  it  is 
familiar  to  every  practical  agriculturist,  that  the  seeds  he  yearly  con- 
signs to  the  soil  require  to  be  protected  from  the  inclemency  of  the 
weather,  and  sprout  most  quickly  when  they  are  stimulated  by  the 
warmth  of  approaching  spring,  or  by  the  heat  of  a  summer's  sun. 

The  same  fact  is  familiarly  shown  in  the  malting  of  barley,  where 
large  heaps  of  grain  are  moistened  in  a  warm  atmosphere.  When  ger- 
mination commences,  the  grain  heats  spontaneously,  and  the  growth 
increases  in  rapidity  as  the  heap  of  corn  attains  a  higher  temperature. 
It  thus  appears  that  some  portion  of  that  heat  which  the  growth  of  the 
germ  and  radicles  requires,  is  provided  by  natural  processes  in  the  grain 
itself;  in  some  such  way  as,  in  the  bodies  of  animals,  a  constant  supply 
of  heat  is  kept  up  by  the  vital  processes — by  which  supply  the  cooling 
effect  of  the  surrounding  air  is  continually  counteracted. 

We  have  seen  in  the  preceding  lecture,  that  the  transformations  of 
which  starch  and  gum  are  susceptible,  take  place  with  greater  certainty 
and  rapidity  under  the  influence  of  an  elevated  temperature.  It  will 
presently  appear  that  such  transformations  are  also  affected  during  ger- 
mination ;  there  is  reason,  therefore,  to  believe  that  the  external  warmth 
which  is  required  in  order  that  germination  may  begin,  as  well  as  the 
internal  heat  naturally  developed  as  germination  advances,  are  both 
employed  in  effecting  these  transformations.  And,  as  the  young  sprout 
shoots  more  rapidly  under  the  influence  of  a  tropical  sun,  it  is  probable 
that  those  natural  agencies  in  general,  by  which  such  chemical  transfor- 
mations are  most  rapidly  promoted,  are  also  those  by  which  the  pro- 
gress of  vegetation  is  in  the  greatest  degree  hastened  and  promoted. 

3°.  It  has  been  observed  that  seeds  refuse  to  germinate  if  they  are  en- 
tirely excluded  from  the  air.  Hence  seeds  which  are  buried  beneath 
such  a  depth  of  soil  that  the  atmospheric  air  cannot  reach  them,  will 
remain  long  unchanged,  evincing  no  signs  of  life — and  yet,  when  turned 
up  or  brought  near  tiie  surface,  will  speedily  begin  to  sprout.  Thus  in 
trenching  the  land,  or  in  digging  deep  ditches  and  drains,  the  farmer  is 
often  surprised  to  find  the  earth,  thrown  up  from  a  depth  of  many  feet, 
become  covered  with  young  plants,  of  species  long  extirpated  from  or 
but  rarely  seen  in  his  cultivated  fields. 

4°.  Yet  light  is,  generally  speaking,  prejudicial  to  germination. 
Hence  the  necessity  o^  covering  the  seed,  when  sown  in  our  gardens  and 
corn  fields,  and  yet  of  not  so  far  burying  it  that  the  air  shall  be  excluded. 
In  the  usual  method  of  sowing  broad-cast,  much  of  the  grain,  even  after 
harrowing,  remains  uncovered  :  and  the  prejudicial  influence  of  light  in 
preventing  the  healthful  germination  of  such  seeds  is  no  doubt  one  rea- 
son why,  by  the  method  of  dibbling,  fewer  seeds  are  observed  to  fail,  and 
an  equal  return  of  corn  is  obtained  from  a  much  smaller  expenditure  of 
seed. 

The  reason  why  light  is  prejudicial  to  germination,  as  well  as  why 
the  presence  of  atmospheric  air  is  necessary,  will  appear  from  the  fol- 
lowing observation  : — 

5*^.  When  seeds  are  mads  o  germinate  in  a  limited  portion  of  atmos- 


132  ,  SEEDb  SPROUT  0]NLY  IN  THE  TKESENCE  OF  OXYGEN. 

pheric  air,  the  bulk  of  the  air  undergoes  no  material  alteration,  but  on 
examination  its  oxygen  is  found  to  liave  diminished,  and  carbonic  acid 
to  have  taken  its  place.  Tlierefore,  during  germination,  seeds  absorb 
oxygen  gas  and  give  off  carbonic  acid. 

Hence  it  is  easy  to  understand  why  the  presence  of  air  is  necessary 
to  germination,  and  why  seeds  refuse  to  sprout  in  hydrogen,  nitrogen, 
or  carbonic  acid  gases.  They  cannot  sprout  unless  oxygen  be  within 
their  reach. 

We  have  seen  also  in  a  previous  lecture  that  the  leaves  of  plants  in 
the  sunshine  give  off  oxygen  gas  and  absorb  carbonic  acid, — while  in 
the  dark  the  reverse  takes  place.  So  it  is  with  seeds  which  have  begun 
to  germinate.  When  exposed  to  the  light  they  give  off  oxygen  instead 
of  carbonic  acid,  and  thus  the  natural  process  is  reversed.  But  it  is  ne- 
cessary to  the  growth  of  tlie  young  germ,  that  oxygen  should  be  absorb- 
ed, and -carbonic  acid  given  of — and  as  tliis  can  take  place  to  the  requir- 
ed extent  only  in  the  dark,  the  cause  of  the  prejudicial  action  of  light  is 
sufficiently  apparent  as  well  as  the  propriety  of  covering  the  seed  with  a 
thin  layer  of  soil. 

6°.  JDuring  germination,  vinegar  (acetic  acid)  and  diastase  are  pro- 
duced. That  such  is  the  case  in  regard  to  the  latter  substance,  has  been 
proved  in  the  j)revious  lecture,  (p.  118.)  That  acetic  acid  is  formed  is 
shown  by  causing  seeds  to  germinate  in  powdered  chalk  or  carbonate  of 
lime,  when  after  a  time  acetate  of  lime*  may  be  washed  out  from  the 
chalk  (Braconnot)  in  whicli  they  have  been  made  to  grow.  The  acid 
contained  in  this  acetate  must  have  been  formed  in  the  seed,  and  after- 
wards excreted  or  thrown  out  into  the  soil. 

7°.  When  the  germ  has  shot  out  from  the  seed  and  attained  to  a  sen- 
sible length,  it  is  Ibund  to  be  possessed  of  a  sweet  taste.  This  taste  is 
owing  to  the  presence  of  grape  sugar  in  the  sap  which  has  already  be^ 
gun  to  circulate  through  its  vessels. 

It  has  not  been  clearly  ascertained  whether  the  vinegar  or  the  dias- 
tase is  first  produced  when  germination  commences,  but  there  seems 
little  doubt  that  the  grape  sugar  is  formed  subsequently  to  the  appejir- 
ance  of  both. 

8^.  The  young  shoot  which  rises  upwards  from  the  seed  consists  of 
a  mass  of  vessels,  which  gradually  increase  in  length,  and  after  a  short 
time  expand  into  the  first  true  leaves.  The  vessels  of  this  first  shoot  do 
not  consist  of  unmixed  woody  fibre.  It  is  even  said  that  no  true  wood 
is  formed  till  the  first  true  leaves  are  developed. — [Lindley's  Theory  of 
Horticulture.]  The  vessels  of  the  young  s[)rout,  therefore,  and  of  the 
early  radicles,  probably  consist  of  the  cellular  Jibre  of  Payen.  They 
are  uncjuestionably  formed  of  a  substance  which  is  in  a  state  of  transition 
between  starch  or  sugar  and  woody  fibre,  and  which  has  a  constitution 
analogous!  ^^  that  of  both. 

Having  thus  glanced  at  the  phenomena  which  attend  upon  germina- 
tion, let  us  now  consider  the  chemical  changes  by  which  these  phenom- 
ena are  accompanied. 

1°.  The  seed  absorbs  oxygen  and  gives  off  carbonic  acid.     We  have 

*  Acetate  of  lime  is  a  compound  of  acetic  acid  (vinegar)  and  lime,  and  may  be  prepared  by 
dissolving  chalk  in  vinegar.    It  is  very  soluble  in  water, 
t  By  analogous  I  mean  vihich  may  be  represented  by  carbon  and  water, 


HOW    AND    WHY    VINEGAR    IS    FORMED.  133 

already  seen  that  the  starch  of  the  seed  (C12  H^o  Oio)  "^^y  he  repre- 
sented by  carbon  and  water, — by  12C  +  lOHO.  Now  it  appears  tbat 
in  contact  with  the  oxygen  of  the  atmosphere,  a  portion  of  the  starch  is 
actually  separated  into  carbon  and  water,  the  carbon  at  the  moment  of  sepa- 
ration uniting  with  the  oxygen,  and  forming  carbonic  acid  (CO2).  This 
acid  is  given  off  into  the  soil  in  the  form  of  gas,  and  thence  partially  es- 
capes into  the  air;  but  for  what  immediate  purpose  it  is  evolved,  or  how 
its  formation  is  connected  with  the  further  development  of  the  germ,  has 
not  hitherto  been  explained. 

2°.  The  formation  of  acetic  acid  (vinegar)   from  the  starch  of  the 
grain  is  also  easy  to  com{)rehend.     For,  as  we  have  already  seen, 
Starch  .  .  .  ^Cj^  H  0  Ojo 
3  of  Vinegar    ..=Ci^H9    O9 


Diirerence    =  H,     Oi  ;  or  the  elements  of 

an  atom  of  Valer.  Therefore,  in  this  early  stage  of  the  growth  of  the 
germ  a  portion  of  the  starch  is  deprived  of  the  elements  of  an  atom  of 
water,  and  at  the  same  time  transformed  into  vinegar. 

Why  is  this  vinegar  formed?  It  is  almost  as  difficult  to  answer  this 
question  as  to  say  why  carbonic  acid  is  evolved  from  the  seed,  though 
both  undoubtedly  serve  wise  and  useful  ends. 

It  has  been  explained  in  the  preceding  lecture  how  the  action  of  dilute 
acids  gradually  changes  starch  into  cane  sugar,  and  the  latter  intograjje 
sugar.  While  it  remain's  in  the  sap  of  the  sprouting  seed,  the  vinegar 
may  aid  the  diastase  in  transforming  the  insoluble  starch  into  soluble 
food  for  the  plant,  and  may  be  an  instrument  in  securing  the  conversion 
of  the  cane  sugar,  which  is  the  first  formed,  into  grape  sugar, — since 
cane  sugar  cannot  long  exist  in  the  presence  of  an  acid. 

After  the  acetic  acid  is  rejected  by  the  plant,  it  may  act  as  a  solvent 
on  the  lime  and  other  earthy  matters  contained  in  the  soil.  Liebig  sup- 
poses the  especial  function  of  this  acid — the  reason  why  it  is  formed  in 
the  germ  and  excreted  into  the  soil — to  be,  to  dissolve  the  lime,  &c.,  which 
the  soil  contains,  and  to  return  into  the  pores  of  the  njots,  bearing  in  so- 
lution the  earthy  substances  which  the  plant  requires  for  its  healthy 
growth.  This  is  by  no  means  an  unlikely  function.  It  is  only  conjec- 
Tural,  however,  and  since  the  experiments  of  Braconnot  have  shown  that 
acetate  of  lime,  even  in  small  quantity,  may  be  injurious  to  vegetation, 
it  becomes  more  doubtful  how  far  the  formation  of  this  compound  in  the 
soil,  and  the  subsequent  conveyance  of  it  into  the  circulation  of  the  plant, 
can  be  regarded  as  the  special  purpose  for  which  acetic  acid  is  so  gene- 
rally produced  during  germination. 

3°.  The  early  sap  of  the  young  shoot  is  sweet ;  it  contains  grape  su- 
gar. This  sugar  is  also  derived  from  the  starch  of  the  seed.  Being 
rendered  soluble  by  the  diastase  formed  at  the  base  of  the  germ,  the 
starch  is  gradually  converted  into  grape  sugar  as  it  ascends.  The  rela- 
tion between  these  two  compounds  has  been  already  pointed  out. 

Starch =Ci2HioOxo 

Grape  Sugar     .     .     .     =^^12^x2^12 


Difference    .     .     ,     .     =  H2    O2;    or  the  ele- 

ments of  two  atoms  of  water.     The  water  which  is  imbibed  by  the  seed 


134  HOW  THE  SUGAR  IS  FORMED  IN  THE  SPROUT, 

from  the  soil;  forms  an  abundant  source  from  which  the  whole  of  the 
starch,  rtindered  soluble  by  the  diastase,  can  be  supplied  with  the  ele- 
ments of  the  two  atoms  of  water  which  are  necessary  to  its  subsequent 
conversion  into  grape  sugar 

4°.  The  diastase  is  formed  when  the  seed  begins  to  sprout,  at  the  ex- 
pense of  the  gluien  or  vegetable  albumen  of  the  seed,  but  as  its  true 
constitution  is  not  yet  known,  we  cannot  explain  the  exact  chemical 
changes  by  which  its  production  is  effected. 

5°.  When  the  true  leaf  becomes  expanded,  true  wood  first  appears 
in  sensible  quantity.  By  what  action  of  tlie  sun's  rays  upon  the  leaf 
the  sugar  already  in  solution  in  the  sap  is  converted  into  woody  fibre, 
we  cannot  explain.  The  conversion  itself  is  in  appearance  simple 
enough,  since 

Grape  Sugar  .     .     =  C12  Hig  Oi2»  and 

Woody  Fibre       *.     .     =Ci2ll3    Og       . 


Difference    .     .     .     .     =  H4    O4 ;  or  the  former 

must  part  with  the  elements  of  four  atoms  of  water  only,  to  be  prepared 
for  its  change  into  the  latter.  But  the  true  nature  of  the  molecular* 
change  by  which  this  transformation  is  brought  about,  as  well  as  the 
causes  which  lead  to  it  and  the  immediate  instruments  by  which  it  is 
effected,  are  all  still  mysterious. 

§2.  Of  the  chemical  changes  which  take  'place  from  the  formation  of  the 
true  leaf  to  the  expansion  of  the  flower. 

When  the  true  leaf  is  formed  the  plant  has  entered  upon  a  new  stage 
of  its  existence.  Up  to  this  time  it  is  nourished  almost  solely  by  the 
food  contained  in  the  seed, — it  henceforth  derives  its  sustenance  from  the 
air  and  from  the  soil.  The  apparent  mode  of  growth  is  the  same,  the 
stem  shoots  upwards,  the  roots  descend,  and  they  consist  essentially  of 
the  same  chemical  substances,  but  they  are  no  longer  formed  at  the  ex- 
pense of  the  starch  of  the  seed,  and  the  chemical  clianges  of  which  they 
are  the  result  are  entirely  different. 

1°.  The  leaf  absorbs  carbonic  acid  in  the  sunshine,  and  gives  off'  ox- 
ygen in  equal  bulk.f  It  is  in  the  light  of  the  sun  that  plants  increase  in 
size — their  growth,  therefore,  is  intimately  connected  with  this  absorp- 
tion of  carbonic  acid. 

If  carbonic  acid  be  absorbed  by  the  leaf  and  the  whole  of  its  oxygen 
given  off*  again, t  carbon  alone  is  added  to  the  plant  by  this  function  of 
the  leaf.  But  it  is  added  in  the  presence  of  the  water  of  the  sap,  and 
thus  is  enabled  by  uniting  with  it  to  form,  as  it  may  he  directed,  or  as 
may  be  necessary,  any  one  of  those  numerous  compounds  which  may 

*  All  bodies  are  supposed  to  consist  of  particles  or  moZecMZes  of  exceeding  minuteness, 
and  all  chemical  changes  wliicli  tiike  place  in  the  same  mass  of  matter  are  supposed  to  be 
owing  to  the  different"  ways  in  which  these  [)articles  arrange  themselves.  We  may  form  a 
remote  idea  of  the  way  in  which  different  positions  of  the  same  particles  may  produce  dif- 
ferent substances,  by  considering  how  different  figures  in  Mosaic  may  be  produced  by  dif- 
ferent arrangements  of  tlie  same  number  of  equal  and  similar  fragments  of  various  colours. 

t  Such  \s sensibly  the  result  of  experiment.  How  far  this  result  can  be  considered  as  uni- 
versally true,  will  be  examined  hereafter 

X  It  will  be  recollected  that  carbonic  acid  contains  its  own  bulk  of  oxygen  gas :  if,  therefrre, 
the  leafgiveotf  tiie  same  bulk  of  oxygen  as:«  absorbs  of  carbonic  acid,  the  result  must  bi  a^ 
stated  in  the  text. 


HOW   PLANTS   ARE    NOURISHED    BT    CARBONIC   ACID  ?  135 

be  represented  by  carbon  and  water,  (p.  Ill,)  and  of  which,  as  we  have 
seen,  the  solid  parts  of  plants  are  chiefly  made  up. 

There  are  two  ways  in  which  we  may  suppose  the  oxygen  given  off 
by  the  leaf  to  be  set  free,  and  the  starch,  sugar,  and  gum,  to  be  subse- 
quently formed. 

A.  The  action  of  light  on  the  leaf  of  the  plant  may  directly  decompose 
the  carbonic  acid  after  it  has  been  absorbed,  and  cause  the  oxyen  to  sep- 
arate from  the  carbon,  and  escape  into  the  air ; — while  at  the  same  in- 
stant the  carbon  thus  set  ^ra^  may  unite  with  the  water  of  the  sap  in 
different  proportions,  so  as  to  produce  either  sugar,  gum,  or  starch. 
Suppose  12  atoms  of  carbonic  acid  (12  COo)  to  be  thus  decomposed,  and 
their  carbon  to  unite  with  10  of  water  (10  HO),  we  should  have 
from  12  of  Carbomc  Acid  .  =  C^a 

which  united  to  10  of  Water      .     .     .  z=  Hm  Oio 


would  give  1  of  Gum  or  of  Cane  Sugar  =  C^o  H^o   ^m 
while  24  of  oxygen  would  be  given  off,  the  whole  of  which  would  have 
been  derived  from  the  carbonic  acid  absorbed  by  the  plant. 

B.  Or  the  action  of  the  sun's  rays  may  be  directed,  in  the  leaf,  to  the 
decomposition,  not  of  carbonic  acid,  but  of  the  water  o?i\\Q  sap.  The  oxy- 
gen of  the  water  may  be  separated  from  the  hydrogen,  while  at  the  same 
instant  the  latter  element  (hydrogen)  may  unite  with  the  carbonic  acid 
to  produce  the  sugar  or  starch.  The  result  here  is  the  same  as  before, 
but  the  mode  in  which  it  is  brought  about  is  very  differently  represented, 
and  appears  much  more  complicated.  Th^is,  suppose  24  of  water 
(24  HO)  to  be  decomposed,  and  to  give  off  their  oxygen  into  the  air,  24  of 
oxygen  would  be  evolved  as  in  the  former  case,  the  whole  oi  which  icould 
he  derived  from  the  decomposition  ofwatcx,  while  there  would  remain 
24  of  Hydrogen  .     .    =  H  ^ 

Let  this  act  on    12  of  Carbonic  Acid  =  C^a  ^24 


and  we  have  as  the  result C12   H24  O24  ; 

Starch,  &c.  Water. 

or  C,2  H,o   0,0   +   14HO. 

According  to  this  mode  of  representing  the  chemical  changes,  water  i« 
first  decomposed  and  its  oxygen  evolved,  then  its  hydrogen  again  com- 
bines with  the  carbon  and  oxygen  of  the  carbonic  acid,  and  forming  two 
products — water  and  sugar  or  starch.  This  view  is  not  only  more  com- 
plicated, but  it  supposes  ihe  same  action  of  light  to  be — continually,  at 
the  same  tiine,  and  in  the  same  circumstances — both  decomposing  wa- 
ter and  re-forming  it  from  its  elements.  While,  therefore,  there  can  be 
no  doubt,  for  other  reasons  not  necessary  to  be  stated  in  this  place,  that 
the  light  of  ihe  sun  really  does  decompose  water  in  the  leaves  of  planis, 
and  more  in  some  than  in  others — yet  it  appears  probable  that  the  oxygen 
evolved  by  the  leaf  is  derived  in  a  great  measure  from  the  carbonic  acid 
which  is  absorbed;  and  that  the  principal  part  of  the  solid  substance  of 
living  vegetables,  in  so  far  at  least  as  it  is  derived  from  the  air,  is  pro- 
duced by  the  union  of  the  carbon  of  this  acid  with  the  elements  of  the 
water  in  the  sap.* 

*  I  ought  not  to  pass  unnoticed  the  opin.on  of  Pcrsoz  (Chemie  Moleculai'-e),  that  the 
starch,  gum,  &c.,  of  plants  are  formed  by  the  union  of  carbonic  oxide  (CO)  with  .he  neces- 


136  IS    CARBONIC    ACID  ABSORBED    FROM   THE   SOIL? 

We  have  seen  reason  to  conclude  (p.  63)  that,  while  plants  derive 
much  of  their  sustenance  from  the  air,  they  are  also  fed  more,  or  less 
abundantly  by  the  soil  in  which  they  grow.  From  this  soil  they  ob- 
tain through  their  roots  the  carbonic  acid  which  is  continually  given  off 
by  the  decaying  vegetable  matter  it  contains.  This  carbonic  acid  will 
ascend  to  the  leaf,  and  will  there  undergo  decomposhion  along  with  that 
which  is  absorbed  by  the  leaf  itself.  At  least  we  know  of  no  function 
of  the  root  or  stem  by  which  the  carbonic  acid  derived  from  tiie  soil  can 
be  decomposed  and  deprived  of  its  oxygen  before  it  reaches  the  leaf. 

It  is  distinctly  stated,  indeed,  by  Sprengel,  [see  above,  p.  92,]  that 
when  the  roots  of  a  plant  are  in  the  presence  of  carbonic  acid,  the  oxy- 
gen given  off  by  the  leaf  is  greater  in  bulk  than  the  carbonic  acid  ab- 
sorbed. But  there  is  one  observation  in  connection  with  this  point  which 
it  seems  to  me  of  importance  to  make.  The  leaves  supply  carbon  to 
the  plant  only  in  the  form  of  carbonic  acid,  and  they  give  off  a  bulk  of 
oxygen  gas  not  exceeding  that  of  the  acid  taken  in,  [see  note,  below.] 
But  if  the  carbon  derived  from  the  soil  be  also  absorbed  in  the  form  of 
carbonic  acid,  and  if  the  oxygen  contained  in  this  portion  of  acid  is  also 
given  off  by  the  leaf — either  the  quantity  drawn  from  the  soil  must  be 
small,  compared  with  that  inhaled  from  the  air,  or  the  oxygen  given  off 
by  the  leaf  must,  in  the  ordinary  course  of  vegetation,  be  sensibly  great- 
er than  the  bulk  of  the  carbonic  acid  which  it  absorbs. 

We  are  too  little  familiar  with  the  chemical  functions  of  the  several 
parts  of  plants  to  be  able  to  pronounce  a  decided  opinion  on  this  point; 
but  it  appears  evident  that  one  or  other  of  the  three  following  conditions 
must  obtain  : — 

(a).  Either  in  the  general  vegetation  of  the  globe  the  bulk  of  the  oxy- 
gen gas  given  off  by  the  leaf  during  the  day  must  always  be  considera- 
bly greater  than  that  of  the  carbonic  acid  absorbed  by  it ;  or 

(b).  The  root  or  stem  must  have  the  power  of  .decomposing  carbonic 
acid  and  of  separating  and  setting  free  its  oxygen  ;  or 

(c).  The  plant  can  derive  no  considerable  portion  of  its  carbon  from 
the  soil,  in  the  form  of  carbonic  acid. 

If  the  experiments  hitherto  made  by  the  vegetable  physiologists  be 
considered  of  so  decisive  a  character  as  to  warrant  us  in  rejecting  the 
two  former  conditions,  the  third  becomes  also  untenable. 

sary  proportions  of  oxygen  and  hydi-ogen  derived  from  the  water  of  the  sap.  This  opinion 
implies  that,  in  the  leaf,  carbonic  acid  (CO2  )  is  flecomposed  into  carbonic  oxide  and  oxy- 
gen (CO  -f  O),  and  that  water  likewise  is  decomposed,— the  oxyiien  produced  by  both  de- 
compositions bein^  given  off  either  into  the  air  by  the  leaves,  or  into  the  soil  by  the  roots. 
The  production  of  grape  sugar,  therefore,  according  to  this  hypothecs,  would  be  thus  repre 
sented :—  There  are  retained,  and  given  off. 

From  12  of  Carbonic  Acid  =  12C02    -    -    -    C12        O12  O12 

From  12  of  Water.    •    -    =  12HO     -    -    -  H12  O12 


C12  H12  Ol2  O24 

grape  sugar 

Of  the  24  of  oxygen  thus  given  off,  the  opinion  of  Persox  is,  that  only  one-half  is  evolved 
by  the  leaf, — and  the  principal  fact  on  which  his  opinion  rests  is  that  observed  by  De  Saus- 
sure,  that  plants  of  Vinca  minor  gave  off  by  their  leaves,  in  his  experiments,  only  two-thirds 
of  the  oxygen  contained  in  the  carbonic  acid  they  absorbed.  Tliis  result  has  led  BerzeUus 
also  to  conjecture  that  the  loaves  of  plants  do  not  retain  merely  the  carbon  of  the  carbonic 
acid,  but  some  compound  of  carbon  wit!)  oxygen,  containing  much  less  of  this  element  than 
the  carbonic  acid  does(7Vai7e  de  C/iCwie,  V,  p.  69).  Tlie  principal  objection  to  this  view, 
however,  is  the  quantity  of  oxygen  it  supposes  to  be  rejected  by  the  root.  The  experimentt 
on  which  it  ia  founded  require  confirmation  and  extension. 


HOW    SUGAR   IS    TRANSFORMED    INTO    STARCH.  137 

3°.  Without  dwelling  at  present  on  this  point,  tlie  above  considera- 
tions may  be  regarded  as  giving  additional  strength  or  probability  to  the 
conclusions  v/e  formerly  arrived  at  (p.  63)  from  other  premises — that 
the  roots,  besides  carbonic  acid,  absorb  certain  other  soluble  organic 
compounds,  which  are  always  present  in  the  soil  in  greater  or  less 
quantity,  and  that  the  plant  appropriates  and  converts  these  into  its  own 
substance.  Some  of  these  organic  compounds  may  readily,  and  by  ap- 
parently simple  changes,  be  transformed  into  the  starch  and  woody  fibre 
of  the  living  vegetable.  The  illustration  of  this  fact  will  be  reserved 
until,  in  the  second  part  of  these  lectures,  I  come  to  treat  of  the  vegeta- 
ble portion  of  soils,  and  of  the  ^chemical  nature  and  constitution  of  the 
organic  compounds  of  which  it  consists,  or  to  which  it  is  capable  of  giv- 
ing rise. 

4°.  The  chemical  changes  above  explained  (a),  show  how,  from 
carbonic  acid  and  the  elements  of  water,  substances  possessed  of  the 
elementary  constitution  of  sugar  and  gum  may,  by  the  natural  processes 
of  vegetable  life,  obtain  the  elements  of  which  they  consist,  and  in  the 
requisite  proportions.  They  throw  no  light,  however,  upon  the  me- 
chanism by  which  these  elements  are  constrained,  as  it  were,  to  assume 
first  the  form  of  gum  or  sugar,  or  soluble  starch,  and  afterwards^  in 
another  part  of  the  plant,  of  insoluble  starch  and  woody  fibre. 

It  is  known  that  the  sap  deposits  starch  and  woody  fibre  in  the  stem, 
only  in  its  descent  from  the  leaf, — and  it  is,  therefore,  inferred  that  the 
action  of  light  upon  the  sap,  as  it  passes  through  the  green  parts,  is  ne- 
cessary to  dispose  the  elements  to  arrange  themselves  in  the  form  of 
vascular  fibre  or  lignin.  And  as,  by  the  agency  of  nitric  acid,  starch 
appears  to  be  convertible  into  woody  fibre  (p.  126),  it  is  not  unlikely 
that  the  soluble  substances,  containing  nitrogen,  which  are  present  in 
the  sap  may — as  diastase  does  upon  starch — exercise  an  agency  in  trans- 
forming the  soluble  sugar,  gum,  &c.,  of  the  sap  into  the  insoluble  starch 
and  woody  fibre  of  the  seed  and  the  stem.  We  are  here,  however,  upon 
uncertain  ground,  and  I  refrain  from  advancing  any  further  conjectures. 

Two  great  steps  "we  have  now  made.  We  have  seen  how  the  germ 
lives  and  grows  at  the  expense  of  the  food  stored  up  in  the  seed — and 
how,  when  it  has  obtained  roots  and  leaves,  the  plant  is  enabled  to  ex- 
tract from  the  air  and  from  the  soil  such  materials  as,  in  kind  and  quan- 
tity, are  fitted  to  build  up  its  several  parts  during  its  future  growth. 
That  considerable  obscurity  still  rests  on  the  details  of  what  takes  place 
in  the  interior  of  the  plant,  does  not  detract  from  the  value  of  what  we 
have  already  been  able  to  ascertain. 

§  3.  On  the  production  of  oxalic  acid  in  the  leaves  and  stems  of  plants. 
In  the  preceding  section  we  have  studied  the  origin  of  those  sub- 
stances only  which  form  the  chief  bulk  of  the  products  of  vegetation, 
and  which  are  characterized  by  a  chemical  constitution  of  such  a  kind 
as  enables  them  to  be  represented  by  carbon  and  water.  But  during 
the  stage  of  vegetable  growth  we  are  now  considering,  other  compounds 
totally  different  in  their  nature  are  also  produced,  and  in  some  plants  in 
sufficient  quantity  to  be  deserving  of  a  separate  consideration.  Such  is 
the  case  with  oxalic  acid.  * 

The  circumstances  under  whichf  this  acid  occurs  in  nature  have  al- 


138  PRODUCTIO*  CF  OXALIC  ACID  IN  PLANTS. 

ready  been  detailed.  It  is  found  in  small  quantities  in  many  plants. 
The  potash  in  forest  trees  is  supposed  to  be  in  combination  with  oxalic 
acid,  while  in  the  lichens  oxalate  of  lime  serves  a  purpose  similar  to  that 
performed  by  the  woody  fibre  of  the  more  perfect  plant;  it  forms  the 
skeleton  by  which  the  vegetable  structure  is  supported,  and  through 
which  its  vascular  system  is  diffused. 

The  production  of  this  acid  in  the  living  plant  is  readily  understood 
when  its  chemical  constitution  (Co  O3)  is  compared  with  that  of  car- 
bonic acid  (COa).     For 

2  of  Carbonic  Acid  =  C2  O4 


Difference     .     .     .     O^ 

That  is  to  say,  2  of  carbonic  acid  are  transformed  into  1  of  oxalic  acid 
by  the  loss  of  1  equivalent  of  oxygen — or  generally,  carbonic  acid  by  the 
loss  of  one-fourth  of  its  oxygen  may  be  converted  into  oxalic  acid. 

But  the  leaf  absorbs  carbonic  acid  and  gives  off^ oxygen.  In  the  lichens, 
therefore,  which  contain  so  much  oxalic  acid,  a  large  portion  of  the  car- 
bonic acid  absorbed  is,  by  the  action  of  light,  deprived  of  only  one-fourth 
of  its  oxygen,  and  is  thus  changed  into  oxalic  acid.  The  same  is  true  to 
a  smaller  extent  of  the  sorrel  leaves  and  stems,  which  owe  their  sour- 
ness to  the  presence  of  oxalic  acid — of  the  leaves  and  stems  of  rhubarb 
also — in  a  still  smaller  degree  of  the  beech  and  other  large  trees,  in 
which  much  potash,  and  probably  also  of  marine  plants,  in  which 
much  soda  is  found  to  exist.  It  must  be  owing  to  the  peculiar  structure 
of  the  leaves  of  each  genus  or  natural  order  of  plants,  that  the  same  ac- 
tion of  the  same  light  decomposes  the  carbonic  acid  in  different  degrees 
— evolving  in  some  a  less  proportion  of  its  oxygen,  and  causing  in  such 
plants  the  formation  of  a.  larger  quantity  of  oxalic  acid. 

The  fact  of  the  production  of  this  oxalic  acid,  to  a  very  considerable 
amount  in  many  plants,  is  a  further  proof  of  the  uncertainty  of  those 
experiments  from  which  physiologists  have  concluded  that  the  leaves 
of  plants  emit  a  bulk  of  oxygen  sensibly  equal  to  that  of  the  carbonic 
acid  absorbed.* 

I  have  referred  the  production  of  more  or  less  oxalic  acid  in  different 
plants  to  the  special  structure  of  each,  and  this  must  be  true,  where,  in 
the  same  circumstances,  different  results  of  this  kind  are  observed  to 
take  place — as  where  sorrels  and  sweet  clovers  grow  side  by  side.  Yet 
the  influence  of  light  of  different  degrees  of  intensity  on  the  same  plant, 
is  beautifully  shown  by  the  leaves  of  the  Sempcrvivum  arboreum,  of  the 
Portulacaria  afra,  and  other  plants  which  are  sour  in  the  mornings  tasteless 

*  Were  we  permitted,  in  the  absence  of  decisive  experiments,  to  state  as  true  what  theo- 
retical considerations  plainly  indicate,  we  should  say — 

1°.  That  plants  containing  much  oxalic  or  other  similar  acids,  and  not  deriving  much  car- 
bonic acid  from  the  soil,  must  give  off  from  their  leaves  a  bulk  of  oxygen  less  than  that  of  the 
carbonic  acid  absorbed. 

2°.  That  plants  containing  no  sensible  quantity  of  such  acids,  nor  fed  by  carbonic  acid 
from  the  soil,  may  evolve  oxygen  sensibly  equal  in  bulk  to  the  carbonic  acid  absorbed. 

3°.  That  if  little  of  these  acids  be  present,  and  mucli  carbonic  acid  be  absorbed  from  the 
soil,  the  volume  of  oxygen  given  off  by  the  green  parts  of  the  plant  must  be  sensibly  greater 
than  that  of  the  carbonic  acid  they  absorb. 

4°.  Tli^the  leaves  of  the  pines  and  other  trees  containing  much  turpentine — in  which 
hydrogerWs  in  excess— must  at  all  times  give  off  oxygen  in  greater  bulk  than  'iie  carbonic 
acid  they  absorb.  They  must  decompose  water  as  well  as  carbonic  acid,  anl  evolve  the 
oxygen  of  both. 


ACTION  OF  THE  FJbC^^ER  LEAVES  ON  THE  AIR.  139 

in  the  middle  of  the  day,  and  hitter  in  the  evening. — [Sprenge  ,  Chemie, 
II.,  p.  321.]  During  the  night  the  oxygen  has  accumulated  in  these  plants 
and  ibrned  acids  containing  oxygen  in  excess  (p.  127.)  As  the  day  ad- 
vances this  oxygen  is  given  off;  under  the  influence  of  light  the  acids  are 
decomposed,  and  the  sourness  disappears. 

In  the  juices  of  plants  before  the  period  of  flowering,  other  acids  are 
met  with  besides  the  oxalic  acid,  though  in  much  smaller  quantity.  As 
the  most  important  of  these,  however,  occur  jnore  abundantly  in  fruits, 
we  shall  consider  the  theory  of  their  formation  in  the  following  section. 

§  4.  Of  the  chemical  changes  which  take  place  bettveen  the  opening  oftJie 
flower  and  the  ripening  of  the  fruit  or  seed. 

The  opening  of  the  flower  is  the  first  and  most  striking  step  taken  by 
the  plant  towards  the  production  of  the  seed  by  which  its  species  is  to  be 
perpetuated.  That  at  this  period  a  new  series  of  chemical  changes  com- 
mences in  the  plant  is  obvious  from  the  following  facts  : — 

1°.  That  the  flower  leaves  absorb  oxygen  and  emit  carbonic  acid  both 
by  day*  and  by  night  (p.  95.) 

2*^.  That  they  also  occasionally  emit  pure  nitrogen  gas. 

3°.  That  the  juice  of  the  maple  ceases  to  be  sweet  when  the  flowers 
are  matured  (Liebig,)  and  that,  in  the  sugarcane  and  beetroot,  the  sugar 
becomes  less  abundant  when  the  plant  has  begun  to  blossom. 

These  facts  sufficiently  indicate  the  commencement  of  new  changes 
in  the  interior  of  plants  at  this  period  of  their  growth.  That  such  changes 
go  on  until  the  ripening  of  the  seed  is  also  evident  from  these  further  ob- 
servations : — 

1°.  That  the  husk  of  the  future  seed,  as  in  the  corn-bearing  grasses 
(wheat,  oats,  &c.,)  is  filled  at  first  with  a  milky  liquid,  which  becomes 
gradually  sweeter  and  more  dense,  and  finally  consolidates  into  a  mix- 
ture of  starch  and  gluten,  such  as  is  presented  by  the  flour  of  different 
species  of  corn. 

2°.  That  the  fruit  in  which  the  seeds  of  many  plants  is  enveloped  is 
at  first  tasteless,  afterwards  more  or  less  sour,  and  finally  sweet.  In  a 
few  fruits  only,  as  in  the  lime,  the  lemon,  and  the  tamarind,  does  a  suf- 
ficient quantity  of  acid  remain  to  be  sensible  to  the  taste,  when  the  seed 
has  become  perfectly  ripe.  The  acid  and  cellular  fibre  both  diminish 
while  the  sugar  increases. 

3°.  That  fruits,  while  green,  act  upon  the  air  like  the  green  leaves  and 
twigs — but  that,  as  they  approach  maturity,  they  also  absorb  or  retain 
oxygen  gas  (De  Saussure.)  The  same  absorption  of  oxygen  takes  place 
when  unripe  fruits  are  j)lucked  and  left  to  ripen  in  the  air  (Berard.) 
After  a  time  the  latter  also  emit  carbonic  acid. 

I. FORMATION  OF  THE  SEED. 

In  the  case  of  wheat,  barley,  or  other  plants,  which  yield  farinaceous 
seeds,  we  have  seen  that  previous  to  flowering  the  chief  energy  of  the 
living  plant  is  expended  in  the  production  of  the  woody  fibre  of  which 
its  stem  and  growing  branches  mainly  consist ;  and  we  have  also  been 
able  to  understand,  in  some  degree,  how  this  woody  fibre  is  produced 
from  the  ordinary  food  of  the  plant.     When  the  flower  expands,  how- 

•  By  day  the  absorption  is  the  greater,  but  the  bulk  of  the  oxygen  taken  in  is  always 
greater  than  that  of  the  carbonic  acid  given  off. 


140  FORMATION  OF  THE  SEED,  AND  RIPENING  OF  THE  FRUIT. 

ever,  the  plant  has  in  general,  and  especially  if  an  annual  plant,  reached 
nearly  to  maturity,  and  woody  fibre  is  little  required.  The  most  im- 
portant of  its  remaining  functions  is  the  production  of  the  starch  and  glu- 
ten of  the  seed,  and  of  the  substances  which  form  the  husk  by  which  the 
seed  is  enveloped. 

In  the  first  stages  of  the  plant's  growth,  the  starch  of  the  seed  is 
transformed  into  gum  and  sugar,  and  subsequently,  when  the  leaves  are 
expanded,  into  woody  fibre.  In  the  last  stages  of  its  existence,  when  it 
is  producing  the  seed,  the  sugar  of  the  sweet  and  milky  sap  is  gradually 
transformed  into  starch — that  is  to  say,  a  process  exactly  the  converse 
of  the  former  takes  place. 

We  are  able,  in  some  measure,  to  explain  the  mode  and  agency  by 
which  the  former  transformation  is  effected — the  latter,  however,  is  still 
inexplicable.  We  can  ourselves,  by  the  agency  of  diastase,  transform 
starch  into  sugar  ;  and,  therefore,  can  readily  believe  such  transforma- 
tions to  be  effected  in  the  young  plant ; — but  we  as  yet  luiow  no  method 
of  re-converting  sugar  into  starch  ;  and,  therefore,  we  can  only  hazard 
conjectures  as  to  the  way  in  which  this  change  is  brought  about  in  the 
interior  of  the  plant  during  the  formation  of  the  seed. 

It  is  said  that  nitrogen  is  given  off*  by  the  flower  leaf.  We  know  that 
this  element  is  present  in  the  colouring  matter  of  the  petal,  and  that  it  is  a 
necessary  constituent  of  the  albumen  and  gluten,  which  are  always  as- 
sociated with  the  starch  of  the  seed.  It  is  plain,  then,  that  the  nitrogene- 
ous  substances  [substances  containing  nitrogen,]  contained  in  the  sap  at 
all  periods  of  the  plant's  growth,  are  carried  up  in  great  quantity  to  the 
flower  and  seed  vessel.  These  substances  are  supposed  to  be  concerned  as 
immediate  agents  in  effecting  the  transformations  which  there  take  place. 
More  than  this,  however,  we  cannot  as  yet  venture  even  to  conjecture. 

II. RIPENING  OF  THE  FRUIT. 

In  these  plants,  again,  which  invest  their  seed  with  a  pulpy  fruit — in 
the  grape,  the  lemon,  the  apple,  the  plum,  &c. — other  changes  take 
place,  at  this  period,  of  a  more  intelligible  kind,  and  other  substances  are 
formed,  on  the  production  of  which  less  obscurity  rests.  At  one  stage  of 
their  growth,  these  fruits,  as  has  been  already  stated,  are  tasteless — in  the 
next,  they  are  sour — in  the  third,  they  are  more  or  less  entirely  sweet. 

I.  In  the  tasteless  state  they  consist  of  little  more  than  the  substance 
of  the  leaf— of  vascular,  or  woody  fibre,  filled  with  a  tasteless  sap,  and 
tinged  with  the  colouring  matter  of  the  green  parts  of  the  plant.  For  a 
time,  this  young  fruit  appears  to  perform  in  reference  to  the  atmosphere 
the  usual  functions  of  the  leaf— it  absorbs  carbonic  acid  and  gives  off  oxy- 
gen, and  thus  extracts  from  the  air  a  portion  of  the  food  by  which  its  growth 
is  promoted,  and  its  size  gradually  increased. 

II.  But  after  a  time  this  fruit  becomes  sour  to  the  taste,  and  its 
acidity  gradually  increases — while  at  the  same  time  it  is  observed  to 
give  off  a  less  comparative  bulk  of  oxygen  than  before.  Let  us  consi- 
der shortly  the  theory  of  the  production  of  the  more  abundant  vegetable 
acids  contained  in  fruits. 

1°.  The  tartaric  acid  which  occurs  in  the  grape  is  represented  by 
C4  H,  O5  (p.  124). 

There  are  two  ways  in  which  we  may  suppose  this  acid  to  be  formed 


rOUMATION  or  TARTARIC,  MALIC,  AND  CITRIC  ACIDS.  141 

in  the  fruit — either  directly  from  the  elements  of  carhonic  acid  and  wa- 
ter with  the  evolution  of  oxygen  gas — or  from  the  gum  and  sugar  al- 
ready present  in  the  sap  aided  by  the  absorption  of  oxygen  from  the  at- 
mosphere.    Thus 

A.  4  of  Carbonic  Acid  =  C4         O3 
2  of  Water     .     .     =        Ha  O2 

Tartaric  Acid. 

Sum     .     .     =  C4  H2  Oio  or  C4  H2  O5  +  50. 
That  is,  one  equivalent  of  tartaric  acid  may  be  formed  from  4  of  carbon- 
ic acid  absorbed  by  the  leaf  or  fruit,  and  2  of  the  water  of  the  sap,  while 
5  of  oxygen  are  at  the  same  time  given  off  by  the  leaf.     Or, 

B.  If  Grape  Sugar  be  C12  H^a  O12 

i  of  Grape   Sugar  =  C4    H3    O3 
3  of  Oxygen    .     .     =  O3 

Tartaric  Acid.         Water. 

Sum     .     .     =64    H3    Oe    or  C4  H2  O5 -j-  HO. 

Thpt  is,  by  the  absorption  from  the  air  of  a  quantity  of  oxygen  equal  to 
that  which  it  already  contains,  ^rape  sugar  may  be  converted  into  tar- 
taric acid  and  water. 

In  the  sorrels  and  other  sour-leaved  plants,  which  contain  tartaric  acid 
in  their  general  sap,  the  acid  may  be  formed  by  either  of  the  processes 
above  explained.  In  the  sunshine  their  green  parts  absorb  carbonic 
acid  and  evolve  oxygen.  If  any  of  these  green  parts  give  off  only  |  of 
the  oxygen  contained  in  the  carbonic  acid  they  drink  in,  tartaric  acid 
may  be  produced  (A.)  In  the  dark  they  absorb  oxygen  and  give  off 
carbonic  acid.  If  the  bulk  of  this  latter  gas  which  escapes  be  less  than 
that  of  the  oxygen  which  enters,  a  portion  of  the  sugar  or  gum  of  the 
sap  may,  as  above  explained  (B.),  be  converted  into  tartaric  acid. 

We  have  as  yet  no  experiments  which  enable  us  to  say  by  which  of 
these  modes  the  tartaric  acid  is  really  produced  in  such  plants — or 
whether  it  may  not  occasionally  be  compounded  by  both  methods. 

In  green  fruits  also,  in  the  sour  grape  for  example,  it  may,  in  like 
manner,  be  produced  by  either  method.  The  only  experiments  we  yet 
possess,  those  of  De  Saussure,  though  not  sufficient  to  decide  the  point, 
are  in  favour  of  the  former  explanation  (A.)  In  the  estimation  of  this 
philosopher,  the  proportion  of  the  oxygen  of  the  carbonic  acid  which  is 
retained  by  the  fruit,  is  sufficient  to  account  for  the  acidity  it  gradually 
acquires. 

2°.  Malic  and  citric  acids. — These  acids  are  represented  (p.  127)  by 
the  common  formulae  C4  H2  O4.  They  may  be  produced  from  water 
and  carbonic  acid,  if  three-fourths  only  of  the  oxygen  of  the  latter  be 
given  off.     Thus 

4  of  Carbonic  Acid  =  C4         O3 
2  of  Water      .     .     =        Ho  Oo 


Malic  Acid. 


Sum       .     .     =C4  H2O10  =€4  H2O4 -f  60. 

That  such  a  retention  of  one-fourth  of  the  oxygen  of  the  carbonic  acid 
occasionally  takes  place  in  the  green  fruit,  is  consistent  with  the  obser- 
vations of  De  Saussure.  The  lime  and  the  lemon  are  fruits  on  which 
the  most  satisfactory  experiments  might  be  made  with  the  view  of  fi- 
nally determining  this  point. 

7 


142  CONVERSION    OF    ACIDS    INTO    SUGAR. 

III.  This  formation  of  acid  proceeds  for  a  certain  time,  the  fruit  be- 
coming sourer  and  sourer ;  the  acidity  then  begins  to  diminish,  sugar  is 
formed,  and  the  fruit  ripens.  The  acid  rarely  disappears  entirely,  even 
from  the  sweetest  fruits,  until  they  begin  to  decay  ;  a  considerable  por- 
tion of  it,  however,  must  be  converted  into  grape  sugar,  as  the  fruit  ap- 
proaches to  maturity.  This  conversion  may  take  place  in  either  of  two 
ways. 

1°.  By  the  direct  evolution  of  the  excess  of  oxygen.     Thus 

3  of  Tartaric  Acid  =  0^2   Hg     Oj^ 

6  of  Water    .     .     .  =  H.     O^ 


Grape  Sugar. 


Sum  .     .     .  ==  Ci2  Hi2  O2,   =  C12  H12  0,3  +  90. 


Or  grape  sugar  may  be  formed  from  3  of  tartaric  acid  and  6  of  the  water 
of  the  sap,  by  the  evolution,  at  the  same  time,  of  9  of  oxygen.  Citric 
and  malic  acids,  in  the  same  proportion,  would  form  grape  sugar  by  the 
evolution  of  6  of  oxygen  only. 

Do  fruits,  when  they  have  reached  their  sourest  state,  begin  thus  to 
give  oflf  an  excess  of  oxygen  ?  I  know  of  no  experiments  which  as  yet 
decide  the  point. 

2°.  By  the  absorption  of  oxygen  and  the  evolution  of  carbonic  acid. 
Thus  in  the  case  of  tartaric  acid, 
1  of  Tartaric  Acid  =  C4  Hg  O5 
1  of  Oxygen  .     .     .  =  O. 


■     . Xth  of  Grape        Carbonic 

Sugai".  Acid. 

Sum  .     .     .  =  C4   H2  Oe  =  C2   H2  O3  +  2  CO2 
Where  one  of  oxygen  is  absorbed  and  two  of  carbonic  acid  given  off. 
Or  in  the  case  of  the  malic  and  citric  acids, 

1  of  Malic  Acid  =  C4  H2  O4 

2  of  Oxygen  .     .  =  O2 

'■  Xth  of  Grape         Carbonic 

Sugar.  Acid. 

Sum  .     .  =  C4  H,  O2    =  Co  H2  O2  +  2  CO, 
Where  2  of  oxygen  are  absorbed  and  2  of  carbonic  acid  given  on. 

We  know  from  the  experiments  of  Berard  that,  when  unripe  fruits 
are  plucked,  they  do  not  ripen  if  excluded  from  the  access  of  oxygen 
gas — but  that  in  the  air  they  rif  en,  absorbing  oxygen  at  the  same  time, 
and  giving  off  carbonic  acid.  This  second  method  (2°)  therefore  ex- 
hibits the  more  probable  theory  of  the  ripening  of  fruits  after  they  are 
plucked;  and  if — as  they  become  coloured — fruits  imitate  the  petals  of 
the  flower  in  absorbing  oxygen  from  the  air  and  giving  off  carbonic  acid, 
it  will  also  represent  the  changes  which  lake  place  when  they  are  per- 
mitted to  ripen  on  the  tree. 

During  the  ripening  of  the  fruit,  it  has  been  stated  that  the  woody  or 
cellular  fibre  it  contains  gradually  diminishes,  and  is  converted  into  su- 
gar. This  is  familiarly  noticed  in  some  species  of  hard  or  winter  pears. 
In  sour  fruit,  the  cellular  fibre  seldom  exceeds  2^  per  cent,  of  their 
whole  weight ; — in  ripe  fruits,  however,  it  is  still  less,  and  as  the  con- 
stitution of  this  substance  is  so  analogous  to  that  of  grape  sugar,  there  is 
no  difficulty  in  understanding  that  it  may  be  readily  converted  into  the 
latter,  though  the  immediate  agency  by  which  the  transformation  is 
effected  is  as  yet  unknown  to  us. 


CHANGES  AFTER  THE  FRUIT  HAS  RIPENED.  143 

§  5.  Of  the  chemical  changes  which  take  place  after  the  ripening  of 
the  fruit  and  seed. 

When  the  seed  is  fully  ripe,  the  functions  of  annual  plants  are  dis- 
charged. They  no  longer  reciuire  to  absorb  and  decompose  carbonic 
acid,  for  their  growth  is  at  an  end.  Their  leaves  begin,  therefore,  to 
take  in  oxygen  only,  become  yellow,  and  prepare  along  with  the  entire 
plant,  for  being  finally  resolved  again  into  those  more  elementary  sub- 
stances from  which  they  were  originally  compounded. 

On  trees  and  perennial  plants,  however,  a  further  labour  is  imposed. 
In  the  ripened  seed  they  have  deposited  a  supply  of  food  sufficient  to 
sustain  the  germ  thai  may  spring  from  it,  until  it  is  able  to  seek  food  for 
itself;  but  the  young  buds  already  formed, — and  which  are  to  shoot  out 
from  the  stem  and  branches  in  the  ensuing  spring, — are  in  reality  so 
many  young  plants  for  which  a  store  of  food  has  yet  to  be  laid  up  in  the 
inner  bark,  and  in  the  wood  of  the  tree  or  shrub  itself. 

In  the  autumn,  the  sap  of  trees  and  permanent  shrubs  continues  to 
flow  rapidly  till  the  leaf  withers  and  falls,  and  the  food  of  the  plant  is 
converted  partly  into  woody  fibre,  as  was  the  case  during  the  earlier 
period  of  the  year,  and  partly  into  starch.  The  former  is  deposited  be- 
neath the  inner  bark  to  form  the  new  layer  of  wood  by  which  the  tree  is 
annually  enlarged ;  the  latter — partly  in  the  same  locality,  as  in  the 
birch  and  pine — partly  throughout  the  substance  of  the  wood  itself,  as  in 
the  willow — while  in  the  palrn  trees  and  cycadeae,  it  is  intermingled 
with  the  central  pith.  The  chemical  changes  by  which  the  food  is  ca- 
pable of  being  converted  into  these  substances  have  already  been  con- 
sidered. They  proceed  during  the  entire  autumn,  do  not  cease  so  long 
as  the  sap  continues  to  move,  and  even  in  the  depth  of  winter  slowly  and 
silently  operate  in  storing  up  farinaceous  matter — in  readiness,  like  the 
starch*^in  the  seed,  to  minister  to  the  nourishment  of  the  young  bud,  when 
the  warmth  of  the  coming  spring  shall  awaken  it  from  its  long  sleep. 

§  6.  Of  the  rapidity  with  lohich  these  changes  take  place^  and  the 
circumstances  by  which  they  are  promoted. 

But  remarkable  as  those  chemical  changes  are,  the  rapidity  with 
which  they  sometimes  take  place  is  no  less  surprising. 

From  carbonic  acid  and  water  we  have  seen  that  the  plant,  by  very 
intelligible  processes,  can  extract  the  elements  of  which  its  most  bulky 
parts  consist — andean  build  them  up  in  many  varied  ways,  most  of  which 
are  probably  beyond  the  reach  of  imitation.  But  who  can  understand  or 
explain  the  extraordinary  activity  which  pervades  the  entire  vascular 
system  of  the  plant,  when  circumstances  are  favourable  to  its  growth? 

A  stalk  of  wheat  has  been  observed  to  shoot  up  three  inches  in  as 
many  days,  of  barley  six  inches  in  the  same  time,  and  a  vine  twig 
almost  two  feet,  or  eight  inches  a  day  (Du  Hamel).  Cucumbers  have 
been  known  to  acquire  a  length  of  twenty-four  inches  in  six  days,  and 
in  the  Botanic  Garden  at  Brussels  I  was  shown  a  bamboo  five  inches  in 
diameter,  which  had  increased  in  height  nine  feet  in  twenty-seven  days, 
sometimes  making  a  progress  of  six  to  eight  inches  in  a  day.  In  our 
climate  we  meet  with  few  illustrations  of  the  rapidity  with  which  plants 
are  capable  of  springing  up  in  the  most  favourable  circumstances,  and 
the  above  examples  probably  give  us  only  an  imperfect  idea  of  the  ve- 


144  INFLUENCE  OF  SALINE  SUBSTANCES  AND  MAKTJRES. 

locity  with  which  the  bamboo,  the  palm,  the  tree  fern,  and  other  vascu- 
lar plants,  may  grow  in  tJieir  native  soil  and  climate.  And  with  what 
numerous  and  complicated  chemical  changes  is  the  production  of  every 
grain  of  the  substance  of  these  plants  attended — how  rapidly  must  tlie 
food  be  selected  and  absorbed  from  the  air  and  from  the  soil — Iiow 
quickly  transformed  and  assimilated  ! 

The  long  period  of  time  during  which,  year  after  year,  these  changes 
may  proceed  in  the  same  living  vessels,  or  in  the  same  tree,  is  no  less 
wonderful.  Oaks  have  lived  to  an  age  of  1500  or  2000  years — yew 
trees  to  3000  years — and  other  species  are  mentioned  as  having  flour- 
ished from  4500  to  6000  years ;  while  even  a  living  rose  tree  {rosa 
canina)  is  quoted  by  Sprengel  as  being  already  upwards  of  1000  years 
old. — [Sprengel,  Lehrc  vom  Diinger,  p.  76.] 

Tlie  rapidity  of  tbe  growth  of  a  plant,  and  the  length  of  its  life,  are 
equally  affected  by  circumstances.  On  a  knowledge  of  these  circum- 
stances, and  of  the  means  of  controlling  or  of  producing  them,  the  en- 
lightened practice  of  agriculture  is  almost  entirely  dependent. 

Over  the  natural  conditions  on  which  vegetation  in  general  depends, 
we  can  exercise  little  control.  By  hedge-rows  and  plantations  we  can 
sheher  exposed  lands,  but,  except  in  our  conservatories  and  hot-houses, 
the  plants  we  can  expect  to  cultivate  with  profit  will  always  be  deter- 
mined by  the  general  climate  in  which  we  live.  So  the  distribution  of 
rain  and  sunshine  are  beyond  our  control,  and  though  it  is  ascertained 
that  a  thundery  condition  of  the  atmosphere  is  remarkably  favourable  to 
vegetable  growth,  [Sprengel,  Lehre  vom  Diinger,  p.  73],  we  cannot 
hope  that  such  a  state  of  the  air  will  ever  be  induced  at  the  pleasure  or 
by  the  agency  of  man.  But  under  the  same  natural  conditions  of  cli- 
mate, there  are  many  artificial  methods  by  the  use  of  which  it  is  within 
our  power  to  accelerate  the  growth,  and  to  increase  the  produce,  of  the 
most  valuable  objects  of  ordinary  culture. 

Thus  the  germination  of  seeds  in  general  is  hastened  by  watering  with 
a  solution  of  chlorine  (Davy),  or  of  iodine  or  bromine  (Blengini),  and 
Davy  found  that  radish  seed  which  germinated  in  two  days  when  wa- 
'ered  with  solutions  of  chlorine  or  sulphate  of  iron,  required  three  when 
(vatered  with  very  dilute  nitric  acid,  and  five  whh  a  weak  solution  of 
sulphuric  acid. 

It  is  familiarly  known  also  in  ordinary  husbandry,  that  the  applica- 
tion of  manures  hastens  in  a  similar  degree  the  development  of  all  the 
parts  of  plants  during  every  period  of  their  growth — and  largely  increases 
•he  return  of  seed  obtained  from  the  cultivated  grains.  Ammonia  and 
its  compounds  likewise,  and  nitric  acid  and  its  compounds,  with  many 
Dther  saline  substances  existing  in  the  mineral  kingdom  and  occurring  in 
soils,  or  which  are  produced  largely  in  our  manufactories,  have  been 
found  to  produce  similar  effects. 

It  would  be  out  of  place  here  to  enter  upon  the  important  and  interest- 
ing field  opened  up  to  us  by  a  consideration  of  the  influence  exercised 
by  these  and  other  substances,  in  modifying  both  in  kind  and  in  degree  the 
chemical  changes  which  take  place  in  living  vegetables.  The  true  mode 
of  action  of  such  substances — their  precise  eflects — the  circumstances 
under  which  these  effects  are  most  certainly  produced — and  the  theoreti- 
cal views  on  which  they  can  be  best  accounted  for — will  form  a  subject  of 
special  and  detailed  examination  in  the  third  part  of  the  present  lectures. 


LECTURE  VIII. 

How  the  supply  of  food  for  plants  is  kept  up  in  the  general  vegetation  of  the  globe. — Propor- 
tion of  their  fo«il  drawn  by  plautsfrom  the  air.— Supply  of  carbonic  acid.—Supply  of  ammo- 
nia and  nitric  acid.— Production  of  both  in  nature.— Theory  of  their  action  on  living  vege- 
tables.— Concluding  observations. 

Having  shown  in  the  preceding  Lecture  in  what  way,  and  by  what 
chemical  changes,  the  substances  of  which  plants  chiefly  consist  naay 
be  produced  from  those  on  which  they  live, — there  remains  only  one 
further  subject  of  inquiry  in  connection  with  the  organic  constituents  of 
plants. 

Plants,  as  we  have  already  seen,  derive  much  of  their  sustenance  from 
the  carbonic  acid  of  the  atmosphere  ;  yet  of  this  gas  the  air  contains  only 
a  very  small  fraction,  and  in  so  far  as  experiments  have  yet  gone,  this 
fractional  quantity  does  not  appear  to  diminish — how,  then,  is  the  sup- 
ply of  carbonic  acid  kept  up  ? 

Again,  plants  most  probably  obtain  much  of  their  nitrogen  either  from 
ammonia  or  from  nitric  acid  ;  and  yet,  neither  in  the  soil  nor  in  the  air 
do  these  compounds  permanently  exist  in  any  notable  quantity, — whence 
then  is  the  supply  of  these  substances  brought  within  the  reach  of  plants  ? 

The  importance  of  these  two  questions  will  appear  more  distinctly,  if 
we  endeavour  to  estimate  how  much  of  their  carbon  plants  really  draw 
from  the  atmosphere — and  how  much  of  the  nitsogen  they  contain  must 
be  derived  from  sources  not  hitherto  pointed  out. 

§  I.  Of  the  proportion  of  their  carhon  which  plants  derive  from  the 
atmosphere. 

On  this  subject  it  is  perhaps  impossible  to  obtain  perfectly  accurate 
results.  Several  series  of  experiments,  however,  have  been  published; 
which  enable  us  to  arrive  at  very  useful  approximations  in  regard  to  the 
proportion  of  their  carbon  which  plants,  growing  in  a  soil  of  ordinary 
fertility,  and  in  such  a  climate  as  that  of  Great  Britain,  actually  extract 
from  the  air  by  which  they  are  surrounded. 

1°.  In  an  experiment  made  in  1824,  upon  common  borage  (Borago 
officinalis),  Lampadius  found  that  after  a  growth  of  five  months  (from 
the  3rd  of  April  to  the  6th  of  September)  this  plant  produced  ten  times 
as  much  vegetable  matter  as  the  soil  in  which  it  grew  had  lost  during 
the  same  period.*  In  other  'woj:(\Sy  it  had  drawn  nine-tenths  of  its  car- 
hon from  the  air. 

2°.  The  experiments  of  Boussingault  were  made,  if  not  with  more 
care,  at  least  upon  a  greater  number  of  plants,  and  were  protracted 
through  a  much  longer  period.  It  is  necessary  that  we  should  under- 
stand the  principle  on  which  they  were  conducted,  in  order  that  we 
may  be  prepared  to  place  confidence  in  the  determinations  at  which  he 
arrived. 

*  The  above  experiment  may  have  been  correctly  made,  but  the  result  appears  at  first 
siglit  too  startling  to  be  readily  received  as  indicative  of  the  proportion  of  their  sustenance 
drawn  by  plants  from  the  air  in  the  general  vegetation  ofthp,  globe. 


146  PROPORTIO>    OF    CARBON    DRAWN    FROM    THE    AIR. 

If  we  were  to  examine  the  soil  of  a  field  on  which  we  are  about  to 
raise  a  crop  of  corn — and  should  find  it  to  contain  a  certain  per-centage, 
say  10  per  cent,  of  vegetable  matter  (or  5  per  cent,  of  carbon) ; — and 
after  the  crop  is  raised  and  reaped  should,  on  a  second  examination, 
find  it  to  contain  exactly  the  same  quantity  of  carbon  as  before,  we 
could  not  resist  the  conviction,  that,  with  the  excejjtion  of  what  was 
originally  in  the  seed,  the  plant  during  its  growth  had  drawn  from  the 
air  all  the  carbon  it  contained.  The  soil  having  lost  none,  the  air  must 
have  yielded  the  whole  supply. 

Or  if  after  examining  the  soil  of  our  field  we  mLx  whh  it  a  supply  of 
farm-yard  manure,  containing  a  known  weight,  say  one  ton  of  carbon, 
and  when  the  crop  is  reaped  find  as  before  that  the  per-centage  of  vege- 
table matter  in  the  soil  has  suffered  no  diminution,*  we  are  justified  in 
concluding  that  the  crop  cannot,  at  the  utmost,  have  derived  from  the 
soil  any  greater  weight  of  its  carbon  than  the  ton  contained  in  the  ma- 
nure which  had  been  added  to  it. 

Such  was  the  principle  on  which  Boussingault's  experiments  were 
conducted.  He  determined  the  per-centage  of  carbon  in  the  soil  before 
the  experiment  was  begun — the  weight  added  in  the  form  of  manure — 
the  quantity  contained  in  the  series  of  crops  raised  during  an  entire  rota- 
tion or  course  of  cropping,  until  in  the  mode  of  culture  adopted  it  was 
usual  to  add  manure  again — and  lastly,  the  ])roporiion  of  carbon  re- 
maining in  the  soil.  By  this  method  he  obtained  the  following  results 
in  pounds  per  English  acre,  in  three  different  courses  of  cropping,  and 
on  the  same  land  : — 

Carbon  Carbon  Difference,  or 

in  the  in  Carbon  derived  Remarks. 

majiure.        the  crops.         from  the  air. 

f  The  first  was  a  5  years' 
course — of  potatoes  or 
red  beet  with  manure, 
wheat,  clover,  wheat, 
oats;  the  second  and 
most  productive  rota- 
tion was  abandoned  on 
account  of  the  climate  ; 
the  third  was  a  3  yeans' 
course. 

The  result  of  the  first  course  indicates  that — the  land  remaining  in 
equal  condition  at  the  end  of  the  four  years  as  it  was  at  the  beginijing — 
the  crops  collected  during  these  years  contained  three  times  the  quantity 
of  carbon  present  in  the  manure,  and  therefore  the  plants,  during  their 
growth,  must  on  the  whole  have  derived  tivo-thirds  of  their  carbon  from 
the  air. 

It  will  be  shown  in  a  subsequent  section  that  even  when  the  soil  is 
lying  naked  the  animal  and  vegetable  matter  it  contains  is  continually 
undergoing  diminution,  owing  to  decomposition  and  the  escape  of  vola- 
tile substances  into  the  air.     It  is  fair,  therefore,  to  assume  that  a  con- 

-*  I  need  scarcely  remark  that,  in  the  hands  of  a  good  farmer,  who  keeps  his  land  in  good 
heart — the  quantity  of  organic  matter  in  the  soil  at  the  end  of  his  course  of  cropping  should 
be  as  great,  atlea.st,  as  it  was  at  the  beginning  of  his  rotation,  before  the  addition  of  the 
manure. 


First  Course         2513  7544  5031 

Second  do.  —  —  6839     { 

Third     do.  —  —  3921 


WEIGHT    OF    CARBON     JN    THE    ATMOSPHERE.  147 

siderable  portion  of  the  carbon  of  the  manure  and  of  the  soil  would 
naturally  disappear  during  the  four  years'  cropping  above-mentioned, 
and  that,  therefore,  the  proportion  of  carbon  derived  from  the  air  in 
Boussingault's  experiments,  nmst  have  been  really  considerably  greater 
than  is  indicated  by  the  numerical  results. 

Let  two-thirds  of  the  entire  quantity  of  carbon  contained  in  a  series  of 
crops  be  taken  as  the  average  proportion,  [Lecture  II.,  p.  31,]  which,  on 
cultivated  land  in  our  climate,  must  be  derived  from  the  air  in  the  form 
of  carbonic  acid — and  let  the  average  weight  of  the  dry  crop  reaped  be 
estimated  at  a  ton  and  a  half  per  acre.  Then,  if  the  crop  contain  half 
its  weight  of  carbon,*  the  plants  grown  on  each  acre  must  annually  ex- 
tract from  the  air  10  cwt.  or  1120  lbs.  of  carbon  in  the  form  of  carbonic  acid. 

• 

§  2.  Of  the  relation  which  the  quantity  of  carbon  extracted  by  plants  from 
the  air,  bears  to  the  whole  quantity  contained  in  the  atmosphere. 

But  the  question  will  here  at  once  suggest  itself  to  you — does  not  the 
quantity  thus  extracted  from  the  air  really  form  a  very' large  proportion 
of  the  whole  weight  of  carbon  which  is  contained  in  the  atmosphere  ?  A 
simple  calculation  will  give  us  clear  ideas  in  regard  to  this  interesting 
point. 

We  have  already  seen  tliat,  by  the  results  of  De  Saussure,  the  aver- 
age quantity  of  carbonic  acid  in  the  atmosphere  of  our  globe  may  be 
estimated  at  o-^o  V'^^^  ^^  i^^  entire  bulk.  This  is  equal  very  nearly 
to  T^(nro  ^^  i^^  weight. f  Or  taking  the  whole  weight  of  the  atmosphere 
at  15  lbs.  on  the  square  inch — that  of  the  carbonic  acid  will  be  0*009  lbs. 
or  63  grs.  per  square  inch.  But  as  carbonic  acid  contains  only  27§  per 
cent,  of  its  weight  of  carbon,  the  weight  of  this  element  which  presses 
on  each  square  inch  of  the  earth's  surface  is  only  17f  (17*39)  grs.  Upon 
an  acre  this  amounts  to  7  tons.} 

But  if  the  crop  on  each  acre  of  cultivated  land  annually  extracts  from 
the  air  half  a  ton  of  carbon,  the  whole  of  the  carbonic  acid  in  the  atmos- 
phere would  sustain  such  a  vegetation  over  the  entire  globe  for  14  years 
only.  And  if  we  even  suppose  such  a  vegetation  to  extentl  over  one 
hundredth  part  of  the  earth's  surface  only,  it  still  appears  sufficient  to 
exhaust  the  carbonic  acid  of  the  air  in  1400  years. 

*  Boussingault  states,  that  of  all  the  plants  usually  cultivated  for  food— so  far  as  his  experi- 
ments have  gone— the  Jerusalem  artichoke  draws  the  largest  portion  of  its  sustenance  from 
the  air — or  yields  the  greatest  weight  of  food  from  tlie  smallest  weight  of  manure.  It  is  true 
generally  indeed  that  all  those  plants,  "which,  like  the  Jerusalem  artichoke  and  the  white 
carrot,  grow  freely  on  sandy  soiis  containing  little  vegetable  matter  and  with  the  addition 
of  little  manure,  extract  the  greatest  proportion  of  their  sustenance  from  the  air.  Such 
plants,  therefore,  are  likely  to  prove  the  most  profitable  articles  of  culture  where  such  soils 
and  a  scarcity  of  manure  simultaneously  prevail. 

t  The  mean  of  225  experiments  made  by  De  Saussure  between  1827  and  1829  gave  as 
above  stated  about  4-10000  or  l-2500th  part  for  the  mean  bulk  of  the  carbonic  acid  in  the  air, 
which  is  nearly  6-lOOOths  of  its  whole  weight.  Among  these  observations  the  maximum 
was  5-8  ten-thousandths,  the  minimum  3-15.  If  we  take  the  maximum  bulk  at  6-10000tb3 
of  the  air— the  maximum  weight  of  the  carbonic  acid  is  nearly  9-lOOOOtlis  of  that  of  the  at- 
mosphere. In  elementary  works  it  is  generally  stated  in  round  numbers  at  l-lOOOth  of  the 
weight  of  the  air,  but  if  the  best  experimental  results  we  possess  are  to  be  any  guide  to  us, 
this  is  at  least  one-third  too  high. 

It  is  also  of  consequence  to  remark,  that  this  estimate  of  the  whole  weight  of  the  carbonic 
acid  in  the  air  is  founded  on  the  supposition  that,  in  the  highest  regions  of  the  atmosphere: 
the  carbonic  acid  is  present  in  a  proportion  nearly  equal  to  that  in  which  it  is  found  imme 
diately  above  the  eartli's  surface— which  is  by  no  means  established. 

t  15-583  lbs.— an  acre  being  4840  square  yards,  containing  each  1296  square  inchesj 


148  HOW    THE    SUPPLY    OF    CARBONIC    ACID    IS    RENEWED. 

A  very  short  period,  com  pared  even  wiih  the  limits  of  authentic  his- 
tory, has  yet  elapsed  since  experiments  began  to  be  made  on  the  true 
constitution  of  the  atmosphere  ;  we  have  no  very  trustworthy  data, 
therefore,  on  which  to  found  a  confident  opinion  in  regard  to  the  perma- 
nence of  the  proportion  of  carbonic  acid  which  it  now  contains.  The 
later  observations  of  De  Saussure  do  give  a  considerably  lower  estimate 
->f  the  quantity  of  this  acid  in  the  air  than  that  which  was  deduced  from 
2ie  results  of  the  earlier  experimenters;  but  the  imperfection  of  the 
<Tiode8  of  analysis  formerly  adopted  was  too  great,  to  justify  us  in  rea- 
soning rigorously  from  the  inferences  to  which  they  led.  We  cannot 
safely  conclude  from  them  that  the  proportion  of  carbon  in  the  atmos- 
phere has  really  diminished  to  any  sensible  extent  during  this  limited 
period;  while  the  recorded  identity  of  all  the  phenomena  of  vegetation 
renders  it  probable  that  the  proportion  has  not  sensibly  diminished  even 
within  historic  times. 

From  what  sources,  then,  is  the  supply  of  carbonic  acid  in  the  atmos- 
phere kept  up? — and  if  the  proportion  be  permanent,  by  what  compen- 
sating processes  is  the  quantity  which  is  restored  to  the  atmosphere 
produced  and  regulated  ? 

§  3.  How  the  supply  of  carbonic  acid  in  the  atmosphere  is  renewed 

and  regulated. 
On  comparing,  in  a  previous  lecture,  the  quantity  of  rain  which  falls 
with  that  of  the  watery  vapour  actually  present  in  the  air,  we  saw  rea- 
son to  believe  that  even  in  a  single  year  the  same  portion  of  water  may 
fall  in  rain  or  dew  and  ascend  again  in  watery  vapour  several  succes- 
sive times.  Is  it  so  also  with  the  carbon  in  the  air  ?  Does  that  which 
feeds  the  growing  plant  to-day,  again  mount  up  in  the  form  of  carbonic 
acid  at  some  future  time,  ready  to  minister  to  the  sustenance  of  new 
races,  and  to  run  again  the  same  round  of  ever-varying  change  ?  Such 
is,  indeed,  the  general  history  of  the  agency  of  the  carbonic  acid  of  the 
atmosphere  ;  but  when  once  it  has  been  fixed  in  the  plant  it  must  pass 
through  many  successive  changes  before  it  is  again  set  free.  The  con- 
ditions, also,  under  which  it  is  restored  to  the  atmosphere  are  so  diver- 
sified, and  the  agencies  by  which,  in  each  case,  it  is  liberated,  are  so 
very  distinct,  as  to  require  that  the  several  modes  by  which  the  carbon 
of  plants  is  reconverted  into  carbonic  acid  and  returned  to  the  air,  should 
be  made  topics  of  separate  consideration. 

I. ON  THE  PRODUCTION  OF  CARBONIC  ACID  BY  RESPIRATION. 

The  air  we  breathe  when  it  is  drawn  into  the  lungs,  contains  2x0*^ 
of  its  bulk  of  carbonic  acid  ;  when  it  returns  again  from  the  lungs,  the 
bulk  of  this  gas  amounts,  on  an  average,*  to  Ysih  of  the  whole  ;  or  its 
quantity  is  increased  one  hundred  times. 

The  actual  bulk  of  the  carbonic  acid  emitted  from  the  lungs  of  a  sin- 
gle individual  in  24  hours  varies  exceedingly  ;  it  has  been  estimated 
however,  on  an  average,  to  contain  upwards  of  five  ounces  of  carbon. f 

*  It  varies  in  different  individuals  from  2  to  8  per  cent,  of  the  expired  air.  In  animals  it 
varies  also  with  tiie  species.  The  air  from  the  lungs  of  a  cat  contains  from  5J  to  7  per  cent., 
of  a  doa  from  Ah  to  6^,  of  a  rabbit  from  4  to  6,  and  of  a  pigeon  from  3  to  4  per  cent,  of  the 
whole  bulk.— DuIong~  Annal.  de  Chim.  etde  P/it/s.,  third  JSeriea,  /.,  p.  455. 


t  I>avy,  and  Allen,  and  Pepys,  estimated  the  weight  of  carbon  evolved  in  a  day  at  upwards 
of  11  ounces,  a  quantity  which  all  writers  have  concurred  in  receiving  with  suspicion. 


THE  COiMBUSTlOA'  OF  OIlGAiMC  MATTKR.  149 

A  full  grown  man,  therefore,  gives  off  from  his  lungs,  in  the  course  of  a 
year,  upwards  of  100  lbs.  of  carbon  in  the  form  of  carbonic  acid. 

If  the  (juanlity  of  carbon  thus  evolved  from  the  lungs  be  in  proportion 
to  the  weight  of  the  animal,  a  cow  or  a  horse  ought  to  give  off  six  tipies 
as  much  as  a  man.*  From  indirect  experiments,  however,  Boussin- 
gault  estimated  the  quantity  of  carbon  actually  lost  in  this  way  by  a  cow. 
at  2200  grammes  in  24  hours,  and  by  ahorse  at  2400  grammes. — [Ann. 
de  Chim.  tide  Phys.,  Ixxi.,  pp.  127  and  136.]  These  quantities  are  equal 
to  6  or  7  times  the  amount  of  carbon  given  off  from  the  lungs  of  a  man. 

If  we  suppose  each  inhabitant  of  Great  Britain,  young  and  old,  to  ex- 
pire only  80  lbs.  of  carbon  in  a  year,  the  twenty  millions  would  emit 
seven  hundred  thousand  tons ;  and,  allowing  the  cattle,  sheep,  and  all 
other  animals,  to  give  off  twice  as  much  more,  the  whole  weight  of 
carbon  returned  to  the  air  by  respiration  in  this  island  would  be  about 
two  millions  of  tons,  or  the  quantity  abstracted  from  the  atmosphere  by 
four  millions  of  acres  of  cultivated  land. 

Whence  is  all  this  carbon  derived  ?  It  is  a  portion  of  that  which  has 
been  conveyed  into  the  stomach  in  the  form  of  food.  Suppose  the  car- 
bon contained  in  the  daily  food  of  a  full  grown  man  to  amount  to  one 
pound — which  is  a  large  allowance — then  it  appears  that,  by  the  ordi- 
nary processes  of  respiration,  at  least  one-third  of  the  carbon  of  his  food 
is  daily  returned  into  the  air. 

In  other  animals  the  proportion  returned  may  be  different  from  what 
it  is  in  man,  yet  the  life  of  all  depends  on  the  emission  to  a  certain  ex- 
tent of  the  same  gas.f  And  since  all  are  sustained  by  the  produce  of 
the  soil,  it  is  obvious  that  the  process  of  animal  respiration  is  one  of 
those  methods  by  which  it  has  been  provided  that  a  large  portion  of  the 
vegetable  productions  of  the  globe  should  be  almost  immediately  re- 
solved into  the  simpler  forms  of  matter  from  which  it  was  originally 
compounded,  and  again  sent  up  into  the  air  to  minister  to  the  wants  of 
new  races. 

II. ON  THE  PRODUCTION   OF  CARBONIC  ACID  BY  COMBUSTION. 

Another  important  source  of  carbonic  acid  is  familiar  to  us  in  the  re  • 
suits  of  artificial  combustion. 

In  the  previous  lecture  I  have  shown  how,  by  the  action  of  the  sun's 
rays  upon  the  leaf,  the  carbonic  acid  absorbed  from  the  atmosphere  is 
deprived  of  its  oxygen,  and  its  carbon  afterwards  united  to  the  elements 
of  water  for  the  ])roduction  of  woody  fibre.  During  the  process  of  com- 
bustion, this  labour  of  the  living  leaf  is  undone — the  carbon  is  made  to 
combine  anew  with  the  oxygen  of  the  atmosphere,  and  the  vegetable 
matter  is  resolved  again  into  carbonic  acid  and  water. 

Thus,  when  wood  (woody  fibre)  is  burned  in  the  air,  oxygen  disap- 
pears, and  carbonic  acid  and  watery  vapour  are  alone  produced.  The 
theory  of  this  change  is  simple. 

*  Estimating  the  ordinary  weight  of  a  man  at  150,  and  of  a  cow  at  800  to  900  Ibs.-'See 
Sprengel,  Lehre  vom  Dilnger,  p.  208. 

*  That  the  proportion  mtcst  be  less  in  the  larger  animals  is  certain,  since  the  daily  food  of 
a  cow  may  be  stated  generally  as  equivalent  to  25  lbs.  of  hay,  containing  upwards  of  10  lbs.  of 
carbon.  If  one-third  of  this  were  given  off  from  the  lungs,  the  quantity  of  carbon  (SJ  lbs.) 
evolved  would  be  ten  times  greater  than  was  indicated  by  the  experiments  of  BoussingauU, 
and  nearly  double  of  what  Uie  weight  of  a  cow,  compared  with  Uiatof  a  man,  requires. 

7* 


150  PRODUCES  CARBONIC  j^CID  AND  WATER. 

It  will  be  recollected  (p.  135)  that  in  forming  an  equivalent  of  woody 
iibre  or  of  sugar,  24  of  oxygen  were  given  off,  chiefly  by  the  leaf — so  in 
again  resolving  these  substances  into  carbonic  acid  and  water,  24  of  oxy 
gen, are  absorbed.     Thus — 

1  of  Woody  Fibre  =  Ci2  Hs    Og 
24  of  Oxygen       .     =  O24 


12  of  8  of 

Carbonic  Acid.    Water. 


Sum.     .     .     =:Ci2H3    O30  =  12CP2 -f  8HO. 

Or,  1  of  Cane  Sugar     =Ci2HioOi„ 
24  of  Oxygen   .     .     =  O-,. 


12  of  10  of 

Carbonic  Acid.      Water. 

Sum.     .     .     =Ci2  Hio  O34  =12CO2  +  10HO. 

The  same  law  holds  in  regard  to  all  other  vegetable  substances.  They 
are  resolved  into  carbonic  acid  and  water,  in  proportions  which  neces- 
sarily vary  with  the  chemical  constitution  of  each. 

It  applies  also  to  all  bodies  of  vegetable  origin,  among  which  nearly 
all  combustible  minerals  may  be  reckoned.  The  peat  and  coal  we  burn 
in  our  houses  and  manufactories,  when  supplied  with  a  sufficiency  of 
atmospheric  air,  are  resolved  during  combustion  into  carbonic  acid  and 
watery  vapour. 

Some  vegetable  substances  contain  a  small  quantity  of  nitrogen. 
"When  these  are  burned,  this  nitrogen  escapes  into  the  atmosphere, — 
generally  in  an  uncombined  state, — and  mingles  with  the  air.  So  in 
animal  substances,  nearly  all  of  which  contain  nitrogen  as  an  essential 
constituent.  During  perfect  combustion  the  whole  of  the  carbon  is  dis- 
sipated in  the  form  of  carbonic  acid,  while  the  nitrogen  rises  along  with 
it  in  an  elementary  state- 

The  result  of  this  uniform  subjection  of  all  combustible  matter  to  the 
operation  of  this  one  law,  is  the  constant  production  on  the  surface  of 
the  globe  of  a  vast  quantity  of  carbonic  acid  ; — the  re-conversion  of  large 
masses  of  organic  matter  info  the  more  elementary  compounds  from 
which  it  was  originally  formed. 

How  interesting  it  is  to  contemplate  the  relations,  at  once  wise  and 
beautiful,  by  which  through  the  operation  of  such  laws,  dead  organic 
matter,  intelligent  man,  and  living  plants,  are  all  bound  together  !  The 
dead  tree  and  the  fossile  coal  lie  almost  useless  things  in  reference  to 
animal  and  vegetable  life, — man  employs  them  in  a  thousand  ways  as 
ministers  to  his  wants,  his  comforts,  or  his  dominion  over  nature — and 
in  so  doing,  himself  directly  though  unconsciously  ministers  to  the  wants 
of  those  vegetable  races,  which  seem  but  to  live  and  grow  for  his  use  and 
sustenance. 

It  is  impossible  to  say  what  proportion  of  the  carbon  absorbed  during 
the  general  vegetation  of  the  globe,  is  thus  annually  restored  to  the  at- 
mosphere by  the  burning  of  vegetable  matter.  That  it  must  be  very 
great,  will  appear  from  the  single  fact,  that  by  far  the  greater  part  of  the 
globe  is  dependent  for  its  supply  of  fuel  on  the  annual  produce  of  its 
forests; — while  even  in  those  more  favoured  countries  where  mineral 
coal  abounds,  the  quantity  of  wood  consumed  by  burning  falls  but  little 
short  of  the  entire  yearly  growth  of  the  land. 


LAW  OF  THE  DECAY  OF  VEGETABLE  MATTER.  15J 

111  connection  with  this  subject,  I  must  draw  your  attention  to  one  in- 
teresting, as  well  as  important,  fact.  I  have  spoken  of  coal  as  a  sub- 
stance of  vegetable  origin,  and  there  is  no  doubt  that  all  the  carbon  it 
contains  once  floated  in  the  air  in  the  form  of  carbonic  acid.  But  the 
period  when  it  was  so  mixed  with  the  atmosphere  is  remote  almost  be- 
yond conception.  When,  therefore,  we  raise  coal  from  its  ancient  bed 
and  burn  it  on  the  earth's  surface,  we  add  to  the  carbon  of  the  air  a  por- 
tion which  has  not  previously  existed  in  the  atmosphere  of  our  time. 

The  coal  consumed  in  Great  Britain  alone  is  estimated  at  20  millions 
of  tons,  containing  on  an  average  at  least  70  per  cent.,  or  14  millions  of 
tons  of  carbon.  But  if  the  annual  produce  of  an  acre  of  cultivated  land 
contain  half  a  ton  (p.  147)  of  carbon  derived  from  the  air,  the  coal  con- 
sumed in  this  country  would  supply  carbonic  acid  to  the  crops  grown 
upon  '28  millions  of  acres.  Or,  since  in  Great  Britain  about  34  millions 
of  acres  are  in  cultivation  (p.  12),  the  coal  we  annually  consume  produces 
a  quantity  of  carbonic  acid  which  is  alone  sufficient  to  supply  food  to  the 
crops  that  grow  upon  seven-eighths  of  the  arable  land  of  this  country. 

IH. PRODUCTION  OF  CARBONIC  ACID  BY  THE  NATURAL  DECAY  OF  VEGE- 
TABLE MATTER.   LAW  OF  THIS  DECAY. 

Over  large  tracts  of  country  in  every  part  of  the  globe,  the  vegetable 
productions  of  the  soil  are  never  cropped  or  gathered,  but  either  accumu- 
late— as  occasionally  in  our  peat  bogs;  or  decay  and  gradually  disappear 
— as  in  the  jungles  of  India  or  in  the  tropical  forests  of  Africa  and  South- 
ern America. 

^ he  final  results  of  this  decay  are  the  same  as  those  which  attend 
upon  ordinary  combustion,  but  the  conditions  under  which  it  takes  place 
being  different,  the  immediate  results  are  to  a  certain  extent  different 
also. 

When  a  vegetable  substance  is  burned  in  the  air,  the  oxygen  of  the  at- 
mosphere is  the  only  material  agent  in  effecting  the  decomposition. 
The  carbon  of  the  burning  body  unites  directly  with  this  oxygen  and 
forms  carbonic  acid. 

In  the  natural  process  of  decay,  however,  at  the  ordinary  temperature 
of  the  atmosphere,  vegetable  matter  is  exposed  to  the  action  of  both  air 
and  water  ;  these  both  co-operate  in  inducing  and  carrying  on  the  decom- 
position, and  hence  carbonic  acid  is  not,  as  in  the  case  of  combustion,  the 
chief  or  immediate  result. 

A  detail  of  all  the  steps  through  which  vegetable  matter  is  known  to 
pass  before  it  is  finally  resolved  into  carbonic  acid  and  water,  would  be 
difficult  for  you  to  understand,  and  is  here  unnecessary.  A  general 
view  of  the  way  in  which  by  the  united  agency  of  air  and  water,  the 
decay  of  organic  substances  is  effected  and  promoted,  may  be  made 
very  intelligible,  and  will  sufficiently  illustrate  the  subject  for  our  pre- 
sent purpose. 

In  combustion,  as  we  have  seen,  the  whole  of  the  vegetable  substance 
is  resolved  directly  into  carbonic  acid  and  water,  at  the  expense  of  the 
oxygen  of  the  atmosphere.  In  natural  decay  a  small  and  variable  por- 
tion only  is  so  changed,  but  to  the  extent  to  which  this  change  does  take 
place  carbonic  acid  is  directly  formed  and  sent  up  into  the  air.  Suppose 
such  a  change — a  slow  corl  ^ustiou  in  reality — to  take  place  to  a  certain 


152  BY  NATURAL  DECAY  IT  IS    FINALLY  RESOLVED 

extent,  and  let  us  consider  what  becomes  of  the  remainder  of  the  vegeta 
ble  matter. 
1°.  If  we  add 

6  of  Carbonic  Acii     .     .     =  Cg  O12 

to  6  of  Light  Carburetted  ? n       u 

Hydrogen  (CHo)      ^  "  ^^     «i2 

we  have  the  sum  .  .  =Ci2Hi2  0i2?  or,  one  of 
grape  sugar; — that  is,  one  of  grape  sugar  may  be  formed  out  of  the  ele- 
ments of  6  of  carbonic  acid,  and  6  of  light  carburetted  hydrogen.  Or, 
conversely,  grape  sugar  being  already  produced,  it  may  be  resolved  or 
decomposed  into  these  two  compounds  in  the  same  proportions,  without 
the  aid  of  the  oxygen  of  the  atmosphere. 
2°.  So  if  to 

1  of  Woody  Fibre  =  C12  H3    O3 
we  add  4  of  Water     .     .    =  H4    O4 

Carbonic      Light  Carbu- 

Acid.      retted  Hydrogen, 
we  have,  as  before,  C12  H12  C)i2  =  6CO2  +  6  CH2; 
Or  by  the  aid  of  the  elements  of  4  atoms  of  water,  woody  fibre  may  be 
resolved  into  6  of  carbonic  acid  and   as  many  of  light  carburetted 
hydrogen. 

3°.  Again,  in  the  case  of  a  vegetable  acid,  if  to 

1  of  Tartaric  Acid  =  C4  Hg  O5 
we  add  1  of  Oxygen     .     .     ==  Oj 

Carbonic    Light  Carbu- 

Acid.      retted  Hydrogen. 

we  have  C^  H2  Og  =  3  CO2  +  CH2  ; 
That  is,  by  the  aid  of  one  of  oxygen  from  the  air,  one  of  tartaric  acid 
may  be  resolved  into  3  of  carbonic  acid,  and  1  of  light  carburetted 
liydrogen.  It  is  easy  to  see  how  any  other  of  the  more  common  vegeta- 
ble productions  may — either  at  the  expense  of  its  own  elements,  as  in 
grape  sugar— or  by  the  aid  of  those  of  water,  as  in  woody  fibre — or  of 
the  oxygen  of  the  atmosphere,  as  in  tartaric  acid — be  resolved  into  car- 
bonic acid  and  light  carburetted  hydrogen,  in  certain  proportions. 

Now,  such  a  resolution  does  really  take  place  to  a  considerable  extent 
in  nature,  during  the  decay  of  organic  substances  in  moist  situations. 
Hence  the  evolution  of  light  carburetted  hydrogen  from  dead  vegetable 
matter  in  marshy  places  and  stagnant  pools — hence  the  production  of 
the  same  gas  in  compost  heaps,  and  especially  in  rich  and  heated  farm- 
yard manure — and  hence  also  its  occurrence  in  such  vast  quantities  in 
many  of  our  coal  mines. 

You  will  now  be  able  to  appreciate  one  of  the  reasons  why  this  light 
carburetted  hydrogen  has  been  supposed  by  some  physiologists  (p.  50) 
to  contribute  as  food  to  the  ordinary  nourishment  of  plants.  It  is  pro- 
duced in  nature  in  many  and  varied  situations,  and  it  has  been  found 
by  experiment  to  exercise  a  visible  influence  upon  the  growth  of  plants; 
— being  so  produced  where  young  plants  grow,  is  it  never  imbibed  by 
them  1 — being  possessed  of  this  influence,  is  it  entrusted  with  no  control 
over  the  general  vegetation  of  the  globe  ? 

However  this  may  be,  by  far  the  greatest  portion  of  both  these  gases 
escapes  into  the  air ; — the  carbonic  acid  to  fulfil  those  purposes  which 


INTO  CARBONIC  ACID  AND  WATER.  153 

have  already  been  considered, — the  light  carburetted  hydrogen  to  under- 
go a  further  change,  by  which  it  also  is  resolved  into  carbonic  acid  and 
water.     Thus,  if  to 

1  of  Light  Carburetted  Hydrogen  =  CH2         we  add 

4  of  Oxygen =  O4 

Carbonic  Acid.  Water. 

We  have  CH2  O,  or  CO2  +  2  HO 

Or  one  of  this  gas  with  4  of  oxygen  may  be  changed  into  1  of  carbonic 
acid  and  2  of  water. 

Now,  when  this  gas  escapes  into  the  air  it  becomes  diffused  through  a 
large  excess  of  oxygen,  and  is  thus  ready,  at  any  instant,  to  be  decom- 
posed. Through  the  atmosphere  streams  of  electricity  are  continually 
flowing,  and  every  wandering  spark  that  passes  athwart  a  portion  of 
this  mixture  decomposes  so  much  of  the  light  gas,  and  produces  in  its 
stead  the  equivalent  proportions  of  carbonic  acid  and  watery  vapour. 
Thus  it  happens  that  of  the  vast  quantity  of  this  and  other  combustible 
gases  which  are  continually  escaping  into  the  air,  so  few  traces  are  dis- 
cernible even  by  the  aid  of  the  most  refined  processes  of  art.  By  a  wise 
provision  of  nature  such  substances  as  are  void  of  use  to  either  animals 
or  plants,  if  not  speedily  removed  from  the  air  altogether,  are  there  con- 
verted into  such  new  forms  of  matter  as  are  fitted  to  minister  to  the  ne- 
cessities of  living  beings. 

Though  therefore  in  the  natural  decay  of  vegetable  matter  in  the  pre- 
sence of  air  and  moisture,  a  certain  portion  of  its  carbon  escapes  into  the 
air  in  the  form  of  light  carburetted  hydrogen,  this  compound  is  but  a 
step  towards  the  final  change  into  carbonic  acid  and  water.  In  the  soil 
the  vegetable  matter  is  continually  undergoing  decay,  various  sub- 
stances are  produced  in  greater  or  less  quantity,  some  solid,  some  liquid, 
and  some  gaseous  like  the  light  gas  of  which  we  have  been  speaking, — 
but  all  of  them,  like  this  gas,  are  only  hastening — some  by  one  road,  so 
to  speak,  and  some  by  another — towards  that  final  destination  which 
sooner  or  later  they  are  all  fated  to  reach  ;  when  in  the  form  of  carbonic 
acid  and  water  they  shall  be  in  a  condition  to  minister  again  to  the  nour- 
ishment of  all  plants. 

While  in  the  soil  some  part  of  this  vegetable  matter  assumes  forms 
which  are  capable  of  entering  again  into  the  roots  of  lixing  plants,  and, 
without  further  resolution  in  the  air,  of  being  converted  by  the  living 
plant  into  portions  of  its  own  substance.  The  nature  and  composition 
of  these  forms  of  matter,  so  far  as  they  are  known,  will  be  considered  in 
a  subsenuent  lecture. — [See  Part  11.,  Lectures  Xl.-XIIl.,  "  On  the 
constitution  of  soils. ^^] 

It  is  upon  the ^naZ  result  of  this  natural  decay  to  which  all  vegetable 
matter  is  subject,  that  the  carbonic  acid  of  the  atmosphere  depends  for 
its  largest  supplies.  The  rapidity  with  which  organized  bodies  perish, 
and  become  resolved  into  gaseous  compounds,  depends  partly  upon  the 
climate  and  partly  on  the  nature  of  the  substances  themselves, — but  all 
hurry  forward  to  the  same  end,  and  it  is  with  difficulty  that  w^e  are  able 
for  a  time  to  arrest  or  even  to  retard  their  steps.  It  is  by  this  perpetual 
and  active  obedience  of  all  dead  matter  to  one  fixed  law  that  the  exist- 
ing condition  of  things  is  maintained  ; — and  thus  it  happens  that  either 
by  the  respiration  of  the  animals  which  live  upon  it,  by  tlie  process  of 


154         EVOLUTION  OF  CARBONIC    ACID     N  VOLCANIC  COUNTRIES. 

combustion,  or  by  that  of  spontaneous  decay,  tlie  entire  crop  of  vegeta- 
ble produce  is  apparently,  year  by  year — taking  the  average  of  a  series 
of  years — resolved  into  the  forms  of  matter  from  which  it  was.originally 
built  up  ; — and  the  substances  on  which  plants  feed  at  length  restored  to 
the  air  in  the  precise  proportion  in  which  they  have  been  taken  from  it. 

VI. NATURAL  EVOLUTION  OF  CARBONIC  ACID  IN  VOLCANIC  COUNTRIES. 

The  above  apparent  conclusion  would  be  absolutely  true,  were  there 
no  causes  in  operation  by  which  the  restoration  to  the  air  of  a  portion  of 
the  carbon  of  animal  and  vegetable  substances  is  prevented — and  no 
other  sources,  independent  of  existing  organic  matter,  from  which  car- 
bonic acid  may  be  supplied  to  the  air. 

If  the  whole  of  the  carbon  be  not  returned  to  the  air,  the  carbonic  acid 
of  the  atmosphere  may  be  undergoing  diminution ;  while — if  a  large 
supply  be  constantly  poured  into  the  air  from  sources  independent  of 
vegetable  matter,  the  proportion  of  carbonic  acid  may  be  continually  on 
the  increase. 

We  have  seen  that  the  combustion  of  fossil  coal  adds  to  the  air  a 
large  quantity  of  carbonic  acid  which  has  never  before  existed  in  the  at- 
mosphere of  our  time.  In  many  volcanic  districts  also,  carbonic  acid  is 
observed  to  issue  in  large  quantity  from  cracks  and  fissures  in  the  earth  ; 
— accompanied  sometimes  by  water,  forming  mineral  springs,  from 
which  the  copious  emisson  of  gas  is  readily  perceived  ;  more  frequently, 
perhaps,  rising  up  alone,  and  thus  escaping  general  observation. 

It  must  obviously  be  exceedingly  difficult  to  estimate  the  (luantity  of 
gas  which  rises  into  the  air  in  such  circumstances  over  an  extensive 
tract  of  country,  fractured  and  broken  up  by  volcanic  agency — where 
the  outlets  are  numerous,  and  the  rate  at  which  the  gas  escapes  very 
variable.  That  in  many  localities  it  must  be  very  great,  however, 
there  can  be  no  question.  In  the  ancient  volcanic  district  of  the  Eifel, 
comprising  an  area  of  many  square  miles  around  the  Laacher  See,  on 
the  left  bank  of  the  Rhine,  the  annual  evolution  of  carbonic  acid  from 
springs  and  fissures  has  been  estimated  by  Bischof  at  not  less  than 
100,000  tons,  containing  27,000  tons  of  carbon.  In  many  other  districts, 
especially  where  active  volcanoes  exist,  the  volume  of  gas  given  off 
may  be  quite  as  great,  though  no  attempts  have  hitherto  been  made  to 
estimate  its  real  amount. 

Yet  though  absolutely  large,  tie  quantity  of  carbonic  acid  disengaged 
in  this  way  from  the  earth,  is  really  small  when  compared  either  with 
the  entire  quantity  supposed  to  be  present  in  the  atmosphere,  or  with 
that  which  is  required  for  the  growth  of  the  yearly  vegetation  of  the 
globe.  Suppose  that  from  a  thousand  spots  on  the  earth's  surface  a 
quantity  of  carbonic  acid  equal  to  the  above  estimate  of  Bischof  escapes 
constantly  into  the  air,  the  weight  of  carbon  (27  millions  of  tons)  thus 
diffused  through  the  atmosphere  would  be  only  ecjual  to  that  which  is 
yearly  drawn  from  the  air  by  54  millions  of  acres  of  land  under  cultiva- 
tion (p.  147),  and  only  twice  as  much  as  that  contained  in  the  coal 
which  is  annually  consumed  in  Great  Britain  alone. 

Still  if  the  whole  of  the  carboi:  contained  in  the  produce  of  the  general 
vegetation  of  the  globe  be  ultimately  restored  to  the  air, — either  by  the 
respiration  of  animals,  by  the  natural  and  slow  decay  of  vegetable  mat- 


155  CARBON  PERAIANENTLY  WITHDRAWN  FROM  THE  AIR. 

ter,  or  by  the  more  rapid  process  of  combustion, — the  constant  addition 
of  carbonic  acid  derived  from  volcanoes,  and  from  the  combustion  of  fos- 
sil coal,  should  gradually,  though  slowly,  augment  the  proportion  of  this 
gas  in  the  air  we  breathe  ; — unless  it  be  perpetually  undergoing  a  per- 
manent diminution,  to  at  least  an  equal  extent,  from  the  operation  of 
other  causes.  In-  reference  to  this  point  there  are  three  circumstances 
which  are  proper  to  be  considered  : — 

1®.  It  has  been  observed  that,  as  we  recede  from  the  land  and  ap- 
proach the  centre  of  great  lakes,  or  sail  into  the  open  sea,  the  quantity 
of  carbonic  acid  in  the  air  gradually  diminishes.  It  is  therefore  inferred 
that  the  sea  is  constantly,  and  to  a  sensible  extent,  absorbing  carbonic 
acid  from  the  atmosf)here,  without  afterwards  restoring  it,  so  far  as  is 
yet  known,  by  any  compensating  process. 

2°.  The  waters  which  flow  into  the  sea  or  great  lakes  constantly 
bear  down  with  them  portions  of  animal  and  vegetable  matter.  These 
fall  along  with  the  mud  which  the  waters  hold  in  suspension,  and  are 
permanently  imbedded  in  the  deposits  of  clay,  silt,  and  sand,  which  are 
continually  in  the  course  of  formation. 

3°.  In  many  parts  of  the  world,  especially  in  the  latitudes  north  and 
south  of  45°,  vegetable  matter  accumulates  in  the  form  of  peat,  becomes 
buried  beneath  clay  and  sand,  and  thus  is  prevented  from  undergoing 
the  ordinary  process  of  natural  decay. 

It  is  impossible  to  say  how  much  carbon  is  permanently  withdrawn 
from  the  atmosphere  by  these  several  agencies.  There  is  reason  to  be- 
lieve that  it  is  quite  as  great  as  the  quantity  added  to  the  air  by  the 
combustion  of  coal,  and  by  the  evolution  of  carbonic  acid  in  volcanic 
districts.  Indeed,  the  supply  from  these  two  sources  appears  to  return 
only  a  small  portion  of  that  carbonic  acid  which  is  abstracted  from  the 
air  by  the  agencies  just  stated,  and  which  have  been  in  operation  during 
every  geological  epoch. 


Conclusions. — The  general  conclusions,  therefore,  which  we  seem  jus- 
tified in  drawing  in  regard  to  the  supply  of  carbonic  acid  to  the  atmos- 
j)here  are  as  follow  : — 

1°.  That  a  large  portion  of  the  carbonic  acid  absorbed  by  plants  is 
immediately  and  directly  restored  to  the  air  by  the  respiration  of  the 
animals  which  feed  upon  vegetable  productions. 

2°.  That  a  still  larger  portion  is  more  slowly  returned  by  the  gradual 
re-conversion  of  vegetable  substances  into  carbonic  acid  and  water  dur- 
ing the  process  of  natural  decay. 

3°.  That  nearly  all  the  remainder  is  given  back  in  the  results  of  or- 
dinary combustion. 

4°.  That  a  further  portion,  which  has  not  previously  existed  in  the 
atmosphere  of  our  time,  is  conveyed  to  it  by  the  burning  of  fossil  fuel, 
and  by  the  emission  of  carbonic  acid  from  cracks  and  fissures  in  the 
surface  of  the  earth  ;  yet  that  the  quantity  thus  added  cannot  be  sup- 
posed to  exceed  that  which  is  constantly  and  permanently  separated 
from  the  atmosphere  by  other  causes. 

The  balance  of  all  the  evidence  we  possess  is  probably  in  favour  of 
the  opinion  that  the  carbonic  acid  in  the  atmosphere  is  slowly  diminish- 


156  AMMONIA  IN  THE  AIR HOW  DECOMPOSED. 

ing;  we  have,  however,  no  satisfactory  evidence  either  from  theory  or 
experiment  that  it  has  undergone  any  sensible  diminution  in  our  time.* 

§  4.   Of  the  supply  of  ammonia  to  plants. 

In  a  previous  lecture  it  has  been  shown  that  in  our  cultivated  fields 
plants  derive  a  portion  of  their  nitrogen  from  the  manure  which  is  added 
to  the  soil.  But  the  quantity  of  this  element  present  in  the  manure, 
supposing  it  all  taken  up  and  appropriated  by  the  plant,  is  seldom  equal 
to  that  contained  in  the  series  of  crops  which  this  manure  assists  in  raising. 

Thus,  in  the  experiments  of  Boussingault  already  described  (p.  144), 
the  manure  added  previous  to  the  first,  or  four  years'  course,  contained 

157  parts  of  nitrogen,  while  the  crops  contained  251  parts, — or  nearly 
two-thirds  more  than  could  be  derived  from  the  artificial  manure. 

Whence  is  this  excess  of  nitrogen  derived,  and  in  what  form  does  it 
enter  into  the  plant?  Liebig  replies  to  these  questions,  that  the  whole 
of  the  nitrogen  absorbed  by  plants  enters  in  the  state  of  ammonia,  and 
that  the  excess  above  what  is  present  in  the  manure  is  drawn  either 
from  the  soil  or  from  the  air.  This  opinion,  advanced  by  so  high  an 
authority,  demands  our  attentive  consideration. 

Ammonia  has  been  detected  in  many  clays,  and  traces  of  it  may  be 
discovered  in  most  soils,  but  it  is  not  known  to  be  a  natural  or  essential 
constituent  of  any  of  the  solid  rocks  of  which  the  crust  of  the  globe  is 
composed.  These  clays  and  soils,  therefore,  may  be  supposed  to  have 
derived  their  ammonia  from  the  atmosphere  ;  and  Liebig  ascribes  the 
fertilizing  action  of  the  air  upon  stiffclays  when  fallowed,  of  burned  clay 
when  applied  as  a  top-dressing,  and  of  gypsum  on  grass  lands  [see  note 
to  page  53],  to  the  larger  quantity  of  ammonia  which  the  surface  of  the 
soil  is  by  these  means  caused  to  absorb  and  retain. 

There  is  no  question  that  ammonia  is  present  in  the  atmosphere  in 
small  and  variable  quantity  (p.  37).  Whence  is  this  ammonia  derived, 
and  is  its  quantity  sufiicient  to  supply  the  demands  of  the  entire  vegeta- 
tion of  the  globe  ? 

When  animal  substances  undergo  decay,  nearly  all  the  nitrogen  they 
contain  is  ultimately  separated  from  the  other  constituents  in  the  form  of 
ammonia.  During  the  decay  of  plants  also,  a  portion  of  their  nitrogen 
escapes  in  the  state  of  ammonia.  Of  the  ammonia  thus  formed,  much 
ascends  into  the  air,  chiefly  in  combination  with  carbonic  acid  as  carbonate 
of  ammonia  (smelling  salts),  and  much  remains  in  the  soil.  Were  the 
whole  of  the  nitrogen  contained  in  plants  and  animals  to  assume  the" 
form  of  ammonia  when  they  decay,  and  to  remain  in  the  soil  or  in  the 
air,  it  would  always  be  within  the  reach  either  of  the  roots  or  leaves  of 
the  living  races;  and  thus  the  same  ammonia  [or  ammonia  containing 
the  same  nitrogen — supposing  the  hydrogen  to  have  been  changed] 
might  again  and  again  return  into  the  circulation  of  new  vegetable  tribes, 
and  be  always  alone  sufficient  to  supply  all  the  demands  of  the  exist- 
ing vegetation  of  the  globe. 

But  of  the  ammonia  thus  formed,  a  portion  is  daily  washed  from  the 
soil  by  the  rains  and  carried  to  the  sea,  and  much  more  probably  is 

In  another  work  {Chemical  Geology)  now  preparing  for  publication,  I  have  discussed 
this  question  in  connection  with  purely  Geological  considerations  and  without  reference  to 
oiir  time ;  but  it  would  be  out  of  place  to  introduce  here  any  train  of  reasoning  which  is  not 
calculated  to  throw  light  on  the  phenomena  of  the  existing  vegetation  ol  the  globe. 


AMMONIA  EVOLVtD  FROM  VOLCANOES.  157 

washed  from  Ine  air  by  the  waters  of  the  sea  itself,  or  by  the  rains  which 
fall  directly  into  the  wide  oceans ;  and  we  know  of  no  compensating 
process  by  which  this  ammonia  can  be  restored  to  the  air,  and  again 
made  useful  to  vegetation. 

Besides,  of  that  which  still  remains  in  the  air  much  must  undergo 
decomposition  by  natural  processes.  In  treating  in  a  preceding  section 
of  the  evolution  of  light  carburetted  hydrogen  during  the  slow  decay  of 
vegetable  matter  (p.  153),  I  have  shown  how,  in  consequence  of  its  ad- 
mixture with  the  oxygen  of  the  atmosphere,  tl]is  gas  is  finely  decom- 
posed, while  carbonic  acid  and  water  are  produced.  Ammonia  in  like 
manner  will  burn  in  oxygen  gas,  and  when  mixed  with  atmospheric  air 
may  be  decomposed  by  the  electric  spark — water  at  the  same  time  being 
formed  and  nitrogen  set  free.     Thus, 

if  with     1  of  Ammonia  =  NH3 

we  mix  3  of  Oxygen    =  O3 

3  of  water.    1  of  nitrogen. 

we  have  the  sum  NH3    O3  =  3  HO  +   N 

or,  when  diffused  through  the  air,  1  of  ammonia,  with  the  aid  of  3  of 
oxygen,  will  yield  3  of  watery  vapour,  while  the  nitrogen  may*  mingle 
with  the  air  in  an  elementary  form.  Can  we  doubt  that  ammonia 
is  tlius  decomposed  in  the  air?  Not  to  speak  of  other  forms  assumed 
by  the  electricity  of  the  atmosphere,  can  the  thunder-storms  of  the  tropi- 
cal regions  pass  unheeded  the  ammoniacal  vapours  they  must  meet 
with  in  their  course  ? 

I  conclude,  then,  that  of  the  ammonia  which  is  formed  from  the  nitro- 
gen actually  existing  in  animal  and  vegetable  substances  during  theit 
decay,  only  a  comimratively  small  portion  ever  returns  again  to  minister 
to  the  wants  of  new  races.f " 

But  if  j)laiits  obtain  all  their  nitrogen  from  ammonia, J  how  is  this 
waste  repaired — whence  are  new  supplies  constantly  derived  ? 

We  have  seen  that,  in  certain  volcanic  countries,  carbonic  acid  is 
evolved  in  vast  quantities  from  rents  and  fissures  in  the  earth.  In  some 
of  these  districts — and  this  has  been  observed  more  especially  in  Italy 
and  Sicily,  and  it  is  said  also  to  some  extent  in  China — ammonia  is 
likewise  given  off,  in  combination  generally  with  some  acid,  and  most 
frequently  with  the  muriatic  acid  in  the  form  of  sal-ammoniac  (muriate 
of  ammonia).  "  This  ammonia,''''  Liebig  is  correct  in  saying,  "-lias  not 
been  jjroduced  by  the  animal  organism  ;"  but  he  assumes  a  very  doubt- 
ful position  when  he  adds,  "zi  existed  before  the  creation  of  human  be- 
ings;  it  is  a  part,  a  primary  constituent  of  the  globe  itself .^^ — [Organic 
Chemistry  applied  to  Agriculture,  p.  112.] 

Where,  we  might  ask,  has  this  ammonia  existed  during  all  past  time 
— from  what  deep  caverns  of  the  earth  does  it  now  escape  ? 

*  1  say  may,  because  it  may  at  the  same  time  combine  with  oxygen  and  form  nitric  acid. 
—See  the  followinjt  section,  p.  239. 

I I  might  add,  that  of  the  ammonia  which  does  return,  and  is  again  absorbed,  a  portion  is 
subsequently  decomposed  in  the  interior  of  hving  plants,  as  is  shown  by  the  evolution  of 
nitrogen  from  the  common  leaves  of  i<ome  and  the  flower  leaves  of  otliers. 

i  "  Wild  plants  obtain  more  nitrogen  from  the  atmosphere,  in  the  form  of  ammonia,  than  they 
require  for  their  growth,  for  the  water  which  evaporates  through  their  leaves  and  blossoms 
emits,  after  a  time,  a  putrid  smell— a  peculiarity  possessed  only  by  such  bodies  as  contain 
nitrogen."— :[Liebig,  Organic  Chemistry  applimi  to  Agj-iculture,  p.  85.]  Does  the  fact  here 
staled,  justify  the  conclusion  which  appears  to  be  drawn  from  it  7 


158  INDIRECT  PRODUCTION   OF  AMMOxXIA- 

This  opinion  of  Liebig,  as  well  as  the  paramount  influence  he  as- 
cribes to  ammonia  over  the  vegetation  of  the  globe,  are  based  chiefly  on 
the  fact  that  we  know  of  no  means  by  which  ammonia  can  be  formed 
by  the  direct  union  of  the  hydrogen  and  nitrogen  of  which  it  consists. 

But  the  production  of  ammonia,  by  the  indirect  union  of  these  ele- 
ments, is  daily  going  on  in  nature,  and  can  even  be  effected  by  differ- 
ent processes  of  art.     Thus — 

1°.  When  organic  substances,  which  contain  no  nitrogen,  are  oxidized 
in  the  air,  ammonia  is  not  unfrequently  f(jnned  (Berzelius).  Hence 
it  must  be  produced  in  unknown  quantity  during  the  annual  decay  of 
all  vegetable  substances. 

2°.  When  organic  substances  are  oxidized  in  the  presence  of  air  and 
water — as  when  moist  iron  filings  are  exposed  to  the  air  (Chevallier), 
or  when  certain  oxidized  substances  are  decom|)Osed  in  the  air  by 
means  of  potassium  (Faraday),  or  when  metals,  such  as  tin  filings,  are 
rapidly  oxidized  by  means  of  nitric  acid,  ammonia  is  also  })roduced  in 
variable  quantity.  Hence  the  absorption  of  oxygen,  even  by  the  inor- 
ganic substances  of  the  soil,  may  give  rise  to  the  formation  of  ammonia. 
But, 

3°.  The  fact  which  most  clearly  illustrates  the  production  of  am- 
monia in  nature,  both  on  the  surface  of  the  earth,  in  t.he  soil,  and  far  in 
the  interior  near  the  seat  of  volcanic  fires,  is  this,  that  if  a  currant  of 
moist  air  be  made  to  pass  over  red-hot  charcoal,  carbonic  acid  and  am- 
monia are  simultaneously  formed.*  This  is  in  reality  only  a  repetition 
in  another  form  of  what  takes  place,  as  above  stated,  when  vegetable 
matter  decays,  or  iron  filings  rust  in  moist  air.  The  carbon  and  the  iron 
decompose  the  watery  vapour  in  the  air,  and  coinbine  with  its  oxygen, 
while,  ar  the  instantf  of  its  liberation,  the  h^'drogen  of  the  water  com- 
bines with  the  nhrogen  of  the  air,  and  forms  ammonia. 

The  source  of  the  ammonia  evolved  in  volcanic  districts,  therefore,  is 
no  longer  obscure.  The  existence  of  combustible  matter  in  such  dis- 
tricts, and  at  great  depths  beneath  the  surface,  can  in  few  cases  be 
doubted,  and  the  passage  of  a  mixed  atmdsphere  of  common  air  and 
steam  over  such  combustible  matter,  at  a  high  tem{)erature,  appears  to 
be  alone  necessary  to  the  production  of  ammonia.  It  is  unnecessary, 
then,  to  have  recourse  to  doubtful  speculations  in  order  to  account  for 
the  natural  reproduction  of  ammonia,  to  a  certain  extent,  in  the  place 

*  This  experiment  is  easily  performed  by  dratcing  a.  current  of  mixed  atmospheric  air 
and  steam  throuj^h  a  red-hot  gun-barrel  filled  with  well-burned  charcoal,  and  causing  the 
current,  on  leaving  the  barrel,  to  piss  through  water  acidulated  with  muriatic  acid.  After 
a  time,  the  water,  on  evaporation,  will  be  found  to  contain  traces  of  sal-ammoniac.  What 
Hi  us  takes  place  in  a  small  experiment  of  tliis  kind  must  more  readily  and  more  largely 
take  place  in  the  interior  of  the  earth,  where  conibu.stible  substances  at  a  high  temperature 
happen  to  be  exposed  to  a  current  of  atmosplieric  air,  mixed  with  watery  vapour. 

t  A  beautiful  illustration  of  the  tpndcncy  which  elementary  substances  have  to  unite  with 
each  other  at  the  instant  of  their  liberation  in  wliat  chemists  call  their  nascent  state,  is  men- 
tioned by  Runge. — Einlcitung  in  die  technische  Chemie,  p.  373. 

If  1  p  irt  of  hydrate  of  potash  and  20  of  iron  filings  be  heated  together,  hydrogen  only  is  . 
given  off. 

If  I  ot  nitrate  of  potash  and  20  of  iron  filings  be  heated  together,  nitrogen  only  is  given  off. 

But  if  40  of  iron  filings  be  mixed  with  1  of  hydrate  and  1  of  nitrate  of  potash,  and  Uien 
healed,  ammotiia  becomes  perceptible. 

The  nitrogen  and  hydrogen  being  given  off  together,  at  the  same  instant,  some  portions 
of  each  find  Lhiemselves  in  a  condition  to  unite,  and  thus  ammonia  is  produced.  The  same 
result  must  follow  in  many  natural  operations,  when  hydrogen  and  nitrogen  are  set  free 
from  a  previous  state  of  combination,  al  the  same  time,  and  in  thc>  presence  of  cue  another. 


NITRIC    ACID    EXISTS    LI  RGELY    IN    NATURE.  159 

o[  that  which  is  constantly  undergoing  decomposition  by  the  agency  ol 
causes  such  as  tliose  above  described. 

lint  is  the  indefinite  quantity  of  ammonia  reproduced  by  these  indi 
rect  melliods  sufficient  to  replace  all  that  is  lost?  Can  it  be  supposed 
to  im])art  to  plants  all  the  nitrogen  they  require  ?  These  questions  will 
be  considered  in  the  following  section. 

§  5.   Of  the  supply  of  nitric  acid  to  plants.' 
In  regard  to  the  action  of  nitric  acid  upon  vegetation  it  is  known — 
1°.  That  when,  in  the  form  of  nitrates  of  soda,  potash,   (tec,  it  is 
spread  upon  the  soil,  it  greatly  promotes  the  growth  and  luxuriance  of 
the  crop  and  increases  its  produce  ;  and 

2°.  That,  when  other  circumstancs  are  favourable  to  vegetation — as 
in  certain  districts  in  India — the  presence  of  an  apj)reciable  quantity  of 
these  nitrates  adds  largely  to  the  fertility  of  the  soil.* 

The  same  effects  are  uncpiesiionably  produced  by  the  addition  of  am- 
monia or  by  its  natural  presence  in  the  soil.     The  beneficial  influenco 
of  both  compounds,  then,  behig  recognized,  the  relative  extent  to  which 
each  operates  u\)on   the  general  vegetation  of  the  globe  will  be  main 
ly  determined  by  the  circumstances  and  the  quantity  in  which  they  res 
pectively  exist  or  are  reproduced. 

In  regard  to  the  existence  of  nitric  acid,  it  is  not  known  to  form  a 
necessary  constituent  of  any  of  the  solid  rocks  of  which  the  crust  of  the 
globe  is  composed,  but  is  diffused  almost  universally  through  the  soil 
which  oversi)reads  the  surface.  In  the  hotter  regions  of  the  earth,  in 
India,  in  Africa,  and  in  South  America  (p.  56),  it  in  many  places  accu- 
mulates in  sufficient  (luantity  to  form  incrustations  of  considerable  thick- 
ness over  very  large  areas,  and  in  many  more  it  can  be  separated  bj 
washing  the  soil.  liven  in  the  climates  of  Northern  Europe,  it  is  rare- 
ly absent  from  the  water  of  artificial  wells,  into  which  the  rains,  aftei 
filtering  through  the  surface,  are  permitted  to  make  their  way.f 

On  the  whole,  nitric  acid  and  its  compounds  apj)ear  to  exist,  ready 
formed  in  nature,  in  larger  quantity  than  either  ammonia  or  any  of  its 
compounds. 

*  For  the  following,  and  other  interesting  notices,  regarding  Indian  agriculture,  I  am  in- 
debted to  Mr  Fleming,  of  IJarochan,  in  Renfrewshire,  whose  long  residence  in  the  districts 
to  which  he  alludes,  as  well  as  the  interest  he  takes  in  practical  agriculture,  renders  his  tes- 
timony very  valuable  : 

"The  districts  of  Ciiaprah,  Tirlmot,  and  Shahabad,  near  Patna,  where  a  large  proportion 
of  the  saltpetre  sent  fri>m  Bengal  is  producei.  are  considered  the  most  fertile  in  Bengal, 
producing  2  and  sometimes  3  crops  yearly.  The  natives  of  these  districts,  particularly  a 
caste  caJledQuirees  (hereditary  gardeners),  Vv?)o  cultivate  the  best  land,  and  produce  the 
best  crops,  are  in  the  liabit  of  irrigating  their  fields  with  water  from  wells  so  strongly  im- 
pregnated witli  saltpetre  and  other  salts  as  to  he  quite  brackish,  and  they  consider  onions, 
turnips,  and  peas,  most  benefitted  by  this  irrigation.  Grain  crops  also  grow  most  luxuriant- 
ly on  lands  yielding  saltpetre,  where  there  is  enough  of  rain  within  a  week  or  two  after  the 
seed  is  sown,  but  if  a  drought  follow.s  the  sowing,  and  continues  for  3  weeks  or  a  month,  the 
leaf  becomes  yellow,  and  the  crop  fails. 

"The  Iliudoos  do  not  generally  manure  their  lands,  as  the  dung  of  the  cattle  is  used  for 
fuel,  but  the  Quirees  collect  the  ashes  of  cow  dung  and  of  burned" wood,  and  use  it  as  a  ma- 
nure in  some  cases,  chiefly  for  the  poppy  plant. 

"The  Hindoos  have  for  ages  been  well  acquainted  with  (he  rotation  of  crops,  and.  the  ad- 
vantages of  fallowing  land,  although  a  great  proportion  of  the  land  is  almost  consfautly  in 
rice,  Indian  corn,  or  millet,  during  the  rainy  season,  and  in  wheat  or  peas  during  the' dry 
season," 

t  It  occurs  in  the  wells  of  the  neighbourhood  of  Berlin  (Mi(schorlich),  in  the  form  of  ni- 
trates of  potash,  lime,  and  magnesia,  in  the  wells  around  Stockholm,  and  may  be  expected 
in  all  wells  that  are  dug  (Berze lius).— 2Vai7c  de  Chrmie,  iv.,  p.  71. 


160  FORMATION  OF  NITRIC  ACID. 

Of  these  nitrates,  as  they  do  of  ammonia,  the  rivers  niiisl  be  continu- 
ally bearing  a  portion  to  the  sea,  but  there  are  in  nature  unceasing  pro- 
cesses of  reproduction,  by  which  not  only  this  waste  of  the  nitrates  is 
repaired,  but  that  further  waste,  also,  which  is  caused  by  their  absorp- 
tion into  the  roots  and  subsequent  decomposition  in  the  interior  of  })lants. 
Let  us  siiortly  consider  these  processes  of  reproduction. 

1°.  When  a  succession  of  electric  sparks  is  passed  through  common 
air,  nitric  acid  (NO 5)  is  slowly  but  sensibly  formed.  The  currents  of 
electricity  which  in  nature  traverse  the  atmosphere  must  produce  the 
same  effect,  and  the  passage  of  each  flash  of  lightning  through  the  air 
must  be  attended  by  the  formation  of  some  portion  of  this  acid. 

After  a  thunder-storm  plants  appear  wonderfully  refreshed ;  in  thun- 
dery weather  they  grow  most  luxuriantly,  and  other  things  being  equal, 
those  seasons  in  which  there  is  much  thunder  are  observed  to  be  the 
most  fruitful.  Some  have  ascribed  these  results  to  the  immediate  agency 
of  electricity  on  the  growth  of  plants. — [Sprengel,  Chemie,  I.,  p.  99.] 
It  is  not  equally  possible  that  they  maybe  connected  with  this  necessary 
production  of  nitric  acid  ? 

Iri  the  rain  which  fell  during  17  thunder-storms,  Liebig  found  nitric 
acid  always  present  and  generally  in  combination  with  lime  and  am- 
monia. In  the  rain  which  fell  on  60  other  occasions,  he  could  detect  it 
only  twice.  In  minute  quantity  nitric  acid  is  difficult  to  detect.  How 
much  then  must  be  formed  in  a  thunder-storm,  even  in  our  climate,  to 
make  the  presence  of  this  acid  always  appreciable  in  the  rain  that  falls 
— how  vast  a  quantity  in  those  warmer  climates  where  such  storms  are 
so  frequent  and  so  appalling! 

2°.  When  a  mixture  of  ammonia  with  oxygon  gas  is  exploded  by 
passing  an  electric  spark  through  it,  a  quantity  of  nitric  acid  is  formed, 
even  when  the  oxygen  is  not  sufficient  to  oxidize  the  whole  of  the  am- 
monia* (Biscliof).  Hence,  if  in  the  air,  as  we  have  seen  reason  to  be- 
lieve, the  ammonia  given  off'  from  decaying  animal  matters,  and  from 
other  sources,  be  decomposed  by  the  atmospheric  electricity, — there  will 
necessarily  be  formed  at  the  same  instant  a  portion  of  nitric  acid,  at  the 
expense  of  the  nitrogen  of  the  ammonia  itself.  This  nitric  acid  will,  as 
necessarily,  combine  with  some  of  the  ammonia  which  still  remains  in 
the  air.  Hence  the  existence  and  production  of  nitrate  ojf  ainmonia  in 
the  atmosphere,  and  the  consequent  presence  of  this  acid  along  with  am- 
monia in  rain  water. 

Thus  the  very  cause  which  in  the  preceding  section  was  shown  to 
operate  in  constantly  diminishing  the  amount  of  ammonia  in  the  air, 
and  the  operation  of  which  certainly  renders  improbable  the  existence 
of  this  compound  in  the  atmosphere  in  the  large  quantity  supposed  by 
some  [see  especially  Liebig's  Organic  Chernistry  applied  to  Agriculture, 
p.  74],  this  same  cause  is  at  the  same  moment  constantly  reproducing 
nitric  acid.  And,  though  much  of  what  is  thus  produced  must  neces- 
sarily, as  in  the  case  of  ammonia,  je  carried  down  to  the  sea  by  the 
rains,  or  be  directly  absorbed  by  the  waters  of  the  ocean  themselves,  yet 

*  It  was  shown  above  (p.  157),  that  I  of  ammonia  (  NHj  )  requires  3  of  oxygen  to  decom- 
pose it,  forming  3  of  water,  and  setting:  the  nitroj^en  free.  But,  in  reality,  as  Bischof  has 
eliown,  the  nitrogen  is  nut  wholly  set  free,  but  a  portion  both  of  its  hydrogen  and  nitrogen 
combine  with  oxygen  (are  oxidized)  at  the  same  instant,  forming  simultaneously  both  water 
(HO),  and  nitric  acid  (  NO5  ). 


ARTIFICIAL  NITRE  BEDS.  161 

it  is  obvious  that  in  whatever  proportion  we  may  suppose  the  ammonia 
of  the  air  to  reach  the  leaves  and  roots  of  plants,  in  no  less  proportion 
must  the  nitric  acid,  with  which  it  is  associated,  he  enabled  to  enter  into 
the  circulating  system  of  the  various  tribes  of  living  vegetables,  that 
flourish  on  every  quarter  of  the  globe. 

3°.  Again,  we  have  seen  that,  during  the  decay  of  vegetable  substan- 
ces in  moist  air,  ammonia  is  formed  at  the  expense  of  the  h^^drogen  of 
the  water  and  of  the  nitrogen  of  the  air.  In  consequence  of,  or  in  con- 
nection with,  such  decay,  nitric  acid  is  also  largely  produced  in  nature. 

The  most  familiar,  as  well  as  the  most  instructive  examples  of  this 
formation  of  nitric  acid  is  in  the  artificial  nitre  beds  of  France  and  the 
north  of  Europe.  These  are  formed  by  mixing  earth  of  different  kinds 
with  stable  manure  or  other  animal  and  vegetable  matters,  and  exposing 
the  mixture  to  the  air  in  long  ridges  or  conical  heaps,  which  are  occa- 
sionally watered  with  liquid  manure,  and  turned  over,  to  expose  fresh 
portions  to  the  air.  After  a  time,  perhaps  once  a  year,  the  whole  is 
washed,  when  the  water  which  comes  off  is  found  to  contain  a  variable 
quantity  of  the  nitrates  of  potash,  soda,  lime,  and  magnesia,  which  are 
employed  for  the  manufacture  of  saltpetre.  In  these  nitre  beds  it  has 
been  observed  that  the  production  of  nitric  acid  either  does  not  take  plaec 
at  all,  or  only  with  extreme  slowness,  unless  animal  and  vegetable  mat- 
ter be  ])resent  in  considerable  proportion.  And  yet  the  quantity  of  nitric 
acid  which  is  formed  is  much  greater  than  could  be  produced  by  the 
oxidation  of  the  whole  of  the  nitrogen  contained  in  the  organic  matters 
present  in  the  mixture.*  It  is  also  observed  that  the  nitre  beds  are  more 
productive  when  a  portion  from  one  outer  face  of  the  heap  is  lixiviated 
from  time  to  time,  and  the  washed  earth  added  to  the  other  side,  than 
when  the  whole  is  lixiviated  at  once,  and  again  formed  into  a  heap  and 
exposed  to  the  air. 

It  appears,  therefore,  that  organic  matters  are  in  our  climate  necessa- 
ry to  cause  the  formation  of  nitric  acid  to  commence,  but  that  after  it  has 
begun  it  will  proceed  in  the  same  heap  for  an  indefinite  period,  and  at 
the  expense  apparently  of  the  nitrogen  of  the  air  only. 

Compost  heaps  are  in  general  only  artificial  nitre  beds,  often  unskil- 
fully prepared  and  badly  managed,  producing,  however,  a  certain  quan- 
tity of  nitrates,  to  the  presence  of  which  their  effect  on  vegetation  may 
not  urfrequently  be  ascribed.     To  this  fact  we  shall  hereafter  recur. 

The  soils  in  the  plains  of  India,  and  in  other  similar  spots  in  the  trop- 
ical regions,  may  be  regarded  as  natural  nitre  beds,  in  which,  the  decay 
of  organic  matter  being  vastly  more  rapid  than  in  our  temperate  regions, 
the  production  of  nitric  acid  is  rapid  in  proportion. f 

4°.  But  in  many  localities  in  which  the  presence  of  organic  matter  is 

*  Dnmas,  Traite  de  Chemie,  II.,  p.  725.  He  ailds,  that  100  lbs.  of  nitre  contain  the  nitrogen 
of  75  lbs.  of  ordinary  animal  matter,  supposed  in  a  dry  state,  or  of  300  or  400  lbs.  in  its  ordi- 
nary state  of  moisture, — a  much  greater  relative  proportion  of  animal  matter  than  is  ever 
added  to  the  heap. 

1  We  are  as  yet  too  little  acquainted  with  the  natural  history  of  the  district  of  Arica  in 
South  America,  in  which,  as  already  stated  (p.  56),  the  nitrate  of  soda  has  been  accumulateu 
in  such  large  quantity,  to  be  able  to  say  to  wtiat  special  cause  the  accumulation  is  due.  But 
as,  from  the  description  of  Mr.  Darwin,  the  locality  appears  to  have  been  the  site  of  an  an- 
cient lake,  it  is  not  unlilcely  that  the  nitrate  may  have  been  derived  from  the  successive 
washings  of  a  soil  similar  t(^iat  of  India,  by  rains  or  periodical  floods,  which  for  a  long  pe- 
riod emptied  themselves  imWor  fed  the  lake. 


U2  NITRE  CAVES. — NITRIC  ACID  FORMED  IN  THE  SOIL. 

not  to  be  recognized  in  sensible  quantity,  the  production  of  this  acid  is 
observed  to  proceed  with  a  constant  and  steady  pace.  Thus,  from  the 
walls  of  certain  caves  in  Ceylon  a  layer  is  yearly  pared  off,  which 
yields  an  abundant  crop  of  saltpetre  (Dr.  John  Davy).  The  celebrated 
Mammoth  cave  in  Kentucky,  situated  in  a  limestone  ridge,  yields  an 
inexhaustible  supply  of  nitrate  of  lime.  During  the  war  with  Great 
Britain,  jfifiy  men  were  constantly  employed  in  lixiviating  the  earth  of 
this  cave,  and  in  about  three  years  the  washed  earth  is  said  to  become 
as  strongly  impregnated  as  at  first.  Through  the  cave  a  strong  current 
of  air  is  continually  rushing — inwards  in  winter,  and  outwards  during 
the  summer  months.  On  the  plaster  of  old  walls,  especially  in  damp 
situations,  an  efflorescence  of  this  and  other  nitrates  is  frequently  ob- 
served over  every  part  of  Europe.  In  China,  according  to  Davis,  the 
old  plaster  of  the  houses  is  so  much  esteemed  as  a  manure,  that  parties 
will  often  purchase  it  at  the  expense  of  a  coating  of  new  plaster.  Old 
clay  walls,  and  especially  the  walls  of  clay-built  huts,  are  said  to  be 
very  fertilizing  to  the  land,  when  applied  as  a  top-dressing,  and  in  some 
parts  of  England,  where  the  land  is  poor,  the  people  are  said  to  pile  up 
the  soil  in  the  form  of  walls,  in  order  to  improve  its  quality.  These  lat- 
ter facts  seem  to  indicate  that  both  in  China  and  England  nitric  acid  is 
produced  in  similar  circumstances,  and  that  to  its  production  the  ferti- 
lizing action  of  the  old  i)laster,  and  of  the  weathered  clay,  is  alike  to  be 
attributed. 

In  the  cultivated  soil  also,  this  acid  is  formed  in  ordinary  circum- 
stances. Braconnot  found  nitrate  of  potash  in  the  botanic  garden  at 
Nancy,  in  a  portion  of  soil  in  which  poj)pies  [papaver  somniferum)  had 
grown  luxuriantly  for  ten  years  in  succession — in  larger  quantity  in  the 
soil  surrounding  the  interlaced  roots  of  an  esclepias  incarnata,  growing 
in  an  ordinary  flower-pot,  with  a  hole  in  the  bottom — as  well  as  in  moss 
earth,  in  which  a  plant  of  euphorbia  hreoni  had  been  grown  in  a  pot. — 
[Ann.  de  Chim.  et  de  Phys.,  Ixxii.,  p.  33  to  35.]  There  is  little  reason 
to  doubt,  indeed,  that  nitrates  are  to  be  found,  in  greater  or  less  quantity, 
in  all  cultivated  soils. 

I  shall  not  enter  into  a  detailed  inquiry  how  this  nitric  acid  is  formed. 
It  is  probable  that  as  in  the  atmosphere  ammonia  may  be  decomf)Osed 
and  give  rise  to  the  formation  of  nitric  acid,  so  in  the  soil  this  acid  may 
result  from  a  similar  decomposition,  proceeding  more  slowly,  but  accord- 
ing to  the  same  natural  laws.  In  warm  climates,  indeed,  it  appears 
certain  that  the  ammonia  which  is  evolved  or  formed  during  the  decay 
of  animal  and  vegetable  substances,  does  speedily,  and  to  a  great  extent, 
undergo  oxidation,*  and  thus  give  rise  to  the  greater  abundance  of  nitric 
acid  with  which  the  tropical  soils  abound. 

Thus,  in  the  economy  of  nature,  much  ammonia  is  decomposed  in  the 
soil  also,  and  hence  another  cause  for  the  constant  diminution  of  the 
quantity  of  this  compound  in  addition  to  those  already  detailed  in  the 
preceding  section. 

But,  besides  the  portion  of  this  nitric  acid,  which  owes  its  existence  to 

*  For  the  perfect  oxidation  cf  1  of  ammonia,  no  less  than  S  of  oxygen  are  required.  Thus 
lof  lof  3  of 


Ammonia.         Nitric  Acid.  Wa 
NH3  +80  =  N05  +  3H' 


m 


QUANTITY  IN  WHICH  IT  IS  REPRODUCEI .  163 

the  decomposition  of  ammonia,  much,  by  far  the  greatest  proportion  in 
all  probability,  derives  its  origin  from  tlie  union  of  the  elements  of  (Jie 
atmosphere  itself.  This  direct  anion  is  elTecled  in  the  air,  as  has  been 
already  shown,  by  the  agency  of  atmospheric  electricity;  but  it  also 
takes  place  in  the  soil  during  the  oxidation  of  the  other  elements  con- 
tained in  the  organic  matters  which  are  there  undergoing  decay.  The 
combination  of  the  elements  of  ammonia  in  such  circumstances  proceeds 
on  the  principle  that  bodies,  themselves  undergoing  oxidation,  dispose 
other  substances  in  contact  with  them  (in  this  instance  the  nitrogen  of 
the  air)  to  unite  with  oxygen  also.  The  presence  of  lime,  potash,  &:c. 
in  the  soil,  further  induces  to  this  oxidation  by  the  tendency  of  these  sub- 
stances to  combine  with  the  acid  which  is  formed  by  this  union  of  the 
elements  of  which  nitric  acid  consists. — It  is  impossible  precisely  to  es- 
timate the  quantity  of  nitric  acid  produced  in  these  various  ways,  through 
these  various  agents,  and  in  these  varied  circumstances,  or  to  balance  it 
accurately  against  the  amount  of  ammonia  continually  reproduced,  as 
we  have  seen,  in  nature,  wherever  the  necessary  conditions  present 
themselves.  But,  as  I  formerly  concluded,  that  the  amount  of  nitric 
acid  actually  existing  in  the  superficial  deposits  of  our  globe  is  greater 
than  that  of  ammonia,  so  I  think  that,  in  regard  to  the  reproduction  also 
of  these  two  compounds,  the  balance  is  in  favour  of  tjie  former. 

Since,  then,  nitric  acid  is  fitted,  by  the  solubihty  of  its  compounds,  to 
enter  into  the  circulation  of  plants  in  any  quantity — since,  when  applied 
to  them,  it  does  undoubtedly  promote,  in  a  remarkable  degree,  the  growth 
of  plants — and  since,  in  nature,  it  is  continually  reproduced  in  every 
country,  and  under  such  varied  circumstances — I  cannot  withhold  my- 
self from  the  conclusion,  that,  over  the  general  vegetation  of  the  globe, 
it  holds  with  ammonia  at  least  an  equal  sway,  and  is  appointed  to  exer- 
cise at  least  an  equal  influence  over  the  growth  of  plants,  both  in  their 
natural  and  in  their  cultivated  state. 

Still  the  influence  of  each  is  not  unvaried  by  locality  or  by  climate. 
The  extent  of  dominion  exercised  by  the  nitrates  probably  diminishes  as 
we  recede  from  the  equator,  while  that  of  ammonia  increases, — it  may 
be  in  an  equal  proportion.  The  reason  of  this  probable  variation  will 
appear  in  the  following  section. 

§  6.   Theory  of  the  action  of  nitric  acid  and  ammonia. 
These  two  compounds  act  so  far  in  common  as  to  yield  a  supply  of 
nitrogen  to  the  plants  into  which  they  enter.     They  do  so,  however,  un- 
der conditions  which  may  be  considerably  different,  and  may  be  attend- 
ed by  unlike  chemical  changes. 

I. THEORY  OF  THE  ACTION  OF  NITRIC  ACID. 

1°.  The  nitric  acid  of  the  nitrates  entering  into  the  circulation  of  the 
roots  will  ascend  to  the  leaf,  and  will  there  be  decomposed  in  the  same 
way  as  the  carbonic  and  other  similar  acids  are,  by  the  action  of  the 
sun's  rays.  It  is  only  in  the  light  of  day  that  carbonic  acid  is  decom- 
posed in  the  green  parts  of  plants — so  must  it  be,  generally,  with  the 
nitric  acid  which  ascends  to  the  leaf.  Its  oxygen  will  be  given  off*, 
while  its  nitrogen  may  be  retained  in  the  circulating  system  of  the  plant. 
The  extent  to  which  this  decomposition  will  take  place  at  each  passage 


164        THEORY  OF  THE  ACTION  OF  NITRIC  ACID  AND  OF  AMMONIA. 

of  the  sap  through  the  leaf  will  depend,  in  some  degree,  on  the  nature 
of  the  base  (whether  potash,  soda,  or  lime,)  with  which  the  acid  is  in 
combination,  but  much  more  on  the  intensity  of  the  light  to  which  the 
green  parts  of  the  plant  are  exposed,  and  on  the  temi)erature  of  the  air  in 
which  the  plant  hapj)ens  to  grow.  ^ 

2°.  It  is  still  uncertain  whether  this  acid  is  capable  of  being  decom- 
posed in  the  roots  or  stems  of  plants  where  it  is  excluded  from  the  light, 
though  it  is  very  probable  that  it  may  be  so,  especially  in  cases  where 
the  juices  naturally  contain  substances  in  which  hydrogen  is  jiresent  in 
excess,  or  where  such  compounds  make  their  way  into  the  circulation 
of  plants  from  the  manure  that  may  be  applied  to  their  roots. 

Thus  in  the  pines,  in  which  turpentine  (C40  Hg^)  naturally  abounds, 
such  a  decomposition  may  the  more  readily  occur,  inasmuch  as  it  would 
not  necessarily  imply  the  production  and  evolution  of  any  gaseous  sub- 
stance.    Thus 

1  of  Oiii  OF  Turpentine,  =  C40  H32  with  the  oxygen  of 

1  of  Nitric  Acid  (NO5)    =  O5  gives 


1  of  Resin, =  C40  H32    O5 

By  uniting  with  the  oxygen  of  the  nitric  acid,  therefore,  oil  ot  turpen- 
tine, in  such  tree*,  might  be  changed  into  resin  during  its  passage 
through  the  stem,  while  the  nitrogen,  being  set  free,  might,  at  the  mo- 
ment of  its  liberation,  unite  with  other  elements  to  form  those  parts  or 
productions  of  the  tree  into  which  this  element  enters  as  a  necessary 
constituent. 

The  above  must  be  considered  merely  as  an  illustration  of  the  kind  of 
changes  which  may  possibly  take  place  in  the  interior  of  certain  plants, 
and  in  the  absence  of  light,  when  the  nitrates  happen  to  be  present. 
Were  I  to  affirm  that  such  changes  actually  do  occur  in  the  presence 
of  nitric  acid,  the  theoretical  chemist  would  have  a  right  to  expect  that 
several  collateral  questions  should  be  discussed,  the  consideration  of 
which  would  here  be  out  of  place. 

3°.  The  nitrates  may  also  act  in  another  way,  which  does  not  involve 
the  necessity  of  the  total  decomposition  of  the  acid  they  contain.  We 
know  that  in  nature  many  substances  are  capable  of  inducing  chemical 
changes  in  other  compound  bodies,  without  themselves  undergoing  de- 
composition. Some  beautiful  illustrations  of  this  have  already  been 
given  in  a  previous  lecture,  when  treating  of  the  action  of  sulphuric  acid 
upon  starch  and  woody  fibre,  [Lecture  VI..  pp.  113,  114.]  But  the  fact 
which  most  immediately  bears  on  the  influence  of  the  nitric  acid  in  the 
living  plant,  is  that  mentioned  in  p.  126, — that  by  solution  in  this  acid 
in  the  cold,  starch  is  converted  into  a  substance  having  the  composition 
of  woody  fibre.  In  the  interior  of  the  plant  changes  of  this  kind  may 
be  produced  by  simple  contact  only,  with  the  nitric  acid,  so  that,  with- 
out being  decomposed,  it  may  be  materially  serviceable  in  promoting 
those  molecular  changes  which  are  necessary  to  the  healthy  and  rapid 
growth  of  the  plant. 

II. — THEORY    OF    THE   ACTION    OF    AMMONIA. 

1°.  Ammonia  is  capable  of  contributing  to  ihe  growth  of  the  plant, 
by  means  of  the  hydrogen,  as  well  as  of  the  nitrogen  it  contains.     We 


iS    AMMONIA    DECOMPOSED    IN    THE    DARK  ?  165 

have  seen  [notes  to  pages  136  and  138,]  that,  according  to  the  results 
of  the  best  experiments,  the  whole  of  the  oxygen  of  the  carbonic  acid 
absorbed,  is  not  given  off  by  the  leaves  of  all  plants  even  in  the  sun- 
shine,— while  in  the  dark  this  gas  is  largely  and  directly  imbibed  from 
the  air.  If  in  the  sap  of  a  plant  there  be  present  at  the  same  time  a 
quantity  of  ammonia,  the  hydrogen  of  this  ammonia  may  unite  directly 
with  the  oxygen  of  the  carbonic  acid,  forming  water  and  a  proportionate 
quantity  of  one  or  other  of  the  several  compounds  (p.  112),  which  may 
be  represented  by  carbon  and  water.     Thus 

3  of  Carbonic  Acid,  =  C3         Oq  and  the  hydrogen  of 
2  of  Ammonia  (NH3)  =        Hg 

X  of  Grape  3  of 

Sugar.  Water, 

give    .     .     .     .     C3  He  Oe  =  C3  H3  O3  -f  3HO 

so  that  where  ammonia  is  present,  and  circumstances  are  favourable, 
sugar  or  starch  may  be  formed  in  variable  quantity,  without  the  neces- 
sary evolution  of  oxygen  gas.  This  change  will  take  place  in  the  inte- 
rior of  the  leaf.  And,  if  the  direct  decomposition  of  carbonic  acid,  and 
the  evolution  of  its  oxygen  by  the  agency  of  the  sun,  take  place  at  the 
same  time — with  a  rapidity  proportioned  to  the  intensity  of  the  light, — 
this  simultaneous  production  of  sugar,  &c.,  from  the  presence  of  ammo- 
nia, must  aid  the  increase  and  growth  of  the  plant;  and  may  be  one 
main  cause  of  the  fertilizing  action  of  this  compound,  which  has  been  so 
long  and  so  generally  recognized. 

When  the  hydrogen  of  the  ammonia  is  thus  worked  up,  the  quantity 
of  ox\gen  which  escapes  from  the  leaf  must  be  less  in  proportion  ;  and 
hence  another  cause  (p.  138)  for  those  discrepancies  which  have  been 
observed  in  regard  to  the  bulk  of  oxygen  given  off,  compared  with  that 
of  the  carbonic  acid  taken  in,  by  the  leaves  of  different  plants. 

But  at  the  same  time  the  nitrogen  is  set  free.  This  nitrogen  will 
either  be  again  compounded  in  the  plant  with  other  elements,  or,  if  not 
required  for  its  healthy  growth — that  is,  if  more  largely  present  than  is 
required  by  the  plant — it  will  be  directl}'  emitted  by  the  leaves,  or  sent 
downwards  and  permitted  to  escape  by  the  root.  Hence  the  reason 
why  pure  nitrogen  is  evolved  from  the  leaves  of  some  plants  (p.  95), 
and  why  ammonia  exercises  a  beneficial  action  upon  vegetation,  in 
cases  where  all  the  nitrogen  it  contains  is  neither  retained  nor  required 
by  the  plant. 

Does  this  decomposition  necessarily  require  the  agency  of  light? 
May  it  not  take  place  in  the  absence  of  the  sun  ? 

I  will  mention  one  or  two  facts  which  seem  to  throw  light  upon  this 
point. 

1°.  Plants  grow  in  the  dark.  Though  feeble  and  blanched,  they  in- 
crease largely  in  bulk ;  they  must,  therefore,  have  the  power  of  assimi- 
lating their  food  to  a  certain  extent,  independent  of  the  sun's  rays. 

2°.  Several  species  of  Poa,  Plantago,  Trifolium  arvense,  Cheiran- 
thus,  (fee,  become  green  in  the  perpetual  darkness  of  mines  (Hum- 
boldt). 

3°.  When  a  little  hydrogen  is  mixed  with  the  air,  plants  become 
greenish,  even  in  the  dark  (Sennebier) ;  and  when  exposed  to  the  sun,  ^ 
the  green  becomes  unusually  intense  in  such  a  mixture  (Ingenhouss). 
8 


166  MODIFYING    EFFECT      OF    CLIMATE. 

The  immediate  and  visible  effect  of  an  application  of  ammonia,  or  of 
soot,  or  of  any  top-dressing  containing  ammonia,  is  to  render  the  green 
colour  much  more  intense,  and  in  the  darkest  weather.  It  is  therefore 
probable,  I  think,  that  the  hydrogen  of  the  ammonia  contributes  to  this 
immediate  effect,  and  that  the  ammonia  itself  may  be  decomposed  and 
its  elements  appropriated  to  the  nourishment  of  the  living  vegetable, 
either  by  the  unaided  vital  powers  of  the  plant,  or  in  the  presence  of  a 
feeble  light  only.  Like  water,  ammonia  is  peculiarly  liable  to  decom- 
position, not  always  of  that  perfect  kind  which, /or  the  sake  of  simplicity  ^ 
I  have  endeavoured  to  explain  in  the  present  lecture,  yet  such  as  to  ren- 
der the  elements  of  which  it  consists  available  to  the  general  nourish- 
ment of  the  plant. 

§  7.  Comparative  influence  jf  nitric  acid  and  of  ammonia  in  different 
climates. 

It  follows,  from  what  is  above  stated,  that  the  beneficial  influence  of 
ammonia  upon  vegetation  will  be  readily  perceived  in  all  climates  in 
which  plants  are  found  to  flourish.  Its  effects  will  be  greater  and  more 
rapid  where  the  heat  and  light  are  more  intense, — only  because  by  these 
agents  the  functions  of  all  life  are  stimulated. 

Not  so  with  the  nitric  acid  in  the  nitrates.  In  the  presence  of  organic 
compounds,  that  is,  in  the  sap  of  the  plant,  it  is  less  easily  decomposed 
than  ammonia.  It  requires  the  interference  of  more  powerful  agents — 
of  a  higher  temperature,  or  of  more  brilliant  light, — and  thus  its  efficacy 
upon  vegetation  will  be  more  dependent  upon  season  and  climate. 

Now,  we  have  seen  that  in  tropical  countries  the  nitrates  are  produced 
in  the  greatest  abundance,  and  there  the  high  temperature  and  the  bril- 
liant sun  should  render  them  most  useful  to  vegetation.  Such  is  well 
known  to  be  the  case,  and  it  may  be  regarded  as  one  of  those  bountiful 
adaptations  with  which  all  nature  is  full — that  in  these  warmer  regions, 
the  ammonia  produced  in  the  soil  is  first  converted  into  nitric  acid,  that 
it  may  remain  fixed,  and  that  this  acid  again  is  decomposed  by  the  same 
agents  (light  and  heat),  when  it  enters  the  living  plant,  and  is  required- 
to  minister  to  its  growth.  On  the  other  hand,  it  may  no  less  be  regarded 
as  a  wise  provision,  that  in  colder  and  more  uncertain  climates,  where 
warm  and  brilliant  summers  are  less  to  be  depended  upon,  that  com- 
pound of  nitrogen  (ammonia)  should  more  abound,  which  is  most  easily 
decomposed  in  the  living  plant,  which  is  fitted  in  comparative  darkness 
to  yield  up  its  nitrogen,  and  by  the  hydrogen  it  contains,  to  corrtpensate 
in  some  slight  degree  for  the  partial  absence  of  the  sun's  rays. 

From  these  views,  therefore,  we  should  draw  this  further  practical 
conclusion — that  in  our  climate,  ammonia  is  sure  to  promote  vegetation, 
and  in  every  season,  while  the  nitrates  will  produce  their  maodmum  e&^ecx^ 
othei  things  being  equal,  in  such  only  as  have  abundant  warmth  and 
sunshine.  Is  this  conclusion  consistent  with  observation?  Will  it 
serve  to  explain  any  of  the  apparent  failures  which  have  occasionally 
been  experienced  in  the  employment  of  the  nitrates  ? 

§  8.  Stimulating  influence  of  these  compounds. 
There  remains  one  other  point  iix  regard  to  the  effect  of  these  two 
compounds  upon  vegetation,  to  which  I  would  request  your  attention. 


STIMULATING  INFLUEI^CE  OF  NITHIC  ACID  AND  OF  AMMONIA.      167 

We  have  seen  that  the  quantity  of  nitrogen  contained  in  a  crop  raised 
by  the  aid  of  farm-yard  manure,  is  very  much  greater  than  that  which 
exists  in  the  manure  itself,  and  the  views  just  exposed  serve  to  indicate 
the  sources  from  which  the  excess  is  derived.  But  suppose  that  upon 
two  patches  of  ground,  of  equal  quality,  the  one  of  which  is  manured 
and  the  other  not,  equal  quantities  of  the  same  seed  be  sown,  it  is 
consistent  with  experience — that  the  crop  reaped  from  the  manured 
poftion  will  not  only  contain  more  nitrogen  than  that  reaped  from  the 
unmanured  portion,  but  so  much  more  as  shall  considerably  exceed  that 
contained  in  the  manure  itself.  Thus  suppose  the  crop  raised  from  the 
unmanured  land  to  contain  lOOlbs.  of  nitrogen,  and  that  the  manure  laid 
on  the  other  portion  contained  100  lbs.  also,  the  crop  which  is  reaped 
from  this  latter  portion,  in  favourable  seasons,  will  exceed,  and  probably 
very  far  exceed,  200  lbs.  Hence  the  effect  of  the  ammonia,  &;c.,  in  the 
farm-yard  manure,  is  not  merely  to  yield  its  own  nitrogen  to  the  plant, 
but  to  enable  it,  in  some  way  hitherto  unexplained,  to  draw  from  other 
sources  a  larger  portion  of  the  same  element  than  it  would  otherwise  do. 
So  also  with  the  nitrates.  If  two  equal  portions  of  the  same  grass  or 
corn-field,  in  early  spring,  be  measured  off,  and  one  of  them  be  top- 
dressed  with  nitrate  of  soda  or  with  saltpetre,  the  weight  of  nitrogen  con- 
tained in  the  crop  of  hay  or  corn  reaped  from  the  latter,  will  generally 
be  found  to  exceed  that  contained  in  the  crop  from  the  former,  by  a 
quantity  much  greater  than  that  which  was  present  in  the  nitrate  with 
which  the  land  was  dressed.*     In  addition,  therefore,  to  the  nitrogen  di- 

•  The  following  calculations  illustrate  the  statement  in  the  text:— Mr.  Gray,  of  Dilston, 
[see  Journal  of  Royal  English  Agricultural  Society,]  applied  nitrate  of  soda  to  grjiss  land  in 
the  proportion  of  112  lbs.  to  the  acre. 

The  produce  without  nitrate  amounted  to  2  tons   81  stones 
with  112  lbs.  of  nitrate  to  3  tons  146  stones 

Increase,    1  ton     65  stones,    or  3150  lbs. 
And  3150 -i-  112  =  28X  lbs.  the  increase  of  hay  from  each  pound  of  nitrate  of  soda.  *^    But  al- 
lowing this  hay  to  contain  only  one  per  cent,  of  nitrogen,  28  lbs.  will  contain  i}4  ounces  of  ni- 
trogen, which  is  nearly  double  the  quantity  actually  present  in  the  nitrate  employed. 

Again,  in  the  case  of  a  crop  of  grain — Mr.  Hyett  applied  nitrate  of  soda  to  a  field  of  wheat, 
and  compared  the  produce  with  that  from  an  equal  p  Ttion  to  which  no  top-dressing  was 
applied. 

CORN.  STRAW. 

Bush.    pks.    pts.  Cwt.    qrs.    lbs. 

Nitrated 43        2        11  31        2         3 

Without  nitrate    .    .    33       2         6  23        1       21 

Excess,         10       0         5  8       0       10 

Calculating  the  bushel  of  com  at  60  lbs.,  the  excess  of  t  ">rn  amounted  to  600  lbs.,  containing 
24>4'  per  cent,  or  147  lbs.  of  gluten  and  albumen.  The  nitrogen  in  these  substances,  when 
properly  dried,  is  from  15  to  17  per  cent.  If  we  suppose  the  gluten  not  to  have  been  quite 
dry,  and  allow  only  14  per  cent,  of  nitrogen,  147  lbs.  would  contain  20X  lbs.  of  this  element. 
But  the  nitrated  corn  contained  5  per  cent,  more  gluten  and  albumen  than  the  un-nitrated, 
which  in  33  bushels  (2000  lbs.)  gives  100  lbs.  of  gluten  in  excess,  containing  14  lbs.  of  nitrogen. 
And  8  cwt.  ofstraw(900  lbs.)  contained  one-third  of  aper  cent,  of  nitrogen,  [Boussingault,] 
or  in  all  3  lbs. 

Therefore  the  quantity  of  nitrogen  present  in  the  nitrated  crop  above  that  in  the  un-nitrated 
was  as  follows : 

1°.  In  600  lbs  of  wheat  at  24)^  percent,  of  gluten 20X  lbs.  Nitrogen. 

2°.  In20001bs.  of  wheat  at  5  percent,  of  gluten  contained  in  excess,    14     lbs.     do. 
3°.  In  900  lbs.  of  straw  at  one-third  per  cent 3     lbs.     do. 

Total  nitrogen =37^  lbs. 

But  the  nitrogen  in  1  cwt.  of  dry  nitrate  of  soda,  as  already  stated,  is  only  19  lbs.  or  little 

['  Dry  nitrate  of  soda  contains  about  J6>^  per  cent,  of  nitrogen,  being  19  lbs.  to  the  cwt., 

or  two  and  three-fifth  ounces  to  the  pound  ;  but  as  it  is  usually  applied,  it  contains  from  5  to 

10  per  cent,  of  water.  The  nitrogen,  therefore,  may  be  estimated  at  2}i  ounces  in  the  poimd.  ] 


168  HOW  THIS  INFLUENCE  IS  MANIFESTED. 

rectly  conveyed  to  the  plant  by  these  nitrates,  they  also  exercise  sortie 
other  influence,  by  which  they  enable  the  hving  vegetable  to  draw  from 
natural  sources  a  much  larger  supply  than  they  would  otherwise  be 
capable  of  doing.     What  is  this  influence,  and  how  is  it  explained? 

This  I  suppose  to  be  that  kind  of  influence  to  which  writers  on  agri- 
culture are  in  the  habit  of  alluding,  when  they  speak  of  certain  substan- 
ces stimulating  plants,  or  acting  as  stimulants  to  their  growth,  though  the 
term  itself  conveys  to  the  mind  no  distinct  idea  of  the  mode  of  opemtion 
intended  to  be  indicated — of  the  way  in  which  the  effect  is  produced. 

In  the  present  case,  this  special  action  of  ammonia  and  the  nitrates, 
and  perhaps  also  of  immediate  applications  of  manure  in  general,  ap- 
pears to  arise  from  their  affording  to  the  plant,  in  its  early  youth,  a  copi- 
ous supply  of  nitrogenous  food,  by  which  it  is  enabled  at  once  to  shoot 
out  in  a  more  healthy  and  vigorous  manner.  It  thrusts  forth  roots  in 
greater  numbers,  and  to  greater  distances,  and  is  thus  enabled  to  extract 
nourishment  from  a  greater  extent  and  depth  of  soil  than  is  ever  reached 
by  the  sickly  plant — it  expands  larger  and  more  numerous  leaves,  and 
thus  can  extract  from  the  air  more  of  every  thing  it  contains  which  is 
fitted  to  supply  the  wants  of  the  living  vegetable;  as  the  stout  and 
healthy  savage  can  hunt  and  fish  to  support  many  lives,  while  the  feeble 
or  sickly  can  scarcely  secure  sustenance  for  himself  alone.  Feed  a  wild 
animal  well  the  first  few  months  of  its  life,  and  you  may  set  it  loose  to 
prey  for  itself;  starve  it  in  its  infancy,  and  its  growth  and  strength  will 
be  stunted,  and  it  may  lead  a  wretched  and  hungry  life.      * 

Even  in  soils,  then,  and  situations,  which  are  capable  of  yielding  to 
the  plant  every  thing  it  may  retjuire  for  its  ordinary  growth,  it  is  an  im- 
portant object  of  the  art  of  husbandry  to  discover  what  substances  are 
especially  necessary  or  grateful  to  particular  crops,  and  to  apply  these 
directly^  and  in  abundance,  to  the  new-born  plant, — in  order  that  it  may 
acquire  sufficient  strength  to  be  able  to  avail  itself  in  the  greatest  degree 
of  the  stores  of  food  which  lie  within  its  reach. 

Concluding  observations  regarding  the  organic  constituents  of  plants. 

We  have  now  considered  the  most  important  of  those  questions  con- 
nected with  the  organic  elements  of  plants,  which  are  directly  interesting 
lo  the  practical  agriculturist.     We  have  seen — 

1°.  That  all  vegetable  productions  consist  of  two  parts — one  the  or- 
ganic part,  which  is  capable  of  being  burned  away  in  the  air — the  other, 
the  inorganic  part,  which  remains  behind  in  the  form  of  asli. 

2°.  That  this  organic  part  consists  of  carbon,  hydrogen,  oxygen,  and 
nitrogen  only. 

3°.  That  plants  derive  the  greater  part  of  their  carbon  from  carbonic 
acid,  of  their  hydrogen  and  oxygen  from  water,  and  of  their  nitrogen 
from  ammonia  and  nitric  acid. 

4°.  That  by  far  the  largest  portion  of  those  substances  which  form 
the  principal  mass  of  plants,  such  as  staxch  and  woody  fibre,  consists  of 
carbon  united  to  oxygen  and  hydrogen  in  the  proportions  in  which  they 

more  than  half  the  quantity,  which  in  consequence  of  the  presence  and  action  of  the  nitrate 
the  wheat  was  enabled  to  obtain  and  appropriate  above  the  quantity  appropriated  by  the 
wheat  in  the  un-nitrated  part  of  the  field. 

It  requires  no  further  proof,  therefore,  to  show  that  the  nitrate  of  soda  and  the  nitrates  must 
act  in  some  other  way  in  reference  to  vegetation,  than  by  simply  supplying  aportion  of  nitrogen. 


CONCLUDING  OBSERVATIONS.  169 

exist  in  water,— or,  in  other  words,  may  be  represented  by  carbon  and 
crater  in  various  proportions. 

5°.  That  the  food  on  which  they  live  enters  by  the  roots  and  leaves 
of  plants, — that  the  leaves,  under  the  influence  of  the  sun,  decompose 
the  carbonic  acid,  give  off  its  oxygen,  and  retain  its  carbon,— rand  that 
this  carbon,  uniting  with  the  elements  of  water  in  the  sap,  forms  those 
several  compounds  of  which  plants  chiefly  consist. 

6°.  That  the  supply  of  carbonic  acid  in  the  atmosphere  is  kept  up 
partly  by  the  respiration  of  animals,  partly  by  the  natural  decay  of  dead 
vegetable  matter,  and  partly  by  combustion.  That  ammonia  is  sup- 
plied to  plants  chiefly  by  the  natural  decay  of  animal  and  vegetable 
substances — and  nitric  acid  partly  by  the  natural  oxidation  of  dead  or- 
ganic matter,  and  partly  by  the  direct  union  of  oxygen  and  nitrogen, 
through  the  agency  of  the  atmospheric  electricity. 

7°.  That  while  both  of  these  compounds  yield  nitrogen  to  plants,  they 
each  exhibit  a  special  action  on  vegetable  life,  in  virtue  of  the  hydrogen 
and  oxygen  they  respectively  contain — and  exercise  also  a  so-called 
stimulating  power,  by  which  plants  are  induced  or  enabled  to  appro- 
priate to  themselves,  from  other  natural  sources,  a  larger  portion  of 
all  their  constituent  elements  than  they  could  otherwise  obtain  or 
assimilate. 

In  illustrating  these  several  points,  it  has  been  necessary  to  enter  oc- 
casionally into  details  which,  to  those  who  have  heard  or  may  read  only 
the  later  lectures,  may  not  be  altogether  intelligible.  I  am  not  aware, 
however,  of  having  introduced  any  thing  of  which  the  full  sense  will 
not  appear  on  a  reference  to  the  statement  by  which  it  is  preceded. 

We  are  now  to  consider  the  inorganic  constituents  of  plants, — their  na- 
ture,— the  source  (the  soil)  from  which  they  are  derived, — their  uses  in 
the  vegetable  and  animal  economy, — how  the  supply  of  these  substan- 
ces is  kept  up  in  nature, — and  how,  in  practical  husbandry,  the  want  of 
them  may  be  at  once  efficaciously  and  economically  supjplied  by  art. 
This  division  of  our  subject,  though  requiring  a  previous  knowledge  of  the 
principles  discussed  in  the  foregoing  lectures,  will  be  more  essentially 
of  a  practical  nature,  and  will  lead  us  to  consider  and  illustrate  the 
great  leading  principle  by  which  the  practical  agriculturist  ought  to  be 
guided  in  the  cultivation  and  improvement  of  his  land. 

We  shall  here  also  find  much  light  thrown  upon  our  path  by  the 
results  of  geological  inquiry  ;  and  it  is  in  the  considerations  I  am  now 
about  to  bring  before  you,  that  I  shall  have  to  direct  your  attention  most 
especially  to  the  principal  applications  of  Geology  to  Agriculture. 


LECTURES 

ON    THE 

APPLICATIONS  OF  CHEMISTRY  AND  GEOLOGY 

TO 

AGRICULTURE. 


mvt  KIF. 


ON  THE  INORGANIC  ELEMENTS  OF  PLANTS. 


LECTURE  IX. 

Inorganic  constituents  of  vegetable  substances. — Relative  proportions  of  organic  and  Inor- 
ganic matter  in  plants. — Unlike  proportions  in  unlike  species. — Kind  of  inorganic  matter 
whicii  exists  in  different  species.— Nature  and  properties  of  the  several  inorganic  elemera 
tary  bodies  found  in  plants. 

*  The  consideration  of  the  inorganic  constituents  of  plants  is  no  less 
important  to  the  art  of  culture  than  the  study  of  their  organic  elements, 
which  has  engaged  our  sole  attention  in  the  preceding  part  of  these  lec- 
tures. 

It  has  already  been  shown  that  when  vegetable  substances  are  heated 
to  redness  in  the  air,  the  whole  of  the  so-called  organic  elements — car- 
bon, hydrogen,  oxygen,  and  nitrogen — are  burned  away  and  disappear ; 
while  there  remains  behind  a  fixed  portion,  commonly  called  the  ash, 
which  does  not  burn,  and  which  in  most  cases  undergoes  no  diminution 
when  exposed  to  a  red  heat.  This  ash  constitutes  the  inorganic  portion 
of  plants. 

The  organic  or  combustible  part  of  plants  constitutes,  in  general, 
from  88  to  99  per  cent,  of  their  whole  weight,  even  after  they  are  dried. 
Hence  the  quantity  of  ash  left  by  vegetable  substances  in  the  green 
state  is  often  exceedingly  small.  It  therefore  long  appeared  to  many, 
that  the  inorganic  matter  could  be  of  no  essential  or  vital  consequence 
to  the  plant — that  being,  without  doubt,  derived  from  the  soil,  it  was 
only  accidentally  present, — and  that  it  might  or  might  not  be  contained 
in  the  juices  and  solid  parts  of  the  living  vegetable,  without  materially 
affecting  either  its  growth  or  its  luxuriance. 

Were  this  the  case,  however,  the  quantity  and  quality  of  the  ash  left  by 
the  same  plant  should  vary  with  the  soil  in  which  it  grew.  If  one  soil 
contained  much  lime,  another  much  magnesia,  and  a  third  much  potash, 
whatever  plant  was  grown  upon  these  several  soils  should  also  contain 
in  greatest  abundance  the  lime,  the  magnesia,  or  the  potash,  which 
abounded  in  each  locality — and  the  nature,  at  least,  of  the  ash,  if  not 
its  proportion,  should  be  nearly  the  same  in  every  kind  of  plant  which 
is  grown  upon  the  same  soil- 
Careful  and  repeated  experiments,  however,  have  shown— 
1°.  That  on  whatever  soil  a  plant  is  grown,  if  it  shoots  up  in  a 
healthy  manner  and  ftxirly  ripens  its  seed,  the  quantity  and  quality  of 
the  ash  is  nearly  the  same  ;  and 

2°.  That  though  grown  on  the  same  soil,  the  quantity  and  quality  of 
the  ash  left  by  no  two  species  of  plants  is  the  same — and  that  the  ash 
differs  the  more  widely  in  these  respects,  the  more  remote  the  natural 
affinities  of  the  several  plants  from  which  it  may  have  been  derived. 
Hence  there  is  no  longer  any  doubt  that  the  inorganic  constituents 
contained  in  the  ash  are  really  essential  parts  of  the  substance  of  plants, 
— that  they  cannot  live  a  healthy  life  or  perfect  all  their  parts  without 
them, — and  that  it  is  as  much  the  duty  of  the  husbandman  to  supply 
these  inorganic  substances  when  they  are  wanting  in  the  soil,  as  it  has 
always  been  considered  his  peculiar  care  to  place  within  the  reach  of 

8* 


178 


WEIGHTS  OF  ASH  LEFT  BY  DIFFERENT  SPECIES. 


the  growing  plant  those  decaying  vegetable  matters  which  are  most 
likely  to  supply  it  with  organic  food. 

For  the  full  establishment  of  this  fact,  we  are  indebted  to  Sprengel. 
Others,  as  De  Saussure,  have  published  many  important  and  very  use- 
ful analyses  of  the  inorganic  matters  left  by  plants,  but  for  the  illustra- 
tion of  the  important  practical  bearing  of  this  knowledge  of  their  inor- 
ganic constituents  on  the  ordinary  processes  of  agriculture,  we  are,  I 
believe,  in  a  great  measure  indebted  to  the  writings  and  numerous  ana- 
lytical researches  of  Sprengel. 

It  is  difficult  to  conceive  the  extent  to  which  the  admission  of  the  es- 
sential nature  and  constant  quality  of  the  inorganic  matter  contained  in 
plants,  must  necessarily  modify  our  notions  and  regulate  our  practice  in 
every  branch  of  agriculture.  It  establishes  a  clear  relation  between  the 
kind  and  quality  of  the  crop,  and  the  nature  and  chemical  composition 
of  the  soil  in  which  it  grows — it  demonstrates  what  soils  ought  to  con- 
tain, and,  therefore,  how  they  are  to  be  improved — it  explains  the  effect 
of  some  manures  in  permanently  fertilizing,  and  of  some  crops  in  per- 
manently impoverishing  the  soil — it  illustrates  the  action  of  mineral 
substances  upon  the  plant,  and  shows  how  it  may  be,  and  really  is,  in  a 
certain  measure,  fed  by  the  dead  earth  : — over  nearly  all  the  operations 
of  agriculture,  indeed,  it  throws  a  new  and  unexpected  light.  Of  this,  I 
am  confident,  you  will  be  fully  satisfied  when  I  shall  have  discussed  the 
various  topics  I  am  to  bring  before  you  in  the  present  part  of  my  lectures. 

§  1.  Of  the  relative  proportions  of  inorganic  matter  in  different 
vegetable  substances. 
As  above  stated,  the  inorganic  matter  contained  in  different  vegetable 
productions  varies  from  I  to  12  per  cent,  of  their  whole  weight.  The 
ifollowing  table  exhibits  the  weight  of  ash  left  by  100  lbs.  of  the  more 
commonly  cultivated  plants — according  to  the  analyses  of  Sprengel 
[Ckefnie,  vol.  ii.,  passim] : — 

Undried.      Dried  in  air.  * 

Potato 0-83  lbs.     2-65  lbs. 

Turnip 0-63  7-05 

Do.     white    .     ...     0-8    J. 

Carrot 0-66  5-09 

Parsnip 0-82  4-34 

Leaf  of  Potato      .     .  4-79 

Turnip    ...     1-8  2-91 

do.   white      .     2-18  J. 

•  Carrot      .     .     .     1-98  10-42 

Parsnip  .     .     .     3-00  15-76 

Cabbage       .     .     0-53  7-55 


Grain  of  Per  ct, 
Wheat      .     .  1-18  lbs. 
Rye      .     .     .  1-04 
Barley       .     .  2-35 
Do.  dried  at  212, 2-52  J 
Oats     .     .     .  2-58 
Field  Beans  .  2-14 
Peas     .  2-46 


Dry  straw  of 
Wheat 
Oats  . 
Barley . 
Rye  . 
Beans  . 
Peas     . 


Perct. 
3-51  lbs. 
5-74 
5-24 
2-79 
3-12 
4-97 


Lucerne 
Red  Clover 
White  Clover 
Rye  Grass  . 


Green. 
2-58  lbs. 
1-57  ' 
1-74 
1-69 


In  hay. 
9-55  lbs 
7-48 
9-13 
5-3 


Of  the  substances  in  this  column  the  potato  lost  by  drying  in  the  air  69  perct.  of  water, 
the  turnip  91,  the  carrot  87,  the  turnip  leaf  86,  the  carrot  leaf,  the  parenip,  and  the  parsnip 
leaf,  each  81,  and  the  cabbage  leaf  93  per  cent. 


IT  VARIES   WITH    THE    SPECIES    OF   PLANTS.  179 

In  the  parts  of  trees  dried  in  the  air  there  are  found  of  inorganic 
matter — 


Wood. 

Leavea. 

Wood. 

Leavea. 

In  the  Elm 

.     1-88 

11-8 

In  the  Oak      .     .     0-21 

4-5 

Willow 

.     0-45 

8-23 

Birch    .     .     0-34 

6-0 

Poplar  . 

.     1-97 

9-22 

Pitch  pine      0-25 

3-15 

Beech    . 

.     0-36 

6-69 

Comm.  furze  0*82 

3-1  J. 

In  looking  at  the  preceding  tables,  you  cannot  fail  to  be  struck  with 
one  or  two  points,  which  they  place  in  a  very  clear  light. 

1°.  That  the  quantity  of  inorganic  matter  contained  in  the  same 
weight  of  the  different  crops  we  raise,  or  of  the  different  kinds  of  vegeta- 
ble food  we  eat,  or  with  which  our  cattle  are  fed,  is  very  unlike.  Thus 
100  lbs.  of  barley,  or  oats,  or  peas,  contain  twice  as  much  inorganic 
(earthy  and  saline  matter,  that  is,)  as  an  equal  weight  of  wheat  or  rye — 
and  the  same  is  the  case  with  lucerne  and  white  clover  hays,  compared 
with  the  hay  of  rye  grass. 

2°.  The  quantity  contained  in  different  parts  of  the  same  plant  is 
equally  unlike.  Thus  100  lbs.  of  the  grain  of  wheat  leave  only  ]|lbs. 
of  ash,  while  100  lbs.  of  wheat  straw  leave  3^  lbs.  So  the  dry  bulb  of 
the  turnip  gives  only  7  per  cent.,  while  the  dry  leaf  leaves  13  per  cent, 
of  ash  when  it  is  burned.  The  dry  leaves  of  the  parsnip  also  contain 
nearly  16  per  cent.,  though  in  its  root,  when  sliced  and  dried  in  the  air, 
there  are  only  4^  per  cent,  of  inorganic  matter. 

In  trees  the  same  fact  is  observed.  The  wood  of  the  elm  contains 
less  than  2  per  cent.,  while  its  leaves  contain  nearly  12  per  cent. ; — the 
wood  of  the  oak  leaves  only  ^ih  of  a  per  cent.,  while  from  Its  leaves  4| 
per  cent,  or  22  times  as  much  are  obtained.  The  leaves  of  the  willow 
and  of  the  beech  also  contain  about  twenty  times  as  much  as  the  wood 
of  these  trees  does,  when  it  has  been  dfled  under  the  same  conditions. 

These  differences  cannot  be  the  result  of  accident.  They  are  con- 
stant on  every  soil,  and  in  every  climate ;  they  must,  therefore,  have 
their  origin  in  some  natural  law.  Plants  of  different  species  must 
draw  from  the  soil  that  proportion  of  inorganic  matter  which  is  adapted 
to  the  constitution,  and  is  fitted  to  supply  the  wants  of  each ; — while  of 
that  which  has  been  admitted  by  the  roots  into  the  general  circulation 
of  the  plant,  so  much  must  proceed  to  and  be  appropriated  by  each  part 
as  is  suited  to  the  functions  it  is  destined  to  discharge.  And  as  from 
the  same  soil  different  plants  select  different  quantities  of  saline  and 
earthy  matter,  so  from  the  same  common  sap  do  the  bark,  the  leaf,  the 
wood,  and  the  seed,  select  and  retain  that  proportion  which  the  healthy 
growth  and  developement  of  each  requires.  It  is  with  the  inorganic,  as 
with  the  organic  food  of  j)lants.  Some  draw  more  from  the  soil,  some 
less,  and  of  that  which  circulates  in  the  sap,  only  a  small  portion  is  ex- 
pended in  the  production  of  the  flower,  though  much  is  employed  in 
forming  the  stem  and  the  leaves.  On  the  subject  of  the  present  section, 
I  shall  add  two  other  observations. 

1°.  From  the  constant  presence  of  this  inorganic  matter  in  plants,  and 
from  its  being  always  found  in  nearly  the  same  proportion  in  the  same 
species  of  plants, — a  doubt  can  hardly  remain  that  it  is  an  essential  pan 
of  their  substance,  and  that  they  cannot  live  and  thrive  without  it.  But 
that  it  really  is  so,  is  placed  beyond  a  doubt,  by  the  further  experimen 


180  QUALITY  OF  THE  ASH  FROM  DIFFERENT  PLANTS. 

tal  fact,  that  if  a  healthy  young  plant  be  placed  in  circumstances  where 
it  cannot  obtain  this  inorganic  matter,  it  droops,  pines,  and  dies. 

2°.  But  if  it  be  really  essential  to  their  growth,  this  inorganic  matter 
must  he  considered  as  part  of  the  food  of  plants  ;  and  we  may  as  cor- 
rectly speak  of  feeding  or  supplying  food  to  plants,  when  we  add  earthy 
and  mineral  substances  to  the  soil,  as  when  we  mix  with  it  a  supply  of 
rich  compost,  or  of  well  fermented  farm-yard  manure. 

I  introduce  this  observation  for  the  purpose  of  correcting  an  erroneous 
impression  entertained  by  many  practical  men  in  regard  to  the  way  in 
which  mineral  substances  act  when  applied  to  the  soil.  By  the  term 
manure  they  generally  designate  such  substances  as  they  believe  to  be 
capable  o^  feeding  tfie  plant,  and  hence  reject  minerat  substances,  such 
as  gypsum,  nitrate  of  soda,  and  generally  lime,  from  the  list  of  manures 
properly  so  called.  And  as  the  influence  of  these  substances  on  vegeta- 
tion is  undisputed,  they  are  not  unfrequently  considered  as  stimulants  only. 

Yet  if,  as  I  believe,  the  use  of  a  wrong  term  is  often  connected 
with  the  prevalence  of  a  wrong  opinion,  and  may  lead  to  grave  errors 
in  practice, — I  may  be  permitted  to  press  upon  your  consideration 
the  fact  above  stated — I  may  ahnost  say  demonstrated — that  plants 
do  feed  upon  dead  unorganized  mineral  matter,  and  that  you  are,  there- 
fore, really  manuring  your  soil,  and  permanently  improving  it,  when 
you  add  to  it  such  substances  of  a  proper  kind. 

§  2.   Of  the  kind  of  inorganic  matter  found  in  plants. 

I  have  said  above,  of  a  proper  kind — for  it  is  not  a  matter  of  indiffer- 
ence to  a  plant,  what  kind  of  earthy  or  saline  matter  it  takes  in  by  its 
roots.  Each  species  of  plant,  we  have  seen,  withdraws  from  the  soil  a 
quantity  of  inorganic  matter,  whi(j^  is  peculiar  to  itself,  and  which,  as  a 
whole,  is  nearly  constant. 

So  also  each  species,  in  selecting  for  itself  a  nearly  constant  weight 
of  inorganic  matter,  while  it  chooses  generally  the  same  kind  of  saline 
and  earthy  ingredients  as  other  plants  do,  to  make  up  this  weight,  yet 
picks  them  out  in  proportions  peculiar  to  itself  Thus  for  example,  lime 
is  present  in  the  ash  of  nearly  all  plants,  but  while  100  lbs.  of  the  ash 
of  wheat  contain  8  pounds  of  Hrae,  the  same  weight  of  the  ash  of  barley 
contains  only  4i  lbs.  So  also  potash  is  contained  iu  the  ash  of  most 
plants  grown  for  food,  but  in  the  ash  of  the  turnip,  there  are  37i  per 
cent,  of  potash,  while  in  that  of  wheat  there  are  only  19  per  cent.  Again, 
in  different  parts  of  the  same  plant,  a  like  difference  prevails.  The  ash 
of  the  turnip  bulb  contains  16i  per  cent,  of  soda, — that  of  the  leaf,  Httle 
more  than  12  per  cent.  On  the  other  hand,  the  lime  in  that  from  the 
bulb  constitutes  less  than  12  per  <:ent.  of  its  weigb%  while  in  that  of  the 
leaf  it  amounts  to  upwards  of  34  per  cent. 

These  relative  proportions  among  the  different  kiuds  of  inorganic  mat- 
ter contained  in  the  ash  of  plants — like  the  whole  weight  itself  of  the 
ash — is  nearly  constant  in  the  same  species,  and  in  the  same  part  of  a 
plant,  when  it  is  grown  in  a  propitious  soil.  It  is  not,  therefore,  as  I  have 
already  said,  a  matter  of  indiilerence  to  the  living  vegetable,  whether 
it  meets  with  this  or  with  that  kind  of  inorganic  matter  in  the  land  on 
which  it  grows — whether  its  roofs  are  supplied  with  lime,  or  with  potash, 
cr  ^ith  soda.     The  soil  must  contain  all  these  substances^  and  in  such 


THE  SOIL  MUST  CONTAIN  WHAT  THE  PLANT  REQUIRES.  181 

quantity  as  easily  to  yield  to  the  crop  so  much  of  each  as  the  hind  of  plant 
specially  requires.  And  if  one  of  these  necessary  inorganic  forms  of 
matter  be  rare  or  wholly  absent,  the  crop  will  as  certainly  prove  sickly 
or  entirely  fail,  as  if  the  organic  food  supplied  by  the  vegetable  matter 
of  the  soil  were  wholly  withdrawn.  It  is,  therefore,  as  much  the  end  of 
an  enhghtened  agricultural  practice  to  provide  for  the  various  require- 
ments of  each  crop  in  regard  to  inorganic  food,  as  it  is  to  endeavour  to 
enrich  the  land  with  purely  vegetable  substances. 

Since,  also,  as  above  shown,  not  only  the  relative  quantity  of  inor- 
ganic matter,  but  its  kind  or  quality,  likewise,  is  different  in  different 
plants, — it  may  be,  that  a  soil  on  which  one  crop  cannot  attain  to  ma- 
turity may  yet  surely  and  completely  ripen  another — a  fact  which  is 
proved  by  every-day  experience.  The  soil,  which  is  unable  to  supply 
with  sufficient  speed  all  the  lime  or  the  potash  required  for  one  crop, 
may  yet  easily  meet  the  demands  of  another,  and  afford  an  ample  re- 
turn to  the  husbandman  when  the  time  of  harvest  comes.* 

On  the  other  hand,  this  consoling,  at  once,  and  stimulating  reflection 
must  arise  in  the  mind  of  the  practical  agriculturist  from  the  considera- 
tion of  the  above  facts — that  if  the  soil  contain  all  the  inorganic  substan- 
ces required  by  plants,  and  in  sufficient  quantity,  it  will  grow,  if  rightly 
tilled,  any  crop  which  is  suited  to  the  climate, — or  conversely  to  make 
it  capable  of  growing  any  crop,  he  has  only — along  with  his  usual  sup- 
plies of  animal  or  vegetable  matter — to  add  in  proper  quantity  these  in- 
organic substances  also.         • 

Here  a  crowd  of  questions  cannot  fail  to  start  up  in  your  minds.  You 
will  ask,  for  example, 

1°.  What  are  the  several  inorganic  substances  usually  present  in 
cultivated  plants,  and  what  their  respective  proportions  ? 

2°.  Which  of  them  are  most  generally  present  in  the  soil? 

3°.  In  what  form  can  those  which  are  less  abundant  be  added  most 
easily,  most  advantageously,  and  most  economically  ? 

We  shall  consider  in  succession  these,  and  along  with  them  other 

•  On  the  same  principle,  also,  some  of  the  interesting  facts  connected  with  the  grafting  of 
trees  are  susceptible  of  a  satisfactory  explanation. 

The  root  of  a  tree  selects  from  the  soil  the  kind  and  gwaZiVi/ of  inorganic  matter  which 
are  required  for  the  healthy  maturity  of  its  own  parts.  Any  other  tree  may  be  grafted  on  it, 
which  in  its  natural  state  requires  the  same  kind  of  inorganic  matters  in  nearly  the  same 
proportion.  This  is  the  case  generally  with  varieties  of  the  same  species— more  rarely 
with  trees  or  plants  of  different  species— and  least  frequently  with  such  as  belong  to  differ- 
ent genera.  The  lemon  may  be  grafted  on  the  orange,  because  the  sap  of  the  latter  con- 
tains all  the  eartliy  and  saline  substances  which  the  former  requires,  and  can  supply  tliem 
in  sufficient  quantity  to  the  engrafted  twig.  But  the  fig  or  the  grape  would  not  flourish  or 
ripen  fruit  on  the  same  stock — because  these  fruits  require  other  substances  than  the  root  of 
the  orange  cares  to  extract  from  the  soil,  or  in  greater  quantity  than  the  sap  of  the  orange 
can  supply  them. 

It  is  not  for  want  of  organic  food,  for  of  this  the  sap  of  nearly  all  plants  i<3  full — and  we 
have  seen  in  our  previous  lectures,  how  the  sugar  of  the  fig,  the  tartaric  acid  of  the  grape, 
and  the  citric  acid  of  the  lemon,  may  all  be  produced  by  natural  processes  from  the  same 
common  organic  food.  When  we  plant  a  tree  or  sow  a  crop  on  a  soil  which  does  not  con- 
tain all  that  the  tree  or  crop  requires,  the  tree  must  slowly  perish, — the  crop  cannot  yield  a 
profitable  return.  So  it  is  in  grafting.  l\e  sap  of  the  stock  must  contain  all  that  t/ie  engrafted 
bud  or  shoot  requires  in  every  stage  of  its  growth.  Or  to  recur  to  our  former  illustration — 
if  the  potash  or  lime  required  by  the  grape  be  not  taken  up  and  in  sulTicient  quantity  by 
the  root  of  the  orange,  it  will  be  in  vain  to  graft  the  former  upon  the  latter  with  the  liope  of 
Us  coming  to  maturity  or  yielding  perfect  fruit. 

This  principle  may  also  serve  to  explain  many  other  curious  and  hitherto  obscure  cir- 
cumstances connected  with  the  practice  of  the  gardener. 


182 


ELEMENTARY  SUBSTANCES  FORMED  IN  THE  ASH. 


subsidiary  questions,  which  will  hereafter  present  themselves  to  our 
notice. 

§  3.  Of  the  several  elementary  bodies  usually  met  ivith  in  the  ash  of  plants 
What  is  understood  by  the  term  element  or  elementary  body  among 
chemists  has  already  been  explained  (Lect.  I.,  p.  22),  as  well  as  the 
number  and  names  of  those  elements  with  which  we  are  at  present  ac- 
quainted. 

Of  »hese  elementary  bodies  we  have  seen  that  the  organic  part  of  plants 
contains  rarely  more  than  four,  namely,  carbon,  hydrogen,  oxygen,  and 
nitrogen,  in  various  proportions.  In  the  inorganic  part  there  occur  nine 
or  ten  others,  generally  in  combination,  either  with  oxygen  or  with  one 
another. 

The  names  of  these  inorganic  elements  are  as  follow  : 


Name. 

Ia( 

combination  with 

Forming 

Chlorine  . 

Metals 

Chlorides. 

Iodine    .     . 

do. 

Iodides. 

Sulphur     . 

do. 

SULPHURETS. 

Hydrogen 

Sulphuretted  Hydrogen.* 

Oxygen 

SuLPHURfc  Acid. 

Phosphorus 

do. 

Phosphoric  Acid. 

Potassium  . 

do. 

Potash. 

Chlorine 

Chloride  of  Potassium. 

Sodium  .     . 

Oxygen 

Soda^ 

Chlorine 

Chloride  of  Sodium  or  > 
Common  Salt.             ^ 

Calcium     . 

do. 

Chloride  of  Calcium. 

Oxygen 

Lime. 

Magnesium 

Magnesia. 

Aluminium 

do! 

Alumina. 

Silicon 

do. 

Silica. 

Iron  and 

\ 

do. 

J  Oxides. 

Manganese 

Sulphur 

(  Sulpuurets. 

Other  elementary  bodies,  chiefly  metallic,  occur  in  some  plants — occa- 
sionally, and  in  very  small  quantity, — but,  so  far  as  is  yet  known,  they  do 
not  appear  to  be  either  necessary  to  their  growth,  or  to  exercise  any  ma- 
terial influence  on  the  general  vegetation  of  the  globe. 

Of  all  the  above  elementary  bodies  it  may  be  said,  generally, 

1°.  That  with  the  exception  of  sulphur,f  they  are  not  known  to  exist 
or  to  be  evolved,  in  any  (juantity,  anywhere  on  the  surface  of  the  globe, 
in  their  simple,  elementary,  or  uncombined  state;  and  that,  therefore, 
in  this  state  they  in  no  way  affect  the  progress  of  vegetable  growth,  or 
require  to  occupy  the  attention  of  the  practical  agriculturist. 

2°.  They  all,  however,  exist  in  nature  more  or  less  abundantly  in  a 
state  of  combination  with  other  substances,  and  chiefly  with  oxygen,  [for 
an  explanation  of  the  meaning  and  of  the  laws  of  chemical  combination^ 
see  Lecture  II.,  p.  32] — but  in  no  state  of  combination  are  they  known 
to  be  generally  diffused  through  the  atmosphere  of  the  globe,  so  as  to  be 

*  Called  also  Hydro-sulphuric  Acid. 

»  Given  off  in  vapour  from  active  volcanoes,  and  from  rents  and  fissures  m  ancient  volcanic 
countries. 


CHLORIDE  AND  MURIATIC  ACID.  183 

capable  of  entering  plants  by  iheir  leaves  or  otber  superior  parts.  They 
must  all,  therefore,  enter  by  the  roots  of  plants, — must  consequently  ex- 
ist in  the  land, — and  must  all  be  necessary  constituents  of  that  soil  in 
which  the  plants  that  contain  them  grow. 

It  will  not  be  necessary,  therefore,  to  consider  so  much  the  relative 
proportions  in  which  these  elementary  bodies  themselves  exist  in  plants, 
as  that  of  the  several  chemical  compounds  which  they  form  with  oxy- 
gen, or  with  one  another — in  which  states  of  combination  they  exist  in 
the  soil,  and  are  found  in  the  circulation  and  substance  of  the  plant.  As 
a  preliminary  to  this  inquiry,  however,  it  will  be  proper  to  lay  before 
you  a  brief  outline  of  the  nature  and  properties  of  these  compound 
bodies  themselves — and  of  the  direct  injfluence  they  have  been  found  to 
exercise  upon  vegetable  life. 

§  4.   Of  those  compounds  of  the  inorganic  elements  which  enter  directly  into 
the  circulation,  or  exist  in  the  substance  and  ash  of  plants. 

I  CHLORINE  AND  MURIATIC  ACID. 

Chlorine. — If  a  mixture  of  common  salt  and  black  oxide  of  manga- 
nese [sold  by  tliis  name  in  the  shops]  be  put  into  a  flask  or  bottle  of 
colourless  glass,  and  sulphuric  acid  (oil  of  vitriol)  be  poured  upon  it,  a 
gas  of  a  greenish-yellow  colour  will  be  given  ofT,  and  will  gradually  fill 
the  bottle.     This  gas  is  distinguished  by  the  name  o^  chlorine. 

It  is  readily  distinguislied  from  all  other  substances  by  its  greenish- 
yellow  colour,  and  its  pungent  disagreeable  smell.  It  extinguishes  a 
lighted  taper,  but  phosphorus,  gold  leaf,  metallic  potassium  and  sodium, 
and  many  other  metals,  take  fire  in  it  and  burn  of  their  own  accord.  It 
is  nearly  4i  times  heavier  than  common  air,  and  therefore  may  be 
readily  poured  from  one  vessel  to  another.  Water  absorbs  twice  its 
own  bulk  of  the  gas,  acquiring  its  colour,  smell,  and  disagreeable  astrin- 
gent taste. 

Animals  cannot  breathe  it  without  suffocation — and,  when  unmixed 
with  air,  it  speedily  kills  all  living  vegetables.  The  solution  of  chlorine 
in  water  was  found  by  Davy  to  promote  the  germination  of  seeds. 

It  does  not  exist,  and  is  rarely  evolved,  [see  Lecture  V.,  p.  94,]  in 
nature  in  a  free  or  uncombined  slate,  and  therefore  is  not  known  to  ex- 
ercise any  direct  action  upon  the'  general  vegetation  of  the  globe.  It 
exists  largely,  however,  in  common  salt  (chloride  of  sodium),  every  100 
lbs.  of  this  substance  containing  upwards  of  60  lbs.  of  chlorine.  Indi- 
rectly, therefore,  it  may  be  supposed  to  influence,  in  some  degree,  the 
grovvth  of  plants,  where  common  salt  exists  naturally  in  the  soil,  or  is 
artificially  applied  in  any  form  to  the  land. 

Muriatic  acid,  the  spirit  of  salt  of  the  shops,  consists  of  chlorine  in 
combination  with  hydrogen.  It  is  a  gas  at  the  ordinary  temperature  of 
the  atmosphere,  but  water  absorbs  between  400  and  500  times  its  bulk 
of  it,  and  the  acid  of  the  shops  is  such  a  solution  in  water,  of  greater  or 
less  strength. 

Muriatic  acid  has  an  exceedingly  sour  taste,  corrodes  the  skin,  and  in 
its  undiluted  state  is  poisonous  both  to  animals  and  plants.  It  dissolves 
common  pearl  ash,  soda,  magnesia,  and  limestone,  with  effervescence  ; 
and  readily  dissolves  also,  and  combines  with,  many  earthy  substances 
which  are  contained  in  the  soil. 


184  IODINE,    SULPHUR,    AND    SULPHUROUS    ACID. 

Wlicn  apjilied  lo  living  vegetables  in  the  state  of  an  exceedingly  di 
lute  solution  in  water,  it  has  been  supposed  upon  some  soils,  and  in 
some  circumstances,  to  be  favourable  to  vegetation.  Long  experience, 
however,  on  the  banks  of  the  Tyne,  and  elsewhere,  in  the  neighbour- 
hood of  the  so-called  alkali*  works,  has  proved  that  in  the  state  of  va- 
pour its  repeated  application,  even  when  diluted  with  much  air,  is  in 
many  cases  fatal  to  vegetable  life. 

Poured  in  a  liquid  stale  upon  fallcnv  land,  or*  land  preparing  for  a 
crop,  it  may  assist  the  growth  of  the  future  grain,  by  previously  forming, 
with  the  ingredients  of  the  soil,  some  of  those  compounds  which  have 
been  occasionally  applied  as  manures,  and  which  we  shall  consider 
hereafter. 

Chlorine  is  represented  by  CI,  and  muriatic  acid  byHCl. 

II. — IODINE. 

Iodine  is  a  solid  substance  of  a  lead  grey  colour,  which,  when  healed, 
is  converted  into  a  beautiful  violet  vapour.  It  exists  in  combination 
chiefly  with  sodium,  as  Iodide  of  Sodium,  in  sea  water  and  in  marine 
plants  ;  but  it  has  not  hitherto  been  detected  in  any  of  the  crops  usually 
raised  for  food. 

Like  chlorine,  it  is  poisonous  both  to  animals  and  plants;  and  was 
found  by  Davy  to  assist  and  hasten  germination.  It  may  possibly  exert 
some  hitherto  unobserved  influence  upon  vegetation,  when  it  is  applied 
to  the  soil  in  districts  where  sea-ware  is  largely  collected  and  employed 
as  a  manure. 

Iodine  is  slightly  soluble  in  whaler,  and  this  solution  has  been  men- 
tioned in  a  previous  lecture  (VI.,  p.  107),  as  affording  a  ready  means 
of  detecting  starch  by  the  beautiful  blue  colour  it  gives  with  this  sub- 
stance. 

III. — SULPHUR,    SULPHUROUS    AND    SULPHURIC    ACIDS,    AND    SUL- 
PHURETTED   HYDROGEN. 

1°.  Suljjlmr  is  a  substance  too  well  known  to  require  any  detailed 
description.  In  an  uncombined  state  it  occurs  cbiefly  in  volcanic  coun- 
tries, but  it  may  sometimes  be  observed  in  (he  form  of  a  thin  pellicle  on 
the  surface  of  stagnant  waters — or  of  mineral  springs,  which  are  natu- 
rally charged  with  sulphurous  vapours.  In  this  slate  it  is  not  known 
materially  to  influence  the  natural  vegetation  in  any  part  of  the  globe. 
It  has,  however,  been  employed  with  some  advantage  in  Germany  as  a 
top-dressing  for  clover  and  other  crops  to  which  gypsum  in  that  country 
is  generally  applied.  The  mode  in  which  it  may  be  supposed  lo  act 
will  be  considered  hereafter.* 

2°.  Sidphurous  acid. — When  sulphur  is  burned  in  the  air  it  gives  off 
a  gaseous  substance  in  the  formof  white  fumes  of  a  well  known  intensely 
suffocating  odour.     These  fumes  consist  of  a  combination  of  the  sulphur 

*  In  these  works  carbonate  of  soda  (the  common  soda  of  the  shops)  and  sulphate  of  soda 
(glauber  salt)  are  manufactured  from  common  salt,  and  in  one  of  the  processes  immense 
quantities  of  muriatic  acid  are  given  ofTfrom  the  furnace,  and  used  to  escape  into  the  air  by 
the  chimney. 

1  The  refuse  heaps  of  the  alkali  works  on  the  Tyne  contain  muoli  sulphur  and  more  gyp- 
sum—but the  farmers,  perhaps,  naturally  enough,  consider  that  if  the  works  themselves  do 
harm  to  their  crops,  the  refuse  of  the  works  cannot  do  them  much  good.  There  are  thou- 
sands of  tons  of  this  mixture  which  may  be  had  for  the  leading  away. 


SULPHURIC  ACID,  AND  SULPHURETTKD  HYDROGEN.  185 

wliich  disappears  with  the  oxygen  of  the  atmos[)here,  and  are  known 
to  chemists  by  the  name  of  sul[)hurous  acid.  This  compound  is  des- 
tructive to  animal  and  vegetable  Hfe,  but  as  it  is  not  known  to  be  directly 
formed  to  any  extent  in  nature,  except  in  the  neighbourhood  of  active 
volcanoes,  it  probably  exercises  no  extensive  influence  on  the  general 
vegetation  of  the  globe. 

This  gas  possesses  the  curious  property  of  bleaching  many  animal  and 
vegetable  substances.  Wool  and  straw  for  plaiting  are  bleached  to  an 
almost  perfect  whiteness — when  they  are  suspended  in  a  vessel  or  room 
into  which  a  plate  of  burning  sulphur  has  been  introduced.  Gardeners 
sometimes  amuse  themselves  also  in  bleaching  roses  and  other  red 
flowers,  by  holding  them  over  a  burning  sulphur  match.  Some  shades  of 
red  resist  this  action  more  or  less  perfectly,  and  the  colour  of  the  bleached 
flowers  may  often  be  restored — by  dipping  them  in  a  dilute  solution  of 
carbonate  of  soda,  or  by  holding  them  over  a  bottle  of  hartshorn  (liquid 
ammonia). 

3.  Sulphuric  acid. — This  is  the  name  by  which  chemists  distinguish 
tlie  oil  of  vitriol  of  the  shops.  It  is  also  a  compound  of  suhihur  and  oxy- 
gen only,  and  is  formed  by  causing  the  fumes  of  sulphur  to  pass  into 
large  leaden  chambers  along  with  certain  other  substances,  from  which 
they  can  obtain  a  further  supply  of  oxygen. 

It  is  met  with  in  the  shops  in  the  form  of  an  exceedingly  sour  corrosive 
liquid,  which  decomposes,  chars,  and  destroys  all  animal  and  vegetable 
substances,  and,  except  when  very  diluted,  is  destructive  to  life  in  every 
form.  It  is  rarely  met  with  in  nature,  in  an  uncombined  state, — though 
according  to  Boussingault,  some  of  the  streams  which  issue  from  the 
volcanic  regions  of  the  Andes  are  rendered  sour  by  the  presence  of  a 
quantity  of  this  acid. 

It  combines  with  potash,  soda,  lime,  magnesia,  &c.,  and  forms  sul- 
phates  which  exist  abundantly  in  nature,  and  have  often  been  benefi- 
cially and  profitably  employed  as  manures. 

Where  the  soil  contains  lime  or  magnesia,  the  acid  may  often  be  ap- 
plied directly  to  the  land,  in  a  very  dilute  state,  with  advantage  to  clover 
and  other  similar  crops.  It  has  in  France,  near  Lyons,  been  observed 
to  act  favourably  when  used  in  this  way,  while  in  Germany  it  has  been 
found  better  to  apply  it  to  the  ploughed  land,  pre-vious  to  sowing.  A  few 
experiments  have  also  been  made  in  this  country  with  partial  success. 
It  is  deserving,  however,  of  a  further  trial,  and  in  more  varied  circum- 
stances. 

4°.  Sulphuretted  Hydrogen. — This  gaseous  compound  of  sulphur 
with  hydrogen,  is  almost  universally  known  by  its  unpleasant  smell. 
It  imparts  their  peculiar  taste  and  odour  to  sulphurous  springs,  such  as 
that  of  Harrogate,  and  gives  their  disagreeable  smell  to  rotten  eggs.  It 
is  often  produced  in  marshy  and  stagnant  places,*  and  fish  ponds,  where 

*  Thia  appears  to  be  especially  the  case  on  the  coasts  of  Western  Africa,  where  the 
hot  sun  is  continually  beating  on  sea  water,  often  shallow,  frequently  stagnant,  and  always 
laden  with  organic  matter,  either  animal  or  vegetable  (Daniell).  Near  the  mouth  of  the 
Tees  in  this  county,  where  a  shallow,  dark  blue,  muddy,  samphire-bearing  tract  stretches 
for  several  miles  inland  from  Seaton  Snook,  the  presence  of  sulphuretted  hydrogen  may  be 
perceived  by  the  smell,  when  on  a  hot  summer's  day  a  gentle  air  skims  along  the  edge  of 
the  Slake.  The  favourable  conditions  are,  a  burning  sun,  a  very  gentle  air,  and  such  a  con- 
dition of  the  sea— tJiat  those  parts  and  pools  which  are  only  reached  by  the  ti)ring  tides 
shall  have  been  several  days  uncovered. 


186  PHOSPHORUS  and  phosphoric  acid. 

vegetable  matter  is  undergoing  denaj'  in  the  presence  of  water  contain- 
ing gypsum,  or  other  sulphates  ;  and  it  may  occasionally  be  detected  by 
the  sense  of  smell  among  the  roots  of  the  sod,  in  old  pasture  land,  lo 
which  a  top-dressing  is  occasionally  given. 

As  in  the  egg,  so  also  in  other  decaying  animal  substances,  especially 
when  the  air  is  in  some  measure  excluded,  this  gas  is  formed.  In  pu- 
trified  cow's  urine,  and  in  night  soil,  it  is  present  in  considerable  quan- 
tity. 

Sulphuretted  hydrogen  is  exceedingly  noxious  to  animal  and  vegeta- 
ble life,  when  diffused  in  any  considerable  quantity  through  the  air  by 
which  they  are  surrounded.  The  luxuriance  of  the  vegetation  in  the 
neighbourhood  of  sulphurous  springs,  however,  has  given  reason  to  be- 
lieve that  water  impregnated  with  this  gas,  may  act  in  a  beneficial 
manner  when  it  is  placed  within  reach  of  the  roots  of  plants.  It  seems 
also  to  be  ascertained  that  natural  or  artificial  waters  which  have  a  sul- 
phurous taste,  give  birth  to  a  peculiarly  luxuriant  vegetation,  when  they 
are  employed  in  the  irrigation  of  meadows. — [Sprengel,  Chemie^  I., 
p.  355.] 

The  relative  constitution  of  these  three  compounds  of  sulphur  is  thus 
represented : — 

Is  repre-  Or  1  of  Sulphur 

One  equivalent  of  Weighing      seated  by  and 

Sulphur 16  S 

Sulphurous  Acid      .     .  32  SOg  2  of  Oxygen 

Sulphuric  Acid   ...  40  SO3  3  of  Oxygen 

Sulphuretted  Hydrogen  17  SH  1  of  Hydrogen.* 

IV. PHOSPHORUS  AND  PHOSPHORIC  ACID. 

1°.  Phosphorus  is  a  solid  substance  of  a  pale  yellow  colour,  and  of  a 
consistence  resembling  that  of  wax.  When  exposed  to  the  air  it  slowly 
combines  with  the  oxygen  of  the  atmos[)here,  and  burns  away  with  a 
pale  blue  flame  visible  only  in  the  dark.  When  rubbed,  however,  or 
exposed  to  a  slight  elevation  of  temperature,  even  to  the  heat  of  the 
hand,  it  readily  bursts  into  a  brilliant  flame,  emitting  an  intense  light 
accompanied  by  dense  white  vapours.  It  does  not  occur  in  nature  in 
an  uncombined  state,  and  is  not  known  to  be  susceptible  of  any  useful 
application  in  practical  agriculture. 

2°.  Phosphoric  Acid. — The  white  fumes  given  off  by  phosphorus,  or 
rather  into  which  it  is  changed,  when  burned  in  the  air  or  in  oxygen 
gas,  consist  of  phosphoric  acid.  This  compound  is  solid  and  colourless, 
attracts  moisture  from  the  air  with  great  rapidity,  is  exceedingly  soluble 
in  water,  has  an  intensely  sour  taste,  and  like  sulphuric  acid  is  capable 
of  corroding  and  destroying  animal  and  vegetable  substances. 

It  does  not  exist  in  nature  in  a  free  state,  and,  therefore,  is  not  directly 
influential  upon  vegetation.  It  unites,  however,  with  potash,  soda,  lime, 
&;c.,  to  form  compounds,  known  by  the  name  o^ phosphates.  In  these 
states  of  combination,  it  is  almost  universally  diffused  throughout  nature 
— and  appears  to  be  essentially  necessary  to  the  healthy  growth  and 
maturity  of  all  living — certainly  of  all  cultivated  vegetables. 

*  For  the  properties  of  oxygen  and  hydrogen  see  above,  pages  34  and  25,  and  for  their 
equivalent  or  atomic  weights  see  page  3i 


WOOD-ASH  AND  CARBONATE  OF  POTASH.  187 

V. POTASSIUM,  POTASH,  CARBONATE,  SULPHATE,  OXALATE,  TARTRATE, 

CITRATE,  AND  SULPHATE  OF  POTASH,  AND  CHLORIDE  OF  POTASSIUM. 

1°.  Carbonate  of  Potash. — In  countries  where  non-resinous  trees 
abound,  it  is  usual  to  burn  the  wood  which  cannot  otherwise  be  employ- 
ed— as  in  the  clearings  in  Canada  and  the  United  States — foF  the  pur- 
pose of  collecting  the  ash  which  remains.  This  ash  is  washed  with 
water  and  the  washings  boiled  to  dryness  in  iron  pots.  In  this  state  it 
forms  the  pot-ash  of  commerce.  When  (his  potash  is  again  dissolved 
in  water,  and  the  clear  liquid  decanted  and  boiled,  the^earZ-ash  of  the 
shops  is  obtained. 

This  pearl-ash  is  an  impure  form  of  the  carbonate  of  potash  of  chem- 
ists. It  readily  dissolves  in  water,  has  a  peculiar  taste — distinguished 
as  an  alkaline  taste — and  dissolves  in  vinegar  or  in  diluted  sulphuric  or 
muriatic  acid,  with  much  effervescence.  The  gas  given  off  during  this 
effervescence  (or  boiling  up)  is  carbonic  acid,  the  same  which,  as  was 
shown  in  a  previous  lecture,  is  obtained  when  a  diluted  acid  is  poured 
upon  chalk  or  common  limestone. 

This  carbonate  of  potash  has  been  long  known  to  exercise  a  powerful 
influence  over  the  growth  of  plants. 

The  use  of  wood-ash  as  a  fertilizer  both  of  pasture  and  of  arable  land, 
goes  back  to  the  most  remote  antiquity  ;  and  though  the  crude  wood-ash 
contains  other  substances  also,  yet  much  of  its  immediate  and  most  ap- 
parent effect  is  due  to  the  carbonate  of  j)otash  it  contains. 

From  what  has  already  been  stated,  at  the  commencement  of  the 
present  lecture,  in  regard  to  the  presence  of  potash  in  the  parts  and 
juices  of  nearly  all  plants,  you  will  already  in  some  measure  under- 
stand why  the  carbonate  of  potash  should  be  useful  to  vegetation,  and— 
since  this  alkali  (potash)  is  present  in  greater  quantity  in  some  than  in 
others — why  it  should  appear  to  be  more  especially  favourable  to  the 
growth  of  one  kind  of  plant  than  of  another. 

In  this  vsray,  it  is  explained  why  moss  and  coarse  grasses  are  extirpa- 
ted from  meadows  by  a  sprinkling  of  wood  ashes — and  why  red  clover, 
lucerne,  esparsette,  beans,  peas,  flax,  and  potatoes,  &c.,  are  greatly 
promoted  in  their  growth  by  a  similar  treatment.  This  substance,  how- 
ever, has  other  functions  to  perform  in  reference  to  vegetation,  besides 
that  of  simply  supplying  the  crop  with  the  potash  it  requires  ;  these  func- 
tions I  shall  explain  more  particularly  hereafter,  when  you  will  perhaps 
be  better  prepared  for  understanding  the  details  into  which  it  will  be  ne- 
cessary to  enter. 

2°.  Potash. — When  12  parts  of  carbonate  of  potash  are  dissolved  in 
water,  and  boiled  with  half  their  weight  of  newly-slaked  quick-lime, 
they  are  gradually  deprived  of  their  carbonic  acid,  and  converted  into 
pure  potash, — or  as  it  is  often  called,  from  its  effect  on  animal  and  ve- 
getable substances,  caustic  j^olash. 

The  caustic  liquid  thus  obtained  decomposes  or  dissolves  most  animal 
and  vegetable  substances,  whether  living  or  dead.  When  applied  to 
the  skin,  unless  it  be  in  a  very  diluted  state,  it  destroys  it,  and  produces 
a  painful  sore.  Potash  does  not  occur  in  nature  in  this  caustic  or  un- 
combined  state,  and  is  not  known,  therefore,  to  exercise  any  direct  in- 
fluence upon  natural  vegetation. 

When  wood-ashes  and  quick-lime  are  mixed  together  in  artificial 


188     POTASSIUM,  CAUSTIC  POTASH,  AND  CHLORIDE  OF  POTASSIUM. 

composts,  it  is  not  unlikely  that  a  portion  of  the  carbonate  of  potash  may 
be  rendered  caustic,  and,  therefore,  be  more  fit  to  act  upon  the  vegetable 
matter  in  contact  with  it — by  rendering  it  soluble  in  water  and  thus  ca- 
pable of  entering  into  the  roots  of  plants.  To  this  point  I  shall  have 
occasion  to  return  hereafter.  In  the  mean  time,  it  is  proper  to  remark, 
that  if  pearl-ash  be  mixed,  as  above  prescribed,  whh  half  its  weight  of 
quick-lime,  and  then  boiled  with  less  than  ten  or  twelve  times  its  weight 
of  water,  a  part  of  the  potash  only  is  rendered  caustic — the  lime  being 
unable  to  deprive  the  pearl-ash  (carbonate  of  [wtash)  of  its  carbonic 
acid,  unless  it  be  largely  diluted.  Hence,  in  dry  composts,  or  mixtures 
of  this  substance  with  quick-lime,  it  is  unlikely  that  any  large  portion  of 
the  potash  can  be  at  once  brought  to  the  caustic  state.  This  fact  is 
really  of  importance  in  reference  to  the  theory  of  the  conjoined  action  of 
quick-lime  and  wood  or  pearl-ash,  when  mixed  together  in  artificial  ma- 
nures, and  applied  to  the  land. 

3°.  Potassium. — When  dry  caustic  potash,  obtained  by  evaporating 
the  caustic  solution  above  described,  is  mixed  with  powdered  charcoal 
and  iron  filings,  and  exposed  to  an  intense  heat  in  an  iron  retort,  it  is  de- 
composed, and  metallic  potassium  distils  over,  and  is  collected  in  the 
form  of  white  shining  silvery  drops. 

It  was  one  of  the  most  remarkable  discoveries  of  Sir  H.  Davy,  that 
potash  was  a  compound  substance,  and  consisted  of  this  metal  potassium 
united  to  oxygen  gas. 

Potassium  is  remarkable  for  the  strong  tendency  it  possesses  to  unite 
again  with  oxygen  and  re-form  potash.  When  simply  exposed  to  the 
air,  it  gradually  absorbs  oxygen  from  the  atmosphere  ;  but  if  it  be  heat- 
ed in  the  air,  it  takes  fire  and  burns.  When  the  combustion  has  ceased, 
a  quantity  o^  caustic  potash  remains,  the  weight  of  which  is  nearly  one- 
fifth  greater  than  that  of  the  potassium  employed.  It  even  bursts  into  a 
flame  when  thrown  upon  water,  depriving  that  liquid  of  its  oxygen,  and 
liberating  its  hydrogen, — and  it  was  justly  considered  as  the  most  aston- 
ishing property  of  this  metal,  when  first  discovered,  that  it  took  fire 
v/hen  placed  upon  the  coldest  ice.  [For  the  composition  of  water,  see 
Lecture  II.,  p.  36.]  When  thus  burned  in  contact  with  water,  potash 
is  formed,  as  before,  and  is  found  dissolved  in  the  liquid  when  the  ex- 
periment is  completed. 

4°.  Chloride  of  Potassium. — This  is  a  compound  of  chlorine  with  po- 
tassium, which,  in  taste,  properties,  and  general  appearance,  has  much 
resemblance  to  common  salt.  It  may  be  formed  by  dissolving  pearl- 
ash  in  dilute  muriatic  acid  (spirit  of  salt)  as  long  as  any  efTervescence 
•appears,  and  afterwards  evaporating  to  dryness.  It  exists  in  small 
^quantity  in  sea  water,  in  the  ash  of  most  plants,  and  frequently  in  the 
'soil.  It  is  not  an  article  of  manufacture,  but  is  occasionally  extracted 
from  kelp,  and  sold  to  the  alum  makers.  Could  it  be  easily  and  cheap- 
ly obtained,  there  is  no  doubt  that  it  might  be  employed  with  advantage 
as  a  manure,  and  especially  in  those  circumstances  in  which  common 
salt  has  been  found  to  promote  vegetation.  The  refuse  of  the  soap-boil- 
ers, where  soap  is  made  from  kelp,  contains  a  considerable  quantity  of 
this  compound.  This  refuse  might  be  obtained  at  a  cheap  rate,  and, 
therefore,  might  be  usefully  collected  and  applied  to  the  land  where 
such  works  are  established. 


SULPHATE,  NITRATE,  OXALATES,  AND  CITRATES  OF  POTASH.        189 

5°-  Sulphate  of  Potash. — This  compound  is  formed  by  adding  pearl- 
ash  to  dilute  sulphuric  acid  (oil  of  vitriol)  as  long  as  effervescence  ap- 
pears, and  then  evaporating  the  solution.  It  is  a  white  saline  sub- 
stance, sparingly  soluble  in  water,  and  has  a  disagreeable  biuerish  taste. 
It  exists  in  considerable  quantity  in  wood-ash,  and  in  the  ash  of  nearly 
all  plants,  and  is  one  of  the  most  abundant  impurities  in  the  common 
potash  and  pearl-ash  of  the  shops.  This  sulphate  itself  is  not  an  article 
of  extensive  manufacture,  but  it  exists  in  common  alum  to  the  amount 
of  upwards  of  18  per  cent,  of  its  weight.  ^ 

Dissolved  in  100  times  its  weight  of  water,  the  sulphate  of  potash  has 
been  found  to  act  favourably  on  red  clover,  vetches,  beans,  peas,  &c., 
and  part  of  the  effect  of  wood  ashes  on  plants  of  this  kind  is  to  be  attri- 
buted to  the  sulphate  of  potash  they  contain.  Turf  ashes  are  also  said 
to  contain  this  salt  in  variable  quantity,  and  to  this  is  ascribed  a  portion 
of  their  efficacy  also  when  applied  to  the  land. 

6°.  Nitrate  of  Potash,  or  saltpetre,  is  a  well  known  saline  substance, 
of  which  mention  has  already  been  made  in  the  preceding  lectures.  [See 
p.  56,  and  pp.  159  to  163.]  It  contains  potash  and  nitric  acid  only,  and 
may  be  readily  formed  by  dissolving  pearl-ash  in  nitric  acid,  and  eva- 
porating the  solution.  It  exists,  and  is. continually  reproduced  in  the 
soil  of  most  countries,  and  is  well  known  to  exercise  a  remarkable  influ- 
ence in  accelerating  and  increasing  the  growth  of  plants. 

7°.  Oxalates  of  Potash. — These  salts  exist  in  the  common  and  wood 
sorrels,  and  in  most  of  the  other  more  perfect  plants  in  which  oxalic 
acid  is  known  to  exist.  [See  pp.  47  and  137.]  The  salt  of  sorrel  is  the 
best  known  of  these  oxalates.  This  salt  has  an  agreeable  acid  taste, 
and  is  not  so  poisonous  as  the  uncombined  oxalic  acid. 

When  this  salt  is  heated  over  a  lamp,  the  oxalic  acid  it  contains  is  de- 
composed, and  carbonate  of  potash  is  obtained.  It  is  supposed  that  a 
great  part  of  the  potash  extracted  from  the  ashes  of  wood  and  of  the 
stems  of  plants  in  general,  in  the  state  of  carbonate,  existed  as  an  oxa- 
late in  the  living  tree,  and  was  converted  into  carbonate  during  the  com- 
bustion of  the  woody  fibre  and  other  organic  matter.  This  compound, 
therefore,  in  all  probability,  performs  an  important  part  in  the  changes 
which  take  place  in  the  interior  of  plants,  though  its  direct  agency  in 
affecting  their  growth  when  applied  externally  to  their  roots  has  not 
hitherto  been  distinctly  recognized.  It  is  probably  formed  occasionally 
in  farm-yard  manure,  and  in  decaying  urine  and  night-soil,  but  nothing 
very  precise  is  yet  known  on  this  subject. 

8°.  Citrates  and  Tartrates  of  Potash. — These  salts  exist  in  many 
fruits.  The  citrates  abound  in  the  orange,  the  lemon,  and  the  lime — 
the  tartrates  in  the  grape.  When  heated  over  a  lamp,  they  are  decom- 
posed, and  like  the  oxalates  leave  the  potash  in  the  state  of  carbonate. 

In  the  interior  of  plants,  both  potash  and  soda  are  most  frequently 
combined  with  organic  acids  (oxalic,  citric,  tartaric,  &;c.,  for  an  ac- 
count of  the  most  abundant  of  which  see  Lecture  VI.,  p.  121,')  and  the 
compounds  thus  formed  are  generally  what  chemists  call  acid  salts — 
that  is  to  say,  they  generally  have  a  distinctly  sour  taste,  redden  vege- 
table blues,  and  contain  much  more  acid  than  is  found  to  exist  in  cer- 
tain other  well  known  compounds  of  the  same  acids  with  potash. 

The  citrates  and  tartrates  are  not  known  to  be  formed  in  nature,  ex- 


190  PHOSPHATES  OF  PC TASH,  AND  CHLORIDE  OF  SODIUM. 

cept  in  the  living  plant,  and  as  they  are  too  expensive  to  be  ever  em- 
ployed as  manures,  it  is  the  less  Jo  be  regretted  that  few  experiments 
have  yet  been  tried  with  the  view  of  ascertaining  their  effect  upon  vege- 
tation. 

9°.  Phospf^tes  of  Potash. — If  to  a  known  weight  of  phosphoric  acid 
(p.  186)  pearl-ash  (carbonate  .of  potash)  be  added  as  long  as  any  effer- 
vescence appears,  and  the  solution  be  then  evaporated,  phosphate  of 
pot^h  is  obtained.  If  to  the  solution  before  evaporation  a  second  por- 
tion of  phosphoric  acid  be  added,  equal  to  the  first,  and  the  water  be 
then  expelled  by  heal,  B\-phosphate  of  potash  will  remain,  [so  called 
from  his^  twice,  because  it  contains  ticice  as  much  acid  as  the  former,  or 
neutral  phosphate.] 

One  or  other  of  ihese  two  salts  is  found  in  the  ash  of  nearly  all  plants. 
Whether  or  not  the  elements  of  which  they  consist  exist  in  this  state  of 
combination  in  the  living  plant  will  be  considered  hereafter,  in  the  mean 
time  it  may  be  stated  as  certain  that  they  are  of  the  most  vital  impor- 
tance not  only  in  reference  to  the  growth  of  plants  themselves,  but  also 
to  their  nutritive  qualities  when  eaien  by  animals  for  food. 

These  phosphates  are  occasionally,  perhaps  very  generally,  present 
in  the  soil  in  minute  quantities,  and  there  is  every  reason  to  believe 
that  could  they  be  applied  to  the  land  in  a  sufficiently  economical  form, 
they  would  in  many  cases  act  in  a  most  favourable  manner  upon  vege- 
tation. They  are  contained  in  urine  and  other  animal  manures,  and  to 
their  presence  a  portion  of  the  efficacy  of  these  manures  is  to  be  ascribed. 

VI. SODIUM,  SODA,  CARBONATE  OF  SODA,  SULPHATE  OF  SODA,  SULPHU- 

RET  OF  SODIUM,  CHLORIDE  OF  SODIUM. 

1°.  Chloride  of  Sodium,  common  or  sea  salt,  exists  abundantly  in  sea 
water,  and  is  found  in  many  parts  of  the  earth  in  the  form  either  of  in- 
crustations on  the  surface  or  of  solid  beds  or  masses  at  considerable  depths. 
The  rock  salt  of  Cheshire  is  a  well  known  example  of  this  latter  mode 
of  occurrence. 

Common  salt  may  also  be  detected  in  nearly  all  soils,  it  is  found  in 
the  ashes  of  all  plants,  but  especially  and  in  large  quantity  in  the  ashes  of 
marine  plants  (kelp),  and  is  sometimes  borne  with  the  spray  of  the  sea  to 
great  distances  inland,  when  the  winds  blow  strong,  and  the  waves  are 
high  and  broken. 

On  some  rocky  shores,  as  on  that  between  Berwick  and  Dunbar,  the 
spray  may  be  seen  occasionally  moving  up  the  little  coves  and  inlets  in 
the  form  of  a  distinct  mist  driving  before  the  wind,  and  the  saline  matter 
has  been  known  to  traverse  nearly  half  the  breadth  of  the  island  before 
it  was  entirely  deposited  from  the  air. 

It  is  impossible  to  calculate  how  much  of  the  saline  matter  of  sea  water 
may  in  this  way  be  spread  over  the  surface  of  a  sea-girt  land  like  ours ; 
but  two  things  are  certain — that  those  places  which  are  nearer  the  sea 
will  receive  a  greater,  and  those  more  inland  a  lesser,  portion ;  and  that 
those  coasts  on  which  sea  winds  prevail  will  be  more  largely  and  more 
frequently  visited  than  those  on  which  land  winds  are  more' commonly 
experienced. 

It  is  well  known  that  common  salt  has  been  employed  in  all  ages  and 
in  all  countries  for  the  purpose  of  promoting  veg3tation,  and  in  no  coun- 


SULPHATE  OF  SODA,  SULPHURET  OF  SODIUM,  CARBONATE  OF  SODA.  191 

try  perhaps  in  larger  quantity  or  more  extensively  than  in  England. 
That  it  has  often  failed  to  benefit  the  land  in  particular  localities,  only 
shows  that  the  soil  ii.  those  places  already  contained  a  natural  supply  of 
this  compound  large  enough  to  meet  the  wants  of  the  crops  which  grew 
upon  it.  The  facts  above  stated  as  to  the  influence  of  the  wind  in  top- 
dressing  the  exposed  coast-line  of  a  country  with  absolution  of  salt,  may 
serve  as  an  important  guide  both  in  reference  to  the  places  in  which  it 
may  be  expected  to  benefit  the  land,  and  to  the  causes  of  its  failing  to 
do  so  in  particular  districts. 

2°.  Sulphate  of  Soda,  or  Glauber's  salt,  is  usually  manufactured  from 
common  salt  by  pouring  upon  it  diluted  sulphuric  acid  (oil  of  vitriol), 
and  applying  heat.  Muriatic  acid  (spirit  of  salt,  so  called  by  the  old 
chemists,  because  thus  given  off  by  common  salt,)  is  given  off  in  the 
form  of  vapour,  and  sulphate  of  soda  remains  behind.  It  may  also  be 
prepared,  though  less  economically,  by  adding  (he  common  soda  of  the 
shops  (o  diluted  sulphuric  acid  as  long  as  any  efTervescence  appears. 

This  well  known  salt  is  met  with  in  variable  quantity  in  the  ashes  of 
nearly  all  plants,  and  is  diflfused  in  minute  proportion  through  most 
soils.  I  have  elsewhere  [see  Appendix,]  directed  your  attention  to  the 
beneficial,efrect  which  it  has  been  observed  to  exercise  on  the  growth 
especially  of  such  plants  as  are  known  to  contain  a  considerable  propor- 
tion of  sulphuric  acid.  Among  these  are  red  clover,  vetches,  peas,  &c. 
And  as  this  salt  is  manufactured  largely  in  this  country  and  can  be  ob- 
tained at  the  low  price  of  ten  shillings  a  cwt.  in  the  dry  state,*  I  have 
recommended  it  to  the  practical  farmer  as  likely  to  be  extensively  useful 
as  a  manure  for  certain  crops  and  on  certain  soils.  The  kind  of  crops 
and  soils  have  as  yet  in  great  measure  to  be  determined  by  practical 
trials. — [See  the  results  of  Mr.  Fleming's  Experiments,  given  in  the 
Appendix.] 

3°.  Sulphuret  of  Sodium. — When  sulphate  of  soda  is  mixed  with 
saw-dust,  and  heated  in  a  furnace,  the  oxygen  of  the  salt  is  separated, 
and  sulphuret  of  sodium  is  produced.  By  a  similar  treatment  sulphate 
of  potash  is  converted  into  sulphuret  of  potassium.  These  compounds 
consist  of  sulphur  and  metallic  sodium  or  potassium  only.  They  do 
not  occur  extensively  in  nature,  and  are  not  manufactured  for  sale;  but 
there  is  reason  to  believe  that  they  would  materially  promote  the  vege- 
tation of  such  plants  as  contain  much  sulphur  in  combination  with  pot- 
ash or  soda.  The  sulphuret  of  sodium  is  present  in  variable  quantity  in 
the  refuse  lime  of  the  alkali  works,  already  spoken  of,  and  might  be  ex- 
pected to  aid  the  other  substances  of  which  it  chiefly  consists,  in  contri- 
buting to  the  more  rapid  growth  of  pulse  and  clover  crops. 

4°.  Carbonate  of  Soda. — I  have  described  the  above  compounds  of 
soda  before  mentioning  this  its  best  known  and  most  common  form,  be- 
cause they  are  all  steps  in  the  process  by  which  the  latter  is  usually  pre- 
pared from  common  salt,  by  the  soda  manufacturers. 

When  the  sulphuret  of  sodium  is  mixed  with  chalk  in  certain  propor- 
tions, and  heated  in  a  furnace,  it  is  deprived  of  its  sulphur,  and  is  con- 
verted into  carbonate  of  soda,  the  common  soda  of  the  shops. 

This  well  known  salt,  now  sold  in  the  state  of  crystals,  [containing  62 

•  Not  in  crystals,  the  for^nn  which  it  is  commonly  sold  as  a  horse  medicine.  These- 
crystals  contain  upwards  of  half  their  weight  (55  per  cent.)  of  water. 


192  SODA    OR    CAUSTIC    SODA. 

per  cent,  of  water,]  at  from  10s.  to  12s.  a  cwt.,  has  not  as  yet  been  ex- 
tensively tried  as  a  means  of  promoting  vegetation.  The  lowness  of  its 
price,  however,  and  the  fact  that  it  is  an  article  of  extensive  home  man- 
ufacture, conjoined  with  the  encouragement  we  derive  from  theoretical 
considerations — all  unite  in  suggesting  the  propriety  of  a  series  of  ex- 
periments with  the  view  of  determining  its  real  value  to  the  practical 
agriculturist.  The  mode  in  which  theory  indicates  that  this  compound 
is  likely  to  act  in  promoting  vegetation — as  well  as  the  crops  to  which  it 
may  be  expected  to  be  especially  useful,  will  come  under  our  considera- 
tion hereafter. 

Besides  the  common  carbonate  of  soda  above  described,  and  which  in 
the  neighbourhood  of  Newcastle  is  manufactured  from  common  salt  to 
the  amount  of  30  or  40  thousand  tons  every  year,  there  occur  in  natuie 
two  other  compounds  of  soda  with  carbonic  acid,  in  which  the  latter 
substance  is  present  in  larger  quantity  than  in  the  soda  of  the  shops. 
The  sesqui-carhonate,  containing  one  half  more  carbonic  acid,  occurs  in 
the  soil  in  many  warm  climates  (Egypt,  India,  South  America,  &c.), 
and  at  Fezzan,  in  Africa,  is  met  with  as  a  mineral  deposit  of  such 
thickness  as  in  that  dry  climate  to  allow  of  its  being  employed  as  a 
building  stone. 

The  6i-carbonate  is  contained  in  the  waters  of  many  lakes?  in  Hunga- 
ry, in  Asia,  &c.,  and  in  many  springs  in  all  parts  of  the  world.  There 
can  be  no  doubt  that  the  waters  of  such  springs  are  fitted  to  promote  the 
fertility,  espeaiftlly  of  pasture  land,  to  which  they  may  be  applied  either 
by  artificial  irrigation,  or  by  spontaneous  overflow  from  natural  outlets. 
Some  of  the  Harrowgate  waters  contain  a  sensible  quantity  of  this  bi- 
carbonate, and  over  a  large  portion  of  the  Yorkshire  coal-field,  a  bed  of 
rock  is  found,  at  various  depths,  the  springs  from  which  hold  in  solution 
a  considerable  portion  of  this  salt.  The  Holbeck  water  of  Leeds,  ac- 
cording to  Mr.  West,  owes  its  softness  to  the  pijesence  of  this  carbonate, 
and  the  water  from  the  coal-mines  in  the  neighbourhood  of  AVakefield 
is  occasionally  so  charged  with  it,  as  to  form  troublesome  saline  incrus- 
tations on  the  bottoms  of  the  steam  boilers.  Where  these  waters-  occur 
in  sufficient  abundance,  they  should  not  be  permitted  to  escape  into  tlie 
rivers,  until  they  have  previously  been  employed  in  irrigating  the  land. 

It  has  occasionally  been  observed  that  natural  springs  in  some  locali- 
ties impart  a  degree  of  luxuriance  to  natural  pasture,  which  is  not  to  be 
accounted  for  by  the  mere  effect  of  a  constant  supply  of  water.  In 
such  cases,  the  springs  may  be  expected  to  contain  some  alkaline,  or 
other  mineral  ingredient,  which  the  soil  is  unable  to  supply  to  the  plants 
which  grow  upon  it,  either  in  sufficient  abundance,  or  with  sutficient 
rapidity. 

5°.  Soda  or  Caustic  Soda. — When  a  solution  of  the  common  soda  of 
the  shops  is  boiled  with  quick-lime,  it  is  deprived  of  its  carbonic  acid, 
and  like  the  carbonate  of  potash  (p.  187)  is  brought  into  the  caustic  state. 
In  this  state  it  destroys  animal  and  vegetable  substances,  and,  unless 
very  dilute,  is  injurious  to  animal  and  vegetable  life. 

When  common  salt  (chloride  of  sodium)  is  mixed  with  quick-lime  in 
compost  heaps,  it  is  deprived  by  the  lime  of  a  portion  of  its  chlorine, 
and  is  partially  converted  into  this  caustic  soda.  The  action  of  the  soda 
in  this  state  is  similar  to  that  of  caustic  potash^  Not  only  does  it  readi- 


SODIUM,  PHOSPHATES  OF  SODA,  AND  CARBONATE  OF  LIME.  193 

ly  supply  3oda  to  the  growing  plant,  to  which  soda  is  necessary,  but  it 
also  acts  upon  certain  other  substances  which  the  plants  require,  so  as 
to  render  them  soluble,  and  to  facilitate  their  entrance  into  the  roots  of 
plants.  To  the  [)resence  of  soda  in  this  caustic  state,  the  efficacy  of 
such  composts  of  common  salt  and  lime  in  promoting  vegetation,  is  in 
part  to  be  ascribed. 

6°.  Sodium  is  a  soft  metal  of  a  silver  white  colour,  and,  like  potassi- 
um, light  enough  to  float  upon  water.  It  is  obtained  by  heating  caustic 
soda  with  a  mixture  of  charcoal  and  iron  filings.  It  takes  fire  upon 
water — though  not  so  readily  as  potassium — and  combines  with  its  oxy- 
gen to  form  soda.  In  the  metallic  state  it  is  not  known  to  occur  in  na- 
ture, and,  therefore,  does  not  directly  act  upon  vegetation.  With  oxy- 
gen it  forms  soda, — with  chlorine,  chloride  of  sodium  (common  salt), — 
and  with  sulptiur,  sulphuret  of  sodium, — all  of  which,  as  already  stated^ 
are  more  or  less  beneficial  to  vegetation. 

7°.  Phosphates  of  Soda. — When  the  common  soda  of  the  shops  is  added 
to  a  solution  of  phosphoric  acid  in  water,  till  effervescence  ceases,  and 
the  solution  is  evaporated  to  dryness,  phos[)hate  of  soda  is  formed,  and 
by  the  subsequent  addition  of  as  much  more  phosphoric  acid — 6i-phos- 
phate.  These  salts  occur  more  or  less  abundantly  in  the  ash  of  nearly 
all  plants ;  they  are  occasionally  also  detected  in  the  soil,  and  one  or 
other  of  them  is  almost  always  present  in  urine  and  other  animal  ma- 
nures. As  we  know  from  theory  that  these  compounds  must  be  grate- 
ful to  plants,  we  are  justified  in  ascribing  a  portion  of  the  efficacy  of  animal 
manures,  in  promoting  the  growth  of  vegetables,  to  the  presence  of  these 
phosphates,  as  well  as  to  that  of  the  phosphates  of  potash  (p.  190). 
They  are  not  known  to  occur  in  the  mineral  kingdom  in  any  large  quan- 
tity, neither  are  they  articles  of  manufacture,  hence  their  direct  action 
upon  vegetation  has  not  hitherto  been  made  the  subject  of  separate  ex- 
periment. 

VII. CALCIUM,  LIME,  CARBONATE  OF  LIME,  SULPHATE  OF  LIME,  NI- 
TRATE OF  LlME,  PHOSPHATES  OF  LIME,  CHLORIDE  OF  CALCIUM,  SUL- 
PHURET OF  CALCIUM. 

1°.  Carbonate  of  Lime. — Chalk,  marble,  and  nearly  all  the  lime 
stones  in  common  use,  are  varieties,  more  or  less  pure,  of  that  com 
pound  of  lime  with  carbonic  acid  which  is  known  to  chemists  as  car- 
bonate of  lime.  It  occurs  of  various  colours  and  of  various  degrees  of 
hardness,  but  in  weight  the  compact  varieties  are  very  much  alike,  be- 
ing generally  a  little  more  than  2i  times  (2*7)  heavier  than  water. 
They  all  dissolve  with  effervescence  in  dilute  muriatic  acid  (spirit  of 
salt),  and  by  the  bubbles  of  gas  which  are  seen  to  escape  when  a  drop 
of  this  acid  is  applied  to  them,  limestones  may  in  general  be  readily  dis- 
tinguished from  other  varieties  of  rock.  They  dissolve  slowly  also  in 
water  which  holds  carbonic  acid  in  solution  ;  and  hence  the  springs 
which  issue  from  the  neighbourhood  of  deposits  of  limestone  are  gene- 
rally charged  in  a  high  degree  with  this  mineral  substance. 

The  value  of  this  carbonate  of  lime  in  rendering  a  soil  capable  of  pro- 
ducing and  sustaining  a  luxuriant  vegetation  depends,  in  part,  it  is  true, 
on  the  necessity  of  a  certain  proportion  of  lime  to  the  growth  and  full 
developement  of  the  several  parts  of  nearly  all  plants,  but  it  performs  also 
0 


194  QUICK-LIME,  CALCIUM,  AND  CHLORIDE  OF  CALCIUM. 

othei  important  offices,  wliich  we  shall  hereafter  have  occasion  more 
fully  to  consider. 

2°.  Lime  or  Quick-lime. — When  limestone  is  burned  aloig  with  coal 
or  wood  in  kilns  so  constructed  that  a  current  of  air  can  pass  freely  through 
them,  the  carbonic  acid  is  driven  off,  and  the  lime  alone  remains,  in 
this  slate  it  is  generally  known  by  the  name  of  burned  or  quick-Wme^ 
from  its  caustic  qualities,  and  is  found  to  have  lost  nearly  44  per  cent,  of 
its  original  weight. 

The  most  remarkable  property  of  quick-lime  is  its  strong  tendency  to 
combine  with  water.  This  is  displayed  by  the  eagerness  with  which  this 
liquid  is  drunk  in  by  the  lime  in  the  act  of  slaking,  and  by  the  great  heat 
which  is  at  the  same  time  developed.  Slaked  lime  is  a  compound  of 
lime  with  water,  and  by  chemists  is  called  a  hydrate  of  lime.  It  con- 
tains 24  per  cent,  of  its  weight  of  water. 

The  action  of  quick-lime  upon  the  land  is  one  of  the  most  important 
which  presents  itself  to  the  observation  of  the  practical  agriculturist. 
Among  other  effects  produced  by  it  is  that  of  hastening  the  decomposi- 
tion of  vegetable  matter  either  in  the  soil  or  in  compost  heaps ;  but  this 
effect  is  materially  promoted  by — if  it  be  not  wholly  dependent  upon 
— the  presence  of  air  and  moisture.  By  this  decomposition  carbonic 
acid  and  other  compound  substances  are  produced,  which  the  roots  are 
capable  of  absorbing  and  converting  into  the  food  of  plants. 

In  this  caustic  state  lime  does  not  occur  in  nature,  nor  when  exposed, 
to  the  air  does  it  long  remain  in  this  state.  It  gradually  absorbs  carbonic 
acid  from  the  atmosphere,  and  is  again  converted  into  carbonate.  This 
change  takes  place  more  or  less  rapidly  in  all  cases  where  quick-lime  is 
applied  to  the  land,  but  the  benefits  arisiug  from  burning  the  lime  do  not 
disappear  when  it  is  thus  reconverted  into  carbonate.  On  the  contrary, 
the  state  of  very  fine  pov/der,  into  which  quick-lime  falls  on  slaking, 
enables  the  carbonate  of  lime,  subsequently  formed,  to  be  intermixed 
with  the  soil  in  a  much  more  minute  state  of  division  than  could  be  ob- 
tained by  any  mechanical  means.  This  we  shall  hereafter  see  to  be  a 
most  important  fact,  when  we  come  to  study  in  more  detail  the  theory 
of  the  action  of  lime  in  the  several  states  of  combination,  and  under  the 
varied  conditions  in  which  it  is  employed  for  the  purpose  of  improving 
the  land. 

3°.  Calcium  is  a  silver-white  metal,  which,  by  its  union  with  oxygen, 
forms  lime.  It  is  not  known  to  exist  in  nature  in  an  uncombined  state, 
is  prepared  artificially  only  with  great  difficulty,  and  therefore  exercises 
no  direct  action  on  vegetable  growth. 

4°.  Chloride  of  Calcium. — When  chalk  or  quick-lime  is  dissolved  in 
muriatic  acid,  a  solution  of  chloride  of  calcium  is  obtained.  This  solu- 
tion occurs  in  sea-water,  in  the  refuse  (mother-liquor)  of  the  salt-pans, 
and  is  allowed  to  flow  away  in  large  quantities  as  a  waste  from  certain 
chemical  works.  I  have  elsewhere  stated  the  effects  it  has  been  ob- 
served to  produce  upon  vegetable  growth,  [see  Appendix,]  and  have  re- 
commended the  propriety  of  making  experiments  with  the  view  of  ren- 
dering useful  some  of  those  materials  which  in  our  manufactories  are 
now  suffered  largely  to  run  to  waste. 

5°.  Sulphuret  of  Calcium  is  a  compound  of  sulphur  and  calcium, 
which  may  be  formed  by  heating  together  chalk  and  sulphur  in  a  covered 


SULPHATE  AND  NITRATE  OF  LIME.  195 

crucioie  It  is  sometimes  produced  in  nature,  where  moist  decaying 
vegetable  and  animal  matters  are  allowed  to  ferment  in  the  presence  of 
gypsum  ;  it  may  sometimes  also  be  delected  in  the  soil,  and  in  the  waters 
of  mineral  springs,  and  is  contained  largely  in  the  recent  refuse  heaps 
of  tlie  alkali  works.  Like  the  sulphurets  of  potassium  and  sodium,  al- 
ready described,  it  is  fitted,  when  judiciously  applied,  to  promote  the 
growth  especially  of  those  plants  in  which  sulphur  has  been  recognized 
as  a  necessary  constituent. 

6°.  Sulphate  of  Lime,  or  gypsum,  is  a  well  known  white  crystalline 
or  earthy  compound,  which  occurs  as  an  abundant  mineral  deposit  in 
numerous  parts  of  the  globe.  It  is  present  in  many  soils,  is  contained 
in  the  waters  which  percolate  through  such  soils,  and  in  those  of  springs 
which  ascend  from  rocky  beds  in  which  gypsum  exists,  and  is  detect- 
ed in  sensible  proportions  in  the  ashes  of  many  cultivated  plants.  It 
is  extensively  employed  in  the  arts,  and  in  some  countries  not  less  ex- 
tensively as  a  means  of  promoting  the  fertility  of  the  land. —  [See  Appen- 
dix, p.  1.] 

The  gypsum  of  commerce  contains  nearly  21  per  cent,  of  its  weight 
of  water,  which  it  loses  entirely  on  being  exposed  to  a  red  heat.  In 
some  countries,  a  variety  which  is  almost  entirely  free  from  water  oc- 
curs in  rocky  masses,  and  is  distinguished  by  the  name  oi  Anhydrite. 

Gypsum,  when  burned,  has  ths  property  of  being  reduced  with  great 
ease  into  the  state  of  an  impalpable  powder.  This  powder,  however, 
combines  so  readily  with  the  21  per  cent,  of  water  it  had  previously  lost, 
that  if  it  be  mixed  with  water  to  the  consistence  of  a  paste  so  thin  that  it  can 
be  poured  into  a  mould,  it  sets  and  hardens  in  a  few  minutes  into  a  solid 
mass.  In  this  way  burned  gypsum  is  employed  in  making  plaster  casts 
and  cornices. 

Burned  gypsum  consists  of  lime  and  sulphuric  acid  only — in  the  pro- 
}.K)rtions  of  41i  of  the  former,  to  58i  of  the  latter.  Its  use  as  a  manure, 
therefore,  will  be  specially  to  promote  the  growth  of  those  plants  by 
which  these  two  substances  are  more  abundantly  required,  and  upon 
soils  in  which  they  are  already  present  in  comparatively  small  propor- 
tion. 

7°.  JSitrate  of  Lime. — The  production  of  nitrate  of  lime  in  artificial 
nitre-beds,  on  old  walls,  and  on  the  sides  of  caves  and  cellars,  especially 
in  damp  situations,  has  already  been  alluded  to  in  Lecture  VIII. ,  [p. 
16L]  It  may  be  formed  artificially  by  dissolving  common  limestone  in 
nitric  acid,  and  evaporating  the  solution.  It  constitutes  a  v  bite  mass, 
which  rapidly  attracts  water  from  the  air,  and  runs  to  a  tiquid.  It  is 
produced  naturally,  and  exists,  as  I  believe,  in  soils  containing  lime, 
more  commonly  than  has  hitherto  been  suspected.  Its  extreme  solubili- 
ty in  water,  however,  renders  it  I'able  to  be  carried  downwards  into  the 
lower  portions  of  the  soil  by  eveiy  shower  of  rain — or  to  be  actually 
washed  away,  when  long  continued  wet  weather  prevails. 

When  heated  to  dull  redness  with  vegetable  matter,  the  nitrate  of 
lime  is  decomposed,  and  is  converted  into  carbonate,  or  when  exposed 
alone  to  a  bright  red  heat,  the  nitric  acid  is  expelled,  and  quick-lime 
alone  remains.  Hence  where  it  really  exists  in  plants,  it  cannot  be  de- 
tected in  the  ash, — and  when  present  in  soils,  it  must  be  separated  by 


196  PHOSPHATE  OF  LIME. 

washing  fhem  in  water,  before  they  are  exposed  to  a  heat  sufficient  to 
burn  away  tlie  organic  matter  they  contain. 

The  details  already  entered  into  in  the  preceding  lecture  (pp.  159  to 
163)  regarding  the  general  action  of  nitric  acid,  in  promoting  the  natural 
vegetation  of  the  globe,  render  it  unnecessary  forme  to  dwell  here  on  the 
special  action  of  its  compound  with  lime — njore  particularly  as  the  entire 
subject  of  the  action  of  lime  upon  the  land  will  hereafter  demand  from 
us  a  separate  consideration. 

The  nitrate  of  lime  cannot,  as  yet,  be  formed  by  art,  at  a  sufficiently 
cheap  rate  to  allow  of  its  being  manufactured  for  the  use  of  the  agricul- 
turist. 

Phosphates  of  Lime. — Lime  combines  with  phosphoric  acid  in  sev- 
eral proportions,  forming  as  many  different  compounds.  Of  these  b^' 
far  the  most  important  and  abundant  in  nature,  certainly  the  most  use- 
ful to  the  agriculturist,  is  the  earth  of  hones.  It  will  be  necessary,  how 
ever,  to  advert  shortly  to  two  others,  with  the  existence  of  which  it  is 
important  for  us  to  be  acquainted. 

A.  Earth  of  Bones  is  the  name  given  to  the  white  earthy  skeleton  that 
remains  when  the  bones  of  animals  are  burned  in  an  open  fire  until 
every  thing  combustible  has  disappeared.  This  earthy  matter  consists 
chiefly  of  a  peculiar  phosphate  of  lime,  composed  of  51i  per  cent,  of 
lime,  and  48i  of  phosphoric  acid.  •  This  compound  exists  ready  formed 
in  the  bones  of  all  animals,  and  is  the  substance  selected  in  the  economy 
of  nature  to  impart  to  thern  their  strength  and  solidity.  It  is  found  in 
smaller  quantit}'  in  those  of  young  animals,  while  they  are  soft,  and 
cartilaginous, — and  the  softening  of  the  bones,  which  in  after-life  occurs 
as  the  result  of  disease,  is  caused  by  the  unnatural  abstraction  of  a  greater 
portion  of  this  earthy  matter  than  is  replaced  by  the  food. 

This  earthy  phosphate  constitutes  about  .57  per  cent,  of  the  dried  bones 
of  the  ox,  is  present  in  lesser  quantity  in  the  horns,  hoofs  and  nails,  and 
is  never  absent  even  from  the  flesh  and  blood  of  healthy  animals.  It 
exists  in  the  seed  of  many  plants,  in  all  the  varieties  of  grain  which  are 
extensively  cultivated  for  food,  and  in  the  ashes  of  most  common  plants. 
The  ashes  of  leguminous,  cruciferous,  and  composite  plants,  are  es- 
pecially rich  in  this  compound. 

If  we  consider  that  when  animals  die,  their  bones  are  chiefly  buried  in 
the  earth,  and  that  over  the  entire  globe,  animal  life,  in  one  or  other  of 
its  forms,  prevails,  we  shall  not  be  surprised  that,  in  almost  every  soil, 
the  earth  of  bones  should  be  found  to  exist  in  greater  or  less  abundance. 
Nor  can  we  have  any  difficulty  in  conceiving,  if  such  be  the  case, 
whence  plants  draw  their  constant  and  necessary  supplies  of  this 
substance. 

At  the  same  time,  it  is  true  of  this  compound,  as  of  all  the  others  we 
have  yet  spoken  q^,  as  occurring  in,  and  as  necessary  to  the  growth  of, 
vegetables, — that  some  soils  contain  it  in  greater  abundance  than  others, 
and  that  from  some  soils,  therefore,  certain  plants  will  not  readily  obtain 
as  much  of  this  substance  as  they  require.  This  is  the  natural  principle 
on  which  the  use  of  bone-dust  as  a  manure  chiefly  depends. 

Hence  of  two  marls  both  containing  carbonate  of  lime,  that  will  be 
miDst  useful  to  the  land  which  contains  also,  as  many  do,  a  notable  por- 
tion of  jihosohate  of  lime ;  and  of  two  limestones,  that  will  be  preferred 


BOILED  BONES  .-,%  A  MANURE.  197 

in  an  agricultural  district  in  which  animal  remains  most  abound.     I 
shall  have  occasion  to  illustrate  this  point  more  fully,  when  in  a  subse- ' 
quent  lecture  I  come  to  explain  the  natural  origin  of  soils,  and  to  trace 
their  chemical  constituents  to  the  several  rocky  masses  from  which  they 
appear  to  have  been  derived. 

Before  dismissing  this  topic,  however,  there  are  one  or  two  proper- 
ties of  this  bone  earth  which  are  of  practical  importance,  and  to  which, 
therefore,  I  must  shortly  request  your  attention.  It  is  insoluble  in  water 
or  in  solutions  of  soda  or  potash,  but  it  dissolves  readily  in  acids,  such  as 
the  nitric  or  muriatic,  and  also,  though  less  easily  and  abundantly,  in 
common  vinegar.  It  exists  in  milk,  arid  is  supposed  to  be  held  in  solu- 
tion by  a  peculiar  acid  found  in  this  liquid,  and  which  is  distinguished  by 
the  name  oHaclic  acid  (acid  of  milk). 

It  is  slightly  soluble  also  in  a  solution  of  cfirbonic  acid,  and  of  certain 
other  organic  acids  which  exist  in  the  soil,  and  it  is  by  means  of  these 
acids  that  it  is  supposed  to  be  rendered  capable  of  entering  into  the  roots 
of  plants.  Wherever  vegetable  matter  exists,  and  is  undergoing  decay 
in  the  soil,  the  water  makes  its  way  to  the  roots  more  or  less  laden  with 
carbonic  .acid,  and  thus  is  enabled  to  bear  along  with  it  not  only  common 
carbonate  of  lime,  as  has  been  shown  in  a  previous-lecture  (p.  47),  but 
also  such  a  portion  of  phosphate  as  may  aid  in  supplying  this  necessary 
food  to  the  growing  plant.* 

In  the  bones  of  animals  the  phosphate  is  associated  with  animal  gela- 
tine, which  can  be  partially  extracted  by  boiling  bones  in  water  under 
a  high  pressure.  It  has  been  observed,  however,  that  the  phosphate, 
when  in  a  minute  state  of  division,  is  slightly  soluble  in  a  solution  of 
gelatine,  and  hence  bones,  from  which  the  jelly  has  been  partially  ex- 
tracted by  boiling,  will  be  deprived  of  a  certain  proportion  of  their  earthy 
matter  also.  They  will  have  lost  their  gelatine,  however,  in  a  greater 
proportion,  and  hence,  if  again  thoroughly  dried,  they  will  contain  a 
larger  per-centage  of  bone  earth  than  when  in  their  natural  state.  In 
this  country,  bones  are  seldom  boiled,  I  believe,  either  for  the  jelly  they 
give,  or  as  in  France  and  Germany  for  the  manufacture  of  glue,  though 
in  certain  localities  they  are  so  treated  in  open  vessels  for  the  sake  of  the 
oil  they  are  capable  of  yielding.  Such  boiled  bones  are  said  to  act  more 
quickly  when  applied  to  the  land,  but  to  be  less  permanent  in  their  ef- 
fects. This  may  be  chiefly  owing  to  their  not  being  so  perfectly  dry  as 
the  unboiled  bones.  Being  thus  moist,  they  will  contain,  in  the  same 
weight,  a  comparatively  smaller  quantity  both  of  the  animal  gelatine 

*  If  to  a  solution  of  bone  earth  in  mnriafic  acid  (spirit  of  salt),  liquid  ammonia  (hartshorn) 
be  added,  the  solution  will  become  mlllty,  and  a  white  powder  will  fall,  which  is  the  earth 
of  bones  in  an  extremely  minute  slate  of  division.  Ifthisjmwder  be  washed  by  repeated  aifu- 
eions  of  pure  water,  and  be  afterwards  well  shaken  witli  water  which  is  saturated  with  car- 
bonic acid,  or  through  which  a  current  of  this  gas  is  made  to  pass,  a  sensible  portion  of  the 
phosphate  will  be  found  to  be  talcen  up  by  the  water.  This  will  appear  on  decanting  the 
solution  and  evaporating  it  to  dryness,  when  a  quantity  of  the  white  powder  will  remain  be- 
hind. Ttie  mean  of  10  experiments  made  in  this  way  gave  me  30  grains  for  the  quantity  of 
phosphate  taken  up  by  an  imperial  gallon  of  water.  What  takes  place  in  this  way  in  our 
hands,  happens  also  in  the  soil.  Not  only  does  that  which  enters  tlie  root  bear  with  it  a  por- 
tion of  this  compound  where  it  exists  in  the  soil,  but  the  superabundant  water  also  which 
runs  off  the  surface  or  sinks  througli  to  the  drains,  carries  with  it  to  the  rivers  in  its  coursft 
a  still  larger  quantity  of  this  soluble  compound,  and  thus  gradually  lessens  tliat  supply  ot 
pliosphate  which  either  exists  naturally  iu  the  soil,  or  has  been  added  as  a  manure  by  the 
practical  agriculturist. 


198  ACID  OR  BI-PHOSPIIATE  OF  LIME. 

and  of  the  earthy  jjhosphate,  while  they  will  also  be  more  susceptible  of 
l^peedy  deconijjosition  when  buried  in  the  soil.* 

In  solutions  of  common  salt  and  of  sal-ammoniac,  the  earth  of  bones 
is  also  slightly  soluble,  and  cases  may  occur  where  the  presence  of 
these  com{)ounds  in  the  soil  may  facilitate  the  conveyance  of  the  earthy 
phosphate  into  the  roots  of  plants. 

B.  Acid  or  B'l- Phosphate  of  Lime. — When  burned  bones  are  reduced 
to  powder,  and  digested  in  sulphuric  acid  (oil  of  vitriol),  diluted  with 
once  or  twice  its  weight  of  water,  the  acid  combines  with  a  portion  of  the 
lime,  and  forms  sulphate  of  lime  (gypsum),  while  the  remainder  of  the 
lime  and  the  whole  of  the  phosphoric  acid  are  dissolved.  The  solution, 
therefore,  contains  an  acid  phosphate  of  lime,  or  one  in  which  the  phos- 
phoric acid  exists,  in  much  larger  quantity  than  in  the  earth  of  bones. 
The  true  bi-phosphate,  when  free  from  water,  consists  of  71i  of  phos- 
phoric acid,  and  28i  of  lime.  It  exists  in  the  urine  of  most  animals,  and 
is  therefore  an  important  constituent  of  liquid  manures  of  animal  origin. 

If  the  mixture  of  gypsum  and  acid  phosphate,  above  described,  be 
largely  diluted  with  water,  it  will  form  a  most  valuable  liquid  manure, 
especially  for  grass  land,  and  for  crops  of  rising  corn.  In  this  liquid 
state,  the  phosphoric  acid  will  diffuse  itself  easily  and  perfectly  through- 
out the  soil,  and  there  will  speedily  lose  its  acid  character  by  combining 
with  one  or  other  of  the  basicf  substances,  almost  always  present  in 
every  variety  of  land. 

Or  if  to  the  solution,  before  it  is  applied  to  the  land,  a  quantity  of  pearl- 
ash  be  added  until  it  begin  to  turn  milky,  a  mixture  of  the  phosphates 
with  the  sulphatcy  of  lime  and  of  potash  will  be  obtained,  or — if  soda  be 
added  instead  of  potash— of  the  phosphates  with  the  sulphates  of  lime 
and  of  soda;  either  of  which  mixtures  will  be  still  more  efficacious 
upon  the  land,  thanihe  solution  of  the  acid  phosphates  alone. 

Or  to  the  solution  of  bones  in  the  acid,  the  potash  or  soda  may  be  added 
without  further  dilution,  and  the  whole  then  dried  up  by  the  addition  of 
charcoal  powder,  or  even  of  vegetable  mould,  till  it  is  in  a  sufficiently 
dry  state  to  be  scattered  with  the  hand  as  a  top-dressing,  or  buried  in 
the  land  by  means  of  a  drill. 

I  have  above  alluded  to  the  employment  of  bones  in  France  and  Ger- 
many, for  the  manufacture  of  glue.  For  this  purpose  the  broken  bones 
are  digested  in  weak  muriatic  acid,  by  which  the  earthy  matter  is  dis- 
solved, and  the  gelatine  left  behind.  The  gelatinous  skeleton  is  boiled 
down  for  glue,  and  the  solution  of  the  bone  earth  is  thrown  away.  This 
solution  contains  a  mixture  of  the  acid  phosphate  of  lime  with  chloride 
of  calcium, — and  might  be  used  up  in  any  of  the  ways  above  described, 
with  manifest  benefit  to  the  land.  The  glue  prepared  by  this  method, 
however,  is  said  to  be  inferior  in  quality,  and  as  the  process  is  not  adopts 
ed  in  this  country,  the  opportunity  of  making  an  economical  application 
of  this  waste  material  is  not  likely  to  be  often  presented  to  the  English 
farmer. 

'  The  relative  value  of  crushed  bones  in  these  two  states,  is  indicated  by  the  price  of  the 
unboiled  being  about  7  guineas,  while  ihat  of  boiled  is  only  about  4  guineas  a  ton. 

t  This  word  has  already  been  used  and  explained--it  is  applied  to  potash,  soda,  ammonia, 
lime,  magnesia,  and  other  substances,  which  have  the  properly  of  combining  with  acids  (sul- 
phuric, nitric,  &c.)  and  of  thus  neutrcUiziiig  them,  or  deprivlT-^  them  of  their  acid  qualities 
and  effects. 


NATIVE    PHOSPHATE    OF    LIME.  199 

C.  Native  Phosphate  of  Lime  or  Apatite, — In  some  parts  of  the  world; 
a  hard  mineral  substance,  commonly  known  by  the  name  of  Apatite, 
occurs  in  considerable  quantity.  It  consists  chiefly  of  a  phosphate  of 
lime,  which  differs  but  slightly  in  its  constitution  from  the  earth  of  bones, 
— containing  54|^  per  cent,  of  lime,  while  the  latter  contains  only  51|^  per 
cent.  Tlie  composition  of  this  mineral  would  lead  us  to  expect  it  to 
possess  a  favourable  action  upon  vegetation,  and  this  anticipation  has 
been  confirmed  by  some  experiments  made  with  it  on  a  limited  scale  by 
Sprengel. — [Cheraie,  I.,  p.  64.] 

It  occurs  occasionally  in  mineral  veins,  especially  such  as. are  found 
in  the  granitic  and  slate  rocks.  Masses  of  it  are  met  with  in  Cumber- 
land, in  Cornwall,  in  Finland,  in  the  iron  mines  of  Arendahl  in  Nor- 
way, and  in  many  other  localities.  A  variety  of  it  distinguished  by  the 
name  of  phosphorite  is  said  to  form  beds  at  Schlachenwalde  in  Bohemia, 
^and  in  the  province  of  Estremadura  in  Spain.  From  the  last  of  these 
localities  being  the  most  accessible,  the  time  may  come  when  the  high 
price  of  bones  may  induce  our  enterprising  merchants  to  import  it,  for 
the  purpose  of  being  employed  in  a  finely  powdered  state  as  a  fertilizer 
of  the  land. 


LECTURE  X. 

Inorganic  constituents  of  plants  continued.— Magnesia,  Alumina,  Silica,  and  the  Oxides  of 
Iron  and  Manganese. — Tabular  view  of  the  constitution  of  the  inorganic  substances  de- 
scribed.— Proportions  in  which  these  several  substances  are  found  in  the  plants  cultivated 
for  food.— Extent  to  which  these  plants  exhaust  the  soil  of  inorganic  vegetable  food.— State 
in  which  the  inorganic  elements  exist  in  plants. 

§  1.  Inorganic  constituents  of  plants  continued. 

VIII. — MAGNKSIUM,    MAGNESIA,  CARBONATE,  SULPHATE,    NITRATE,  ANT> 
^  PHOSPHATE    OF    MAGNESIA,    CHLORIDE    OF    MAGNESIUM. 

1°.  Carbonate  of  Magnesia  is  a  tasteless  earthy  compound,  which  in 
some  parts  of  the  world  forms  rocky  masses  and  veins  of  considerable 
height  and  thickness.  It  occurs  more  largely,  however',  in  connection 
with  carbonate  of  lime  in  the  magnesian  limestones,  so  well  known  in 
the  eastern  and  northern  parts  of  England, — and  in  similar  rocks,  dis- 
tinguished by  the  name  of  dolomites  or  of  dolomitic  limestones,  in  va- 
rious countries  of  Europe.  The  pure,  exceedingly  light,  white  magne- 
sia of  the  shops,  is  partly  extracted  from  the  magnesian  limestone,  and 
partly  from  the  mother  liquor  of  the  salt  pans,  which  generally  contains 
much  magnesia. 

When  pure  and  dry,  carbonate  of  magnesia  consists  of  43^^  of  magne- 
sia, and  51 1  of  carbonic  acid.  It  dissolves  readily  in  diluted  acids  (sul- 
phuric, muriatic,  and  acetic,)  the  carbonic  acid  at  the  same  time  esca- 
ping with  effervescence. 

Existing  as  it  does  in  many  solid  rocks,  this  carbonate  of  magnesia 
may  be  expected  to  be  present  in  the  soil,  and  it  is  found  in  the  ashes  of 
many  plants.  Of  the  ashes  of  some  parts  of  plants  it  constitutes  one- 
sixth  of  the  entire  weight. 

When  exposed  to  the  air  in  a  finely  divided  state,  it  gradually  absorbs 
a  quantity  of  moisture  from  the  atmosphere,  equal  to  two-thirds  of  its 
own  weight.  In  this  state,  it  dissolves  in  48  times  its  weight  of  water, 
though,  when  dry,  it  is  nearly  insoluble.  Like  carbonate  of  lime  it  is 
also  soluble  -in  water  impregnated  with  carbonic  acid,  but  in  a  some- 
what greater  degree.  In  this  state  of  solution  it  may  be  readily  carried 
into  the  roots,  and  be  the  means  of  supplying  to  the  ])arts  of  living  ve- 
getables a  portion  of  that  magnesia  which  is  necessary  to  their  perfect 
growth. 

Soils  containing  much  of  this  carbonate  of  magnesia  are  said  to  be 
highly  absorbent  of  moisture,  and  to  this  cause  is  ascribed  the  coldness  of 
such  soils. — [Sprengel,  Chemie,  I.,  p.  645.]  This  opinion  is,  however, 
open  to  doubt. 

2°.  Magnesia  or  Caustic  Magnesia,  the  calcined  magnesia  of  the 
shops. — When  the  carbonate  of  magnesia  is  heated  to  redness  in  the 
open  air,  it  parts  with  its  carbonic  acid  much  more  readily  than  lime 
does,  and  is  brought  into  the  state  of  pure  or  caustic  magnesia.  In  this 
state  it  does  not  occur  in  nature,  but  it  is  occasionally  met  with  in  com- 


CAUSTIC    OR   CALCINED 


jvAgnesia.  201 


bination  with  about  30  per  cent,  of  water.  When  magnesian  lime- 
stones or  dolomites  are  burned,  the  quick-lime  obtained  often  contains 
caustic  magnesia  also  in  considerable  quantity.  This  mixture  is  fre- 
quently appHed  to  the  land,  and,  as  is  well  known  in  many  parts  of 
England,  with  injurious  effects,  if  laid  on  in  too  large  quantities.  The 
cause  of  this  hot  or  burning  nature,  as  it  is  called,  of  magnesian  lime,  is 
not  very  satisfactorily  ascertained.  I  shall,  however,  slate  two  or  three 
facts,  which  may  assist  in  conducting  us  to  the  true  cause. 

1°.  Quick-lime  dissolves  in  750  times  its  weight  of  water,  at  the  or- 
dinary temperature  of  the  atmosphere,  while  pure  magnesia  requires 
5142  times  its  weight.  The  magnesia,  therefore,  is  not  likely  to  injure 
living  plants  directly  by  entering  into  their  roots  in  its  caustic  state,  since 
lime  which  is  seven  times  more  soluble  produces  no  injurious  effect. 

2°.  It  seems  to  be  the  result  of  experience,  that  magnesia  in  the  state 
of  carbonate  is  but  slightly  injurious  to  the  land  ;  some  deny  that  in  this 
state  it  has  any  injurious  effect  at  all.  This  I  fear  is  doubtful ;  we  may 
infer,  however,  with  some  degree  of  probability,  that  it  is  from  some 
property  possessed  by  magnesia  in  the  caustic  state,  and  not  possessed, 
or  at  least  in  an  equal  degree,  either  by  quick-lime  or  by  carbonate  of 
magnesia,  that  its  evil  influence  is  chiefly  to  be  ascribed. 

3°.  When  exposed  to  the  air,  quick-lime  speedily  absorbs  water  and 
carbonic  acid  from  the  air,  forming  first  a  hydrate*  in  fine  powder,  and 
then  a  carbonate.  Caustic  magnesia  absorbs  both  of  these  more  slowly 
than  lirnedoes,  and  in  the  presence  of  the  latter,  or  wjien  mixed  with  it, 
must  absorb  them  more  slowly  still,  since  the  lime  will  seize  on  the 
greater  portion  of  the  moisture  and  carbonic  acid  which  exists  in  tlie  air, 
immediately  surrounding  both.  When  slaked  in  the  air  also,  the  lime 
may  be  transformed  in  great  part  into  carbonate,  while  the  magnesia 
still  remains  in  the  state  of  hydrate,  and  it  is  a  property  of  this  hydrate 
to  attract  carbonic  acid  more  feebly  and  slowly,  even  than  the  newly 
burned  magnesia  as  it  comes  from  the  kiln.  Hence  when  buried  in  the 
soil,  after  the  lime  has  become  nearly  all  transformed  into  carbonate,  the 
magnesia  may  still  be  all  either  in  the  dry  caustic  state,  or  in  that  of  a 
hydrate  only. 

4°.  Now  there  exist  in  the  soil,  and  probably  are  exuded  from  the 
living  roots,  various  add  substances,  both  of  organic  and  of  inorganic 
origin,  which  it  is  one  of  the  functions  of  lime,  when  applied  to  the  land, 
to  combine  with  and  render  innoxious.  But  these  acid  cojn pounds  unite 
rather  with  the  caustic  magnesia,  than  with  the  lime  which  is  already 
in  combination  with  carbonic  acid — and  {orm  salts,]  which  generally- are 
much  more  soluble  in  ivater  than  the  compounds  of  lime  with  the  same 
acids.  Hence  the  water  that  goes  to  the  roots  reaches  them  more  or 
less  loaded  with  magnesian  salts,  and  carries  into  the  vegetable  circula- 
tion more  magnesia  than  is  consistent  with  the  Jiealthy  growth  of  the 
j)lant. 

It  is  hazardous  to  reason  from  the  phenomena  of  animal  to  those  of 

•  Compounds  of  substances  with  watftr  are  called  hydrates  (from  the  Greek  word  for  wa 
t^.)  Thus  slaked  lime,  a  compound  of  lime  with  water,  is  called  hydrate  oflime—Sind  the 
native  compound  of  magnesia  with  water,  alluded  to  in  the  text,  is  called  hydrate  of  mag- 
nesia. 

•  t  Compounds  of  the  bases, — potash,  soda,  lime,  magnesia,  &c., — with  acids, — sulphuric, 
muriatic,  nitric,  acetic  (or  vinegar),  &c.,— are  called  salts. 

9* 


202  MAGNE3IUM,%ND  CHLORIDE  OF  MAGNESIUM. 

vegetable  physiology,  yet  if  lime  and  magnesia  have  the  power  of  dif- 
ferently afiecting  the  animal  economy,  why  may  they  not  also  very 
differently  adect  the  vegetable  economy  ?  And  since  in  the  same  cir- 
cumstances, and  in  combination  with  the  substances  they  meet  with 
in  the  same  soils,  magnesia  is  capable  of  entering  more  largely  into 
a  plant  by  its  roots — may  not  magnesia  be  considered  capable  of  poi- 
soning a  plant,  when  lime  in  the  same  condition  would  only  improve 
the  soil  ? 

I  have  said  that  it  may  be  doubted  whether  magnesia  in  the  state  of 
carbonate  is  wholly  unhuriful  to  the  land.  This  doubt  rests  on  the  fact 
that  the  magnesia  retains  its  carbonic  acid  more  feebly  than  lime  does 
— and  therefore  its  carbonate  is  the  more  easily  decomposed  when  an 
acid  body  comes  in  contact  with  both.  Though,  therefore,  the  mag- 
nesian  carbonate  will  not  lay  hold  of  all  acid  matter  so  readily  and  surely 
as  caustic  magnesia  may,  still  occasions  may  occur  where  acid  matters 
being  abundant  in  the  soil,  so  much  carbonate  of  magnesia  may  be  de- 
composed and  dissolved  as  to  render  the  water  absorbed  by  its  roots 
destructive  to  the  health  or  life  of  a  plant. 

In  reference  to  this  point,  however,  it  must  be  distinctly  understood, 
that  magnesia  is  one  of  the  kinds  of  inorganic  food  most  necessary  to 
plants,  that  a  certain  quantity  of  it  in  the  soil  is  absolutely  necessary  to 
the  growth  of  nearly  all  cultivated  plants,  and  that  it  is  only  when  it  is 
conveyed  to  the  roots  in  too  large  a  quantity,  that  it  proves  injurious  to 
vegetable  life. 

5°.  Magnesium  is  the  metallic  basis  of  magnesia.  Little  is  known 
of  its  properties,  owing  to  the  difficulty  of  preparing  it  in  any  consider- 
able quantity  for  the  purpose  of  experiment.  It  is  a  white  metal,  which, 
when  heated  in  the  air,  takes  fire  and  burns,  combining  with  the  oxygen 
of  the  atmosphere,  and  forming  magnesia.  It  is  not  known  to  occur  in 
nature  in  an  elementary  form,  and  therefore  is  not  supposed  directly  to 
influence  vegetation. 

6°.  Chloride  of  Magnesium. — When  calcined  or  carbonated  magne- 
sia is  dissolved  in  muriatic  acid,  and  the  solution  evajwrated  to  dryness, 
a  white  mass  is  obtained  which  is  a  chloride  of  magnesium,  consisting  of 
magnesium  and  chlorine  only.  This  compound  occurs  not  unfrequently 
in  the  soil,  associated  with  chloride  of  calcium.  It  is  met  with  also  in 
the  ash  of  plants,  while  in  sea  water,  and  in  that  of  some  salt  lakes,  it 
exists  in  very  considerable  (juantity.  Thus  100  parts  of  the  water  of 
the  Atlantic  have  been  found  to  contain  3i  of  chloride  of  magnesium, 
while  that  of  the  Dead  Sea  yields  about  24  parts  of  this  compound.* 
Hence  it  is  present  in  great  abundance  in  the  mother  liquor  of  the  salt 
pans,  and  it  is  from  the  refuse  chloride  in  this  liquor  that  the  magnesia 
of  the  shops,  as  above  stated,  is  frequently  prepared. 

The  chloride  of  magnesium  has  not  hitherto  been  made  the  subject  of 
direct  experiment  as  a  fertilizer  of  the  land.  From  the  fact,  however, 
that  plants  require  much  magnesia  and  some  chlorine,  there  is  reason  to 
believe  that,  if  cautiously  applied,  it  might  prove  beneficial  in  some  soils, 
and  especially  to  grain  crops.  Its  extreme  solubility  in  water,  however, 
suggests  the  use  of  caution  in  its  application.     The  safest  method  is  to 

*  100  parts  of  the  water  of  the  Dead  Sea  contain  also  about  lOJ  of  chloriUfi  jpf  p^l&iumi 
and  nearly  8  of  common  salt.  '  ' ": ;.'  "^  ^y  ^•^' ' 


NITRATE,  SULPHATE,  AND  niOSPHATE  OF  MAGNESIA.  203 

dissolve  it  in  a  large  quantity  of  water,  and  to  apply  it  to  the  young 
plant  by  means  of  a  water-cart.  In  this  way  the  refuse  of  the  salt 
works  miglit,  in  some  localities,  be  made  available  to  useful  purposes. 

Tlie  chloride  of  magnesium  is  decomposed  both  by  quick-lime  and  by 
carbonate  of  lime  ;  hence  when  applied  to  a  soil  containing  lime  ip 
either  of  these  states,  chloride  of  calcium  and  caustic  or  carbonated  mag 
nesia  will  be  produced. 

7°.  Nitrate  of  Magnesia  is  formed  by  dissolving  carbonate  of  magne- 
sia in  nitric  acid,  and  evaporating  the  solution.  It  attracts  moisture  from 
the  air  with  great  rapidity,  and  runs  into  a  liquid.  It  is  probably  formed 
naturally  in  soils  containiftg  magnesia,  in  the  same  way  as  nitrate  of 
lime  is  known  to  be  produced  in  soils  containing  lime.  [See  Lecture 
VIII.,  p.  159.]  No  direct  experiments  have  yet  been  made  as  to  its 
effects  upon  vegetation  ;  but  there  can  be  no  doubt  that  it  would  prove 
liighly  beneficial,  could  it  be  procured  at  a  sufficiently  cheap  rate  to  ad- 
mit of  its  economical  application  to  the  land. 

8°.  Sulj)hate  of  Magnesia — the  common  Epsom  salts  of  the  shops — 
is  formed  by  dissolving  carbonate  of  magnesia  in  diluted  sulphuric  acid. 
It  exists  in  nearly  all  soils  which  are  formed  from,  or  are  situated  in, 
the  neighbourhood  of  rocks  containing  magnesia.  In  some  soils  it  is  so 
abundant  that  in  dry  weather  it  forms  a  while  efflorescence  on  the  sur- 
face. This  has  been  observed  to  take  place  in  Bohemia,  Hungary,  and 
parts  of  Germany,  and  it  may  be  frequently  seen  in  warm  summer 
weather  in  the  neighbourhood  of  Durham.* 

This  salt  has  been  found  by  Sprengel  to  act  upon  vegetation  precisely 
in  the  same  way  as  gypsum  does,  and  on  tlie  same  kind  of  plants.  It 
must  be  used,  however,  in  smaller  quantity,  owing  to  its  great  solubili- 
ty. Its  higher  price  will  prevent  its  ever  being  substituted  for  gypsum, 
as  a  top-dressing  for  clover,  &c.,  but  it  is  worth  the  trial,  whether  corn 
))lants,  the  gtain  of  which  contains  much  magnesia,  might  not  be  bene- 
fitted by  the  application  of  a  small  quantity  of  this  sulphate — along  with 
such  other  substances  as  are  capable  of  yielding  the  remaining  constit- 
uents which  compose  the  inorganic  matter  of  the  grain.  Its  price  is  not 
too  high  to  admit  of  this  more  restricted  application. f 

9°.  Phosphate  of  Magnesia. — Magnesia  exists  in  combination  with 
phosphoric  acid,  in  the  solids  and  fluids  of  all  animals,  though  not  so 
abundantly  as  tlie  phosphates  of  lime.  In  most  soils  phosphate  of  mag- 
nesia is  probable  present  in  minute  quantity,  since  in  the  ashes  of  some 
varieties  of  grain  it  is  found  in  very  considerable  proportion. 

Its  action  upon  vegetation  has  never  been  tried  directly,  but  as  it 
exists  in  urine,  and  in  most  animal  manures,  a  portion  of  their  efficac^)^ 
may  be  due  to  its  presence.  In  turf  ashes,  which  often  prove  a  valua- 
ble manure,  it  is  sometimes  met  with  in  appreciable  quantity,  and  their 
beneficial  operation  in  such  cases  has  been  attributed  in  part  to  the  agen- 
cy of  this  phosphate. 

'  It  occasionally  collects  beneath  the  plaster  of  old  walls  in  Durham.  In  one  of  the  lower 
rooms  of  the  old  Exchequer  buildings,  I  found  it  forming  an  extensive  layer  nearly  half  an 
inch  thick,  beneath  the  damp  plaster.  The  magnesia  is  derived  from  the  magnesian  lime- 
stone, used  both  for  mortar  and  for  building  stone. 

t  Its  price  in  Newcastle  in  the  state  of  crystals,  is  about  10s.  a  cwt.  The  impure  salt  col- 
lected at  the  alum  works  on  the  Yorkshire  coast,  might  be  obtained,  I  should  supj  ose,  for 
little  more  than  half  this  price. 


204  ALUMINA  THE  PRINCIPAL  CONSTITUENT  OF  CLAYS. 

IX. ALUMINIUM,    ALUMINA,    SULPHATE    AND    PHOSPHATE    OF 

ALUMINA — ALUM. 

1°.  Aluminium  is  another  of  those  rare  and  Httle  known  metals,  the 
existence  of  which  was  established  by  Sir  H.  Davy.  In  combination 
with  oxygen  it  forms  alumina,  and  in  this  state  it  exists  in  such  abun- 
dance in  nature,  as  to  form  a  large  pt 'tion  of  the  entire  crust  of  the 
globe. 

2°.  Alumina,  the  earth  of  Alum. — When  common  alum  is  dissolved 
in  water,  and  a  solution  of  carbonate  of  soda  or  of  ammonia  is  added  to 
it,  a  bulky  white  powder  falls,  which,  when  collected  on  a  filter,  well 
washed  and  dried,  is  nearly  pure  alumina.  This  substance  occurs  on 
the  surface  of  the  earth  in  a  pure  state  only  in  some  rare  minerals,  such 
as  the  corundum,  the  sapphire,  and  the  ruby, — but  it  constitutes  a  large 
proportion  of  all  the  slaty  and  shaley  rocks.  It  is  the  principal  ingre- 
dient also  of  all  clays  (pipe-clay  for  example)  and  clayey  soils,  which 
increase  in  tenacity  in  proportion  to  the  quantity  of  alumina  they  contain. 

"When  pure,  it  is  a  white  tasteless  earthy  substance,  which  adheres  to 
the  tongue,  has  a  density  of  2-00,  and  is  insoluble  in  water,  but  dissolves 
readily  in  caustic  potash  and  soda  and  in  most  acids,  at  least  when  new- 
ly thrown  down  from  a  solution  of  alum.  When  heated  to  redness, 
however,  it  becomes  hard  and  dense,  as  in  burned  clay  and  fire  bricks, 
and  can  then  only  be  dissolved  with  extreme  difficulty,  even  by  the 
strongest  acids.  Though  it  exists  so  largely  in  the  soil,  it  contributes 
but  little  in  a  direct  manner  to  the  nourishment  of  plants.  The  ash  they 
leave  contains  in  general  but  a  very  small  per-centage  of  alumina,  as 
will  more  clearly  appear  hereafter, — the  principal  agency,  therefore,  of 
this  ingredient  of  the  soil  is  most  probably  of  an  indirect,  perhaps  of  a 
mechanical  kind. 

It  has  been  stated  in  a  preceding  Lecture  (p.  23),  that  charcoal  has 
the  property  of  absorbing  gaseous  substances,  such  as  ammonia,  from 
the  atmosphere,  and  that  the  action  of  charcoal  powder,  in  promoting 
vegetation,  has  been  in  a  great  measure  ascribed  to  this  property.  The 
same  property,  we  have  also  seen  (p.  136),  is  ascribed  to  gypsum,  and 
hence  its  fertilizing  action  has  been  explained  in  a  similar  way.  Alum- 
ina is  said  to  be  equally  absorbent  of  ammonia ;  and  the  use  of  burned 
clay  as  a  top-dressing,  so  strongly  recommended  by  General  Beatson, 
[iVew  System  of  Cultivation,  London,  1820,]  is  ascribed  to  its  power 
of  abstracting  ammonia  from  the  air,  and  fixing  it  in  the  soil  ready  to  be 
conveyed  by  the  rains  to  the  roots  of  the  plants  that  grow  upon  it  [Liebig, 
p.  90.]  It  has  been  already  shown  (p.  136,)  that  this  mode  of  ac- 
counting for  the  action  of  gypsum  is  not  satisfactory  as  a  sole  cause — in 
the  case  of  alumina,  the  fact  of  its  absorbing  ammonia  is  hypothetical,* 
and  therefore  the  explanation  founded  upon  this  fact  is  not  to  be  impli- 
citly relied  upon. 

3°.  Sulphate  of  Alumina. — When  alumina  is  digested  in  diluted  sul- 

Because  clays  of  many  varieties— pipe-clay  for  example— contain  traces  of  ammonia, 
which  they  evolve  when  moistened  with  a  solution  of  caustic  potash,— it  is  inferred  that 
they  have  absorbed  this  ammonia  from  the  atmosphere.  The  same  inference  is  drawn 
from  tlie  fact  of  its  presence  in  oxide  of  iron. — [Liebig's  Organic  Chemistry  applied  to  Agri- 
culture, p.  89.] — In  neither  case  does  the  inference  appear  to  me  to  be  necessary.  Much  of 
the  ammonia  may  have  been  formed  in  the  soil,  during  the  oxidation  of  the  iron  itself,  oi 
during  tlic  decay  of  vegetable  and  animal  substances.— See  above.  Lecture  VIII.,  p.  153. 


SULPHATE  AND  PHOSPHATES  OF  ALUMINA,  ALUM.        205 

phuric  acid,  it  readily  dissolves,  and  forms  a  solution  of  sulphate  of 
alumina.  This  solution  is  characterized  by  a  remarkable  and  almost 
peculiar  sweetish  astringent  taste.  When  evaporated  to  dryness  it  yields 
a  white  salt,  which  dissolves  in  twice  its  weight  of  water  only,  and  when 
exposed  to  the  air,  attracts  moisture  rapidly,  and  spontaneously  runs  to 
a  liquid.  This  salt  exists  in  some  soils,  especially  in  those  of  wet, 
marshy,  and  peaty  lands. 

No  experiments  have  yet  been  made  with  the  view  of  determining  its 
direct  influence  upon  vegetation. 

4°.  Phosphates  of  Alumina. — In  combination  with  phosphoric  acid, 
alumina  forms  one  compound  well  known  to  mineralogists,  by  the  name 
o(  wavetlite.  This  mineral,  however,  occurs  in  too  small  quantity  to  be 
an  object  of  interest  to  the  agriculturist. 

Phosphoric  acid  is  disseminated  in  some  form  or  other  throughout  our 
clayey  soils,  though  in  very  small  and  variable  quantity.  It  is  most 
probable  that  in  these  soils  a  portion  of  the  acid  at  least  is  in  combina- 
tion with  the  alumina  in  the  state  of  phosphate.  One  of  the  most  diffi- 
cult problems  in  analytical  chemistry  is  toefTect  a  perfect  separation  of  a 
small  proportion  of  phosphoric  acid  from  alumina,  and  rigorously  to  esti- 
mate its  quantity ;  hence  in  the  greater  part  of  the  analyses  of  soils  hitherto 
published,  this  most  important  ingredient  in  a  fertile  soil  (the  phosphoric 
acid),  when  in  combination  with,  or  in  presence  of  alumina,  has  either 
been  altogether  neglected,  or  rudely  guessed  at,  or  indicated  by  a  rough 
approximation  only.  We  have  no  direct  proof,  therefore,  of  the  extent 
to  which  the  phosphates  of  alumina  exist  in  different  soils. 

5°.  Alum. — The  common  alum  of  the  shops  owes  its  well  known 
sweetish  astringent  taste  to  the  presence  of  the  above  sulphate  of  alumi- 
na. It  consists  in  100  parts  of  about  40  of  sulphate  of  alumina,  14^  of 
potash,  [described  p.  189,]  and  45j  of  water.  Alum  is  formed  naturally 
on  many  parts  of  the  earth's  surface,  especially  as  an  efHorescence  on 
certain  soils,  and  on  some  rocks  when  exposed  to  the  air, — as  on  the 
alum  shales  of  the  Yorkshire  coast.  It  is  largely  manufactured  by  cal- 
cining, and  afterwards  washing  these  alum  shales. 

Alum  has  not  been  extensively  tried  as  a  manure.  Its  composition, 
liowever,  would  lead  us  to  expect  it  to  exert  a  beneficial  influence  on  the 
growth  of  many  plants — while  the  price,  especially  of  the  less  pure  va- 
rieties, is  such  as  to  admit  of  its  being  applied  to  the  land  at  a  compara- 
tively small  cost.  From  some  experiments  made  on  a  small  scale, 
Sprengel  considers  it  highly  worthy  the  attention  of  the  practical  agri 
culturist. 

X. SILICA,  SILICON,  SILICATES  OF  POTASH,  OF  SODA,  OF  LIME,  OF 

MAGNESIA,  AND  OF  ALUMINA. 

1°.  Silica. — The  chief  ingredient  in  all  sand-stones  and  in  nearly  all 
sands  and  sandy  soils,  is  known  to  chemists  by  the  name  of  silica.  Flints 
are  nearly  pure  silex  or  silica — common  quartz  rock  is  another  form  of 
the  same  substance — while  the  colourless  and  more  or  less  transparent 
varieties  of  rock  crystal  and  chalcedony  present  it  in  a  state  of  almost 
perfect  purity-  It  exists  abundantly  in  almost  all  soils,  constituting 
what  is  called  their  siliceous  portion,  and  is  found  in  the  ashes  of  all 
plants  without  exception,  but  especially  in  those  of  the  grasses.     Silica 


806  SILICA,  SILICON,  SILICATES  OF  POTASH  A^TD    jODA. 

is  without  colour,  taste,  or  smell,  and  cannot  be  melted  by  the  strongest 
heat.  As  it  occurs  in  the  mineral  kingdom — in  the  state  of  flint,  of 
quartz,  or  of  sand — it  is  perfectly  insoluble  in  pure  water,  either  cold  or 
hot,  does  not  dissolve  in  acid  and  very  slowly  in  alkaline  solutions. 
"When  mixed  with  potash,  soda,  or  lime,  and  heated  in  a  crucible  to  a 
high  temperature,  it  melts  and  forms  a  glass.  Window  and  plate  glass 
consists  chiefly  of  silica,  lime,  and  soda,  Jlint  glass  contains  litharge 
[oxide  of  lead]  in  place  of  the  lime.  But  though  the  various  forms  of 
more  or  less  pure  silica,  which  are  met  with  in  the  mineral  kingdom, 
are  absolutely  insoluble  in  water,  j'et  it  sometimes  occurs  in  nature,  and 
can  readily  be  prepared  in  a  state  in  which  pure  water,  and  even  acid 
solutions,  will  take  it  up  in  considerable  quantity.  In  tiiis  stale  it  may 
be  obtained  by  reducing  crown-glass  to  a  fine  powder,  and  digesting  it 
in  strong  muriatic  acid,  or  by  melting  quartz  sand  in  a  large  quantity  of 
potash  or  soda,  and  afterwards  tre£'*^ng  the  glass  that  is  formed  with  di- 
luted muriatic  acid. 

Silica  is  one  of  jtfae  most  abunda.  i  substances  in  nature,  and  in  com- 
bination with  potash,  soda,  lime,  magnesia,  and  alumina,  it  forms  a 
large  portion  of  all  the  so-called  crystalline  (granitic,  basaltic,  &c.) 
rocks.  The  compounds  of  silica,  with  these  bases,  are  called  silicates. 
By  the  action  of  tiie  air,  and  other  causes,  these  silicates  undergo  decom- 
position, as  glass  does  when  digested  with  muriatic  acid,  and  the  silica 
is  separated  in  the  soluble  state.  Hence  its  presence  in  considerable 
quantity  in  the  waters  of  many  mineral  and  especially  hot  mineral 
springs,  and  in  appreciable  proportion  in  nearly  all  waters  that  rise  from 
any  considerable  depth  beneath  the  surface,  or  have  made  their  way 
through  any  considerable  extent  of  soil. 

In  the  substance  of  living  vegetables  it  exists,  for  the  most  part,  in 
this  state  of  combination — as  well  as  in  the  form  of  an  extrf  mely  deli- 
cate tissue,  of  which  the  fibres  are  exceedingly  minute,  and  therefore 
expose  a  large  surface  to  the  action  of  any  decomposing  agent,  or  of  any 
liquid  capable  of  dissolving  it.  In  the  compost  heaps  these  silicates 
undergo  decomposition, — and  the  more  readily  the  less  they  have  been 
previously  dried,  or  the  greener  they  are, — and  the  silica  of  the  plant  is 
liberated  in  a  soluble  slate.  Whether  or  not,  when  thus  liberated,  it 
will  be  carried,  uncombined,  into  the  roots  of  the  plants  by  the  water 
they  absorb,  will  depend  upon  the  quantity  of  potash  or  soda  in  the 
compost  or  in  the  soil,  and  upon  other  circumstances  hereafter  to  be 
explained. 

2°.  Silicon  is  known  only  in  the  state  of  a  dark  brown  powder,  which 
has  not  as  yet  been  met  with  in  nature  in  an  elementary  form,  and  is 
jirepared  by  the  chemist  with  considerable  difficulty.  Whefi  heated  in 
the  air,  or  in  oxygen  gas,  it  burns,  combines  with  oxygen,  and  is  con- 
verted into  silica.  Silica,  therefore,  in  its  various  forms,  is  a  compound 
of  silicon  with  oxygen.  It  consists  of  48  per  cent,  of  the  former  and  62 
per  cent,  of  the  latter. 

3°.  Silicates  of  Potash  and  Soda. — When  finely  powdered  quartz, 
flint,  or  sand,  is  mixed  with  from  one-half  to  three  limes  its  weight  of 
dry  carbonate  of  potash  or  soda,  and  exposed  to  a  strong  heat  in  a  cruci- 
ble, it  readily  unites  with  the  potash  or  soda,  and  forms  a  glass.  This 
glass  is  a  silicaf.i  or  a  mixture  of  two  or  more  silicates  of  potash  or  soda. 


DECOMPOSED  BY  THE  CARBONIC  ACID  Of  THE  AIR.  207 

Silica  combines  with  these  alkalies*  in  various  proportions.  If  it  be 
melted  with  much  potash,  the  glass  obtained  will  be  readily  soluble  in 
water*  if  with  little,  the  silicate  which  is  formed  will  resist  the  action 
of  water  for  any  length  of  time.  Window  and  plate-glass  contain 
much  silicate  of  potash  or  soda.  A  large  quantity  of  alkali  renders 
these  varieties  of  glass  more  fusible  and  more  easily  worked,  but  at  the 
same  time  makes  them  more  susceptible  of  corrosion  or  tarnish  by  the 
action  of  the  air. 

The  insoluble  silicates  of  potash  and  soda  exist  also  in  many  mineral 
substances.  In  the  felspar  and  mica,  of  which  granite  in  a  great  mea- 
sure consists,  they  are  present  in  considerable  quantity.  The  former 
(felspar)  contains  one-third  of  its  weight  of  an  insoluble  silicate  of  potash, 
consisting  of  nearly  equal  weights  of  potash  and  silica.  In  the  variety 
called  albite  or  cleavelandite,  silicate  of  soda  alone  is  found,  while  in 
some  other  varieties  a  mixture  of  both  silicates  is  present.  In  mica  from 
12  to  20  per  cent,  of  the  same  silicate  of  potash  occurs,  but  soda  can 
rarely  be  detected  in  this  mineral.  The  trap-rocks  also  (whin,  basalt, 
green-stone),  so  abundant  in  many  parts  of  our  island,  consist  almost 
entirely  of  silicates.  Among  these,  however,  the  siUcates  of  potash  and 
Boda  rarely  exceed  5  or  6  per  cent,  of  the  whole  weight  of  the  rock,  and 
are  often  entirely  absent. 

Thes^  insoluble  silicates  also  exist  in  the  stems  and  leaves  of  nearly 
all  plants.  They  are  abundant  in  the  stems  of  the  grasses,  especially 
in  the  straw  of  the  cultivated  grains,  and  form  a  large  proportion  of  the 
ash  which  is  left  when  these  stems  are  burned  [p.  178.] 

It  is  important  to  the  agriculturist  to  understand  the  relation  which 
the  carbonic  acid  of  the  atmosj)here  bears  to  these  alkaline  silicates  which 
occur  in  the  mineral  and  vegetable  kingdom.  Insoluble  as  they  are  in 
water,  they  are  slowly  decomposed  by  the  united  action  of  the  moisture 
and  carbonic  acid  of  the  air,  the  latter  taking  the  potash  or  soda  from  the 
silica",  and  forming  carbonates  of  these  bases.  In  consequence  of  this 
decomposition  the  rock  disintegrates  and  crumbles  down,  while  the  so- 
luble carbonate  is  washed  down  by  the  rains  or  mists,  and  is  borne  to 
the  lower  grounds  to  enrich  the  alluvial  and  other  soils,  or  is  carried  by 
the  rivers  to  the  sea. 

In  some  cases,  as  in  the  softer  felspar  of  some  of  the  Cornish  granites, 
this  decomposition  is  comparatively  rapid,  in  others,  as  in  the  Dartmoor 
and  many  of  the  Scottish  granites,  it  is  exceedingly  slow, — but  in  all 
cases  the  rock  grumbles  to  powder  long  before  the  whole  of  the  silicates 
are  decomposed,  so  that  potash  and  soda  are  always  present  in  greater 
or  less  quantity  in  granitic  soils,  and  will  continue  to  be  separated  from 
the  decaying  fragments  of  rock  for  an  indefinite  period  of  time. 

But  the  silica  of  the  felspar,  or  mica,  or  zeoliticf  trap,  when  thus  de- 
prived of  the  potash  with  which  it  was  combined,  is  in  that  peculiar  state, 
in  which,  as  above  described  [p.  206],  it  is  capable  of  being  dissolved 
in  small  quantity  by  pure  water,  and  more  largely  by  a  solution  of 
carbonate  of  potash  or  soda.     Hence  the  same  rains  or  mists  which  dis- 

•  Potash,  soda,  and  ammonia  are  called  alkalies;  lime  and  magnesia  are  alkaline  earths. 
See  Lecture  III.,  p.  51,  note. 

t  The  trap-rocks  always  mors  or  less  abound  in  zeolitic  minerals,  of  which  there  is  a  great 
variety,  and  in  which  nearly  al  Jie  alkali  present  in  these  (trap)  rocks  is  contained. 


208  SILICATES  OF  LIME  IN  THE  TRAP- ROCKS. 

solve  the  alkaline  carbonates  so  slowly  formed,  iske  up  also  a  portion  of 
the  silica,  and  convey  it  in  a  state  of  solution  to  the  soils  or  to  the  rivers. 
Ti)us,  with  the  exception  of  the  dews  and  rains  which  fall  directly  from 
the  heavens,  few  of  the  suppHes  of  water  by  which  plants  are  refreshed 
and  fed,  ever  rea^h  their  roots  entirely  free  from  silica,  in  a  form  in 
which  it  can  readily  enter  into  their  roots,  and  be  appropriated  to  their 
nourishment. 

In  the  farm-yard  and  the  compost-heap,  wl^ere  vegetable  matters  are 
undergoing  decomposition,  the  silicates  they  contain  undergo  similar  de- 
compositions, and,  by  similar  chemical  change*  their  silica  is  rendered 
soluble,  and  thus  fitted,  when  mixed  with  the  soil,  again  to  minister  to 
the  wants  and  to  aid  the  growth  of  new  races  of  living  vegetables. 

4°.  Silicates  of  Lime. — A  mixture  of  sand  or  flint  with  quick-lime 
readily  melts  and  forms  a  glassy  silicate  or  a  mixture  of  two  or  more 
silicates  of  lime.  These  siHcates  are  also  present  in  large  quantity  in 
window  and  plate-glass,  and  in  some  of  the  crystalline*  (granite  and 
trap)  rocks.  In  felspar  and  mica,  which  abound,  as  we  have  seen,  in 
the  alkaline  siHcates,  it  is  rare  that  any  lime  can  be  detected.  In  that 
variety  of  granite,  however,  to  which  the  name  of  syenite  is  given  by 
mineralogists,  hornhlende  takes  the  place  of  mica,  and  some  varieties  of 
this  hornblende  contain  from  20  to  35  per  cent,  of  silicate  of  lime.  This 
silicate  (containing  38  per  cent,  of  lime)  is  almost  always  presen^  in  the 
basaltic  and  trap-rocks,  and  sometimes,  as  in  the  augiticf  traps,  in  a 
proportion  much  larger  than  that  in  which  it  exists  in  the  unmixed  horn- 
blende. To  this  fact  we  shall  have  occasion  to  revert  when  we  come 
to  consider  the  relative  fertility  of  different  soils  and  the  causes  on  which 
the  ditTerence  of  their  several  productive  powers  most  probably  depends. 

Silicates  of  lime  are  also  found  in  the  ash,  and  probably^  exist  in  the 
living  stem  and  leaves  of  plants. 

Like  the  similar  compounds  of  potash  and  soda,  the  silicates  of  lime 
are  slowly  decomposed  by  the  united  agency  of  the  moisture  and"  the 
carbonic  acid  of  the  atmosphere.  Carbonate  of  lime  is  formed,  and 
silica  is  set  at  liberty.  This  carbonate  of  lime  dissolves  in  the  rains  or 
dews  which  descend  loaded  with  carbonic  acid,  [see  page  46,]  and  the 
same  waters  take  up  also  a  portion  of  the  soluble  silica  and  diffuse  both 
substances  uniformly  through  the  soil  in  which  the  decomposition  takes 
place,  or  bear  them  from  the  higher  grounds  to  the  fivers  and  plains. 
The  sparing  but  constant  and  long-continued  supply  of  lime  thus  af- 
forded to  soils  which  rest  upon  decayed  trap,  or  which  ar^  wholly  made 
up  of  rotten  rock,  has  a  material  influence  upon  their  well-known  agri- 
cultural capabilities. 

5°.  Silicates  of  Magnesia. — In  combination  with  magnesia  in  differ- 
ent proportions,  silica  forms  nearly  the  entire  mass  of  those  common 
minerals  known  by  the  names  of  serpentine  and  talc.  In  hornblende 
also  and  augite,  silicates  of  magnesia  exist  in  considerable  quantity. 

*  So  called  because  the  minerals  of  which  they  consist  are  generally  in  a.  cryatallized  state 
t  Rocks  of  which  the  mineral  called  augite  forms  a  more  or  less  considerable  part. 
1 1  Sdiy  probably,  because  if  uncombined  silica  be  present  in  hay  or  straw  along  with  cai 
bonate  or  oxalate  of  lime,  the  heat  employed  in  completely  burning  away  the  organic  mattei 
may  be  sufficient  to  cause  the  lime  and  silica  to  unite  and  form  a  silicate  wliicli  will  after- 
wards be  found  in  the  ash,  though  none  previously  existed  in  the  stem. 


SILICATES  OF  ALUMINA.  20i9 

They  must,  therefore,  be  present  in  greater  or  less  quantity  in  soils 
which  are  directly  formed  from  the  decomposition  of  such  rocks.  Like 
the  silicates  of  lime,  however — though  more  slowly  than  these — they 
will  undergo  gradual  decomposition  by  the  action  of  the  carbonic  acid 
of  the  atmosphere,  and  of  the  acids  produced  in  the  soil  by  vegetation 
and  by  the  decay  of  organic  matter.  The  magnesia,  like  the  lime,  will 
thus  be  gradually  brought  down,  in  a  state  of  solution  (p.  200),  from  the 
higher  grounds,  or  washed  out  of  the  soil,  till  at  length  it  may  wholly 
disappear  from  any  given  spot.* 

6°.  Silicates  of  Alumina. — Silica  combines  with  alumina  also  in  vari- 
ous proportions,  forming  silicates,  which  exist  abundantly  in  nature  in 
iJie  crystalline  rocks,  and  may  also,  like  the  other  silicates,  be  formed 
by  art.  Felspar,  mica,  hornblende,  and  the  augites,  which  abound  in 
the  trap-rocks,  all  contain  much  alumina  in  combination  with  silica,  and 
we  shall  probably  not  be  very  far  from  the  truth  in  assuming  that  up- 
wards of  one-half  by  weight  of  the  trap-rocks  in  general — as  well  as  of 
the  hornblendes,  micas,  and  felspars,  of  which  so  large  a  part  of  the 
granitic  rocks  is  composed — consists  of  silicaies  of  alumina.  The  alu- 
mina itself  in  these  several  minerals  varies  from  11  to  38  per  cent.,  but 
generally  averages  about  20  per  cent,  of  their  entire  weight. 

These  silicates,  when  they  occur  alone,  unmixed  or  uncombined  with 
other  silicates,  decompose  very  slowly  by  the  action  of  the  atmosphere. 
They  disintegrate,  however,  and  fall  to  powder,  when  the  alkaline  sili- 
cates with  which  they  are  associated  in  felspar,  &c.,  are  decomposed  and 
removed  by  atmospheric  causes.  In  this  way  the  deposits  of  porcelain 
clay,  so  common  in  Cornwall  and  in  other  countries,  have  been  pro- 
duced from  the  disintegration  of  the  felspathic  rocks,  and  the  clayey  soils 
wiiich  occur  in  granite  districts  have  not  unfrequently  had  a  similar  origin. 

When  contained  in  the  soil,  the  silicates  of  alumina  undergo  a  slow 
decomposi\ion  from  the  action  of  the  various  acid  substances  to  which  they 
are  exposed.  A  portion  of  their  alumina  is  dissolved  and  separated  by 
these  acids,  and  in  this  soluble  state  is  either  conveyed  to  the  roots  of 
plants  or  is  washed  from  the  soil  by  the  rains-^or  by  the  waters  that 
arise  from  beneath. 

The  ash  of  plants  contains  only  a  very  small  proportion  of  alumina, 
yet  even  this  small  quantity  they  cannot  derive  from  the  silicates  of  this 
substance,  since  these  are  all  insoluble  in  water — as  alumina  itself  is. 
They  obtain  it,  therefore,  from  some  of  those  soluble  compounds  of  alu- 
mina of  which  I  have  spoken  as  being  either  occasionally  present  (pp. 
204-5),  or  as  being  naturally  formed  in  the  soil. 


General  remarks  on  these  Silicates. — Of  all  these  silicates  it  may  be 
remarked  in  general — 

1°.  That  besides  existing  in  the  minerals  above-mentioned,  and  from 
which  they  are  conveyed  into  the  soil,  they  are  also  slowly  formed  in  the 

*  I  am  indebted  to  Sir  Charles  Lemon  for  the  analysis  of  a  soil,  on  part  of  his  own  proper 
ty,  resting  on  serpentine,  and  bearing  only  Erica  vagans,  which  illustrates  the  statement  in 
the  text.  This  soil  consists  of  silica  70,  alumina  with  a  trace  of  gypsum  20,  oxide  of  iron  62, 
and  vegetable  matter  3-8  percent.  If  this  soil  has  been  formed  from  the  rock  on  which  it 
rests,  the  magnesia  has  been  wholly  washed  out.  Its  constitution,  however,  points  rather  to 
a  decayed  felspar  or  slate  rock,  as  the  source  from  which  it  has  been  derived. 


-     21G  GENERAL  REMARKS  ON  THESE  SILICATES. 

sail  tself,  when  the  ingredients  of  which  tliey  severally  consist  are  na- 
turally present  in,  or  are  artificially  added  to,  the  soil.  Hence,  the  ad- 
dition of  potash  or  soda  to  the  land  may  cause  the  production  of  sili- 
cates of  these  alkalies — probahly  soluble  silicates — which  water  will 
be  capable  of  dissolving  and  bearing  to  the  extremities  of  the  roots. 
Hence  also,  in  a  sandy  soil,  the  addition  of  lime  may  give  rise  to  the 
production  of  insoluble  silicates  of  this  earth, — and  the  beneficial  effect 
of  the  lime  upon  the  land  may  thus  sooner  cease  to  be  observable  than 
in  soils  of  a  different  character,  where  it  is  not  so  liable  to  be  locked  up 
in  an  insoluble  state  of  combination  ;  and 

2°.  That  with  the  exception  of  those  of  potash  and  soda,  which  con- 
fain  much  alkali,  these  silicates  are  all  insoluble  in  water,  and  thus  not 
directly  available  to  the  nutrition  of  plants.  Except  those  of  alumina, 
however,  they  are  all  slowly  decomposed  by  atmospheric  agents,  and 
their  constituent  elements  thus  brought,  to  a  certain  extent,  within  the 
reach  of  plants;  while,  without  exception,  they  are  all  capable  of  de- 
composition in  the  soil  by  the  agency  of  the  acid  substances,  chiefly  or- 
ganic, which  there  exisf,  or  which  are  produced  during  the  growth  and 
decay  of  vegetable  substances.  From  this  latter  source,  the  chief  supply 
of  the  ingredients  contained  in  the  silicates,  is,  in  most  soils,  derived  by 
living  plants. 

To  this  cause  is  attributed  the  surprising  effect  often  observed  to  fol- 
low from  the  addition  of  vegetable  matter  to  a  sandy  soil  on  which  a 
prcN'ious  addition  of  lime  had  ceased  to  produce  any  further  beneficial 
effect.  The  organic  acids  formed  by  the  vegetable  matter  during  its  de- 
cay desompose  the  silicates  of  lime  previously  produced,  and  thus  liber- 
ale  the  lime  from  its  insoluble  stale  of  combination.  But  when  the  sili- 
cates have  been  all  decomposed  by  this  agency,  the  further  addition  of  ve- 
getable matter  ceases  necessarily  to  produce  the  same  remarkable  effects. 


XI. THE  OXIDES,  SULPHURETS,  SULPHATES,  AND  CARBONATES  OF  IRON. 

1°.  Oxides  of  Iron. — It  is  well  known  that  when  metallic  iron  is  ex- 
posed to  moist  air,  it  gradually  rusts  and  becomes  covered  with,  or  whol- 
ly changed  into,  a  crumbling  ochrey  mass  of  a  reddish  brown  colour. 
This  powder  is  a  compound  of  iron  and  oxygen  only,  containing  69j  per 
cent,  of  the  former,  and  30|  per  cent,  of  the  latter. 

When  iron  is  heated  in  the  smith's  forge,  and  then  beat  on  the  anvil,  a 
scale  flies  off"  which  is  of  a  black  colour,  and  when  crushed  gives  a  black 
powder.  This  also  consists  of  iron  and  oxygen  only,  but  the  proportion 
of  oxygen  is  not  so  great  as  in  the  red  powder  above  described.  In^both 
cases  the  iron  has  derived  its  oxygen  from  the  atmosphere. 

To  these  compounds  of  iron,  with  oxygen,  the  name  n£  oxides  is  given. 
There  are  only  two  which  are  of  interest  to  the  agriculturist,  namely, 

CONSISTING  OP 
/ —  ■  -/ ^ 

Iron,  Oxygen.  Symbol.  Colour. 
The ^rs«  oxide*  .  .  77-23  22-77  Fe  Of  Black 
The  second  oxide       .     69-34     30-66     FeaOg      Red. 

•  The  first  is  also  called  the  prot-oxide,  the  secona  either  the  sesqui,  or  more  usuallt/ th9 
oer  oxide  of  iron, 
t  Iron  is  represented  by  the  symbol  Fe,  the  initial  loUers  of  its  Latin  name  (ferrum). 


THE    OXIDES    OF    IRON.  211 

Both  of  these  ex  st  abundantly  in  nature,  and  are  present  to  a  greatef 
or  less  extent  in  all  soils.  The  second  or  ^er-oxide,  however,  is  by  far 
the  most  abundant  on  the  earth's  surface,  and  the  reddish  colour  obser- 
vable in  so  many  soils  is  principally  due  to  the  presence  of  this  oxide. 

The  first  oxide  rarely  occurs  in  the  soil  except  in  a  state  of  combina- 
tion with  some  acid  substance, — and  so  strong  is  its  tendency  to  combine 
with  more  oxygen,  that  when  exposed  to  the  air,  even  in  a  state  of  com- 
bination, it  rapidly  absorbs  this  element  from  the  atmosphere  and 
changes  into  per-oxide.  This  change  is  observable  in  all  chalybeate 
springs,  in  which,  as  they  rise  to  the  surface,  the  iron  is  generally  held 
in  solution  in  the  state  of  the  first  oxide.  After  a  brief  exposure  to  the 
air,  more  oxygen  is  absorbed,  and  a  reddish  pellicle  is  formed  on  the 
surface,  which  gradually  falls  and  coals  the  channel  along  which  the 
water  runs,  with  a  reddish  sediment  of  insoluble  per-oxide. 

Both  oxides  are  insoluble  in  pure  water,  and  both  dissolve  in  water 
containing  acids  in  solution.  The  first  oxide,  however,  dissolves  in 
much  greater  quantity  in  the  same  weight  of  acid,  and  it  is  the  com- 
pounds of  this  oxide  which  are  usually  present  in  the  soil,  and  which,  in 
boggy  lands,  prove  so  injurious  to  vegetation.* 

The  second  oxide  possesses  two  properties  which,  in  connection  with 
practical  agriculture,  are  not  void  of  some  degree  of  importance. 

1°.  In  a  soil  which  contains  much  vegetable  matter  in  a  state  of  de- 
cay, the  per-oxide  is  frequently  deprived  of  one-third  of  its  oxygen  by 
the  carbonaceous  matter,f  and  is  thus  converted  into  the  first  oxide 
which  readily  dissolves  in  any  of  the  acid  substances  with  which  it  may 
be  in  contact.  In  this  state  of  combination  it  is  more  or  less  soluble  in 
water,  and  in  some  localities  may  be  brought  to  the  roots  of  plants  in 
such  quantity  as  to  prove  injurious  to  their  growth. 

2°.  The  red  oxide  of  iron  is  said,  like  alumina  (p.  197),  to  have  the 
property  of  absorbing  ammonia,  and  probably  other  gaseous  substances 
and  vapours,  from  the  atmosphere  and  from  the  soil.  In  that  which 
occurs  in  nature,  either  in  the  soil  or  near  the  surface  of  mineral  veins, 
traces  of  ammonia  can  generally  be  detected.  Since  then  ammonia  is 
so  beneficial — according  to  some  so  indispensably  necessary — to  vegeta- 
tion, the  property  which  the  per-oxide  of  iron  possesses  of  retaining  this 
ammonia  when  it  would  otherwise  escape  from  the  soil,  or  of  absorbing 
it  from  the  atmosphere,  and  thus  bringing  it  within  the  reach  of  plants, 
must  also  be  indirectly  favourable  to  vegetation — where  the  soil  contains 
it  in  any  considerable  quantity. 

An  important  practical  precept  is  also  to  be  drawn  from  these  two  pro- 
perties of  this  oxide.  A  red  irony  soil,  to  which  manure  is  added, 
should  be  frequently  turned  over,  and  should  be  kept  loose  and  pervious 
to  the  air,  in  order  that  the  formation  of  prot-oxide  (first  oxide)  may  be 

•  "That  layer  of  soil  (says  Sprengel),  is  always  especially  rich  in  iron,  over  which  the  heel 
of  the  plough  glides  in  preparing  the  land.  The  friction  of  the  soil  continually  rubs  off  par- 
ticles of  iron,  which  absorb  oxygen  and  change  into  the  first  oxide.  Hence  this  part  of  the 
soil  is  always  darker  in  colour  than  the  rest;  hence  also  the  reason  why  the  soil  after  deep 
ploughing,  remains  unproductive  sometimes  for  several  years."— CAemt'e,  I.,  p.  428.  While 
we  admit  that  the  presence  of  (he  first  oxide  of  iron  in  the  subsoil  affects  its  fertility,  when 
brought  to  the  surface,  we  may  doubt  whether  much  of  that  iron  can  have  been  derived 
from  the  tear  and  wear  of  the  plough. 

t  The  carbon  of  the  vegetable  matter  combines  with  the  oxygen  of  the  oxide  to  form  cor- 
bonic  octd.— See  p.  63. 


212  SULPHURETS,  AND  SULPHATES  OF  IRON. 

prevented  as  much  as  possible ;  and  it  may  occasionally  be  summer- 
fallowed  with  advantage,  in  order  also  that  the  per-oxide  may  absorb 
from  the  air  those  volatile  substances  which  are  likely  to  prove  benefi- 
cial to  the  growth  of  the  future  crops. 

2°.  Sulpfiurets  of  Iron. — Iron  occurs  in  nature  combined  with  sulphur 
in  two  proportions,   forming  a  sulphuret  and    a   fez-sulphuret.     These 

consist  respectively — 

Iron.  Sulphur.        Symbol. 

The  sulphuret  .     .     .     62-77         37-23         Fe  S 
The  bi-sulphuret  of    .     45-74         54-26         Fe  83 
and  are  both  tasteless  and  insoluble  in  water. 

1°.  The  first  of  these,  the  sulphuret  (Fe  S),  occurs  occasionally  in 
boggy  and  marshy  soils,  in  which  salts  of  iron  exist,  or  into  which  they 
are  carried  by  rains  or  springs.  It  is  notitself  directly  injurious  to  vege- 
tation, but  when  exposed  to  the  air  it  absorbs  oxygen  and  forms  sulphate 
of  iron,  which,  when  present  in  sufficient  (]uantity,  is  eminently  so.* 

2°.  The  bi-sulphuret,  or  common  iron  pyrites  (Fe  So),  is  exceedingly 
abundant  in  nature.  It  occurs  in  nearly  all  rocky  formations — and  in 
most  soils.  It  abounds  in  coal,  and  is  the  source  of  the  sulphurous  smell 
which  many  varieties  emit  while  burning.  It  generally  presents  itself 
in  masses  of  a  yellow  colour  and  metallic  lustre,  more  or  less  perfectly 
crystallized  in  cubical  forms,  so  brittle  and  hard  as  to  strike  fire  with 
steel,  and  of  a  specific  gravhy  four  and  a  half  times  greater  than  that  of 
water  (Sp.  gr.  4,  5).  When  heated  in  close  vessels  it  parts  with  nearly 
one-half  of  its  sulphur,  and  hence  is  often  distilled  lor  the  sulphur  it 
yields. 

In  the  air  it  absorbs  oxygen,  in  some  cases — as  in  the  waste  coal 
heaps — with  such  rapidity  as  to  heat,  take  fire,  and  burn.  By  this  ab- 
sorption of  oxygen  (oxidation),  sulphuric  acid  and  sulphate  of  iron  are 
produced."  In  the  alum  shales  the  iron  pyrites  abounds,  and  these  are 
often  burned  for  the  purpose  of  converting  the  sulphur  and  sulphuric 
acid  for  the  subsequent  manufacture  of  alum. 

3°.  Sulphates  of  Iron. — Of  the  sulphates  of  iron  which  are  known, 
there  is  only  one — the  common  green  vitriol  o^  ihe  shops — that  occurs  in 
the  soil  in  any  considerable  quantity.  There  are  few  soils,  perhaps,  in 
which  its  presence  may  not  be  detected,  though  it  is  in  bogs  and  marshy 
places  that  it  is  most  generally  and  most  abundantly  met  with.  It  is 
often  exceedingly  injurious  to  vegetation  in  such  localities,  but  it  is  de- 
composed by  quick-lime,  by  chalk,  and  by  all  varieties  of  marl,  and 
thus  its  noxious  effects  may  in  gereral  be  entirely  prevented.  To  soils 
which  abound  in  lime,  it  may  even  be  applied  with  a  beneficial  effect. 

When  a  solution  of  this  salt  is  exposed  to  the  air  it  speedily  becomes 
covered  with  a  pellicle  of  a  yellow  ochrey  colour,  which  afterwards  falls 
as  a  yellow  sediment.  This  sediment  consists  of  per-oxide  of  iron,  con- 
taining a  little  sulphuric  acid ;  but  by  the  separation  of  this  oxide  the 
sulphuric  acid  is  left  in  excess  in  the  solution,  which  becomes  sour,  and 

*  Yet  in  small  quantity  it  may  be  beneficial.  Thus  Sprengel  mentions  that  the  subsoil  of 
a  moor  near  Hanover,  which  contains  some  of  this  sulphuret  of  iron,  produces  astonishing 
effects  when  laid  as  a  top-dressing  on  the  grass  lands.  Tlie  explanation  of  this  is,  that  ihe 
pyrites  absorb  oxygen  and  is  converted  into  sulptiale,  and  thus  re-produces  the  remarkable 
effects  observed  on  the  additijnof  gypsum,  of  sulphuric  acid,  or  of  sulphate  of  soda,  to  simi- 
lar grass  lands. 


CARBONATES  OF  IRON,  OXIDES  AND  SALTS  OF  MANGANESE.  213. 

Still  more  injurious  to  vegetation  than  before.  In  boggy  places  the 
waters  impregnated  with  iron  are  generally  more  or  less  in  this  acid 
state,  and  lime,  chalk,  and  marl,  with  perfect  drainage,  are  the  only 
available  means  by  which  such  lands  can  be  sweetened  and  rendered 
fertile. 

When  iron  pyrites  is  exposed  to  the  air  it  slowly  absorbs  oxygen,  and  is 
converted  into  sulphate  of  iron  and  sulphuric  acid  ;  on  the  other  hand,  the 
sour  solution  above  mentioned,  when  placed  in  contact  with  vegetable 
matter,  where  the  air  is  excluded,  parts  with  its  oxygen  to  thedecaying 
carbonaceous  matter,  and  is  again  converted  into  iron  pyrites.  These 
two  opposite  processes  are  both  continually  in  progress  in  nature,  and 
often  in  the  same  locality, — the  one  on  the  surface,  where  air  is  present ; 
the  other  in  the  subsoil,  where  the  air  is  excluded. 

4°.  Carbonates  of  Iron. — When  a  solution  of  the  sulphate  of  iron, 
above  described,  is  mixed  with  one  of  carbonate  of  soda,  a  3'ellow  powder 
falls,  which  is  carbonate  of  iron.  This  carbonate  is  found  abundantly  in 
nature.  It  is  the  state  in  which  the  iron  exists  in  the  ore  (clay-iron  ore,) 
from  which  this  metal  is  so  largely  extracted  in  our  iron  furnaces,  and 
in  the  similar  ore  often  found  in  the  subsoil  of  boggy  places,  which  is 
distinguished  by  the  name  of  bog-iron  ore. 

Like  the  carbonate  of  lime,  it  is  insoluble  in  water,  but  dissolves  with 
considerable  readiness  in  water  charged  with  carbonic  acid.  In  this 
stale  of  solution  it  issues  from  the  earth  in  most  of  our  chalybeate  springs, 
and  it  is  owing  to  the  escape  of  the  excess  of  carbonic  acid  from  the 
water,  when  it  reaches  the  open  air,  that  the  yellow  deposit  of  carbonate 
of  iron  more  or  less  speedily  falls. 

The  carbonate  of  iron,  being  insoluble  in  water,  cannot  be  directly  in- 
jurious to  vegetation.  When  exposed  to  the  air  it  gradually  parts  with 
its  carbonic  acid,  and  is  converted  into  per-oxide  of  iron. 

The  ash  of  nearly  all  plants  contains  a  more  or  less  appreciable  quan- 
tity of  oxide  of  ironic  This  may  have  entered  into  the  roots  either  in  the 
state  of  soluble  sulphate  or  of  carbonate  dissolved  in  carbonic  acid,  or  of 
some  other  of  those  numerous  soluble  compounds  of  iron  with  organic 
acids,  which  may  be  expected  to  be  occasionally  present  in  the  soil. 

XII. — manganese:  oxides,  chlorides,  carbonates,  and  sulphates 
or  manganese. 

1°.  Manganese  is  a  metal  which,  in  nature,  is  very  frequently  asso- 
ciated wiih"iron  in  its  various  ores.  It  also  resembles  this  metal  in 
many  of  its  properties.  In  the  metallic  state,  however,  it  is  not  an  ob- 
ject of  manufacture,  nor  is  it  used  for  any  purpose  in  the  arts. 

2°.  Oxides  of  Manganese. — Manganese  combines  with  oxygen  in 
several  proportions.  The  first  oxide  is  of  a  light  green  colour,  the  se- 
cond and  third  are  black.  The  first  is  not  known  to  occur  in  nature  in 
an  uncombined  state,  the  two  others  exist  abundantly  in  the  common 
ores  of  manganese,  and  are  extensively  diffused,  though  in  small  quan- 
tity, through  nearly  all  soils.  They  are  all  insoluble  in  water,  but  the 
two  former  dissolve  in  acids  and  form  salts.  Traces  of  these  two  oxides 
are  also  to  be  detected  in  the  ash  of  nearly  all  plants. 

3°.  Chloride^   Carbonate,  and  SulphaH  of  Manganese. — If  any  of 


214 


COMPOSITION  Cy  THE  OXIDES  AND  CHLORIDES. 


these  oxides  be  dissolved  in  muriatic  acid  a  solution  of  chloride  of  maL- 
ganese  will  be  obtained. 

If  this  solution  of  chloride  of  manganese  be  mixed  with  one  of  car- 
bonate of  soda,  a  white  insoluble  powder  will  fall,  which  is  carbonate  of 
maganese. 

If  this  carbonate  be  dissolved  in  diluted  sulphuric  acid,  or  if  any  of 
the  oxides  be  digested  in  this  acid,  a  solution  of  sulphate  of  manganese 
will  be  formed. 

The  carbonate  of  manganese,  and  its  oxides,  will  also  dissolve,  though 
more  slowly,  in  acetic  acid  (vinegar),  and  in  other  organic  acids  which 
may  be  present  in  the  soil,  and  will  form  with  them  other  soluble 
salts. 

The  compounds  of  manganese  exist  in  plants  in  much  less  quantity 
than  those  of  iron;  but  as  its  oxides,  like  those  of  iron,  are  insoluble  in 
pure  water,  this  metal  most  hkely  finds  its  way  into  the  state  of  one 
or  other  of  the  soluble  compounds  above  described. 


§2. 


Tabular  view  of  the  constitution  of  the  compounds  of  the  inorganic 
elements  above  described. 


Having  in  the  preceding  section  briefly  described  the  several  compounds 
of  the  inorganic  elements  of  plants,  which  either  enter  into  the  constitution 
of  vegetable  substances,  or  are  supposed  to  minister  to  their  growth — it 
may  prove  useful  hereafter,  if  I  exhibit  at  one  view  the  composition  per 
cent,  of  the  various  oxides,  chlorides,  sulphurets,  and  oxygen-acid  salts,* 
to  which  I  have  had  occasion  to  direct  your  attention. 

We  shall  have  occasion  to  refer  to  the  numbers  in  the  following  tables 
in  our  subsequent  calculations. 

1°. — Oxygen  per  cent,  in  the  oxides  of  the  inorganic  elements. 

Oxygen  Oxygen 

per  cent.  per  cent. 

.     49-85  Alumina 46-70 

.     59-86  Silica 51-96 

.     56-04  Prot-oxide  of  Iron        .     .  22-77 

.     16-95  Per-oxide  oflron  .     .     .  30-66 

.     25-58  Prot-oxide  of  Manganese  22-43 

.     28-09  Sesqui-oxide         do.  .     .  30-25 

.     38-71  Per-oxide  do.  .     .  36-64 


Sulphurous  Acid 
Sulphuric  Acid 
Phosphoric  Acid 
Potash  .  .  . 
Soda  .... 
Lime  .  .  . 
Magnesia     .     . 


2°. — Chlorine  or  Sulphur  per  ce'it.dn  the  chlorides  and  sulphurets. 


Chloride  of  Potassium 

Sodium 

Calcium 

Magnesium 

First  Chloride  of  Iron 
Second     do.         do. 


Chlorine 
per  cent. 
47-47 
60-34 
63-38 
73-65 
56-62 
66-19 


Sulphuret  of  Potassium 

Sodium     .     . 

Calcium    .     . 

Iron 


Bi-Sulphuret  oflron, 
(Iron  Pyrites)    . 


Sulphur 
per  cent. 
29-11 
40-88 
44-00 
37-23 

47-08 


So  called  because  the  acid  they  pontain  has  oxygen  for  one  of  its  constitaenta 


COMPOSITION    OF    THE    SALINE    COMPOUNDS. 


215 


3'=. — Cwnposition  per  cent,  of  the  Saline  comhinations  above  described. 


Carbonate  of  Po(ash 
Bi-carbonate  of  do. 
Sulphate  of  do. 

Nitrate  of  do. 

Binoxalate  of  do. 
Bitartrate  of  do. 
Phosphate  of  do. 
Bi-phosphate  of  do. 


(Salt  of  sorre7) 
(Cream  of  tartar 


Carbonate  of  Soda  (dry)    . 

(crystallized) 


Bi-carbonate  of  Soda 
Nitrate  of  do. 

Sulphate  of         do.  (dry) 

do.  (crystallized) 

Phosphate  of      do. 
Bi-phosphate  of  do. 

Carbonate  of  Lime    . 
Sulphate  of    do.     (Gypsum)     . 
(burned) 


Nitrate  of  Lime 
Phosphate  of  Lime  (Apatite) 
Bi-phosphate  of  Lime 
i  Earth  of  Bones 

Carbonate  of  Magnesia 
Bi-carbonate  of    do. 
Sulphate  of  do.  (Epsom 

Nitrate  of  do. 

Phosphate  of        do. 

Sulphate  of  Alumina 
Phosphate  of    do. 

Silicate  of  Potash  (soluble) 

Bi-silicate  of  do.  (do.) 

Silicate  of  Soda  (do.) 

Bi-silicate  of  do.  (do.) 
Silicate  of  Lime 

Magnesia  . 

Alumina  . 


Carbonate  of  Iron       .... 
Sulphate  of    do.  (crystallized) 

Carbonate  of  Manganese    . 
Sulphate  of        do.  (crystallized) 


Acid. 


31-91 
48-38 
45-93 
63-44 
52-64 
70-28 
43-06 
60-20 

41-42 
15-43 

58-58 
63-40 
56-18 
24-85 
53-30 
69-54 

43-71 
46-31 

58-47 
65-54 
45-52 

71-48 
48-45 

51-69 
68-15 
32-40 
72-38 
63-33 

70-07 
67-57 

49-46 
66-19 
59-63 
74-71 
61-85 
69-08 
72-95 

38-63 
31-03 

38-27 
33-20 


Base. 

Water. 

68-09 

51-62 

54-07 

46-56 

34-29 

13-07 

24-96 

4-76 

56-94 

39-80 

58-58 

21-81 

62-76 

41-42 

36-60 

43-82 

19-38 

55-77 

46-70 

30-46 

56-29 

32-90 

20-79 

41-53 

34-46 

54-48 

28-52 

51-55 

48-31 

31-85 

16-70 

50-90 

27-62 

;56-67 

29-93 

32-43 

50-54 

33-81 

40-37 

25-29 

38-15 

30-92 

27-05 

61-37 

27-19 

41-78 

61-73 

i 

29-54 

37-26  1 

216  COMPOSITION  OF  THE  ASH  OF  WHEAT  AND   OF  BARLEY. 

§  3-  On  the  relative  proportions  of  the  different  inorganic  compounds 
present  in  the  ash  of  plants. 

Having  thus  made  you  acquainted  with  the  general  properties  and 
composition  of  tlie  several  compound  substances  of  which  the  ash  of 
plants  consists,  we  now  advance  to  the  consideration  of  the  relative  pro- 
portions in  which  these  substances  exist  in  the  ash  of  the  different  kinds 
of  plants  usually  cultivated  for  f(X)d. 

We  have  seen  (p.  178)  that  different  species  of  plants  leave  very  dif- 
ferent quantities  of  ash  when  burned  ; — the  ash  left  by  diflferent  species 
contains  also  the  above  earthy  and  saline  substances  in  very  unlike  pro- 
portions. This  fact  has  already  been  stated  generally  (p.  180) ;  we  are 
now  to  illustrate  it  more  fully,  and  to  show  the  important  practical  de- 
ductions to  which  it  leads. 

I. OF    THE    ASH    OF    WHEAT. 

According  to  the  analysis  of  Sprengel,  1000  lbs.  of  wheat  leave  11-77 

lbs.,  and  of  wheat  straw  35-18  lbs.  of  asti,  consisting  of — 

Grain  of  Straw  of 

Wheat.  Wheat. 

Potash 2-25  lbs.       0-20  lbs. 

Soda 2-40  0-29 

Lime 0-96  2-40 

Magnesia 0-90  0-32 

Alumina,  with  a  trace  of  Iron  0-26  0-90 

Silica 4-00  28-70 

Sulphuric  Acid      ....  0-50  0-37 

Phosphoric  Acid     .     .     ,     .  0-40  1-70 

Chlorine 0-10  Q-30 

11-77  lbs.     35-18  lbs. 
If  the  produce  of  a  field  be  at  the  rate  per  acre  of  25  bushels  of 
wheat,  each  60  lbs.,  and  if  the  straw*  be  equal  to  twice  the  weight  of 
the  grain,  the  quantity  of  each  reaped  per  acre  will  be 

Grain  .  .  .  1500  lbs.  }  c  j  mc  u     u  i 

Straw  .  .  .  3000  lbs.  \  ^''^^^  ^  P'°^""^  "^^^  ^"'^^^'' 
so  that  the  quantity  of  the  different  inorganic  compounds  carried  off  from 
the  soil  of  each  acre  will  be,  in  the  grain  i  more  than  is  represented  in 
the  second  column,  and  in  the  straw  3  times  as  much  as  is  represented 
in  the  third  column.  '^ 

II. — OF  THE  ASH  OF  BARLEY. 

A  thousand  pounds  of  the  grain  of  barle}^  (two-rowed,  hordeum  di$ti- 
chon,)  leave  23i  lbs.,  and  of  the  ripe  dry  straw  52-42  lbs.  of  ash.  This  ash 
consists  of — 

*  The  proportion  of  the  straw  to  the  seed  in  g^in  of  all  kinds  is  very  variable.  In  wheat 
St  is  said  to  average  twice  the  weight  of  the  grai  i,  but  it  is  very  often,  even  in  heaty  crops, 
3  to  3}^  times  that  weight. 


OF  THE  ASH  OF  OATS.  317 

Grain.  Straw. 

Potash 2-78  lbs.  .1-80  lbs. 

Soda 2-90  0-48 

Lime 1-06  5-54 

Magnesia 1-80  0-76 

Alumina 0-25  1'46 

Oxide  of  Iron.     .     .     .  a  trace.  0*14 

Oxide  of  Manganese     .     —  0*20 

Silica    .  • 11-82  38-56 

Sulphuric  Acid  .     .     .     0-59  1-18 

Phosphoric  Acid      .     .     2-10  1-60 

Chlorine 0-19  0-70 


23-49  lbs.      52-42  lbs. 
If  the  produce  of  a  crop  of  barley  amount  to  38  bushels  of  63  lbs.  each 
per  acre,  and  the  straw  exceed  the  grain  in  weight  one-sixth,  the  weight 
of  each  reaped  per  acre  will  be  about 

2000  lbs.  of  grain,  )  ^  ,  r  oo  u    i,  i 

2300  lbs.  of  Law,  ^''^^^  ^  P'°^"^®  °^  ^^  bushels  ; 
and  the  inorganic  matters  carried  off  from  the  soil  by  each  will  be  ob- 
tained by  multiplying  those  contained  in  the  second  column  (above)  by 
2,  and  in  the  third  by  2^. 

III. — or  THE  ASH  OF  OATS. 

in  1000  lbs.  of  the  grain  of  the  oat  are  contained  about  26  lbs.,  and  of 
the  dry  straw  about  57i  lbs.  of  inorganic  matter,  consisting  of — 

Grain.  Straw. 

Potash 1-50  lbs.        8-70  lbs. 

Soda 1-32  0-02 

Lime 0-86  1-52 

Magnesia  .     .     .     I     .     0-67  0-22 

Alumina 0-14  0-06 

Oxide  of  Iron.     .     .     .     0-40  0-02 

Oxide  of  Manganese     .     0-00  0-02 

Silica 19-76  45-88 

Sulphuric  Acid    ...     0  35       '        0-79 
Phosphoric  Acid.     .     .     0-70  0-12 

Chlorine 0-10  0-05 


25-80  lbs.      57-40  lbs. 
If  an  acre  of  land  yield  50  bushels,  each  54  lbs.,  of  oats,  and  two-thirds* 
more  in  weight  of  straw,  there  will  be  reaped  per  acre, 
Of  grain  2250  lbs.,  ?  ^  .  rr^u     ui 

Of  straw  3750  lbs.,  I  ^'"""^  ^  produce  of  50  bushels; 
and  the  weight  of  the  inorganic  matters  carried  off  will  be  equal  to  2i 
tunes  the  quantities  contained  in  the  second  column,  and  3|  times  those 
contained  in  the  third  column. 

*  Oi  all  kinda  of  grain,  the  oat  gives  the  most  variable  proportion  of  straw,  that  which  is 
obtained  at  one  time,  and  in  one  locality,  being  two  or  three  times  greater  than  that  reaped 
in  another. 

10  ^ 


218                           ASH  or  RYE,  BEANS,  PEAS,  AND  VETCHES. 
IV. OF  THE  ASH  OF  RYE. 

The  weight  of  ash  contained  in  1000  lbs.  of  the  grain  of  rye  Is  lOJ  lbs., 
and  of  the  straw  28  lbs.     This  ash  consists  of 

Grain.  Straw. 

Potash  I                               r;  Qo  IK.  S  0-32  Ibs. 

Soda     I ^'^^^^''  iO'U 

Lime 1-22  1-78 

Magnesia 1-78  •  0-12 

Alumina 0*24 


Oxide  of  Iron.     .     .     .  0-42^  ^'^^ 

Oxide  of  Manganese     .  0-34 

Silica 1-64  22-97 

Sulphuric  Acid   .     .     .  0-23  1-70 

Phosphoric  Acid       .     .  0-46  0-51 

Chlorine 0-09  0-17 


10-40  lbs.      27-93  lbs. 
Rye  is  remarkable  for  the  quantity  of  |[|:aw  it  yields,  which  is  often 
from  3  to  4  times  the  weight  of  the  grain.     The  return  in  grain  reaches 
about  the  same  average  as  that  of  wheat.     From  an  acre  of  land  yield- 
ing a  crop  of  25  bushels,  each  54  lbs.,  there  would  be  reaped 

Of  grain  1350  lbs. ;  of  straw  4000  lbs. ; 
the  whole  weight  of  inorganic  matters  contained  in  which  is  equal  to  ^- 
more  than  is  represented  in  the  second  column,  added  to  4  times  the  weights 
contained  in  the  third  column. 

V. OF  THE  ASH  OF  BEANS,  PEAS,  AND  VETCHES. 

The  ash  of  the  seed  and  straw  of  the  jfield  bean,  the  field  pea,  and  the 
common  vetch  {vicia  sativa,}  dried  in  the  air,  contains  in  1000  lbs.  the 
several  inorganic  compounds  in  the  following  proportions : 

PIKLD  BEAN.  FIELD  PEA.  COMMON   VETCH. 


Seed. 

Straw. 

Seed. 

Straw. 

Seed. 

Straw. 

Potash     .... 

4-15 

16-56 

8-10 

2-35 

8-97 

18-10 

Soda 

8-16 

0-50 

7-39 

— 

6-22 

0-52 

Lime       .... 

1-65 

6-24 

0-58 

27-30 

1-60 

19-55 

Magnesia     .     .     . 

1-58 

2-09 

1-36 

3-42 

1-42 

3-24 

Alumina      .     .     . 

0-34 

0-10 

0-20 

0-60 

0-22 

0-15 

Oxide  of  Iron    .     . 

_ 

0-07 

0-10 

0-20 

0-09 

0-09 

Oxide  of  Manganese 

— 

0-05 

— 

0-07 

0-05 

0-08 

Silica      .... 

1-26 

2-20 

4-10 

9-96 

2-00 

4-42 

Sulphuric  Acid 

0-89 

0-34 

0-53 

3-37 

0-50 

1-22 

Phosphoric  Acid    . 

2-92 

2-26 

]-90 

2-40 

1-40 

2-80 

Chlorine      .     .     . 

0-41 

0-80 

0-38 

0-04 

0-43 

0-84 

21-36     31-21     24-64     49-71     22-90     51-01 
On  comparing  the  numbers  in  these  columns,  we  cannot  fail  to  remark, — 
1°.  How  much  potasn  there  is  in  the  straw  of  the  bean  and  the  vetch. 
2°.  That  while  there  is  only  a  trace  of  soda  in  any  of  the  three  straws, 
there  is  a  considerable  quantity  in  all  the  seeds. 


ASH  OF  THE  TURNIP,  CARROT,  PARSNIP,  AND  POTATO.  219 

3°.  How  large  a  proportion  of  lime  exists  in  the  straw  of  the  pea  and 
of  the  vetch — compared  with  that  of  the  hean — and  how  much  larger  the 
proportion  is  in  all  the  straws  than  in  any  of  the  grains — and 

4°.  That  the  quantity  of  silica  in  pea  straw  is  double  of  what  is  con- 
tained in  the  straw  of  the  vetch,  and  4  limes  that  of  the  bean  straw. 

The  produce  of  straw  from  these  three  varieties  of  pulse  is  very  bulky, 
but  varies  in  weight  from  1  to  If  tons — or  is  on  an  average  about  2300 
lbs.  per  acre.     The  produce  of  grain  is  still  more  variable. 

The  bean  gives  from  16  to  40  bushels,  of  about  63  lbs. 
The  pea        .         .     12  to  84         *'  "      64  lbs. 

The  vetch      .         .     16  to  40         "  ♦'       66  lbs. 

The  mean  return  from  beans  is  estimated  by  Schweriz  [Anleitung 
Zum  Praktischen  Ackerbau,  II.,  p.  346,]  at  25  bushels  (1600  lbs.),  from 
peas  at  15  bushels  (1000  lbs.),  and  from  vetches  at  17  bushels  (1100 
lbs.)  per  acre. 

The  quantity  of  the  several  inorganic  matters,  therefore,  carried  off 
from  an  acre  in  the  straw  of  these  crops,  will  be  about  2^  times  the 
weights  given  in  the  table — and  in  the  grains,  where  the  crop  is  near 
the  above  average,  1|  times  the  weights  in  the  tables  for  beans  and  for 
peas,  and  for  vetches  very  nearly  the  actual  weights  above  given. 

VI. OF  THE  ASH  OF  THE  TURNIP,  CARROT,  PARSNIP,  AND  POTATO. 

These  four  roots,  as  they  are  carried  from  the  field,  contain  respective 
ly  in  ten  thousand  pounds — 

TURNIP.  CARROT.     PARSNIP.  POTATO. 


--^-. 


Roots.  Leaves.  Rods.  Tops. 

23-86  32-3  35-33  20-79  40-28  81-9 

10-48  22-2  9-22  7-02  23-34  0-9 

7-52  62-0  6-57  4-68  3-31  129-7 

2-54  5-9  3-84  2-70  3-24  17-0 

0-36  0-3  0-39  0-24  0-50  0-4 

0-32  1-7  0-33  0-05  0-32  0-2 


Potash 

Soda     . 

Lime     . 

Magnesia 

Alumina 

Oxide  of  Iron 

Oxide  of  Manganese     —         —       0-60       —  —         — 

Silica    ....         3-88     12-8       1-37       1-62       0-84     49-4 

Sulphuric  Acid    .         8-01     25-2       2-70       1-92       5-40       4-2 

Phosphoric  Acid  .         3-67       9-8       5-14       1-00       4-01     19-7 

Chlorine     .     .     .         2-39       8-7       0-70       1-78       1-60       5-0 


63-03  180-9     66-19     41-80     82-83  308-4 


These  roots,  as  already  staled  (note,  p.  178),  contain  very  much  water, 
so  that,  in  a  dry  slate,  the  pr(yportion  of  inorganic  matter  present  in  them 
is  very  much  greater  than  is  represented  by  the  above  numbers.  I 
have,  however,  given  the  quantities  contained  in  the  crop  as  it  is  carried 
from  the  field,  as  alone  likely  to  be  of  practical  utility. 

The  crops  of  these  several  roots  vary  very  much  in  different  localities, 
being  in  some  places  twice  and  even  thrice  as  much  as  in  others — every 
nine  tons,  however,  which  are  carried  off  the  ground,  contain  about 
twice  the  weight  of  saline  and  earthy  matters  indicated  by  the  numbers 
in  the  table. 


220  ASU    OF    THE    GRASSES    ANE    .  ..OVERS. 

VII. OF    THE    ASH    OF    THE    GRASSES    AND    CLOVERS. 

The  following  table  might  have  been  much  enlarged.  I  have 
thought  it  .necessary,  however,  to  introduce  in  this  place  only  those 
species  of  grass  and  clover  which  are  in  most  extensive  use.  I  have 
also  calculated  the  weights  given  below,  for  these  plants  in  the  state  of 
hay  only,  as  the  succulency  of  the  grasses, — that  is,  the  quantity  of  wa- 
ter contained  in  the  green  crop, — varies  so  much  that  no  correct  esti- 
mate could  be  made  of  the  quantity  of  inorganic  matter  present  in  hay 
or  grass,  from  a  knowledge  of  its  weight  in  the  green  state  ouly  : 


Rye  Grass 

Red 

White 

'Hay. 

Clover. 

Clover. 

Lucerne. 

Sainfoin. 

Potash    .     .     . 

8-81 

19-95 

3i-05 

13-40 

20-57 

Soda  .... 

3-94 

5-29 

5-79 

6-15 

4-37 

Lime       .     .     . 

7-34 

27-80 

23-48 

48-31 

21-95 

Magnesia     .     . 

0-90 

3-33 

3-05 

3-48 

2-88 

Alumina       .     . 

0-31 

0-14 

1-90 

0-30 

0-66 

Oxide  of  Iron    . 

— 

— 

0-63 

0-30 

— 

Oxide  of  Manganese 

— 

— 

— 

— 

— 

Silica      .     .     . 

. 

27-72 

3-61 

14-73 

3-30 

5-00 

Sulphuric  acid  . 

. 

3-63 

4-47 

3-53 

4-04 

3-41 

Phosphoric  acid 

0-25 

6-57 

5-05 

13-07 

9-16 

Chlorine .     .     . 

• 

0-06 

3-62 

2-11 

3-18 

1-57? 

52-86        74-78        91-32        95-53        69-57 

The  above  quantities  are  contained  in  a  thousand  pounds  of  the  dry 
hay  of  each  plant. 

On  comparing  the  numbers  opposite  to  potash,  lime,  magnesia,  alu- 
mina, silica,  and  })hosphoric  acid,  we  see  very  striking  differences  in 
the  quantities  of  these  substances  contained  in  equal  weights  of  the 
above  different  kinds  of  hay.  These  differences  lead  to  very  important 
practical  inferences  in  reference, — 

1°.  To  the  kind  of  soil  in  which  each  will  grow  most  luxuriantly. 

2°.  To  the  artificial  means  by  which  the  growth  of  each  may  be  pro- 
moted— in  so  far  as  this  growth  depends  upon  the  supply  of  inorganic 
food  to  the  growing  plant. 

3°.  To  the  feeding  properties  of  each,  and  to  the  kind  of  stock  they 
are  severally  most  fitted  to  nourish. 

To  these  and  other  important  practical  deductions  suggested  by  the 
above  tabulated  analyses — as  well  as  by  those  previously  given — of  the 
inorganic  matters  contained  in  the  several  varieties  of  vegetable  produc- 
tions usually  raised  for  food,  we  shall  hereafter  have  frequent  occasion 
to  revert.  In  the  mean  time,  a  preliminary  inquiry  demands  our  at- 
tention, which  we  shall  proceed  to  consider  in  the  following  section. 

§  4.  To  what  extent  do  the  crops  most  vsually  cultivated,  exhaust  the  soil 
of  inorganic  vegetable  food  ? 

A  bare  inspection  of  the  tabular  results  exhibited  in  the  preceding 
section  gives  but  a  faint  idea  of  the  extent  to  which  the  inorganic  ele- 
mentary bodies  are  necessarily  withdrawn  from  the  soil  in  the  ordinary 
course  of  cropping. 


EFFECT  OF  A  THREE  TEAUS'  COURSE  OF  CROPPING.       221 

I.  Lei  us  consider  the  effect  upon  the  soil  of  a  still  too  common  three 
years'  course  of  cropping— /aZZoi^;,  wheat,  oals."^  If  the  produce  of  such 
a  course  be  25  bushels  of  wheat  and  50  bushels  of  oats,  there  would  be 
carried  from  the  soil  every  three  years  in  pounds — 

WHEAT.  OATS. 

, ^ ,        , • <•      Total. 

Grain.        Straw.        Grain.        Straw. 

Potash      ....  3-3  0-6  3-75  32-7  40-35 

Soda 3-5  0-9  3-3  —  7-7 

Lime 1-5  7-2  2-5  57  16-9 

Magnesia.     ...  1-5  1-0  1-7  0-8  5-0 

Oxide  of  Iron     .     .  —  —  1-0  —  1-0 

Silica 6-0  86-0  500  172-0  314-0 

Sulphuric  Acid .     .  0-75  1-0  0-9  3-0  5-65 

Phosphoric  Acid     .  0-6  5-0  1-43  0-5  7-53 

398-13 
The  gross  weight  carried  off  in  these  crops  is  large — amounting  to 
about  400  lbs.     It  will  vary,  however,  with  the  kind  of  wheat  and  oats 
which  are  grown,  and  may  often  be  greater  than  this. — [See  the  follow- 
ing section  (§  5)   of  the  present  Lecture.]     The  greatest  portion  of  the 
matter  carried  off,  however — upwards  of  three-fourths  of  the  whole- 
consists  of  silica;  the  rest  of  the  materials  are  equal  to 
60  lbs.  of  dry  pearl-ash, 
36  lbs.  of  the  common  soda  of  the  shops, 
28  lbs.  of  bone-dust, 
12  lbs.  of  gypsum, 
5  lbs.  of  quick-lime, 

5  lbs.  of  magnesia, — or  for  the  last  three  may  be  substi- 
tuted 33  lbs.  of  common  Epsom  salts  and  17  lbs.  of  quick-lime. 

The  form  in  which  the  silica  may  be  restored  to  the  soil  in  a  state  in 
which  the  plant  can  absorb  it,  will  be  considered  hereafter. 

Though  large  as  a  whole,  the  weight  of  each  of  the  ingredients,  taken 
singly,  is  not  great;  and  yet  it  is  not  difficult  to  understand  that  if  a 
constant  drain  be  kept  up  on  the  soil  year  after  year,  and  the  practical 
farming  adopted  is  of  such  a  kind  as  not  to  restore  to  the  soil  a  due  pro- 
portion of  each  of  the  substances  carried  off— the  time  must  come  when, 
under  ordinary  circumstances,  the  soil  will  no  longer  be  able  to  supply 
the  demands  of  a  healthy  and  luxuriant  vegetation. 

II.  Let  us  next  consider  the  effect  of  a  four-years'  course  system  in 
withdrawing  these  inorganic  substances  from  the  soil.  And  for  this 
purpose  let  us  adopt  one  suited  to  the  lighter  soils — as  to  that  of  Norfolk — 
turnips,  barley,  clover  and  rye  grass,  wheat. 

Let  the  crop  of  turnips  arnount  to  25  tons  of  roots  per  acre,  of  barley  to 
38  bushels,  of  clover  and  rye  grass  each  to  one  ton  of  hay,  and  of  wheat 
as  before  tb'  25  bushels.  Then  we  have  from  the  entire  rotation  in 
pounds — 

•  Common,  among  other  counties,  in  that  of  Durham.  There  are  cases,  however,  in 
which  this  three  years'  course  may  not  be  indefensible,  and  it  never  could  be  compared  with 
some  of  the  so-called  improved  rotations  in  East  Lothian  in  the  time  of  Lord  Karnes ;  as  for 
instance,  fcMow,  barley,  clover,  manure  on  the  clover  stubble,  then  tcbeat,  barley,  oats. — See 
The  Gentlenmn  Farmer  (1802),  p.  147. 


222  EFFECT  OF  A  FOUR-YEARS'  COURSE. 

BAKLBY.  WHEAT. 

Turnip    . .     Red         Rye   , .    Total. 

Roots.    Grain.  Straw.  Clover.    Grass.  Grain.  Straw. 

Potash 145-5  5-6  4-5  45-0  28-5  3-3  0-6  233-0 

Soda 64-3  5-8  1-1  12-0  90  35  09  96-6 

Lime 45-8  2-1  12-9  63-0  16-5  1-5  7-2  149-0 

Magnesia.  .  .  .  15-5  3-6  1-8  7-5  2-0  1-5  1-0  32-9 

Alumina   ....  2-2  0-5  3-4  0-3  0-8  0-4  2-7  10-3 

Silica 23-6  23-6  90-0  8-0  62-0  6-0  860  299-2 

Sulphuric  Acid .  490  1-2  2-8  10-0  8*0  0-8  1-0  72-8 

Phosphoric  do.  .  22-4  4-3  3-7  15-0  0-6  0-6  5-0  51-5 

Chlorine    ....  14-5  0-4  1-5  8-0  0-1  0-2  0-9  25  6 

970-9* 
On  comparing  the  numbers  in  the  last  column — containing  the  total 
quantity  of  matter  abstracted — with  those  contained  in  the  three  years' 
rotation  (p.  221),  we  see  how  very  much  larger  an  addition  must  be 
made  to  the  land  every  fourth  year,  if  we  are  to  restore  to  it  any  thing 
like  an  equivalent  for  the  inorganic  matter  carried  off'. 

It  will  be  especially  observed  that  the  quantity  of  potash,  and  of  soda, 
and  indeed  of  nearly  every  ingredient  except  the.  silica,  carried  off  in 
this  course  of  cropping,  is  much  greater,  even  in  proportion  to  the  time 
it  occupies,  than  in  the  three-year  shift — and  that  nine-tenths  of  the  pot- 
ash and  soda  withdrawn  from  the  soil  are  contained  in  the  green  crops. 

To  place  the  relative  effect  of  the  green  and  corn  crops  upon  the  soil 
in  a  clearer  light,  I  shall  exhibit  the  several  quantities  of  common  and 
artificial  salts  and  manures  which  it  would  be  necessary  to  add  to  each 
acre  at  the  beginning  of  this  rotation,  in  order  to  supply  the  various  inor- 
ganic substances  about  to  be  taken  from  the  land  in  the  next  four  years' 
cropping.     These  quantities  are  as  follow,  in  pounds : — 

For  the  .  For  the 

Total.         Green  Crops.      Com  Crops. 

Dry  Pearl-ash     .....  325  316  9 

Crystallized  Carbonate  of  Sodaf  333  290  43 

Common  Salt 43  38  5 

Gypsum —  30  — 

Quick-Hme 150  100  7 

Epsom  Salts 200  150    '  50 

Alum 83  27  56 

Bone-dust 210  150  60 

"With  the  exception  of  the  silica,  the  substances  above-named,  in  the 
quantities  given,  will  replace  all  the  inorganic  matters  contained  in  the 
whole  crop  reared,  the  turnip  tops  alone  not  included.  A  single  glance 
at  the  second  and  third  columns  shows  how  much  greater  a  proportion 
of  all  these  substances  is  necessary  to  return  what  the  green  crops  have 
taken  from  the  land. 

That  the  fertility  of  the  soil  depends  in  some  considerable  degree  on 

*  This  is  exclusive  of  the  turnip  tops,  which  I  have  omitted,  from  not  knowing  what  pro- 
portion their  weight  in  the  green  state  generally  bears  to  that  of  the  roots. 

t  Or  for  every  100  lbs.  of  the  common  carbonate  of  soda  may  be  substituted  40  lbs.  of 
common  salt  or  60  lbs.  jI  dry  nitrate  of  soda. 


WHY  WHEAT  PREFERS  A  HEAVY  SOIL.  223 

the  quantity  of  the  alkaline  and  other  compounds  present  in  it,  there  can 
be  no  question, — since  not  only  do  we  find  extraordinary  natural  luxuri- 
ance of  vegetation  where  some  of  these  happen  to  be  present  in  the  soil, 
but  we  can  often  greatly  increase  the  apparent  productiveness  of  our 
fields  by  spreading  such  substances  over  them  in  sufficient  quantity. 

How  comes  it,  then,  that  the  green  crops  which  carry  off  all  these 
substances  in  the  greatest  quantity  by  very  much,  should  yet  least  injure 
the  land, — nay,  should  rather  renew  and  prepare  it  again  for  the  growth 
of  crops  of  corn  ? 

This  is  one  of  the  most  interesting  practical  questions  which  can  pre- 
sent its6lf  to  us  in  the  existing  state  of  theoretical  agriculture ; — but  it 
would  carry  us  away  from  our  more  immediate  object,  were  we  prema- 
turely to  enter  upon  the  discussion  of  it  in  this  place.  It  will  hereafter 
demand  our  especial  attention,  when  we  shall  have  become  familiar 
with  the  nature  and  origin  of  soils. 

I  may  be  permitted,  however,  to  draw  your  attention  here  for  a  mo- 
ment— as  neither  out  of  place,  nor  uninteresting,  for  many  reasons, — to 
an  opinion  expressed  by  Liebig  on  the  question  why  wheat  prefers  stiff 
and  clayey  soils.  "  Again,"  he  says,  "how  does  it  happen  that  wheat 
does  not  flourish  in  a  sandy  soil,  and  that  a  calcareous  soil  is  also  un- 
suitable for  its  growth,  unless  it  be  mixed  with  a  considerable  quantity 
of  clay?  It  is  because  these  soils  do  not  contain  alkalies  insufficient 
quantity,  the  growth  of  wheat  being  arrested  by  this  circumstance,  even 
should  all  other  substances  be  presented  in  abundance." — {^Organic 
Chemistry  applied  to  Agriculture,  p.  151,] 

Without  dwelling  on  the  fact  that  excellent  crops  of  wheat  are  reaped 
in  some  parts  of  our  island  from  sandy  and  calcareous*  soils-:- what  kind 
of  crops,  we  may  ask,  can  be  reared  with  success  on  the  lighter  soils  to 
which  wheat  seems  least  adapted  ?  The  turnip  rejoices  in  light  land, 
and  the  potato  not  unfrequently  attains  the  greatest  perfection  on  a  sandy 
soil.  Yet  ten  tons  of  potato  roots,  or  twenty  of  turnip  bulbs, — exclu- 
sive of  the  tops — contain  nearly  ten  times  as  much  of  the  two  alkalies, 
potash  and  soda,  as  fifty  bushels  of  wheat  with  its  straw  included. f 
What  ground  is  there,  then,  for  the  explanation  given  by  Liebig — of  the 
peculiar  qualities  of  the  so-called  wheat  lands  ?  We  might  with  far 
greater  show  of  reason  assume  the  converse  of  his  proposition,  and  infer 
that  wheat  does  not  prefer  sandy  soils,  because  they  are  too  rich  in  alkali! 
It  is  singular,  and  would  almost  seem  to  strengthen  this  converse  propo- 
sition, that  beans,  peas,  and  vetches,  which  are  so  often  resorted  to  as  a 
good  preparative  for  wheat,  contain  also  a  much  larger  quantity  of  alkali 
than  the  latter  grain.  Thus  the  grain  and  straw  together  of  twenty-six 
bushels  of  beans  contain  71  lbs.,  of  twenty  bushels  of  peas  26  lbs.,  and 
of  twenty  bushels  of  vetches  74  lbs.  of  potash  and  soda  taken  together. 

As  I  have  already  stated,  however,  we  are  not  yet  prepared  for  dis- 
cussing this  very  curious  and  interesting  question. 

*  On  the  thin  chalk  soils  of  the  Yorltshire  Wolds  a  crop  of  wheat  is  taken  every  four  or 
five  years,  yielding  an  average  of  24  or  25  bushels.  The  rotation  is  turnips,  barley,  clover  or 
beans,  wheat. 

t  According  to  the  analyses  of  Sprengel  given  in  the  previous  pages,  ten  tons  of  potatoes 
contain  143  lbs.  of  alkalies,  twenty  tons  of  turnips  154  lbs.,  and  fifty  bushels  of  wheat  wRh 
its  straw  only  16  lbs. 


224         ARE  THE  INORGANIC  CONSTITUENTS  REALLY  CONSTANT  ? 


§  5.  O/*  the  alleged  constancy  of  the  inorganic  constituents  of  plants,  in 
kind  and  quantity. 

In  the  preceding  lecture  (ix.,  p.  177),  it  was  stated  that  the  ash  of  the 
same  plant,  if  ripe  and  healthy,  is  nearly  the  same  in  kind  and  quality 
in  whatever  circumstances  (if  favourable)  of  soil  and  climate  it  may 
grow.  This  general  observation,  however,  is  consistent  with  certain 
(lifferences  in  the  above  respect,  whicfh  are  not  without  interest  in  their 
bearing  upon  agriculture  botJs  in  theory  and  practice.     Thus, 

1°.  The  different  parts  of  the  same  plant  contain  quantities  of  inor- 
ganic matter,  not  only  different  in  their  gross  weights,  but  unlike  also  in 
the  relative  proportions  of  the  several  substances  of  which  the  entire  ash 
consists.  Both  of  these  points  have  been  previously  illustrated  (pp.  179, 
180),  and  they  are  placed  in  the  clearest  light  by  the  tabulated  analyses 
introduced  into  the  preceding  section. 

2°.  The  quantity  and  relative  proportions  of  the  different  inorganic 
substances  also  vary  with  the  season  of  the  year  at  which  the  examina- 
tion is  made.  Thus,  according  to  De  Saussure,  plants  of  the  same  wheat 
which  a  month  before  flowering  left  7-9  per  cent,  of  ash,  left  when  in 
flower  only  5*4,  and  when  ripe  3'v3  per  cent.  The  quantity  of  potash 
in  the  potato  leaf  diminishes  very  much  as  the  plant  approaches  to  ma- 
turity (MoUerat) — and  the  same  has  been  observed  in  many  saltworts 
and  other  sea-side  plants.  In  the  young  plant  of  the  salsola  clavifolia 
there  is  much  potash  and  no  soda,  but  as  its  age  increases  the  latter  alkali 
appears,  and  gradually  takes  the  place  of  the  former.* 

It  is  probably  true,  therefore,  of  all  plants — that  the  ash  both  in  kind 
and  quantity  is  affected  by  the  age  at  which  the  plant  has  arrived.  It 
would  appear  that  the  unlike  chemical  changes  which  take  place  in  the 
interior  of  the  plant,  at  the  successive  periods  of  its  growth,  require  the 
presence  of  different  chemical  agents — or  that  the  production  of  new 
parts  demands  the  co-operation  of  new  substances. 

3°.  Similar  differences  are  sometimes  observed  also  when  the  same 
plant  is  grown  in  different  soils.     Thus  it  is  known  that  the  straw  of  the 
oat  grown  upon  boggy  land  is  very  different  in  colour  and  lustre,  from 
that  yielded  by  the  same  variety  of  seed,  when  grown  upon  sound  and 
solid  soil.     I  lately  examined  two  such  portions  of  straw  from  the  same 
seed — grown  on  the  same  farm  on  the  estate  of  Dunglass,  the  one  on 
boggy,  the  other  on  sound  stiff  land,  when  the  straw  from  the 
Sound  land  left  6-64  per  cent,  of  ash,  and  from  the 
Boggy  land  "■    6-2    per  cent,  of  ash ; 
while  the  silica  contained  in  the  ash  from  the 

Sound  land  amounted  to  3-42  per  cent.,  and  from  the 

Boggy  land        "         to  1*90  per  cent,  of  the  weight  of  the  straw. 

A  remarkable  difference,  therefore,  existed  in  the  relative  proportions, 

•  Meyen,  Jahresberickt,  1839,  p.  125.  In  regard  to  these  salt-loving  plants,  which  generally 
aboSnd  in  soda,  a  curious  observation  was  long  ago  made  by  Cadet.  He  states  that  if  a  plant 
of  common  salt- wort  (salaola  aali)  be  transplanted  into  an  inland  district — and  seed  from  this 
plant  be  afterwards  sown,  the  second  race  of  plants  will  contain  much  potash,  but  scarcely  a 
trace  of  soda.— Gmelin's  Handbuch  der  Chemie,  JI.  p.  1492.  Potash  may  thus  take  the 
place  of  soda  for  a  time,  but  removed  from  its  native  habitat,  the  plant  would  in  a  few  gene- 
rations die  out  and  disappear. 


THE  ASH  FROM  WHEAT  STRAW  IS  VARIABLE.  225 

at  least  of  the  silica,  in  these  two  varieties  of  straw,  and  this  difference 
can  be  attributed  only  to  the  unlike  nature  of  the  soils  in  which  the  two 
samples  were  grown.  But  on  boggy  soils  the  oat  plant  is  unhealthy, 
and  in  general  neither  fills  its  ear,  nor  ripens  a  perfect  seed  ; — the  dif- 
ference in  the  ash  in  this  case,  therefore,  cannot  be  considered  as  entirely 
opposed  to  the  general  proposition,  that  in  a  healthy  state,  plants  at 
the  same  period  of  their  growth  always  yield  nearly  the  same  weight 
of  ash. 

But  that  different  experimenters  have  obtained  very  unlike  quantities 
of  ash,  from  the  most  common  cultivated  plants,  apparently  in  a  state 
of  health,  when  grown  under  different  circumstances  of  soil  and  climate, 
— does  appear  to  contradict  this  general  propositior.  Thus  100  lbs.  of 
ripe  ivheat  straw  leave  of  ash 

4-3  lbs.  De  Saussure  ; 
4 '4  lbs.  Berthier; 
3-5  lbs.  Sprengel ; 
15-5  lbs.  Sir  H.  Davy  ; 
while  the  straw  of  one  variety  of  red  wheat  grown  on  a  clay-loam,  at 
Aykley  Heads,  near  Durham,  gave  me  6-6  per  cent.,  and  that  of  two 
other  varieties  of  red  wheat,  grown  near  Dalton,  in  Ravensworth  Dale, 
Yorkshire,  a  country  abounding  in  limestone — and  on  the  same  field — 
left  respectively  12*15  and   16-5  per  cent,  of  ash.     The  difference  of  4 
per  cent,  between  these  last  two  results,  shows  that  the  quantity  of  ash 
depends  much  upon  the  variety  of  grain  examined — though  to  what  ex- 
tent all  the  great  differences  obtained,  as  above  shown,  are  to  be  ascribed 
to  this  cause  alone,  it  is  impossible  to  say,  until  numerous  other  experi- 
ments shall  have  been  instituted. 

One  thing,  however,  is  manifest,  that  the  quantities  of  inorganic  mat- 
ter necessarily  contained  in  a  crop  of  wheat,  given  in  a  previous  page 
(p.  216)  on  the  authority  of  Sprengel,  must  be  considered  as  probably 
far  below  the  mean  proportion,  since  some  varieties  yield,  in  the  form 
of  ash,  about  six  times  as  much  as  is  there  stated. 

Every  one  knows  how  uncertain  general  conclusions  are, — or  expla- 
nations of  natural  phenomena, — when  deduced  from  single  observations 
only,  and  of  this  truth  the  above  results  present  us  with  a  useful  illus- 
tration. Thus  Liebig,  in  his  Organic  Chernistry  applied  to  Agriculture 
p.  152,  to  which  we  have  had  frequent  occasion  to  refer — explains 
why  land  will  refuse  to  grow  wheat,  and  may  yet  produce  good  crops 
of  oats  or  barley  in  the  following  manner  : — "One  hundred  parts  of  the 
stalks  of  wheat  yield  15-5  parts  of  ashes  (H.  Davy) :  the  same  quantity 
of  the  dry  stalks  of  barley  8*54  (Schrader),  and  one  hundred  parts  of  the 
stalks  of  oats  only  4-42.  The  ashes  of  all  are  of  the  same  composition. 
We  have  in  these  facts  a  clear  [)roof  of  what  plants  require  for  their 
growth.  Upon  the  same  field  which  will  yield  only  one  harvest  of 
wheat,  two  crops  of  barley  and  three  of  oats  may  be  raised." 

In  this  passage  it  has  been  assumed  that  the  ash  of  wheat  and  other 
straws  is  constant  in  quantity,  that  wheat  straw  always  contains  much 
more  than  that  of  oats  or  barley,  and  that  the  ash  is  in  each  case  of  the 
same  composition  (see  above,  pp.  216  to  217), — all  of  which  premises 
being  incorrect,  the  conclusion  must  of  course  be  rejected. 

But  the  straw  of  barley  and  oats  also,  accordina:  to  different  authorities, 
10* 


226  ASH    FROM    OAT    AND    BARLEY    STRAW    ALSO    VARIABLE. 

leaves  very  unlike  quantities  of  ash.     Thus,  according  to  Sprengel  and 
Schrader,  100  lbs.  of 

Sprengel.  SchracJer. 

Oat  Straw  leave     .     5-74  lbs.         4-42  lbs.  6-6  J. 

Barley  straw    .     .     5-24  lbs.         8-54  lbs. 
We  cannot  help  conceding,  therefore,  generally,  in  regard  to  the  cereal 
grasses,  that  different  varikties,  at  least,  of  the  same  plant,  may  contain 
inorganic  matter  in  different  proportions. 

But  certain  analyses  which  have  been  made  seem  to  demand  a  still 
further  concession.  Thus  De  Saussure  found  that  the  ash  left  by  the 
same  tree  or  shrub — by  the  fir  or  the  juniper  for  example — differed  both 
in  kind  and  in  quantity,  according  as  it  grew  uj)on  a  granitic  or  calca- 
reous soil.  Berthier  also  found  the  ash  of  a  piece  of  Norway  pine  {pi- 
nus  abies)  to  differ  very  much  from  that  of  the  wood  of  the  same  pine 
grown  in  France.  From  these  and  a  few  other  observations,  the  con- 
clusion has  been  very  generally  drawn  by  vegetable  physiologists,  that 
the  ash  of  plants  in  general  is  determined  both  in  kind  and  quantity  by 
the  soil  in  which  they  grow. 

This  is  very  likely  to  be  true  to  a  certain  extent,  as  we  have  seen  in 
the  straw  of  the  bog  oat  above  adverted  to,  but  a  sufficient  number  of 
accurate  comparative  analyses  of  the  ash  of  cultivated  plants*  has  not 
yet  been  published,  to  enable  us  to  determine  the  precise  influence  of  the 
soil  in  all  cases.  It  is  impossible,  however,  that  the  prevailing  charac- 
ter of  the  soil  can  have  more  than  a  general  influence  on  the  character  ot 
the  ash  of  any  living  vegetable — so  long  as  the  plant  retains  a  healthy 
state.  The  experiments  of  De  Saussure  do  not  appear  to  have  been 
made  with  sufficient  care,f  while  the  only  comparative  experiment  of 
Berthier  is  open  to  objections  of  another  kind. 

I  have  said  that  the  quantity  and  kind  of  the  ash  is  likely  to  be  affected 
by  the  character  of  the  soil  to  a  certain  extent.  The  following  considera- 
tions seem  to  embody  nearly  all  the  sources  of  such  variation,  of  which 
we  can  at  present  speak  with  any  degree  of  certainty  : — 

1°.  Plants  at  different  periods  of  their  growth  reciuire  for  the  produc- 
tion of  their  several  parts,  and  therefore  appropriate  from  the  soil,  differ- 
ent inorganic  substances  ;t  hence  the  ash  will  vary  with  the  age  of  the 
plant. 

•  Five  samples  of  the  same  variety  of  wheat  (Hunter's  wheat)  grown  on  different  soils  in 
the  neighbourhood  of  Haddington,  gave  me  very  nearly  the  same  proportions  of  ash.  Thus 
the  sample  grown  on  a 

Per  cent. 
1°.  Deep  reddish  clay  loam,  subsoil  gravel,  left    1776 

2°.  Red  clay  on  gravel 1787 

3°.  Stiff  clay  on  retentive  subsoil 1-903 

4°.  Liiiht  clay  on  rather  retentive  subsoil     .     .     1-917 

5°.  Light  turnip  land 1-824 

These  results  approach  very  near  each  other.  The  differences  are  perhaps  too  slight  to' 
justify  us  in  concluding  that  the  ash  is  greatest  in  quantity  when  the  subsoil  is  most  reten- 
tive. 

t  The  accuracy  of  De  Saussure's  analyses  is  rendered  very  doubtful  by  the  fact  that,  In 
the  ash  o{  ail  the  different  trees  and  shrubs  he  examined,  he  found  a  large  quantity,  in  that 
of  the  juniper  as  much  as  43  per  cent,  of  alumina,  and  in  that  of  the  pine  from  12  to  16  per 
cent.,  while  Berthier,  whose  skill  is  undisputed,  found  no  alumina  in  the  ash  of  any  of  the 
numerous  trees  on  which  his  experiments  were  made. 

}  This  fact  indicates  an  exceedingly  interesting  field  of  chemical  research  in  connection 
with  practical  agriculture.  What  substance  will  bring  this  or  that  seed  into  early  leaf? — 
what  will  hasten  its  growth  in  middle  life  1—  what  will  bring  it  to  ear,;  maturity  1    The  wheat 


.   SOME  SUBSTANCES  ACT  AS  MEDIA  OR  AGENTS  ONLY.  227 

2°.  If  the  substances  necessary  for  the  perfection  of  one  or  more  parts 
of  a  plant  abound  in  the  soil,  its  chief  developement  will  take  the  direc- 
tion of  those  parts.  Thus  one  plant  will  run  to  leaf  or  straw,  another  to 
flower  and  seed.  Thus  also  in  the  grain  of  one  crop  of  wheat  more  glu- 
ten is  produced  «han  in  that  of  another,  and  as  this  gluten  appears  to 
contain  the  phosphates  of  lime  and  magnesia,  as  essential  constituents, 
the  ash  will  necessarily  vary  with  the  gluten  of  the  seed. 

3°.  Some  substances  ap{)ear  to  enter  into  the  circulation  of  plants  not 
so  much  as  actual  and  necessary  ccnstituents  of  the  parts  of  the  vegetable, 
as  to  serve  as  media  or  agents  by  which  other  compounds,  both  organic 
and  inorganic,  may  be  conveyed  to  the  plant.  Thus  common  salt  ap- 
pears to  enter  many  plants  for  the  purpose  of  supplying  soda,  its  chlo- 
rine being  discharged  by  the  leaf.  Silica  enters  the  plant  chiefly  in  the 
form  of  silicate  of  potash  or  soda.  When  it  reaches  its  proper  destina- 
tion— the  stalks  of  the  grasses  for  instance — this  silicate  is  decomposed 
chiefly  by  the  carbonic  acid,  which  is  always  present  in  the  pore^of  the 
green  stem,  the  silica  is  deposited  and  the  alkali  proceeds  downwards 
with  the  sap  as  a  soluble  carbonate,  or  in  combination  with  some  other 
organic  acid.  Thus  the  same  portion  of  alkali  may  return  many  times 
into  the  circulation  with  this  or  with  other  materials  which  the  parts  of 
the  plant  require,  and  every  new  burden  it  deposits  will  necessarily 
cause  a  new  variation  in  the  relative  proportions  of  the  several  inorganic 
constituents  which  are  afterwards  detected  in  the  ash. 

4°.  As  the  water  which  enters  by  the  roots  always  brings  with  it  some 
soluble  substances,  the  quantity  of  these  conveyed  into  the  plant  will  be 
materially  affected  by  the  amount  of  evaporation  from  the  leaves;  and 
hence,  after  a  long  drought,  the  leaves  of  the  turnip,  the  potato,  and 
other  plants,  will  yield  a  larger  proportion  of  ash  than  will  be  obtained 
from  them  in  moist  and  rainy  weather. 

5°.  In  the  mineral  kingdom  it  is  found  that  one  substance  may  not 
unfrecjuently  take  the  place,  and  perform  the  functions,  of  another.  Thus 
potash  and  soda  replace  each  other  in  certain  minerals,  as  do  also  lime 
and  magnesia  and  the  phosphoric  and  arsenic  acids.  It  has  been  sup- 
posed that  a  similar  interchange  may  take  place  in  the  vegetable  king- 
dom— that  when  the  plant  cannot  get  potash  it  will  take  soda — that 
when  it  can  get  neither,  it  will  appropriate  lime, — and  so  on.  Such  a 
conjectural  interchange  may  possibly  take  place  in  a  small  degree,  for  a 
limited  time,  and  in  certain  plants,  without  materially  affecting  their  ap- 
parent heahh — but  it  is  not  by  trusting  to  such  resources  of  nature  that 
a  luxuriant  vegetation  or  plentiful  crops  will  ever  be  reared  by  the  prac- 
tical agriculturist. 

Admitting,  however,  all  these  sources  of  variation  in  the  kind  and 
quantity  of  the  ash  obtained  from  different  plants,  the  sound  practical 
conclusions  from  all  we  know  on  the  subject  at  present  seem  to  be — 

1°.  That  certain  inorganic  substances,  in  certain  proportions,  are  ne- 
cessary to  all  plants  usually  cultivated  for  food — if  they  are  to  be  reared 
or  maintained  in  a  healthy  state. 

stalk  and  the  potato  require  more  potash  while  in  rapid  growth.  This  growth  may  be  con. 
tinued  and  prolonged  by  the  presence  of  ammonia ;  while  lime  is  said  to  bring  it  sooner  to 
a  close,  and  to  give  an  earlr.jr  harvesst.  How  valuable  would  be  the  multiplication  of  such 
facts! 


228  BASIS    OF   ENLIGHTENED    PRACTICAL   AGRICULTURE. 

2°.  That  we  must  seek  for  these  necessary  substances  in  the  inorganic 
constituents  which  are  present  in  the  richest  crops  of  every  kind — in  the 
produce  of  the  most  fertile  soils.* 

3°.  That  where  these  necessary  substances  are  not  jjresent  in  any 
soil,  we  may  infer  that  it  will  prove  unfit  to  yield  a  luxuriant  crop  of  a 
given  kind ;  or,  on  the  other  hand,  where  these  substances  are  not  to  be 
detected  in  the  ash  of  the  plant,  that  thefault  of  the  crop,  if  any,  maybe 
ascribed  to  their  partial  or  total  absence  from  the  soil  on  which  it  grew. 

These  conclusions  form  the  basis  of  an  enlightened  and  scientific  prac- 
tical agriculture.  This  basis,  however,  requires  to  be  strengthened  and 
enlarged  by  further  experimental  investigations. 

•  "I have  examined,"  says  Sprengel,  "the  finest  seed-corns  from  many  localities,  and  I 
have  invariably  found  the  quantities  not  only  of  the  organic  substances— starch,  sugar,  &c.— 
but  also  of  the  inorganic  compounds  in  all  the  celebrated  seed-corns,  so  perfectly  alike,  that 
one  would  have  thought  they  had  all  grown  on  one  and  the  same  soil."— i^Are  vom  Diingtr^ 
p.  43. 


LECTURE  XI. 

Nature  and  origin  of  soils.— Organic  matter  in  the  soil.— General  constitution  of  the  earthy 
part  of  the  soil. — Classification  of  soils  from  their  chemical  constituents. — Method  of  ap- 
proximate analysis  for  the  purposes  of  classification.— General  origin  of  soils  and  subsoils. 
—Structure  of  the  earth's  crust.— Stratified  and  unstratified  rocks.— Crumbling  or  degra- 
dation of  rocks. — Diversity  of  soils  produced.— Superficial  accumulations.— Tabular  view 
of  the  character  and  agricultural  capabilities  of  the  soils  of  the  different  pans  of  Great 
Britain. 

Such  are  the  inorganic  compounds  which  minister  to  the  growth  of 
plants,  and  such  the  proportions  in  which  they  severally  occur  in  the 
living  vegetable.     Whence  are  these  inorganic  constituents  all  derived  1 

We  have  seen  that  the  atmosphere,  when  pure,  contains  no  inorganic 
matter,  and  that  if  dust,  spray,  or  vapours  occasionally  float  in  the  air, 
and  are  carried  by  the  winds  to  great  distances — yet  that  they. are 
only  accidentally  present,  and  cannot  be  regarded  as  a  source  from 
which  the  general  vegetation  of  the  globe  derives  a  constant  supply  of 
those  mineral  substances  which  are  necessary  to  its  healthy  existence. 

The  soil  on  which  they  grow  is  the  only  natural  source  from  which 
their  inorganic  food  can  be  derived.  We  are  led,  therefore,  as  the  next 
subject  of  our  study,  to  inquire  into  the  nature  and  origin  of  soils.* 

§  1.  Of  the  organic  matter  in  the  soil. 

Soils  differ  much  as  regards  their  immediate  origin,  their  physical 
properties,  their  chemical  constitution,  and  their  agricultural  capabili- 
ties ;  yet  all  soils  which  in  their  existing  state  are  capable  of  bearing  a 
profitable  crop,  possess  one  common  character — they  all  contain  organic 
matter  in  a  greater  or  a  less  proportion. 

This  organic  matter  consists  in  part  of  decayed  animal,  but  chiefly  of 
decayed  vegetable  substances,  sometimes  in  brown  or  black  fibrous  por- 
tions, exhibiting  still,  on  a  careful  examination,  something  of  the  origi- 
nal structure  ofthfe  organized  substances  from  which  they  have  beende- 
ri,ved — sometimes  forming  only  a  fine  brown  powder  intimately  inter- 
mixed with  the  mineral  matters  of  the  soil — sometimes  scarcely  percep- 
tible in  either  of  those  forms,  and  existing  only  in  the  state  of  organic 
compounds  more  or  less  void  of  colour  and  at  times  entirely  soluble  in 
water.  In  soils  which  appear  to  consist  only  of  pure  sand,  or  clay,  or 
chalk,  organic  matter  in  this  latter  form  may  often  be  detected  in  con- 
siderable quantity. 

The  proportion  of  organic  matter  in  soils  which  are  naturally  produc- 
tive of  any  useful  crops,  varies  from  one-half  to  70  per  cent,  of  their 
whole  weight.  With  less  than  the  former  proportion  they  will  scarcely 
support  vegetation — with  more  than  the  latter,  they  require  much  ad- 
mixture before  they  can  be  brought  into  profitable  cultivation.     It  is 

•  On  the  subject  of  this  and  the  following  lecture,  the  reader  will  consult  with  advantage 
an  excellent  little  work,  "  On  the  nature  and  property  of  soils,"  by  Mr.  John  Morton. 


230  PROPORTION  OF  ORGANIC  MATTER  IN  SOILS. 

only  in  bdagy  and  peaty  soils  that  the  latter  large  proportion  is  evci 
found — in  tfie  best  soils  the  organic  matter  does  not  average  five  per  cent., 
and  rarely  exceeds  ten  or  twelve.  Oats  and  rye  will  grow  upon  land 
containing  only  one  or  one  and  a  half  per  cent. — barley  where  two  or 
three  per  cent,  are  present — but  good  wheat  soils  contain  in  general  from 
4  to  8  per  cent.,  and,  if  very  stiff  and  clayey,  from  10  to  12  per  cent, 
may  occasionally  be  detected. 

Though,  however,  a  certain  proportion  of  organic  matter  is  always 
found  in  a  soil  distinguished  for  its  fertility,  yet  the  presence  of  such  sub- 
stances is  not  alone  sufficient  to  impart  fertility  to  the  land.  I  do  not 
allude  merely  to  such  as,  like  peaty  soils,  contain  a  very  large  excess  of 
vegetable  matter,  but  to  such  also  as  contain  only  an  average  proportion. 
Thus  of  two  soils  in  the  same  neighbourhood — the  one  contained  4-05 
per  cent,  of  organic  matter,  and  was  very  fruitful — the  other  4-19  per 
cent.,  and  was  almost  barren.  This  fact  is  consistent  with  what  has  been 
stated  in  the  two  preceding  lectures,  in  regard  to  the  influence  exercised 
by  the  dead  inorganic  matter  of  the  soil,  on  the  general  health  and  luxu- 
riance of  vegetation. 

§  2.   General  constitution  of  the  earthy  part  of  the  soil. 

From  what  is  above  stated,  it  appears  that,  on  a  general  average,  the 
earthy  part  of  the  soil  in  our  climate  does  not  constitute  less  than  96  pei 
cent,  of  its  whole  weight,  when  free  from  water.  This  earthy  part  con- 
sists principally  of  three  ingredients: — 

1°.  Oi'  Silica.,  siliceous  sand,  or  siliceous  gravel— of  various  degrees 
of  fineness,  from  that  of  an  imi>alpable  powder  as  it  occurs  in  clay  soils, 
to  the  large  and  more  or  less  rounded  sandstones  of  the  gravel  beds. 

2°.  Alumina — generally  in  the  form  of  clay,  but  occasionally  occur- 
ring in  shaly  or  slaty  masses  more  or  less  hard,  intermingled  with  the 
soil. 

3°.  Lime,  or  carbonate  of  lime — in  the  form  of  chalk,  or  of  fragments 
more  or  less  large  of  the  various  limestones  that  are  met  with  near  the 
surface  in  different  countries.  Where  cultivation  prevails  it  often  hap- 
pens that  all  the  lime  which  the  soil  contains  has  been  added  to  it  for 
agricultural  purposes — in  the  form  of  (juick-lime,  of  chalk,  of  shell-sand, 
or  of  one  or  other  of  the  numerous  varieties  of  marl  which  different  dis- 
tricts are  known  to  produce. 

It  is  rare  that  a  superficial  covering  is  anywhere  met  with  on  the 
surface  of  the  earth,  which  consists  solely  of  any  one  of  these  three  sub- 
stances— a  soil,  however,  is  called  sandy  in  which  the  siliceous  sand 
greatly  predominates,  and  calcareous,  where,  as  in  some  of  our  chalk 
and  limestone  districts,  carbonate  of  lime  is  present  in  considerable  abun- 
dance. When  alumina  forms  a  large  proportion  of  the  soil,  it  constitutes 
a  clay  of  greater  or  less  tenacity. 

The  term  clay,  however,  or  pure  clay,  is  never  used  by  writers  on 
agriculture  to  denote  a  soil  consisting  of  alumina  only,  for  none  such  ever 
occurs  in  nature.  The  pure  porcelain  clays  are  the  richest  in  alumina, 
but  even  when  free  from  water  they  contain  only  from  42  to  48  per  cent, 
of  this  earth,  with  from  52  to  58  of  silica.  These  occur,  however,  only 
in  isolated  patches,  and  never  alone  form  the  soil  of  any  considerable 


COMTOSITIOX  OF  PORCELAIN  AND  AG  HIC  ULT  TR/L  CLAYS.  C3l 

district.  The  strongest  clay  soils  which  are  anywhere  in  culiivation 
rarely  contain  more  than  35  per  cent,  of  alumina.' 

Soils  in  general  consist  in  great  part  of  the  three  substances  abpve 
named  in  a  state  of^ mechanical  mixture.  This  is  always  the  case  with 
the  siliceous  sand  and  with  the  carbonate  of  lime — but  in  the  clays  the 
silica  and  the  alumina  are,  for  the  most  part,  in  a  state  of  clieinical  com- 
bination. Thus,  if  a  portion  of  a  stiff  clay  soil  be  kneaded  or  boiled 
with  repeated  portions  of  water  till  its  coherence  is  entirely  destroyed, 
and  if  the  water,  with  the  finer  parts  which  float  in  it,  be  then  poured 
into  a  second  vessel,  the  whole  of  the  soil  will  be  separated  into  two  por- 
tions— a  fine  impalpable  powder  consisting  chiefly  of  clay,  poured  off 
with  the  water,  and  a  quantity  of  siliceous  or  other  sand  in  particles  of 
various  sizes,  which  will  remain  in  the  first  vessel.  This  sand  was 
only  mechanically  mixed  with  the  soil.  The  fine  clay  retains  still  some 
mechanical  admixtures,  but  consists  chiefly  of  silica  and  alumina  chem- 
ically combined. 

Of  the  porcelain  clays  above  alludwd  to,  there  are  several  varieties, 
three  of  which,  containing  the  largest  proportion  of  alumina,  co*»Jst  res- 
pectively of — 


I. 

II. 

III. 

Silica     .     , 

.     47-03 

46-92 

46-0 

Alumina 

.     39-23 

34.81 

40-2 

Water    . 

.     13-74 

18-27 

13-8 

100-00       100-00       lOO-Of 
But,  as  already  stated,  these  clays  rarely  form  a  soil — the  stiffest 
clays  treated  by  the  agriculturist  containing  a  further  portion  of  silica, 
some  of  which  is  mechanically  mixed,  and  can  be  partially  separated  by 
mechanical  means. 

The  strongest  agricultural  clays  {pipe-clays)  of  which  trustworthy 
analyses  have  yet  been  published,  consist,  in  the  dry  state,  of  56  to  62 
of  silica,  from  36  to  40  of  alumina,  3  or  4  of  oxide  of  iron,  and  a  trace  of 
lime.  Clays  of  this  composition  are  distinguished  by  the  foreign  agri- 
cultural writers  as  pure  clays.  They  are  all  probably  made  up  of  some 
of  the  varieties  of  porcelain  clay,  more  or  less  intimately  mixed  with 
siliceous  and  ochrey  particles — in  so  minute  a  state  of  division  that  they 
cannot  be  separated  by  the  method  of  decantation  above  described. 

These  clays  are  adopted  by  the  German  and  French  writers  as  a 
standard  to  which  they  can  liken  clay  soils  in  general,  and  by  compari- 
son with  which  they  are  enabled  distinctly  to  classify  and  name  "them. 
As  the  use  of  the  term  clay  in  this  sense  has  been  introduced  into  Eng- 

•  In  an  interesting  paper  on  subsoil  ploughing  by  Mr.  H.  S.  Thompson,  in  the  report  of 
the  Yorkshire  Agricultural  Society  for  1837,  p.  47,  it  is  stated  that  the  lias  clays,  which  form 
the  subsoil  in  certain  parts  of  Yorkshire,  contain  sometimes,  in  the  dry  state,  as  much  cw  51 
per  cent,  of  alumina  (?) 

t  When  heated  to  redness  the  whole  of  U»  -  water  is  driven  off  from  these  clays,  and  they 
then  consist  respectively  of— 

Silica 54-5  574  534 

Alumina 45-5  42  6  46  6 

1000         1000         ¥300 

Which  numbers  are  in  accordance  with  those  given  at  the  foot  of  the  preceding  page. 


232  CLASSIFICATION    OF    SOILS. 

lish  agricultural  books,*  and  as  it  is  really  desirable  to  possess  a  word  to 
which  the  above  meaning  can  be  attached,  I  shall  venture  in  future  to 
employ  it  always  strictly  in  this  agricultural  sensed 

By  alumina,  then,  I  shall  in  all  cases  express  the  pure  earth  of  alum, 
which  exists  in  clays,  and  to  which  they  owe  their  tenacity — by  clay,  a 
finely  divided  chemical  compound^  consisting  very  nearly  of  QQ  of  silica 
and  40  of  alumina,  ivith  a  little  oxide  of  iron,  and  from  which  no  siliceous 
or  sandy  matter  can  be  separated  mechanically  or  by  decantati&n. 

Of  this  clay  the  earthy  part  of  all  known  soils  is  made  up  by  mere 
mechanical  admixture  with  the  other  earthy  constituents  (sand  and 
lime),  in  variable  proportions.  On  a  knowledge  of  these  proportions  the 
following  general  classification  and  nomenclature  are  founded. 

§  3.   Of  the  classification  of  soils  from  their  chemical  constituents. 

Upon  the  principles  above  described  soils  may  be  classified  as  fol- 
lows : — 

1°.  Pure  clay  (pipe-clay)  consisting  of  about  60  of  silica  and  40  of 
alumina  and  oxide  of  iron,  for  the  most  part  chemically  combined.  It 
allows  no  siliceous  sand  to  subside  when  diffused  through  water,  and 
rarely  forms  any  extent  of  soil. 

2°.  Strongest  clay  soil  (tile-clay,  unctuous  clay)  consists  of  pure  clay 
mixed  with  5  to  15  per  cent,  of  a  siliceous  sand,  which  can  be  separated 
from  it  by  boiling  and  decantation. 

3°.  Clay  loam  differs  from  a  clay  soil,  in  allowing  from  15  to  30  per 
cent,  of  fine  sand  to  be  separated  from  it  by  washing,  as  above  described. 
By  this  admixture  of  sand,  its  parts  are  mechanically  separated,  and 
hence  its  freer  and  more  friable  nature. 

4°.  A  loamy  soil  deposits  from  30  to  60  per  cent,  of  sand  by  mechani- 
cal washing. 

5°.  A  sandy  loam  leaves  from  60  to  90  per  cent,  of  sand,  and 

6°.  A  sandy  soil  contains  no  more  than  10  per  cent,  of  pure  clay. 

The  mode  of  examining  with  the  view  of  naming  soils,  as  above,  is 
very  simple.  It  is  only  necessary  to  spread  a  weighed  quantity  of  the 
soil  in  a  thin  layer  upon  writing  paper,  and  to  dry  it  for  an  hour  or  two  in 
an  oven  or  upon  a  hot  plate,  the  heat  of  which  is  not  sufficient  to  dis- 
colour the  paper — the  loss  of  weight  gives  the  water  it  contained.  While 
this  is  drying,  a  second  weighed  portion  may  be  boiled  or  otherwise 
thoroughly  incorporated  with  water,  and  the  whole  then  poured  into  a 
vessel,  in  which  the  heavy  sandy  parts  are  allowed  to  subside  until  the 
fine  clay  is  beginning  to  settle  also.  This  point  must  be  carefully 
watched,  the  liquid  then  poured  off,  the  sand  collected,  dried  as  before 
upon  paper,  and  again  weighed.  This  weight  is  the  quantity  of  sand 
in  the  known  weight  oi  moist  soil,  which  by  the  previous  experiment  has 
been  found  to  contain  a  certain  quantity  of  water. 

Thus,  suppose  two  portions,  each  2'"J  grs.,  are  weighed,  and  the  one 
in  the  oven  loses  50  grs.  of  water,  a  ^d  the  other  leaves  60  grs.  of  sand, 
— then,  the  200  grs.  of  moist  are  equal  to  150  of  dry,  and  this  150  of  dry 

•  As  in  British  Husbandry,  p.  113,  and  in  Loudon's  EncydopcRdia  of  Agriculture,  p.  315, 
where  classifications  of  soils  are  given  chiefly  from  Von  Thaer,  though  neither  work,  ex- 
hibits with  sufficient  prominence  the  meaning  to  be  attached  to  af^ricultural  clay,  as  distia> 
guished  from  alumina,  sometimes  called  pure  clay  by  the  chem:s; 


MARLY  AND  CALCAREOUS  SOILS,  AND  VEGETABLE  MOULDS.        233 

soil  contain  60  of  sand,  or  40  in  100  (40  per  cent.)     It  would,  therefore, 
be  properly  called  a  loam,  or  loamy  soil.  ^ 

But  the  above  classification  has  reference  only  to  the  clay  and  sano; 
while  we  know  that  lime  is  an  important  constituent  of  soils,  of  which 
they  are  seldom  entirely  destitute.     We  have,  therefore, 

7°.  Marly  soils,  in  which  the  proportion  of  lime  is  more  than  5  but 
does  not  exceed  20  per  cent,  of  the  whole  weight  of  the  dry  soil.  The 
marl  is  a  sandy,  loamy,  or  clay  marl,  according  as  the  proportion  of 
clay  it  contains  would  place  it  under  the  one  or  other  denomination,  sup- 
posing it  to  be  entirely  free  from  lime,  or  not  to  contain  more  than  5  per 
cent.,  and 

8°.  Calcareous  soils,  in  which  the  lime  exceeding 20  per  cent,  becomes 
the  distinguishing  constituent.  These  are  also  calcareous  clays,  calca- 
reous loams,  or  calcareous  sands,  according  to  the  proportion  of  clay  and 
sand  which  are  present  in  them. 

The  determination  of  the  lime  also,  when  it  exceeds  5  per  cent.,  is 
attended  with  no  difficulty. 

To  100  grs.  of  the  dry  soil  diffused  through  half  a  pint  of  cold  water, 
and  half  a  wine-glass  full  of  muriatic  acid  (the  spiritof  saltof  the  shops), 
stir  it  occasionally  during  the  day,  and  let  it  stand  tver-nlght  to  settle. 
Pour  ofTthe  clear  liquor  in  the  morning  and  fill  up  the  vessel  with  water, 
to  wash  away  the  excess  of  acid.  When  the  water  is  again  clear,  pour  • 
it  off',  dry  the  soil  and  weigh  it — the  loss  will  amount  generally  to  about 
one  per  cent,  more  than  the  quantity  of  lime  present.  The  result  will 
be  sufficiently  near,  however,  for  the  purposes  of  classification.  If  the 
loss  exceed  5  grs.  from  100  of  the  dry  soil,  it  may  be  classed  among  the 
marls,  if  more  than  20  grs.  among  the  calcareous  soils. 

Lastly,  vegetable  matter  is  sometimes  the  characteristic  of  a  soil, 
which  gives  rise  to  a  further  division  of 

9°.  Vegetable  moulds,  which  are  of  various  kinds,  from  the  garden 
mould,  which  contains  from  5  to  10  per  cent.,  to  the  peaty  soil,  in  which 
the  organic  matter  may  amount  to  60  or  70.  These  soils  also  are  clayey, 
loamy,  or  sandy,  according  to  the  predominant  character  of  the  earthy 
admixtures. 

The  method  of  determining  the.  amount  of  vegetable  matter  for  the 
purposes  of  classification,  is  to  dry  the  soil  well  in  an  oven,  and  weigh 
it;  then  to  heat  it  to  dull  redness  over  a  lamp  or  a  bright  fire  till  the 
combustible  matter  is  burned  away.  The  loss  on  again  weighing  is  the 
quantity  of  organic  matter. 

Summary. — The  several  steps,  therefore,  to  be  taken  in  examining  a 
soil  with  the  view  of  so  far  determining  its  constitution  as  to  be  able  pre- 
cisely to  name  and  classify  it,  will  be  best  taken  in  the  following  order : — 

1°.  Weigh  100  grains  of  the  soil,  spread  them  in  a  thin  layer  upon 
white  paper,  and  place  them  for  some  hours  in  an  oven  or  other  hot 
place,  the  heat  of  which  may  be  raised  till  it  only  does  not  discolour  the 
paper.     The  loss  is  water. 

2'\  Let  it  now  (after  drying  and  weighing)  be  burned  over  the  fire  as 
above  described.  The  second  loss  is  organic,  chiefly  vegetable  matter, 
with  a  little  water,  which  still  remained  in  the  soil  after  drying. 

3°.  After  being  thus  bu7:>3d,  let  it  be  put  into  half  a  pint  of  water 


234  SUMMARY    OF    THE    METHOD    OF    EXAMINATION. 

with  half  a  wine-glass  full  of  spirit  of  salt,  and  frequently  stirred, 
^''hen  minute  bubbles  of  air  cease  to  rise  from  the  soil  on  settling,  this 
p'ocess  may  be  considered  as  at  an  end.  The  loss  by  this  treatment 
will  be  a  little  more  than  the  true  per  centage  of  lime,*  and  it  will  gen- 
erally be  nearer  I  he  truth  if  that  portion  of  soil  be  employed  which  has 
been  previously  heated  lo  redness. 

4°.  A  fresh  portion  of  the  soil,  perhaps  200  grs.  in  its  moist  State,  may 
now  be  taken  and  washed  to  determine  ihe  (]uantity  of  siliceous  sand  it 
contains.  If  the  residual  sand  be  supposed  to  contain  calcareous  matter 
its  amount  may  readily  be  determined  by  treating  the  dried  sand  with 
diluted  muriatic  acid,  in  the  same  way  as  when  determining  the  whole 
amount  of  lime  (3°.)  contained  in  the  unwashed  soil.f 

Let  me  illustrate  this  by  an  example. 

Example. — Along  the  outcrop  of  some  of  the  upper  beds  of  the  green 
sand  in  Berkshire,  Wiltshire,  and  Hampshire,  and  probably  also  in 
Buckingham  and  Bedford,  occur  patches  of  a  loose  friable  grey  soil 
mixed  with  occasional  fragments  of  flint,  which  is  noted  for  producing 
excellent  crops  of  wheat  every  other  year.  It  is  known  in  the  valley  of 
Kingsclere,  at  Wantage,  and  Newbury.  I  select  a  portion  of  this  soil 
from  the  latter  locality  for  my  present  illustration. 

1°.  After  being  dried  in  the  air,  and  by  keeping  some  time  in  paper,  it 
was  exposed  for  some  hours  to  a  temperature  sufficient  to  give  the  white 
paper  below  it  a  scarcely  perceptible  tinge :  by  this  process  104^  grs. 
lost  4  grs. 

2°.  When  thus  dried,  it  was  heated  to  dull  redness.  It  first  black- 
ened, and  then  gradually  assumed  a  pale  brick  colour,  the  change,  of 
course,  beginning  at  the  edges.     The  loss  by  this  process  was  4^  grs. 

3°.  After  this  heating,  it  was  put  into  half  a  pint  of  pure  rain  water 
with  half  a  wine-glass  full  of  spirit  of  salt.  After  some  hours,  when  the 
action  had  ceased,  the  soil  was  washed  and  dried  again  at  a  dull  red 
heat.     The  loss  amounted  to  3  grs. 

The  soil,  therefore,  contained 

Water 4  grs. 

Organic  matter  (less  than)   .     .       4^ 
Carbonate  of  lime  (less  than) 


Clay  and  sand 93 


4°.  By  boiling  and  washing  with  water,  291  grs.  of  the  undried  soil 
left  202^  grs.  of  very  fine  sand  chiefly  siliceous, — 104i,  therefore,  would 
have  left  73  grs.,  or  the  soil  contained  per  cent. — 

*  A  more  rigrorous  method,  of  determining  the  lime  when  less  than  5  per  cent,  will  be 
given  in  the  following  lecture. 

*  The  weighings  for  the  purposes  here  described  may  be  made  in  a  small  balance  with 
grain  weights,  sold  by  the  druggists  for  5s.  or  6s.,  and  the  vegetable  matter  may  be  burned 
away  on  a  slip  of  sheet  iron  or  in  an  untinned  iron  table-spoon  over  a  bright  cinder  or  char- 
coal fire— care  being  taken  that  no  scale  of  oxide,  which  may  be  formed  on  the  iron,  be  al- 
lowed to  mix  with  the  soil  when  cold,  and  thus  to  increase  its  weight.  Those  who  are  in- 
clined to  pert'orm  the  latter  operation  more  neatly,  may  obtain  for  about  6s.  each — from  the 
dealers  in  chemical  apparatus — fiin  light  platinum  capsules  from  1  to  IX  inches  in  diame- 
ter, capable  of  holding  100  grs.  r'.:'  soil— and  for  a  few  shillings  more  a  spirit  lamp,  over 
which  tlie  vegetable  matter  of  thi  soil  may  je  burned  away.  With  care,  one  of  these  little 
capsules  will  serve  a  life-time. 


DIFFERENCE    BETWEEN  SOIL  AMD  SUBSOIL.  235 

Water 3-9  per  cent. 

Organic  matter  (less  than)     .     .       4-1 
Carbonate  of  lime  (less  than)     .       3-0 

Clay 19-0 

Sand  (very  fine) 70.0 

100-0* 
This  soil,  therefore,  containing  70  per  cent,  of  sand,  separable  by 
decantation,  is  properly  a  sandy  loam. 

§  4.   Of  the  distinguishing  characters  of  soils  and  subsoils. 

Beneath  the  immediate  surface  soil,  through  which  the  plough  makes 
its  way,  and  to  which  the  seed  is  entrusted,  lies  what  is  commonly  dis- 
tinguished by  the  name  of  subsoil.  This  subsoil  occasionally  consists 
of  a  mixture  of  the  general  constituents  of  soils  naturally  different  from 
that  which  forms  the  surface  layer — as  when  clay  above  has  a  sandy 
bed  below,  or  a  light  soil  on  the  surface  rests  on  a  retentive  clay  beneath. 

This,  however,  is  not  always  the  case.  The  peculiar  characters  of 
the  soil  and  subsoil  often  result  from  the  slow  operation  of  natural  causes. 

In  a  mass  of  loose  matter  of  considerable  depth,  spread  over  an  extent 
of  country,  it  is  easy  to  understand  how — even  though  originally  alike 
through  its  whole  mass — a  few  inches  at  the  surface  should  gradually 
acquire  different  physical  and  chemical  characters  from  the  rest,  and 
liow  there  should  thus  be  gradually  established  important  agricultural 
distinctions  between  the  first  12  or  15  inches  (the  soil),  the  next  15  (the 
subsoil),  and  the  remaining  body  of  the  mass,  which,  lying  still  lower, 
does  not  come  under  the  observation  of  the  practical  agriculturist. 

On  the  surface,  plants  grow  and  die.  Through  tlie  first  few  inches 
their  roots  penetrate,  and  in  the  same  the  dead  plants  are  buried.  This 
portion,  therefore,  by  degrees,  assumes  a  brown  colour,  more  or  less  dark, 
according  to  the  quantity  of  vegetable  matter  which  has  been  permitted 
to  accumulate  in  it.  Into  the  subsoil,  however,  the  roots  rarely  pene- 
trate, and  the  dead  plants  are  still  more  rarely  buried  at  so  great  a  depth. 
Sill  this  inferior  layer  is  not  wholly  destitute  of  vegetable  or  other  or- 
ganic matter.  However  comparatively  impervious  it  may  be,  still  water 
makes  its  way  through  it,  more  or  less,  and  carries  down  soluble  organic 
substances^  which  are  continually  in  the  act  of  being  produced  during  the 
decay  of  the  vegetable  matter  lying  above.  Thus,  though  not  sensibly 
discoloured  by  an  admixture  of  decayed  roots  and  stems,  the  subsoil  in 
reality  contains  an  appreciable  quantity  of  organic  matter  which  may 
be  distinctly  estimated. 

Again,  the  continual  descent  of  the  rains  upon  th^surface  soil  washes 
down  the  carbonates  of  lime,  iron,  and  rriagnesia,  as  well  as  other  soluble 
earthy  substances — it  even,  by  degrees,  carries  down  the  fine  clay  also, 

•  Some  of  these  numbers  differ  by  a  minute  fraction  from  those  in  the  preceding  page : 
this  is  because  they  are  calculated  from  the  more  correct  decimal  fractions  contained  in  my 
own  note-book.  The  organic  matter  is  said  to  be  less  than  tlie  number  here  given,  because 
by  simple  drying,  as  here  prescribed,  the  whole  of  the  water  cannot  be  driven  off— a  portion 
being  always  retained  by  the  clay,  which  is  not  entirely  expelled,  till  the  soil  is  raised  nearly 
to  a  red  heat.  Hence  the  loss  by  this  second  heating  must  always  be  greater  than  the  actual 
weight  of  organic  matter  present.  The  lime  is  aho  less  than  the  number  given,  because,  as 
already  stated,  the  acid  dissolves  a  ittle  alumina  as  well  as  any  carbonate  of  magnesia  which 
may  be  present. 


236  HOW  THE  SUBSOIL  IS  PRODUCED. 

SO  as  gradually  to  establish  a  more  or  less  manifest  difference  between 
the  upper  and  lower  layers,  in  reference  even  to  the  earthy  ingredients 
which  they  respectively  contain. 

But,  except  in  the  case  of  very  porous  rocks  or  accumulations  of  earthy 
matter,  these  surface  waters  rarely  descend  to  any  great  depth,  and  hence 
after  sinking  through  a  variable  thickness  of  subsoil,  we  come,  in  gene- 
ral, to  earthy  layers,  in  which  little  vegetable  matter  can  be  detected, 
and  to  whicii  the  lime,  iron,  and  magnesia  of  the  superficial  covering 
has  never  been  able  to  descend. 

Thus  the  character  of  the  soU  is,  that  it  contains  more  brown  organic, 
chiefly  vegetable,  matter,  in  a  state  of  decay — of  the  subsoil,  that  ihe  or- 
ganic  matter  is  less  in  quantity  and  has  entered  it  chiefly  in  a  soluble 
state,  and  that  earthy  matters  are  presi.'nt  in  it  which  have  been  washed 
out  of  the  superior  soil — and  of  the  subjacent  mass,  that  it  has  remained 
nearly  unaffected  by  the  changes  which  vegetation,  culture,  and  atmos- 
pheric agents  have  produced  upon  the  portions  that  lie  above  it. 

From  what  is  here  stated,  the  effect  of  trench  and  subsoil  ploughing, 
in  altering  more  or  less  materially  the  proportions  of  the  earthy  constitu- 
ents in  the  surface  soil,  will  be  in  some  measure  apparent.  That  which 
the  long  action  of  rains  and  frosts  has  caused  to  sink  beyond  the  ordinary 
reach  of  the  plough  is,  by  such  methods,  brought  again  to  the  surface. 
When  the  substances  thus  brought  up  are  directly  beneficial  to  vegeta- 
tion or  are  fitted  to  improve  the  texture  of  the  soil,  its  fertility  is  increased. 
Where  the  contrary  is  the  case,  its  productive  capabilities  may  for  a 
longer  or  a  shorter  period  be  manifestly  diminished. 

§  5.   On  the  general  origin  of  soils. 

On  many  parts  of  the  earth's  surface  the  naked  rocks  appear  ovei 
considerable  tracts  of  country,  without  any  covering  of  loose  mate- 
rials from  which  a  soil  can  be  formed.  This  is  especially  the  case  in 
mountainous  and  granitic  districts,  and  in  the  neighbourhood  of  active 
or  extinct  volcanoes,  where,  as  in  Sicily,  streams  of  naked  lava  stretch 
in  long  black  lines  amid  the  surrounding  verdure. 

But  over  the  greater  portion  of  our  islands  and  continents  the  rocks 
are  covered  by  accumulations,  more  or  less  deep,  of  loose  materials — 
sands,  gravels,  and  clays  chiefly — the  upper  layer  of  which  is  more  or 
less  susceptible  of  cultivation,  and  is  found-  to  reward  the  exertions  of 
human  industry  with  crops  of  corn  in  greater  or  less  abundance. 

This  superficial  covering  of  loose  materials  varies  from  a  few  inches  to 
one  or  two  hundred  feet  in  depth,  afid  is  occasionally  observed  to  consist 
of  different  layers  on  beds,  placed  one,  over  the  other — such  as  a  bed  of 
clay  over  one  of  gravel  or  sand,  and  a  loamy  bed  under  or  over  both. 
In  such  cases  the  characters  and  capabilities  of  the  soil  must  depend 
upon  which  of  these  layers  may  chance  to  be  uppermost — and  its  char- 
acter may  often  be  beneficially  altered  by  a  judicious  admixture  with 
portions  of  the  subjacent  layers. 

It  is  often  observed,  where  naked  rocks  present  themselves,  either  in 
cliffs  or  on  more  level  parts  of  the  earth,  that  the  action  of  the  rains  and 
frosts  causes  their  suri'aoes  gradually  to  shiver  off*,  crumble  down,  or 
wear  away.  Hence  at  the  base  of  cliffs  loose  matter  collects — on  com- 
parativeh  level  surfaces  the  crumbling  of  the  rock  gradually  forms  a  soil — 


CRUMBLJNG  OR  DEGRADATION  OF  ROCKS.  237 

while  from  those  which  are  sufficiently  inclined  the  rains  wash  away 
the  loose  materials  as  soon  as  they  are  separated,  and  carry  them  down 
to  the  vallies. 

The  superficial  accumulations  of  which  we  have  spoken,  as  covering 
the  rocks  in  many  places  to  a  depth  of  one  or  two  hundred  feet,  consist 
of  materials  thus  washed  down  or  otherwise  transported — hy  water,  hv 
winds,  or  by  other  geological  agents.  Much  of  these  heaps  of  transported 
matter  is  in  the  state  of  too  fine  a  powder  lo  permit  us  to  say  from  whence 
it  has  been  derived — but  fragments  of  greater  or  less  size  are  always  to 
be  found,  even  among  the  clays  and  fine  sands,  which  are  sufficient  to 
point  out  to  the  skilful  geologist  the  direction  from  which  the  whole  has 
been  brought,  and  often  the  very  rocks  from  which  the  entire  accumula- 
tions have  been  derived. 

Thus  the  general  conclusion  is  fairly  drawn,  that  the  earthy  matter  of 
all  soils  has  been  produced  by  the  gradual  decay,  degradation,  or  crumb- 
ling down  of  previously  existing  rocks.     It  is  evident  therefore — 

1°.  That  whenever  a  soil  rests  immediately  upon  the  rock  from  which 
it  has  been  derived,  it  may  be  expected  to  partake  more  or  less  of  the 
composition  and  characters  of  that  rock. 

2°.  That  where  the  soil  forms  only  the  surface  layer  of  a  considerable 
depth  of  transported  materials,  it  may  have  no  relation  whatever  either 
in  rriineralogical  characters  or  in  chemical  constitution  to  the  immedi- 
ately subjacent  rocks.  * 

The  soils  of  Great  Britain  are  divisible  into  two  such  classes.  In 
some  counties  an  acquaintance  with  the  prevailing  rock  of  the  district 
enables  us  to  predict  the  general  characters  and  quality  of  the  soil ;  in 
others — and  nearly  all  our  coal  fields  are  in  this  case — the  general 
character  and  capabilities  of  the  soil  have  no  relation  whatever  to  the 
rocks  on  which  the  loose  materials  rest. 

§  6.  On  the  general  structure  of  the  earth's  crust. 

Beneath  the  soil,  and  the  loose  or  drifted  matters  on  which  it  rests,  we 
everywhere  find  the  solid  rock.  This  rock  in  most  countries  is  seen — 
in  mines,  quarries,  and  cliffs — to  consist  of  beds  or  layers  of  varied  thick- 
ness placed  one  over  the  other.  To  these  layers  geologists  give  the 
name  of  strata;  and  hence  rocks  which  are  thus  made  up  of  many  se- 
parate layers  are  called  stratified  rocks. 

But  in  some  places  entire  mountain  masses  are  met  with,  in  which  no 
parting  into  layers  or  beds  is  seen,  but  which  appear  to  consist  of  one 
unbroken  rock  of  the  same  material  from  their  upper  surface  down- 
wards, and  often  as  far  beneath  as  we  have  been  able  to  penetrate  into 
the  earth.  Such  rocks  are  said  to  be  unstratified.  Among  these  are 
included  the  granites,  the  trap,  green-stone,  or  basaltic  rocks,  and  the 
lavas.  Geologists  have  ascertained  that  all  these  unstratified  rocks  have, 
like  the  volcanic  lavas,  been  in  a  more  or  less  perfectly  melted  state — 
that  their  present  appearance  is  owing  to  the  action  of  fire — and  hence 
they  are  often  called  igneous*  rocks.  They  often  also  exhibit  a  more  or 
less  crystalline  or  glassy  structure,  or  contain,  imbedded  in  them,  nu- 
merous regular  crystals  of  mineral  substances ;  hence  they  are  some- 
times called  also  crystalline  rocks.     The  terms  igneous,  crystalline,  and 

•  Sometimea  pyrogenous,  produced  by  fire ;  but  this  is  an  unnecessarily  hard  word. 


238 


STRATIFIED  AND  'JNSTRATiriED  ROCKS. 


unstratified,  therefore,  apply  to  tL«  same  class  of  rocks — the  first  indica- 
ting their  origin,  the  second  their  structure  in  the  small,  the  third  their 
structure  in  the  large,  as  distinguished  from  that  of  the  rocks  which  occur 
in  beds. 

The  following  diagram  exhibits  the  general  appearance  of  tlje  strati 
fied  rocks  as  they  are  found  to  occur  in  contact  with  unstratified  masses 
in  various  parts  of  the  globe  : — 

J) 


A  represents  an  unstratified  mountain  mass  or  other  similar  rock  rising 
up  through  the  stratified  deposits.  The  bending  up  of  the  edges  of  the 
latter  indicates  that  after  the  beds  were  deposited  in  a  nearly  level  posi- 
tion, the  mass  A  was  intruded  or  forced  up  through  them,  carrying  the 
broken  edges  of  the  beds  along  with  it. 

B  shows  the  more  quiet  way  in  which  veins  or  dykes  of  unstratified 
green-stone,  or  trap,  or  lava,  cut  through  the  beds  without  materially 
displacing  them — as  if  when  in  a  fluid  state  it  had  risen  up  and  filled  a 
previously  existing  crack  or  chasm.  In  Devonshire,  in  the  North  of 
Scotland,  a'nd  in  Ireland,  the  granite  rises  i«  many  places  exactly  as  is 
shown  at  A,  and  nearly  all  our  coal  fields  exhibit  in  their  whin  dyke.s 
numerous  illustrations  of  what  is  shown  at  B. 

C  and  D  exhibit  the  manner  in  which  the  strata  overlie  one  another 
in  nearly  a  horizontal  position — 1,  2,  3,  indicating  difl!erent  kinds  of  rock, 
— as  a  lime-stone,  a  sand-stone,  and  a  clay — which  again  are  subdivided 
into  beds  or  thinner  layers,  by  the  partings  exhibited  in  the  wood-cut. 

The  stratified  rocks  lie  sometimes  nearly  level  or  horizontal  over  large 
tracts  of  country — as  in  the  above  diagram, — sometimes  they  are  more 
or  less  inclined  or  appear  to  dip  in  one  and  to  rise  in  the  opposite  direc- 
tion— as  if  a  surface,  formerly  level,  had  been  pushed  down  at  the  one 
end  and  raised  up  at  the  other, — and  sometimes  they  seem  to  rest  entire- 
ly upon  their  edges.  Upon  the  mode  in  which  they  thus  lie,  the  unifor- 
mity of  the  soil,  in  a  district  where  it  reposes  immediately  on  the  rocks 
from  which  it  is  derived,  is  materially  dependent.  In  the  following  dia- 
gram the  surface  from  A  to  S  represents  a  tract  of  country  in  which  the 


rocks  have  in  different  parts  these  different  degrees  of  inclination,  at  A 
vertical,  at  B  more  inclined,  and  from  C  to  E  nearly  horizontal.  Now, 
it  is  obvious  that  if  the  outer  surface  of  these  several  rocks  crumble  and 
form  a  soil  which  rests  where  it  is  produced — then  the  quality  of  the  soil 
on  every  spot  will  be  determined  by  the  nature  of  the  rock  beneath. 
Hence,  in  proc^eeding  from  E  over  the  comparatively  level  strata,  we 
shall  find  the  soil  pretty  uniform  in  quality  till  we  come  to  the  edge  of 


TERTICAL,  INCLINED,  AND  lORlZONTAL  STRATA.  239 

the  bed  D,  ihence  it  will  again  be  uniform,  though  perhaps  different  from 
the  former,  till  we  reach  the  stratum  C,  when  again  it  will  prove  uni- 
form over  a  considerable  space  till  we  begin  to  climb  the  bill  to  B.  So 
the  whole  hill-side  in  ascending  to  B  will  be  of  one  and  the  same  kind 
of  soil.  But  as  we  descend  on  the  other  side  and  pass  B,  we  get  upon 
the  edges  of  the  beds,  and  then  as  we  proceed  from  one  bed  to  another, 
the  quality  of  the  soil  may  vary  every  few  yards,  more  or  less,  ac- 
cording as  the  members  of  this  group  of  heds  are  more  or  less  differ- 
ent from  each  other.  But  when  we  ascend  the  hill  to  A,  where  the 
beds,  besides  being  vertical,  are  also  very  thin,  the  soil  may  change  at 
almost  every  step,  provided — which  is,  however,  rarely  the  case  among 
the  rocks  (slate  rocks)  which  occur  most  frequently  in  this  position — pro- 
►vided  the  mineralogical  characters  of  the  several  vertical  layers  be  sen- 
sibly unlike.  Such  dissimilarities  in  the  angular  position  of  the  strata, 
as  are  represented  in  the.  above  diagram,  are  of  constant  occurrence,  not 
only  in  our  islands,  but  in  all  parts  of  the  globe  ;  and  they  illustrate  very 
clearly  one  important  natural  cause  of  that  want  of  uniformity  in  the  na 
ture  and  capabilities  of  the  soil  which  is  more  or  less  observable  in  ever^ 
undulating  and  in  some  comparatively  level  countries  also. 

It  may  be  stated,  as  the  general  result  of  an  extended  examination 
of  all  the  stratified  rocks  yet  known — that  they  consist  of  alternations  or 
admixtures  of  three  kinds  of  rock  only — of  sand-stones,  of  lime-stones, 
and  of  clays.  The  sand-stones  are  of  various  degrees  of  solidity  and 
hardness,  from  the  loose  sand  of  some  parts  of  the  lower  new-red  and 
green-sand  formations,  to  the  almost  perfect  quartz  rock  not  unfrequently 
associated  with  the  oldest  strata.  The  lime-stones  vary  in  like  manner 
from  the  soft  chalk  to  the  hard  mountain  lime-stone  and  the  crystalline 
statuary  marble  ;  while  the  clays  are  found  of  all  degrees  of  hardness 
from  that  of  the  London  and  Kimmeridge  clays,  which  soften  in  water, 
to  that  of  the  roofing  slates  of  Cumberland  and  Wales, — and  even  to 
that  of  the  gneiss  rocks  which  rest  immediately  upon  the  granite,  and 
which  appear  to  be  only  the  oldest  cla3's  altered  by  the  action  of  heat. 

But  the  stratified  rocks,  though  thus  distinguishable  into  three  main 
varieties — rarely  consist  of  any  one  of  these  substances  in  an  unmixed 
state.  The  sand-stones  not  unfrequently  contain  a  little  clay  or  lime, 
while  the  lime-stones  and  clays  are  often  mixed  with  sand  and  whh 
each  other. 

If  the  stratified  rocks  thus  consist  essentially  of  these  three  substances, 
the  soils  formed  from  them  by  natural  crumbling  or  decay  must  have  a 
similar  composition.  A  sandy  soil  will  be  formed  from  a  sand-stone,— 
a  calcareous  soil  from  a  lime-stone, — a  clay  from  a  slate  or  shale, — and 
from  a  mixed  rock,  a  soil  containing  a  mixture  of  two  or  more  of  these 
earthy  ingredients — in  proportions  which  will  depend  upon  the  relative 
quantities  of  each  which  are  contained  in  the  rock  from  which  they  have 
been  derived. 

§  7.  Relative  positions  and  peculiar  characters  of  the  several  strata. 

1°.  The  several  strata,  or  series  of  strata,  which  present  themselves 
in  the  crust  of  the  globe,  always  maintain  the  same  relative  positions. 
Thus  the  numbers  3,  2,  1,  in  the  annexed  diagram,  represent  three  series 
of  beds  known  by  the  names  of  the  magnesian  lime-stone,  the  lower  new- 


240      tiip:3e  strata  are  often  continuous  ovkr  larue  arkas 


red  sand-stone,  and  the  coal-measures,  lying  over  each  other  in  their 
natural  positions — the  lime-stone  uppermost,  the  sand-stone  next,  and 
the  coal  beneath  both.  Whenever  these  three  rocks  are  met  with,  near 
each  other,  they  always  occupy  the  same  relative  position,  the  coal 
never  appears  above  this  lime-stone,  and  the  sand-stone,  if  present,  is 
always  between  the  two  other  series  of  beds.  The  same  is  true  of  every 
other  group  of  strata — the  order  in  which  they  are  placed  over  each  othe# 
is  universally  the  same. 

2°.  These  beds  are  generally  continuous  also  over  very  large  areas— 
or  are  found  to  stretch,  without  interruption,  over  a  great  extent  of  coun- 
try. Hence  when  they  dip  beneath  other  beds,  as  they  are  seen  to  do 
in  the  above  diagrams,  we  can  still,  with  a  high  degree  of  probability, 
infer  their  presence  at  a  greater  or  less  depth,  wherever  we  observe  oa 
the  surface  those  other  beds  which  are  known  usually  to  lie  immediate- 
ly above  them.  Thus,  if  in  a  tract  of  country  consisting  of  the  magne- 
sian  lime-stone  (3)  above-mentioned,  it  is  known  that  deep  vallies  occur, 
it  becomes  probable  that  the  soil  in  those  vallies  will  rest  upon,  and  may 
be  formed  from,  the  underlying  red  sand-stones  or  coal-measures ;  and 
that  it  will  therefore  possess  very  different  agricultural  capabilities  from 
the  soil  that  generally  prevails  around  it.  Or  in  chalk  districts,  beneath 
which  usually  lies  the  green-sand,  the  presence  of  a  deep  valley  cutting 
through  the  chalk  almost  necessarily  implies  in  the  hollow  a  very  differ- 
ent soil  from  that  which' is  cultivated  in  the  chalk  wolds  above.  This  is 
the  case  in  the  valley  of  Kingsclere,  where  the  peculiar  wheat  soil  oc- 
curs, of  which  an  approximate  analysis  has  been  given  in  page  234. 

3°.  It  has  been  already  stated  that  the  stratified  rocks,  though  so  very 
numerous  and  so  varied  in  appearance,  yet  consist  generally  of  repeated 
alternations  of  lime-stones,  sand-stones,  and  clays,  or  of  mixtures  of  two 
or  more  of  these  earthy  substances.  But  the  several  series  of  strata  are 
nevertheless  distinguished  from  each  other  by  peculiar  and  often  well- 
marked  characters. 

Thus  some  are  soft,  crumble  readily,  and  soon  form  a  soil, — while 
others,  though  consisting  of  the  same  ingredients,  long  refuse  to  break 
into  minute  fragments,  and  thus  condemn  the  surface  of  the  country 
where  they  occur  to  more  or  less  partial  barrenness. 

In  others,  again,  the  proportions  of  sand  or  lime  are  so  varied,  from 
bed  to  bed,  that  the  character  of  the  mixture  in  each  is  entirely  different 
- — so  that  while  one,  on  crumbling  down,  will  give  a  stiff  clay,  another 
will  produce  a  loam,  and  a  third  a  sandy  marl. 

Or,  in  some  rocks  the  remains  of  vegetables  are  present  in  considera- 
ble quantity, — as  in  the  neighbourhood  of  our  coal-beds — or  the  bones  or 
shells  of  animals  in  greater  or  less  abundance,  by  each  of  which  the 
agricultural  characters  and  capabilities  of  the  soils  formed  from  them, 
will  be  more  or  less  extensively  affected. 

Or  lastly,  the  mixture  of  other  earthy  substances  gives  a  peculiar 


THEIR    PECULIAR    CHARACTERS    ALSO    CONTINUOUS.  2it 

character  to  many  rocks.  Thus  the  per-oxide  of  iron,  which  imparts 
their  red  colour  to  many  strata — as  to  the  red  sandstones — influences 
not  only  the  mineralogical  character  of  the  rock,  but  also  the  quality  of 
the  soil  which  is  formed  by  its  decay.  In  like  manner  the  presence  of 
magnesia,  sometimes  in  large  quantity,  in  many  lime-stones,  produces 
an  important  modification  in  the  chemical  constitution  and  mineralogical 
characters  of  the  rock,  as  well  as  in  its  relations  to  practical  agriculture. 

In  consequence  of  these  and  other  similar  causes  of  diversity,  if  not 
every  stratum,  at  least  every  series  of  strata,  exhibits  distinguishing  and 
characteristic  peculiarities,  by  means  of  which  it  may  be  more  or  less 
readily  recognized.  On  these  peculiarities  the  special  agricultural  ca- 
pabilities of  those  parts  of  the  globe  in  which  each  series  of  beds  occurs 
are  in  a  great  degree  dependent. 

4°.  This  peculiar  character  is  also  more  or  less  continuous  over  very 
large  areas.  Thus  if  a  given  stratum  be  found  on  the  surface  in  any 
part  of  England,  and  again  in  any  part  of  Russia,  the  soil  formed  from 
that  bed  will  generally  exhibit  very  nearly  the  same  qualities  in  both 
countries.  A  knowledge  of  the  geology,  therefore, — that  is,  of  the  kind 
of  rock  which  appears  on  the  surface  in  every  part  of  a  country — ena- 
bles us  to  predict  generally  the  kind  of  soil  which  ought  to  rest  upon  it, 
if  it  be  not  covered  by  foreign  accumulations ;  while,  on  the  other  hand, 
a  knowledge  of  the  agricultural  capabilities  of  any  one  district  in  which 
certain  rocks  are  known  to  lie  immediately  beneath  the  soil,  and  of  the 
agricultural  practice  suited  to  that  district,  will  indicate  the  probable  ca- 
pabilities of  any  other  tract  in  which  the  same  kind  of  rock  is  known  to 
appear  on  the  surface,  and  of  the  kind  of  culture  which  may  be  most 
successfully  applied  to  it. 

It  is  evident,  then,  that  a  familiar  acquaintance  with  the  general 
characters  and  relative  positions  of  all  the  series  of  strata  that  have  hith- 
erto been  observed,  and  of  the  classifica'.ion  of  rocks  considered  geologi- 
cally, to  which  this  knowledge  has  led,  must  be  fitted  to  throw  much 
light  upon  the  principles  of  a  general,  enlightened,  and  philosophical 
agriculture. 

§  8.   Classification  of  the  stratified  rocks,  their  extent,  and  the  agricultu- 
ral relations  of  the  soils  derived  from  them. 

It  is  a  received  principle,  I  may  say  rather,  an  obvious  fact,  that  in 
the  crust  of  the  earth,  as  in  the  walls  of  a  building,  those  layers  which  lie 
lowest  or  undermost  have  been  first  deposited,  or  are  the  oldest.  In  re- 
ference to  this  their  relative  age,  the  stratified  rocks  are  divided  into  the 
primary,  the  first  deposited  and  most  ancient — the  secondary,  which  are 
next  in  order — and  the  tertiary,  which  overlie  both. 

These  three  series  of  strata  are  again  subdivided  into  systems,  and 
these  into  minor  groups,  called  formations, — the  several  members  of 
each  system  and  formation  having  such  a  common  resemblance,  either 
in  mineralogical  character  or  in  the  kind  of  animal  and  vegetable  re 
mains  found  in  them,  as  to  show  that  they  were  deposited  under  very 
nearly  the  same  general  physical  conditions  of  the  globe. 

The  following  table  exhibits  the  names,  relative  positions,  thicknesses 
and  mineralogical  characters  of  the  stratified  rocks,  in  descending  order 
as  they  occur  in  our  islands.     The  annexed  remarks  indicate  also  the 
11 


242  CLASSIFICATION    OF    TIIF    3TRATIF1KD    ROCKSj 

districts  where  each  of  these  groups  of  rocks  forms  the  surface,  and  the 
general  agricultural  character  of  the  soils  that  rest  upon  them. 

I.  Tertiary  Strata — characterized  by  containing,  among  other  fos- 
sils, the  remains  of  animals,  which  are  identical  with  existing  species 

NAME    AND    THICKNESS.  MINERALOGICAJL  CIIARACTEKS. 

1°.   Crag.  50  ft.  A  mass  of  rolled  pebbles  mixed  with 

marine  shells — resting  on  beds  of  sand 
and  sandy  lime-stone ;  the  whole  more 
or  less  impregnated  with  oxide  of  iron. 
Extent. — The  Crag  forms  a  stripe  of  land  a  few  miles  in  width  in  the  east- 
em  part  of  Norfolk  and  SuflFoUc,  and  in  the  soiith-eastem  part  of  the  latter  coun- 
ty.   It  is  a  flat,  and  generally,  it  is  said,  a  fertile  arable  district. 

2°.  Fresh-water  Marls.  100  ft.  Marls  and  marly  lime-stones,   with 

fresh-water  shells  divided  into  two  se- 
ries by  an  estuary  deposit,  containing 
marine  shells. 
Extent. — On  these  beds  reposes  the  soil  of  the  northern  half  of  the  Isle  of 

Wight,  the  only  part  of  England  in  which  they  appear  at  the  surface. 

3°.  London  Clay.    200  to  500  ft.  Stiff,  almost  impervious,  brown,  blue, 

and  blackish  clay,  rich  in  marine  shells, 
and  containing  layers  of  lime-stone  no- 
dules. 
Extent. — The  greater  part  of  the  county  of  Middlesex,  the  south-eastern 
half  of  Essex,  and  the  southern  half  of  Hampshire,  rest  upon  the  London  Clay. 
Soil. — The  soil  is  naturally  strong,  heavy,  wet,  and  tenacious,  "sticking  to 
the  plough  like  pitch,"  and  shrinking  and  cracking  in  dry  weather.     Where  it 
is  mixed  with  sand,  it  forms  a  fertile  loam ;  and  hence  where  the  sand  of  the 
subjacent  plastic  clay  is  easily  accessible,  it  may  readily  be  improved  by  ad- 
mixture.    Repeated  dressings  of  London  manure  convert  it  into  rich  meadow 
land,  and  even  where  this  cannot  be  obtained,  the  difficulty  and  expense  of  cul- 
ture have  caused  a  very  large  portion  of  it  to  be  retained  in  pasture.     That 
which  is  under  culture  is  said  to  be  too  strong  for  turnips  and  barley,  but  to 
grow  excellent  crops  of  wheat  and  beans. 

4°.  Plastic  Clay.     300  to  iOO  ft.  Alternating  beds  of  clay  and  sand,  of 

various  colours  and  thicknesses.  Some 
of  the  beds  of  clay  are  pure  white,  and 
so  fine  as  to  be  used  for  making  pipes. 

Extent. — This  formation  surrounds  the  London  clay  with  an  indented,  gen- 
erally low,  and  flat  belt,  of  varying  breadtli,  occupying  a  large  space  in  Hamp- 
shire and  Dorset,  in  Essex,  Suffolk,  and  Norfolk, — stretching  along  the  north- 
ern part  of  Kent  and  Surrey,  and  throwing  out  aiTns  into  Berks,  Buckingham, 
and  Hertford. 

Soil. — The  soil  is  very  various,  the  alternate  beds  of  sand  and  clay  of  differ- 
ent qualities  producing  soils  of  the  most  unlike  quality  of\en  within  very  short 
distances.  The  greatest  portion  of  this  tract  is  in  arable  culture,  but  there  are 
extensive  heaths  and  wastes  in  Berks,  Hampshire,  and  Dorset. 

In  Norfolk  and  Suffolk,  where  the  lower  beds  of  this  sand  rest  upon  chalk, 
the  soil  is  readily  changed,  by  an  admixture  with  this  chalk,  into  a  good  sandy 
loam,  which  will  yield  large  crops  of  turnips,  barley,  and  wheat,  instead  of  the 
heath  and  bent,  its  sole  original  produce.  This  chalking  is  gener£dly  repeated 
once  in  8  years,  at  an  expense  of  50s.  an  acre.  In  Hampshire  and  Berkshire, 
th,e  same  method  is  adopted  with  great  success,  and  the  rich  crops  now  reaped 
from  Hounslow  Heath  are  the  result  of  this  method  cf  imorovement. 


SOIL   OF    THE    UrPER   AND    LOWER   CHALKS.  243 

II.  The  Secondary  Strata — contain  no  animal  remains  which 
can  be  identified  with  existing  species.  Those  which  are  found  in  them 
are  nearly  all  different  from  those  which  occur  either  in  the  tertiary 
above  or  the  primary  strata  below. 

A. — Cretaceous  System. 
5°.   Chalk.  600  ft.  The  upper  part  softer,  and  contain- 

ing layers  of  flints,  witli  many  marine 
^  remains.     Below,  the  chalk  is  harder, 

and  towards  the  bottom  passes   into 
beds  of  marl — (chalk  marl). 

Extent. — The  chalk  occupies  a  very  large  area  in  the  south-eastern  part  of 
the  island.  It  forms  a  broad  band  of  from  15  to  25  miles  in  breadth,  running 
north-east  and  south-west  from  the  extreme  south-western  part  of  Dorset,  to 
the  extreme  north  of  Norfolk, — it  there  turns  nearly  at  a  right  angle,  into  the 
centre  of  Lincolnshire,  where  it  is  10  to  15  miles  in  breadth,  and  thence  stretches 
into  Yorkshire,  in  the  south-eastern  part  of  which  county  it  covers  a  large  area, 
and  about  Flamborough  Head  attains  a  breadth  of  35  miles.  In  passing 
through  Berkshire  and  Suirey,  it  is  partially  interrupted  by  the  plastic  clay 
which  it  embraces  on  every  side ;  and  hence,  in  following  the  outline  of  this  for- 
mation it  encircles  with  a  broad  fringe  the  southern  edges  of  Sussex  and  Surrey 
and  the  northern  borders  of  Kent. 

Soil. — The  soils  formed  from  the  upper  chalk  are  all  more  or  less  mixed 
with  flints,  and  they  produce  naturally  a  very  short  but  excellent  sheep  pasture. 
A  great  portion  of  this  chalk-land  in  Dorset,  Wilts,  and  Berks,  has  been  occu- 
pied as  a  sheep-walk  for  ages,  though  under  proper  cultivation  it  is  said  to  be 
convertible  into  good  arable  land,  producing  oarley,  turnips,  wheat,  and  sain- 
foin. The  lower  chalk  soils  (chalk  marl)  consist  of  a  deep,  strong,  calcareous 
grey  or  white  loam,  very  productive,  and  when  mixed  with  the  green  sand  be- 
low it,  becoming  still  richer,  more  friable,  and  more  productive  of  every  kind  of 
crop.  It  is  better  suited  for  wheat  than  tlie  upper  chalk,  but  is  less  adapted  for 
turnips. 

The  porous  nature  of  the  chalk  renders  the  soil  very  dry,  and  in  many  locali- 
ties th^e  only  method  of  obtaining  a  sufiicient  supply  of  water  is  by  forming 
ponds  to  catch  and  retain  the  rain-water. 

In  Norfolk  and  Suffolk,  on  the  Lincolnshire,  and  more  recently  on  the  York- 
shire Wolds,  great  improvement  has  been  effected  by  dressing  the  chalk-soil 
with  fresh  chalk  brought  up  from  a  considerable  depth  below,  and  laid  on  at  the 
rate  of  50  to  80  cubic  yards  per  acre.  The  explanation  of  this  procedure  is  to 
be  found  in  the  fact  above  stated,  that  the  lower  chalk  marls,  without  flints,  pro- 
duce an  excellent  soil,  fitted  therefore,  by  admixture  with  the  poorer  upper-chalk 
soils,  for  materially  improving  their  quality.  It  is,  therefore,  only  in  localities 
v/here  this  lower  chalk  can  be  obtained,  that  the  above  method  of  improve- 
ment can  be  with  any  material  advantage  adopted.  This  is  proved  by  the 
practice  at  Sudbury,  in  Suff"olk,  which  rests  upon  the  upper  beds,  where  it  is 
found  to  be  more  profitable  to  import  the  lower  chalk  from  Kent,  to  lay  upon 
these  lands,  than  to  dress  them  with  any  of  the  chalks  (only  upper  beds)  which 
are  immediately  within  their  reach.* 

6°.   Green  Sand.         500  ft.  The  upper  beds  consist  of  layers  of 

a  Upper,    100.  a   greenish  sand  or   sand-stone,   often 

b  GaiUt,     150,  chalky.     The  gault  is  a  solid  compact 

c  Lower,   250.  mass  of  an  impervious  blue  clay,  some- 

times marly.     The  lower  green  sand 
contains  a  series  of  ochrey  resting  on  a 

•  A.  rigorous  chemical  analysis  of  characteristic  specimens  of  these  two  chalks  might  lead 
to  interesting  results. 


244   UPPER  GREEN  SAND,  WEALDEN,  AND  UPPER  OOLITE  K0CK3. 

series  of  greenish  sandy  strata.  The 
whole  of  these  beds  are  in  m£iny  places 
full  of  fossils. 

Extent. — The  Green  Sand  forms  a  narrow  border  round  the  whole  of  the 
northern  and  western  edge  of  the  chalk,  except  in  Yorkshire,  where  it  has  not 
as  yet  been  anywhere  discovered  at  the  surface.  It  skirts  also  the  southern 
edge  of  the  chalk  in  Surrey  and  Kent,  and  its  eastern  boundaiy  in  Hampshire, 
where  it  attains  a  breadth  of  eight  or  ten  miles.  It  forms  likewise  the  southern 
portion  of  the  Isle  of  Wight. 

Soil. — The  upper  beds,  which  are  the  greenest  and  most  chalky,  form  an 
open  fiiable  soil,  easily  worked,  and  of  the  most  productive  character.  It  con- 
sists in  general  of  an  exceedingly  fine  sand,  mixed  with  more  or  less  of  clay 
and  calcareous  matter  (see  analysis,  p.  234),  coloured  by  greenish  grains.  It  is 
rich  and  productive  of  every  species  of  crop,  and  the  peculiar  richness  of  this 
soil  has  been  remarked  not  only  in  England  but  also  in  the  United  States  of 
North  America.  In  some  parts  of  Bedfordshire  the  soils  of  this  formation  form 
the  most  productive  garden  lands  in  the  kingdom.  In  other  localities,  again, 
where  tlie  soil  is  formed  from  layers  of  black  or  of  white  silvery  sand,  it  produ- 
ces naturally  nothing  but  heath. 

The  impervious  gault  clay  forms  in  Cambridge  and  Huntingdon  "  a  tliin, 
coid  clay  soil,  which,  when  wet,  becomes  as  sticky  as  glue,  is  most  expensive 
to  cultivate  as  arable  land,  and  naturally  produces  a  poor,  coarse  pasture." 
Much  of  this  tract,  though  unenclosed,  is  yet  generally  in  arable  culture,  under 
two  crops  and  a  naked  fallow — tlie  enclosed  parts  are  chiefly  in  pasture,  and 
yield  a  rich  herbage. 

The  lower  green-sand  presents  itself  over  a  comparatively  small  surface, 
is  in  some  localities  (Sussex)  laden  with  iron  ochre,  and  is  there  naturally  un- 
productive. 

B. — Oolitic  System. 

7°.    Wealden.  950  ft.  The  upper  part  consists  of  a  fresh- 

a  Weald  Clay,  300.        water  deposit  of  brown,  blue,  or  fawn- 

d  Hastings  Sand,        400.        coloured  clay,  often  marly  and  almost 

c  Purbeck  lime-stone,  250.        always  close  and  impervious  to  water. 

Beneath  this  are   the   iron   or  ochrey 

Hastings  sands,  which  again  rest  upon 

the  Purbeck  beds  of  alternate  fresh- war 

ter  lime-stones  and  marls. 

Extent. — The  Wealden  rocks  appear  at  the  sui-face  only  in  Sussex  and 

Kent,  of  which  they  form  the  entire  central  portion. 

Soil. — The  soil  formed  from  the  Weald  Clay  is  fine  grained  and  unctuous — 
often  pale  coloured,  emd  containing  much  fine  grained  siliceous  sand.  It  forms  a 
paste  which  dries  and  hardens  almost  like  a  brick,  so  that  the  roots  of  plants 
cannot  penetrate  it.  From  the  expense  of  cultivating  such  land,  much  of  it 
is  in  wood  (Tilgate  Forest),  and  some  is  in  poor  wet  pasture.  On  the  whole 
of  this  tract,  therefore,  there  is  much  room  for  improvement.  The  Hastings 
sands  produce  a  poor  brown  sandy  loam  which  naturally  yields  only  heath  and 
brush-wood.  Much  of  this  soil  is  in  pasture,  but,  under  proper  cultivation,  it 
yields  good  crops  of  all  kinds.  Where  the  ruins  of  the  Purbeck  mai-ls  are  in- 
tenriixed  with  it,  the  soil  is  of  a  superior  quality. 

8°.    Upper  Oolite.         600  ft.  The  upper  part  of  this  formation  con- 

a  Portland  Beds,         100.        sists  of  the  oolite*  limestones  and  cal- 

b  Kimmeridge  Clay,  500.        careous   sand-stones   long   worked    at 

Portland— the  lower  of  the  blue  slaty 

*  So  named  because  they  consist  of  small  fig'^'-shaped  granules,  like  the  roe  of  a  fish. 


IMPERVIOUS  SOIL  OF  THE  OXFORD  CLAY.  345 

or  greyish,  often  calcareous  and  bitu 
minous  beds  of  the  Kimmeridge  clay. 

Extent,— The  Upper  Oolite  runs  north-east  along  the  northern  edge  ot 
the  green  sand,  from  the  western  extremity  of  Dorset  to  the  extreme  north  of 
Norlblk,  It  is  in  general  only  2  or  3  miles,  but  in  a  few  places  expands  to 
6  or  8  miles  in  breadth.  It  appears  again  on  the  western  edge  of  tne  green 
sand  in  Lincolnshire,  and  in  Yorkshire  forms  a  sti-ipe  5  or  6  miles  in  breadth, 
which  crosses  the  country  from  Helmsley  to  Filey  Bay.  In  the  Isle  of  Port- 
land also  it  is  found,  and  it  stretches  in  a  narrow  stripe  along  part  of  the  south 
coast  of  Dorset. 

Soil. — The  soil  from  tlie  Portland  rocks,  in  consequence  of  the  prevalence 
of  siliceous  and  the  absence  of  clayey  matter,  produces  naturally,  or  when  laid 
down  to  grass,  only  a  poor  and  benty  herbage.  Its  loose  and  sandy  nature 
makes  it  also  very  cheap  to  work,  and  hence  it  is  chiefly  in  arable  culture.  It 
is  easily  affected  by  drought,  but  in  damp  seasons  it  produces  abundant  crops 
— especially  in  those  parts  where  the  soil  is  naturally  mixed  with  the  detritus 
of  the  over-lying  Hastings  sand,  and  of  the  calcareous  Purbeck  beds. 

The  Kimmeridge  clay  forms  a  tough,  greyish,  impervious,  often  however 
very  calcareous  soil  and  subsoil.  From  the  difficulty  of  working  it,  much  Oi" 
the  surface  over  which  this  formation  extends  is  laid  down  to  grass,  and  the  old 
pasture  land  afibrds  excellent  herbage.  The  celebrated  pasture  lands  of  the  vale 
of  North  "Wilts  rests  partly  on  this  clay.  The  relative  thicknesses  of  the  Portland 
beds  and  the  Kimmeridge  clay  will  readily  account  for  the  fact  of  this  clay  be- 
ing spread  over  by  far  the  greatest  part  of  the  area  occupied  by  this  formation. 
In  Yorkshire,  clay  of  a  great  thickness  is  the  only  member  of  this  series  that 
has  hitherto  been  obsei-ved.  On  this,  as  well  as  on  tlie  subjacent  Oxford  clay, 
the  judicious  investment  of  capital  might  produce  a  much  greater  annual  breadth 
of  com. 

9°.  Middle  Oolite.       500  ft.  The  uppei-most  bed  in  this  formation 

Upper  Calcareous  Grit,  )  is  a  sand-stone  containing  a  consider- 

Coral  Rag,  >  100.     able  quantity  of  lime— next  is  a  coral- 

Calcareous  Grit,  )  line  lime-stone  (coral  rag)  restin;^  upon 

Oxford  Clay,  )  other  sand-stones,  which  contain  much 

Kelloways  Rock,  >  400,     lime  in  their  upper  and  Httle  or  none  in 

Blue  Clay,  )  their  lower  beds.     Below  these  is  an 

enormous  deposit  of  adhesive  tenacious 
dark  blue  clay,  frequently  calcareous 
and  bituminous,  and  towards  the  lower 
part  containing  UTCgular  beds  of  sand- 
stones and  lime-stones(Kelloways  rock) 
beneatli  which  the  clay  again  recurs. 
Extent. — The  middle  adjoins  the  upper  oolite  on  the  north  and  west — ac- 
companying it  from  the  extremity  of  Dorset,  into  Wilts,  Oxford,  Huntingdon, 
Lincolnshire,  and  Yorkshire.     Until  it  reaches  Huntingdon,  it  rarely  exceeds 
6  or  8  miles  in  width,  but  in  this  county  and  in  Lincoln  it  expands  to  a  width 
of  nearly  20  miles.     In  Yorkshire  it  nearly  surrounds  the  upper  oolite,  and 
on  the  northern  border  of  the  latter  formation  attains  a  width  from  north  to 
south  of  6  or  8  miles. 

Sou.. — The  higher  beds  of  both  the  upper  and  lower  calcareous  grits  produce 
good  land.  They  contain  lime  in termmgled.  with  the  other  materials  of  the 
siliceous  sand-stone.  The  upper  calcareous  grits  are  no  doubt  improved  by 
their  proximity  to  tlie  Kimmeridge  clay  above  them,  while  the  lower  calcareous 
grit  is  in  like  manner  benefitted  by  the  lime  of  the  super-incumbent  coral  rag. 
The  under  beds  of  both  groups  are  the  more  gritty,  and  form  a  poor,  baxren, 
almost  worthless  soil,  much  of  which  in  Yorkshire  is  still  unreclaimed. 
Upon  the  hills  of  the  coral  rag  itself  occurs  the  best  pasture  which  is  met  with 


246  ARABLE  LANDS  OF  THE  OOLITE. 

in  that  part  ofUie  Nctth  Riding  of  Yorkshire  through  which  this  formation 
extends. 

The  Oxford  clay,  which  is  by  far  the  most  important  member  of  this  forma- 
tion, and  forms  the  surface  over  by  far  tlie  largest  portion  of  the  area  occupied 
by  it — produces  a  close,  heavy,  compact  clay  soil,  difficult  to  work,  and  which 
is  one  of  the  most  expensive  of  all  the  clays  to  cultivate.  This  is  especially 
the  case  in  Bedford,  Huntingdon,  Northampton,  and  Lincoln,  in  which  coun- 
ties, neveriheless,  a  considerable  extent  of  it  is  under  the  plough.  In  Wilts, 
Oxford,  and  Gloucester,  it  is  chiefly  in  pasture,  and  as  over  these  districts  it  as- 
sumes the  character  rather  of  a  clayey  loam,  the  herbage  is  thick  and  luxuriant. 
The  impervious  nature  of  this  clay  has  caused  the  stagnation  of  water  upon 
its  lower  lying  portions,  the  consequent  accumulation  of  vegetable  matter,  and 
the  formation  of  bogs.  The  extensive  fens  of  Lincoln,  Northampton,  Hunt- 
ingdon, Cambridge,  and  Norfolk,  rest  upon  the  Oxford  clay.  This  tract  of 
fenny  country  is  70  miles  in  length,  and  about  10  in  average  breadth.  When 
drained  and  covered  with  the  clay  from  beneath,  it  is  capable  of  being  converted 
into  a  most  productive  soil.  In  Lincolnshire,  there  are  about  a  million  acres 
of  fen,  which  have  their  drainage  into  the  Wash,  about  50,000  of  which  are  at 
present  in-eclaimable,  on  account  of  the  state  of  the  outlet. 

In  the  neighbourhood  of  the  Kelloways  rock  the  clay  becomes  more  loamy 
and  less  difficult  to  work. 

Both  in  Yorkshire  and  in  the  southern  districts,  the  Oxford  clay  is  found  to 
favour  the  growth  of  the  oak,  and  hence  it  is  often  distinguished  by  the  name 
of  tlie  oak  tree  clay. 

^0°.  Inferior  Oolite.      600  ft.  Thin,  impuare,  rubbly  beds  of  shelly 

a  Combrash,  30.  lime-stone  form  the  upper  part  of  this 

b  Forest  Marble,          50.  series.     These  rest  upon  alternate  beds 

c  Bradford  Clay,  50.  of  oolitic  shelly  lime-stone  and  sand- 

d  Bath  Oolite,  130.  stone,  more  or  less  calcareous,  having 

g  Fuller's  Earth,         140.  partings  of  clay ;  these  again  upon  beds 

/  Inferior  Oolite,      )  ^nn  of  blue  marly  clay,  immediately  under 

g  Calcareous  Sand,  ]  which  are  the  thick  beds  of  the  Ught-co- 

loured  oolite  hme-stone  of  Bath.     Be- 
neath these  follow  other  beds  of  blue 
clay,  with  Fuller's  earth,  based  upon 
another  oolitic  lime-stone,  which  is  fol- 
lowed by  slightly  calcareous  sands. 
Extent. — This  formation  commences  also  at  the  south-westem  extremity  of 
Dorset,  and  runs  north-east,  swelling  out,  here  and  there,  and  in  Gloucester, 
Oxford,  and  Northampton  attaining  a  width  of  15  to  20  miles.     It  occupies 
nearly  the  whole  of  these  three  counties,  covers  almost  the  entire  area  of  Rut- 
land, a  large  portion  of  the  north-east  of  Leicester,  and  tlien,  in  a  narrow  stripe, 
stretches  north  through  Lincoln,  and  disappears  at  the  Humber.     It  appears 
again  in  the  North  Riding  of  Yorkshire,  skirting  the  outer  edge  of  the  middle 
oolite,  on  the  north  of  which  it  attains  a  breadth  of  15  miles,  and  stretches 
across,  with  little  interruption,  from  near  Thirsk  to  the  North  sea.     A  small 
patch  of  it  appears  farther  north,  on  the  south-eastern  coast  of  Sutherland,  and 
on  the  east  and  south  of  the  Isle  of  Sky. 

Soil. — It  will  be  understood  from  what  has  been  already  stated  in  reference 
to  other  formations,  that  one  wliich  contains  so  many  different  rocks,  as  this 
does,  must  also  present  many  diversities  of  soil.  Where  the  upper  beds  come 
to  the  surface,  the  clay-partings  give  the  character  to  tlie  soil— fonning  a  calca- 
reous clay,  which,  when  dry  or  dredned,  is  of  good  quaUty.  In  other  places  it 
forms  a  close  adhesive  clay,  which  is  naturally  almost  sterile.  The  Bath  oolite 
weathers  and  crumbles  readily.  The  soil  upon  it  is  thin,  loose,  and  dry.  The 
rock  is  full  of  vertical  fissures,  which  carrj-  off  the  water  and  drain  its  surface. 


OLD    PASTURES    OF    THE    HAS.  247 

Wuen  free  from  fragments  of  the  rock,  the  soil  is  often  close  and  impervious, 
and,  though  of  a  brown  colour,  deep,  and  apparently  of  good  quality,  it  is  really 
worthless,  or,  as  the  farmers  call  it,  dead  and  sleepy.  Most  of  tl^  land,  how- 
ever, is  in  arable  cultivation.  The  heavy  soils,  which  rest  on  the  clay  contain- 
ing Fuller's  earth,  are  chiefly  in  pasture. 

The  inferior  oolite  varies  much  in  its  character,  containing,  in  some  places, 
much  lime-stone,  while  in  others,  as  in  Yorkshire,  it  forms  a  thick  mass  of  sand- 
stones and  clays,  with  occasional  thin  beds  of  coal.  In  Gloucester,  Oxford, 
Northampton,  and  Rutland,  these  lower  beds  form  a  tract  of  land  about  12  miles 
in  width.  The  soil  is  generally  soft,  sandy,  micaceous,  of  a  brown  colour,  and 
of  a  good  fertile  quality.  It  is  deep,  contains  many  fragments  of  the  subjacent 
rock,  is  porous,  and  easily  worked.  Where  the  sand-stones  prevail,  it  is  of  in- 
ferior quality.  In  these  counties  it  is  principally  enclosed,  and  in  arable  culture, 
the  sides  of  the  oolitic  hills  and  the  clayey  portions  being  in  pasture.  In  York- 
shire, much  of  the  unproductive  moor  land  of  the  North  Riding  rests  upon  this 
formation.  Nearly  all  the  arable  land  in  the  county  of  Sutherland  rests  on  the 
narrow  stripe  of  the  lower  oolite  rocks  which  occurs  on'  its  south-east  coast. 
The  debris  of  these  rocks  has  formed  a  loamy  soil,  which,  when  well  limed, 
produces  heavy  crops  of  turnips. 

1 1°.  Lias.  500  to  1000/^  This  great  deposit  consists  chiefly  of 

an  accumulation  of  beds  of  blue  clay, 
more  or  less  indurated — interrupted  m 
various  places  by  beds  of  marl,  and  of 
blue,  more  or  less  earthy,  lime-stones, 
which  especially  abound  in  the  lower 
part  of  the  series.     The  whole  is  full  of 
shells,  and  of  the  remains  of  large  ex- 
tinct animals. 
Extent. — Wherever  the  lower  oolites  are  to  be  traced  in  England,  the  lias 
is  seen  coming  up  to  the  surface  on  its  northern  or  western  edge,  pursuing  an 
exceedingly  tortuous  north-eastern  course,  throwing  out  m  its  course  many 
arms  (outliers),  and  varying  in  breadth  from  2  to  6  or  10  miles.     It  may  be 
traced  from  the  mouth  of  the  Tees,  in  Yorkshire,  to  Lyme  Regis,  in  Dorset,  the 
continuity  being  broken  only  by  the  coal  field  of  Somerset.     In  Scotland  and 
Ireland  no  traces  of  this  formation  have  yet  been  detected. 

Soil. — Throughout  the  whole  of  this  formation  the  soil  is  a  blue  clay,  more 
or  less  sandy,  calcareous,  and  tenacious.  Where  the  lime  or  sand  prevails  the 
soil  is  more  open,  and  becomes  a  loam ;  where  they  are  less  abundant,  it  is  of- 
ten a  cold,  blue,  unproductive,  wet  clay.  This  latter,  indeed,  may  be  given  as 
the  natural  character  of  the  entire  formation.  Where  it  rests  upon  a  gravelly 
or  open  subsoil,  or  contains  a  large  quantity  of  vegetable  matter,  it  may  be 
cultivated  to  advantage,  and  it  is  found  especially  to  produce  good  herbage.  In 
all  situations,  it  is  an  expensive  soil  to  work,  and  hence  by  far  the  greater  por- 
tion of  it  is  in  old  pasture.  The  celebrated  dairy  districts  of  Somerset,  Glou- 
cest^,  Warwick,  and  Leicester,  rest  for  the  most  part  on  the  lias,  as  does  also 
much  of  the  best  grazing  and  pasture  land  in  Nottingham  and  Yorkshire. 
Through  the  long  lapse  of  time  an  artificial  soil  has  been  produced  on  the  un- 
disturbed surface  of  these  clay  districts,  which  is  peculiarly  propitious  to  the 
growth  of  gjass.  With  skilful  drainage  and  judicious  culture,  it  is  capable  of 
producing  heavy  crops  of  wheat. 

C. — New  Red  Sand-stone  System. 
12°.    Upper  and  Lmoer  "i  .^^   /.  The  upper  and  lower  red  sand-stones 

RedSand-stcmts.  ^  -^  consist  of  alternate  layers  of  sand,  sand- 
stones, and  marls  sometimes  colourless, 
but  generally  of  a  red  colour — sprinkled 
in  the  upper  series  with  frequent  green 


248  FERTILE  MARLS  OF  THE  NEW  RED  SAND-STONE. 

spots.    The  lower  beds  are  sometimcji 
^  full  of  rolled  pebbles.     Few  of  the  sand- 

^  stones  of  this  formation  are  sufficiently 

hard  to  form  building  stones— many  of 
the  layers  consist  of  loose  friable  sand, 
and  the  marls  universally  decay  and 
crumble  to  a  fine  red  powder  under  the 
influence  of  the  weather. 
Extent. — The  new  red  sand-stone  extends  over  a  larger  portion  of  the  surface 
of  England  than  any  other  formation.  It  commences  at  I'orbay,  in  the  south 
of  Devon,  runs  north-east  into  Somersetshire ;  from  Bristol  ascends  both  sides 
of  the  Severn,  accompanies  it  into  the  vale  of  Gloucester,  stretches  along  the 
base  of  the  Malvern  hills,  and  north  of  the  city  of  Worcester  expands  into  a 
gently  undulating  plain,  nearly  80  miles  in  width  at  its  broadest  parL  compre- 
hending nearly  the  whole  of  the  counties  of  Warwick  and  Stafford  and  the 
greater  part  of  that  of  Leicester.  From  this  central  plain  it  parts  into  two  di- 
visions. One  of  these  runs  west  over  the  whole  of  Cheshire — (in  which 
county  it  contains  salt  springs  and  mines  of  rock  salt) — the  western  part  of 
Flint,  and  on  the  south-west  surrounds  the  county  of  Lancashire.  It  is  there 
interrupted  by  the  rising  of  the  older  rocks  in  Westmoreland,  but  re-appears  in 
the  eastern  corner  of  this  county,  runs  north-west  through  Cumberland,  forai- 
ing  the  plain  of  Carlisle — and  thence  round  and  across  the  Solway  Frith  till  it 
finally  disappears  about  20  miles  north  of  Dumfries.  The  other  arm,  proceed- 
ing from  the  towns  of  Derby  and  Nottingham,  runs  due  north  through  Notting- 
ham and  the  centre  of  Yorkshire,  skirting  the  outer  edge  of  the  lias,  and  finally 
disappears  in  the  county  of  Durham  to  the  nox'th  of  the  river  Tees.  The  south- 
ern portion  of  this  arm  has  a  width  of  20  to  30  miles,  until  it  reaches  the  neigh- 
bourhood of  Knaresborough,  whei-e  it  suddenly  contracts  to  6  or  8,  and  does 
not  again  expand  to  more  than  10  or  12  miles. 

North  of  Dumfries-shire  these  rocks  are  not  known  to  occur  in  our  island 
In  the  north-east  of  Ireland  they  form  a  stripe  of  land  a  few  miles  in  width,  run- 
ning from  Lough  Foyle  to  Lough  Neagh,  and  thence,  with  slight  interruptions, 
to  the  south  of  Belfast. 

Soil. — These  rocks,  by  their  decay,  almost  always  produce  a  deep  red 
soil.  Where  the  red  clay  and  marl  predominate,  this  soil  is  a  red  clay  or 
clayey  loam  of  the  richest  qualify,  capable  of  producing  almost  every  crop,  and 
remarkable  therefore  for  its  fertility.  It  is  chiefly  in  arable  culture,  because  of 
the  comparative  ease  with  which  it  is  worked,  but  the  meadovi^s  are  rich,  and 
produce  good  herbage.  Where  the  rocks  are  more  sandy,  and  contain  few 
marly  bands,  the  soil  produced  is  poorer,  yet  generally  forms  a  good  sandy  loam, 
suitable  for  turnips  and  barley. 

In  Devonshire,  as  in  the  vale  of  Taunton  and  other  localities,  where  the  lias 
and  the  red  sand-stone  adjoin  each  other,  or  run  side  by  side,  the  difference  in 
the  fertility  and  general  productiveness  of  the  two  tracts  is  very  striking.  On 
the  former,  as  already  observed,  good  old  grass  land  is  seen,  but  the  arable  land 
on  the  latter  produces  the  richest  and  most  luxuriant  crops  to  be  seen  on  any 
soil  in  the  kingdom.  In  this  county,  and  in  Somerset,  the  only  manure  it  eeems 
to  require  is  lime,  on  every  repetition  of  which  it  is  said  to  produce  increased 
crops.  The  same  remarks  as  to  its  comparative  fertility,  apply  with  more  or 
less  force  to  the  whole  of  the  large  area  occupied  by  this  formation  in  our  island 
— wherever  the  soil  has  been  chiefly  formed  by  the  decomposition  of  the  rock 
on  which  it  rests.  In  some  localities  (Dumfries-shire)  the  micaccmis,  marly 
rock  is  dug  up,  and,  after  being  crumbled  by  exposure  to  a  winter's  fiost,  is  laid 
on  with  advantage  as  a  top-dressing  to  grass  and  other  lands. 

In  the  south  of  Lancashire,  and  along  its  western  coast,  and  on  the  shores  of 
the  Solway,  in  Dumfries-shirc^  a  great  breadth  of  this  formation  is  covered  with 
peat. 


SOILS  OF  THE  MAGNESIAN  LIMESTONE  AND  COAL  MEASURES.        249 

13°.  Magnesian  Limestone.  The  magnesian  lime-stone  is  gene- 

rally of  a  yellow,  sometimes  of  a  ;D;rey, 
colour.  In  the  upper  part  it  occasion- 
ally presents  itself  in  thin  beds,  which 
crumble  more  readily  when  exposed  to 
the  air.  In  some  places,  also,  it  assumes 
a  marly  character,  forming  masses 
which  are  soft  and  friable ;  in  general, 
however,  it  is  in  thick  beds,  hard  and 
compact  enough  to  be  used  for  a  build- 
ing stone  or  for  mending  the  roads.  The 
quantity  of  carbonate  of  magnesia  it 
contains  varies  from  1  to  45  per  cent. 
It  is  in  the  north  of  England  generally 
traversed  by  vertical  fissures,  which  ren- 
der the  surface  dry,  and  make  water  in 
many  places  difficult  to  be  attained. 
Extent. — The  magnesian  limestone  stretches  in  an  almost  unbroken  line 
nearly  due  north  from  the  city  of  Nottingham  to  the  mouth  of  the  river  Tyne. 
It  is  in  general  only  a  few  miles  in  width,  its  principal  expansion  being  in  the 
county  of  Durham,  where  it  attains  a  breadth  of  8  or  10  miles. 

Soil. — It  forms,  for  the  most  part,  a  hilly  country,  covered  by  a  reddish 
brown  soil,  often  thin,  light  and  poor,  where  it  rests  immediately  on  the  native 
rock — producing  indifferent  herbage  when  laid  down  to  grass,  but  under  skilful 
management  capable  of  yielding  average  crops  of  turnips  and  barley.  In  the 
eastern  part  of  the  county  of  Durham  tracts  of  the  poorest  land  rest  upon  this 
rock,  but  as  this  formation  is  for  the  most  part  covered  with  deep  accumulations 
of  transported  materials — the  quality  of  the  soil  is  in  very  many  plv^  more 
dependent  upon  the  character  of  this  superficial  covering  than  upon  tTOnature 
of  the  rock  beneath. 

During  the  slow  degradation  of  this  rock,  the  rains  gradually  wash  out  great 
part  of  the  magnesia  it  contains,  so  that  it  seldom  happens  that  the  soil  formed 
from  it,  though  resting  on  the  parent  rock,  contains  so  much  magnesia  as  to  be 
necessarily  hurtful  to  vegetation. 

D. — Carboniferous  System. 

14°.   Coal  Measures.       3i}0ft.  Consisting  of  alternate  beds  of  indu- 

rated bluish-black  clay  (coal  shale),  of 
siliceous  sand-stone  generally  grey  in 
coiour  and  containing  imbedded  plants, 
and  of  coal  of  various  qualities  and  de- 
grees of  thickness.     Beds  of  lime-stone 
rarely  appear  in  this  formation  till  we 
approach  the  lowest  part  of  the  series. 
Extent. — Fortunately  for  the  mineral  resources  of  Great  Britain,  the  coal 
measures  occupy  a  large  area  in  our  island.     Most  of  the  districts  in  which 
they  occur  are  so  well  known  as  to  require  only  to  be  indicated.     The  south 
Welsh  coal-field  occupies  the  south  of  Pembroke,  nearly  the  whole  of  Glamor- 
gan, and  part  of  Monraouth-shire,     In  the  north  of  Somerset  are  the  coal  mea- 
sures of  the  Bristol  field,  which  stretch  also  across  the  Severn  into  the  forest  of 
Dean.     In  the  middle  of  the  central  plain  of  the  new  red  sand-stone,  lie  the  coal- 
fields of  Ashby-de-la-Zouch,  of  Coventry,  and  Dudley,  and  on  its  western 
borders  are  those  of  Shropshire,  Denbigh,  and  Flint  (North  Wales),     To  th« 
north  of  this  plain  extends  on  the  right  the  Yorkshire  coal-field  from  Tfotting- 
ham  to  Leeds,  while  on  the  left  is  the  small  coal-field  of  Newcastle-under-Line, 
and  the  broader  Lancashire  field  which  crosses  the  country  from  near  Liverpool 
to  Manchester.    Almost  the  entire  eastern  half  of  the  county  of  Durham,  and 

11* 


2r)0  MOOR-LANDS  OF  THE  MILLSTONE  GRIT. 

of  the  low  country  of  Northumberland,  is  covered  with  these  measures  -but 
tli8  largest  area  covered  by  these  rocks  is  in  that  part  of  the  low  country  of 
Scotland  which  extends  in  a  north-easterly  direction  from  the  west  coast  of 
Ayrshire  to  the  eastern  coast  of  Fife,  They  there  form  a  broad  band,  having 
an  average  breadth  of  30  miles,  interrupted  often  by  trap  or  green-stone  rocks, 
yet  lying  immediately  beneath  the  loose  superficial  matter,  over  the  largest  por- 
tion of  this  extensive  district.  They  do  not  occur  further  north  in  our  island.  In 
Ireland  they  form  a  tract  of  limited  extent  on  the  northern  borders  of  the  county 
of  Monaghan — cover  a  much  larger  area  in  the  south-east  in  Kilkenny  and 
Clueen's  counties — and  towards  the  mouth  of  the  Shannon,  spread  on  either 
bank  over  a  large  portion  of  the  counties  of  Clare,  Kerry,  and  Limerick. 

Soil. — The  soil  produced  by  the  degradation  of  the  sand-stones  and  shales 
of  the  coal  formation  is  universally  of  inferior  quality.  The  black  shales  or 
schists  form  alone  a  cold,  stiff,  ungrateful  clay.  The  sand-stones  alone  form 
thin,  unproductive  soils,  or  barren — almost  naked — heaths.  When  the  clay 
and  sand  are  mixed  a  looser  soil  is  produced,  which,  by  heavy  liming,  by  drain- 
ing, and  by  skilful  culture,  may  be  rendered  moderately  productive.  In  the 
west  of  the  counties  of  Durham  and  Northumberland,  and  on  the  higher  edges 
of  most  of  our  coal  fields,  there  are  extensive  tracts  of  this  worthless  sand-stone 
surface,  and  thousands  of  acres  of  the  improveable  cold  clays  of  the  shale  beds 
These  latter  soils  appear  very  unpromising,  and  can  only  be  rendered  remune- 
ratively productive  in  skilful  hands.  They  present  one  of  those  cases  in  which 
the  active  exertions  of  zealous  agriculturists,  and  the  efforts  of  the  friends  of 
agriculture,  might  be  expended  with  the  promise  of  much  benefit  to  the  country. 

16°.  Millstone  Grit.      600  ft.  This  formation  consists  in  some  lo- 

calities of  an  entire  mass  of  coarse  sand- 
^1^  stone,  of  great  thickness — in  others  of 

'^  alternations  of  sand-stones  and  shales, 

resembling  those  of  the  coal-measures 
— while  in  others,  again,  lime-stones, 
more  or  less  siliceous,  are  interposed 
among  the  sand- stones  and  shales. 
Extent. — A  large  portion  of  Devonshire  is  covered  with  these  rocks — they 
form  also  the  high  land  which  skirts  to  the  north  and  west  the  coal-measures  of 
Yorkshire,  Lancashire,  and  Durham,  and  over  which  is  the  first  ascent  to  the 
chain  of  mountains  that  run  northward  through  these  three  counties.   In  Scot- 
land, they  have  not  been  observed  to  lie  immediately  beneath  any  part  of  the  sur- 
face.    In  the  north  of  Ireland  they  cover  a  considerable  area,  stretching  across 
the  county  of  Leitrim  between  Sligo  and  Lough  Erne. 

Soil,— The  soils  resting  upon,  and  formed  from,  these  rocks  are  generally  of 
a  very  inferior  description.  Where  the  sand-stones  come  to  the  surface,  miles 
of  naked  rock  appear;  other  tracts  bear  only  heath,  or,  where  the  rains  have 
only  a  partial  outlet,  accumulations  of  peat.  The  shale-beds,  like  those  of  the 
coal-measures,  afford  a  cold,  unproductive,  yet  not  unimproveable  soil — it  is 
only  where  lime-stones  occur  among  them  that  patches  of  healthy  verdure  are 
seen,  and  fields  which  are  readily  susceptible  of  profitable  arable  culture. 

It  is  true,  therefore,  of  this  formation  in  general,  that  the  high  grounds  form 
extensive  tracts  of  moor-land.  In  the  lower  districts  of  country  over  which  it 
extends,  the  soil  generally  rests  not  on  the  rocks  themselves,  but  on  superficial 
accumulations  of  transported  materials,  which  are  often  of  such  a  kind  as  to 
form  a  soil  either  productive  in  itself  or  capable  of  being  rendered  so  by  skilful 
cultivation. 

16°.  Mountain      )    ^^..  f.  In  this  formation,  as  its  name  implies, 

Lime-stone.  S  lime-stone  is  the  predominating  rock. 

It  is  generally  hard,  blue,  and  more  or 


SWEET  PASTURES  OF  THE  MOUNTAIN  LIME-STONE.  251 

less  full  of  organic  remains.     In  some 
localities,  it  occurs  in  beds  of  vast  thick- 
ness— (Derby   and  Yorkshire) — while 
in  others — (Northumberland) — it  is  di- 
vided into  numerous  layers,  with  inter- 
posed sand-stones  and  beds  of  shale,  and 
occasional  thin  seams  of  coal. 
Extent. — The  greater  portion  of  the  counties  of  Derby  and  Northumberland 
are  covered  by  this  formation,  and  from  the  latter  county  it  stretches  along  the 
west  of  Durham  through  Yorkshire  as  far  as  Preston,  in  Lancashire — forming 
the  mountains  of  the  well  known  Pennine  chain,  which  throw  out  spurs  to  the 
east  and  west,  and  thus  present  on  the  map  an  irregular  outline  and  varying 
breadth  of  country.     In  Scotland  these  rocks  cover  only  a  small  portion  of  the 
county  of  Berwick,  immediately  on  the  Border;  but  in  Ireland,  almost  the  en- 
tire central  part,  forming  upwards  of  one-half  of  the  whole  island,  is  occupied 
by  the  mountain  lime -stone  formation. 

Soil. — From  the  slowness  with  which  this  rock  decays,  many  parts  of  it  are 
quite  naked ;  in  others,  it  is  covered  with  a  thin  light  porous  soil  of  a  brown 
colour,  which  naturally  produces  a  short  but  thick  and  sweet  herbage.  Much 
of  the  mountain  lime-stone  country,  therefore,  is  in  natural  pasture. 

Where  the  lime-stones  are  mixed  or  interstratified  with  shale  beds,  Avhich  de- 
cay more  easily,  a  deeper  soil  is  found,  especially  in  the  hollows  and  towards 
the  bottom  of  the  valleys.  These  are  often  stiff  and  naturally  cold,  but  when 
well  drained  and  limed  produce  excellent  crops  of  every  kind.  In  Northumber- 
land, much  of  the  mountain  lime-stone  country  is  still  in  moor-land,  but  the  ex- 
cellence of  border  farming  is  gradually  rescuing  one  improveable  spot  after  ano- 
ther from  the  hitherto  unproductive  waste.  In  Yorkshire  and  Devonshire  also 
improvements  are  more  or  less  extensively  in  progress,  though,  in  all  these  dis- 
tricts, there  are  large  tracts  which  can  never  be  re-claimed. 

E. — Old  Red  Sand-stone  or  Devonian  System. 

17°.   Old  Red  Sand-  ?      500  to  The  upper  part  of  this  formation  con- 

stcme.  I  10,000  ft.      sists  of  red  sand-stones  and  conglomer- 

Old  Red  Conglomerate.  ates  (indurated  sandy  gravel),  the  mid- 

Corn-stone  and  Marls.  ^^^  of  spotted,   red  and  green,  clayey 

Tile-stone.  marls,  with  irregular  layers  of  hard,  of- 

ten impure   and   siliceous   lime-stones 
(cornstones)  likewise  mottled,  and  the 
lowest  of  thin  hard  beds  of   siliceous 
sand-stones,  sometimes  calcareous,  mot- 
tled, and  splitting  readTly  into  thin  flags 
(tile-stones). 
Extent. — Though  occasionally  of  vast  thickness,  the  old  red  sand-stone  does 
not  occupy  a  very  extensive  area  in  our  island.     In  the  south  of  Pembroke  it 
forms  a  tract  of  land  on  either  side  of  the  coal-field — surrounds  on  the  north  and 
east  the  coal-field  of  Glamorgan,  and  immediately  north  of  this  county  covers  a 
large  area  comprehending  the  greater  portion  of  Brecknock  and  Hereford,  and 
part  of  Monmouth.     A  small  patch  occurs  in  the  Isle  of  A  nglesey,  and  in  the 
north-eastern  corner  of  Westmoreland — but  it  does  not  again  present  itself  till 
we  reach  the  western  flank  of  the  Cheviot  Hills.     It  there  appears  on  either 
side  of  the  Tweed,  and  extends  over  a  portion  of  Berwick  and  Roxburgh  to  the 
base  of  the  Lammermuirs.     On  the  north  of  the  same  hills  it  again  presents  it- 
self, and  stretching  to  the  south-west,  forms  a  considerable  tract  of  country  in 
the  counties  of  Haddington  and  Lanark.     On  the  north  of  the  great  Scottish 
coal-field  it  forms  a  broad  band,  which  runs  completely  across  the  island  in  a 
south-western  direction  along  the  foot  of  the  Grampians,  from  Stonehaven  to 


252  RICH    WHEAT    LANDS    ?F    THE    OLD    RED    SAND-STONt. 

the  Firth  of  Clyde,  is  to  be  discovered  in  the  Island  of  Arran,  and  at  the  Mull 
of  Cantire,  and — along  the  prolongation  of  the  same  line — at  various  places  on 
the  northern  flank  of  the  great  mountain  lime-stone  formation  of  Ireland,  and 
especially  in  the  counties  of  I'yrone,  Fermanagh,  and  Monaghan.  In  the 
north  of  Scotland,  it  lines  either  shore  of  the  Moray  Firth,  skirts  the  coast  to- 
wards Caithness,  where  it  covers  nearly  the  whole  county,  and  still  further 
north,  forms  the  entire  surface  of  the  Shetland  Islands,  Along  the  north-west- 
ern coast,  it  also  appears  in  detached  patches  till  we  reach  the  southern  ex- 
tremity of  the  Isle  of  Sky. 

In  Ireland,  it  occurs  also  on  the  extreme  southern  edge  of  the  mountain  lime- 
stone, in  Waterford  and  the  neighbouring  counties — and  in  the  middle  of  this 
formation  on  the  upper  waters  of  the  Shannon,  in  the  south  of  Mayo,  and 
round  the  base  of  the  slate  mountains  of  Tipperary. 

Soil. — The  soil  on  the  old  red  sand-stone  admits  of  very  nearly  the  same 
variations  as  on  the  new  red  sand-stone  formation.  Where  it  is  formed,  as  in 
parts  of  Pembroke,  from  the  upper  sand-stones,  and  conglomerates,  it  is  either 
worthless  or  it  produces  a  poor  hungry  soil,  "which  eats  all  the  manure,  and 
drinks  all  the  water."  These  upper  rocks  are  sometimes  so  siliceous  as  to  be 
almost  destitute  both  of  lime  and  clay — in  such  cases,  the  soils  they  form  are 
almost  valueless. 

The  marly  beds  and  lime-stones  of  the  second  division,  yield  warm  and  rich 
soils — such  as  the  mellow  lands  of  Herefordshire,  and  the  best  in  Brecknock 
and  Pembroke  shires.  The  soil  in  every  district  varies  according  as  the  partings 
of  marl  are  more  or  less  numerous.  These  easily  crumble,  and  where  they 
abound  form  a  rich  stiff  wheat  soil — like  that  of  East  Lothian  and  parts  of  Ber- 
wickshire ; — where  they  are  less  frequent  the  soil  is  lighter  and  produces  excellent 
turnips  and  barley.  Where  the  subsoil  is  porous,  this  land  is  peculiarly  fa- 
vourable to  the  growth  of  fruit  trees.*  The  apple  and  the  pear  are  largely  grown 
in  Hereford  and  the  neighbouring  counties,  long  celebrated  for  the  cider  and 
perry  they  produce. 

The  tile-stones  reach  the  surface  only  on  the  northern  and  western  edges  of 
this  formation  in  England.  In  Ayrshire,  in  Lanarkshire,  in  Ross-shire,  and  in 
Caithness,  larger  tracts  of  land  rest  on  these  lower  beds.  In  all  these  districts 
rich  corn  lands  are  produced  from  the  rocks  of  the  middle  series.  The  fertility 
of  Strathmore  in  Perthshire,  and  of  other  vallies  upon  this  formation,  is  well 
known — Easter  Ross  and  Murray  have  been  called  the  granary  of  Scotland, 
and  even  in  Caithness  rich  corn-bearing  (oat)  lands  are  not  unfrequent.  Yet 
in  the  immediate  neighbourhood  of  these  rich  lands,  tracts  of  tile-stone  country 
occur,  which  are  either  covered  with  useless  bog  (Ayrshire  and  Lanarkshire), 
or  with  a  thin  covering  of  soil  which  is  almost  incapable  of  profitable  culture. 
In  this  latter  condition  is  the  moor  of  Beauly  on  the  Cromarthy  Firth,  an  area 
of  50  square  miles,  which,  till  within  a  few  years,  lay  as  an  unclaimed  common 
— and  in  the  county  of  Caithness  still  more  extensive  tracts. 

In  South  Devon  and  part  of  Cornwall  a  very  fertile  district  rests  also  on  tlie 
middle  series  of  these  rocks.  Instead  of  red  sand-stones,  however,  the  country 
there  consists  of  green  slates,  more  or  less  siliceous,  of  sand-stones  and  of  lime- 
stones, which  by  their  decay  have  formed  a  very  productive  soil.  These  rocks 
in  the  above  counties  abound  in  fossil  remains,  and  it  is  chiefly  for  this  reason 
that  the  term  Devonian  has  been  applied  to  the  rocks  of  the  old  red  sand-stone 
formation. 

♦  The  most  loamy  pf  these  red  soils  of  Hereford  afford  the  finest  crops  of  wheat  and  hops, 
and  bear  the  most  prolific  apple  and  pear  trees,  whilst  the  whole  region  (eminently  in  the 
heavier  clayey  tracts)  is  renowned  for  the  production  of  the  sturdiest  oaks,  which  so  abound 
as  to  be  styled  the  "  weeds  of  Herefordshire."  Th/js,  though  this  region  contains  no  mines, 
the  composition  of  its  rocks  is  directly  productive  cf  its  great  agricultural  wealth.— ilfwrcAi. 
•on,  Silurian  System,  I.,  p.  I9a 


MUDDY    S  OILS    OF    THE    LOWER    LUDLOW    ROCKS.  263 

III.  Primary  Strata. — In  these  rocks  slates  abound,  and  lime- 
stones are  more  rare.  Organic  remains  are  also  less  frequently  met 
with  than  in  the  superior  rocks.  These  remains  belong  all  to  extinct 
species,  the  greater  part  to  extinct  genera  and  families,  and  are  frequent- 
ly so  wholly  unlike  to  existing  races  that  it  is  often  difficult  to  trace  any 
resemblance  between  l.\e  animals  which  now  live  and  those  which  appear 
to  have  inhabited  the  waters  of  those  ancient  periods. 

F. — Silurian  System. 

18°.    Upper  Silurian.     3800 /^  The  upper  Ludlow  rocks  consist  of 

1°.  Ludlow  formation.  sand-stones  more  or  less  calcareous  and 

a  Upper  Ludlow  )  argdlaceous.     These  rest   upon   hard, 

b  Aymestry  Lime-stone  i  2000     somewhat  crystalhne,  earthy  hme-stones 

•    tf  Lower  Ludlow  )  (Aymestry   hme-stones.)     The   lower 

''  Ludlow  rocks  are  masses  of  shale  more 

2°.  Wenlock  formation.  free  from  lime  and  sand  than  the  upper 

^  ~'Pl^"S*°"®  \  1800      beds,  and  from  the  mode  in  which  they 

0  Shale  )  decay  into  7nnd  are  locally  known  by 

the  name  of  "  mud-stones." 

The  Wenlock  or  Dudley  formation 
consists  in   the  upper  part  of  a  great 
thickness  of  lime-stone  beds  often  argil- 
laceous, and  abounding  in  the  remains 
of  marine  animals;    and  in  the   lower 
part  of  thick  beds  of  a  dull  clayey  shale 
— in  its  want  of  cohesion,  and  in  its 
mode  of  decay,  very  much  resembling 
the  mud-stones  of  Ludlow. 
Extent. — The  principal  seat  of  these  rocks  in  our  island  is  in  the  eastern 
counties  of  Wales,  where  they  lie  immediately  beneath  the  surface  over  the 
eastern  half  of  Radnor,  and  the  north  of  Montgomery. 

Soil. — The  prevailing  character  of  the  soils  upon  these  formations  is  derived 
from  the  shales  and  mud-stones — and  from  the  earthy  layers  of  the  sand-stones 
and  lime-stones  which  decay  more  readily  tlian  the  purer  masses  of  these  rocks. 
The  traveller  is  immediately  struck  in  passing  from  the  rich  red  marls  and 
clays  of  the  old  red  sand-stone  in  Hereford,  on  to  the  dark,  almost  black,  soils 
of  the  upper  and  lower  Ludlow  rocks  in  Radnor,  not  merely  by  the  change  of 
colour,  but  by  their  obviously  diminished  value  and  productiveness.  The  up- 
per Ludlow  is  crossed  by  many  vertical  cracks  and  fissures,  and  thus,  though 
clayey,  the  soil 'which  rests  upon  it  is  generally  diy,  and  susceptible  of  cultiva- 
tion. 

Not  so  the  muddy  soils  of  the  lower  Ludlow  and  Wenlock  rocks.  They  are 
generally  more  or  less  impervious  to  water,  and  being  subject  to  the  drainage 
of  the  upper  beds,  form  cold  and  comparatively  unmanageable  tracts.  It  is  Only 
where  the  intermediate  lime-stones  (Aymestry  and  Wenlock  lime-stones)  come 
to  the  surface  and  mingle  their  debris  with  those  of  the  upper  and  lower  rocks, 
that  the  stiff  clays  become  capable  of  bearing  excellent  crops  of  wheat.  This 
fact,  however,  indicates  the  method  by  which  the  whole  of  these  cold  wet  clays 
might  be  greatly  improved.  By  perfect  artificial  drainage  and  copious  limeing, 
the  unproductive  soils  of  the  lower  Ludlow  and  of  the  Wenlock  shales  might  be 
converted  into  wheat  lands  more  or  less  rich  and  fertile.  It  unfortunately  hap- 
pens, however,  that  in  those  districts  of  North  and  South  Wales,  where  the 
dark  grey  or  black  "  rotchy'^  land  of  the  mud-stones  prevails,  lime  is  often  so 
scarce,  or  has  to  be  brought  from  so  great  a  distance,  as  to  render  this  means  of 
improvement  ahnost  unattainable. 


254  MOUNTAINOUS    COUNTRY    OF    THE    SLATE    ROCKS. 

19°.  Lower  Silurian.     3700  ft.  The  Caradoc  beds  consist  of  thicK 

Caradoc  Sand-stones    2500       ^^y^^^  ^^  sand-stone  of  various  colours, 
Llandeilo '  Fl&gs  1200       ^^^^'^S  "P?"'  ^"^  <^oyejed  by,  and  oc- 

°  casionally  interstratined  with,  thm  beds 

of  impure  lime-stone.     The  Llandeilo 
flags  which  he  beneath  them  consist  of 
thin  calcareous  strata,  in   some  locali- 
ties  alternating  with   sand-stones   and 
shales. 
Extent. — These  rocks  form  patches  of  land  in  Shropshire  and  the  north  of 
Montgomery — and  skirt  the  southern  and  eastern  edge  of  Caermarthen.     None 
of  the  Silurian  rocks  have  yet  been  found  to  extend  over  any  large  portion  of 
either  Scotland  or  Ireland. 

Soil. — The  Caradoc  sand-stone,  when  free  from  lime,  produces  only  a 
naked  surface  or  a  barren  heath.  The  Llandeilo  flags  form  a  fertile  and  arable 
soil,  as  may  be  seen  in  the  south  of  Caermarthen,  where  they  are  best  devel- 
oped, and  especially  on  the  banks  of  the  Towey,  which  for  many  miles  before 
it  reaches  the  town  of  Caermarthen  runs  over  this  formation. 

In  this  formation,  as  in  every  other  we  have  yet  studied,  the  soil  changes  im- 
mediately on  the  appearance  of  a  new  rock  at  the  surface.  The  soil  of  the 
Wenlocic  shale  is  sometimes  more  sandy  as  it  approaches  the  Caradoc  beds, 
and  on  favourable  slopes  forms  good  arable  land  and  sustains  luxuriant  woods, 
but  where  the  Caradoc  sand-stones  reach  the  surface,  a  wild  heath  or  poor 
wood-land  stretches  over  the  country,  until  passing  over  their  edges  we  reach 
the  lime-containing  soils  of  the  Llandeilo  flags,  when  fertile  arable  lands  and 
lofty  trees  again  appear.* 

G. — Cambrian  System. 

20°.    Vjjper  Sf  Loiver  Cam-  )  These  rocks,  which  are  many  thou- 

brian  Rocks.  \  ^ondi  yards  in  thickness,  con^st  chiefly 

of  thin  slates,  often  hard  and  cleaving 
readily,  like  roofing  slates,  occasionally 
intermingled  with  sandy  and  thin  lime- 
stone beds.     They  contain  few  organic 
remains. 
Extent. — These  rocks   cover  the  whole  of  Cornwall,  part  of  North  and 
South  Devon,  the  western  half  of  Wales,  the  entire  centre  of  the  Isle  of  Man, 
and  a  large  part  of  Westmoreland  and  South  Cumberland.     In  Scotland,  they 
foiTH  a  band  between  30  and  40  miles  in  width,  which  crosses  the  island  from 
the  Mull  of  Galloway  to  St.  Abbs  Head.     They  form  also  a  narrow  stripe  of 
land,  which  recrosses  the  island  along  the  upper  edge  of  the  old  red  sand-stone 
from  Stonehaven  to  the  Isle  of  Bute,  and,  further  north,  spread  over  a  consider- 
able portion  of  Banffshire.     In  the  south-west  of  Ireland  they  attain   a  great 
breadth,  are  narrower  at  Waterford,  but  form  a  broad  band  along  the  granite 
mountains  from  that  city  to  Dublin.     They  extend  over  a  large  portion  of  the 
counties  of  Louth,  Cavan,  Mona^han,  Armagh,  and  Down,— form  a  narrow 
stripe  also  along  the  coast  of  Antrim  as  far  north  as  the  Giant's  Causeway, — 
and,  in  the  interior  of  Ireland,  re-appear  in  the  mountainous  district  of  Tip- 
perary. 

Soil. — The  predominance  of  slaty  rocks  in  this  formation  imparts  to  the  soils 
of  the  entire  surface  over  which  they  extend  one  common  clayey  character. 
They  generally  form  elevated  tracts  of  country,  as  in  Wales,  Cumoerland, 
Scotland,  and  Ireland,  where  the  rigours  of  the  climate  combine  with  the  fre- 
quent thinness  and  poverty  of  the  soil  to  condemn  extensive  districts  to  worth- 

*  Such  a  passage  from  one  formation  to  another  is  exhibited  in  the  diagrams  inserted  in 
page  238. 


HEATHS  AXD  BOGS  ON  THE  GNEISS  ROCKS.  255 

less  heath  or  to  widely  extended  bogs.  Yet  the  slate  rocks  themselves,  especi- 
ally when  they  happen  to  be  calcareous,  are  capable  of  producing  fertile  soils. 
Such  are  found  in  the  valleys,  on  the  hill  sides,  and  by  the  margins  of  the  lakes 
that  are  often  met  with  in  the  slate  districts.  More  extensive  stripes  or  bands 
of  such  productive  land  occur  also  at  lower  levels,  as  in  the  north  of  Devon,  and 
in  the  south  of  Cornwall.  In  the  latter  county,  the  soils  on  the  horTiblende  slate 
(which  lies  near  the  bottom  of  the  slate  seriesjare  extremely  fertile,  exhibiting  a 
striking  contrast  with  those  which  are  formed  from  the  neighbouring  Serpentine 
rocks,  that  extend  over  a  large  area  immediately  north  of  the  Lizard  (see.  p.  265.) 

Where *the  clay-slate  soils  occur,  therefore,  however  cold  and  stiff  they  may 
be,  a  favourable  climate,  drainage,  if  necessary,  and  lime,  either  naturally  pre- 
sent, or  artificially  added,  appear  to  be  the  first  requisites  to  insure  fertility. 

The  mode  in  which  these  rocks  lie,  or  the  degree  of  inclination  which  the 
beds  exhibit,  exercises  an  important  influence  upon  the  agricultural  character 
of  the  soils  that  rest  upon  them.  In  the  diagram  inserted  in  page  238,  the 
rocks  (A)  represent  the  highly  inclined,  often  nearly  vertical  position,  in  which 
the  slate  rocks  are  most  frequently  found.  The  soil  formed  from  the¥*i  must, 
therefore,  rest  on  the  thin  edges  of  the  beds.  Thus  it  happens  in  many  lo- 
calities that  the  rains  carry  down  the  soluble  parts  of  the  soil  and  of  the  manure 
within  the  partings  of  the  slates — and  hence  the  lands  are  hungry  and  unprofit- 
able to  work. 

On  the  slopes  of  the  clay  slate  hills  of  the  Cambrian  and  Silurian  system?, 
flourish  the  vineyards  of  the  middle  Rhine,  the  Moselle,  and  the  Ahr. 

H. — Mica-Slate  and  Gneiss  Systems. 
21°.  Mica-Slale,  Gneiss  Rock.  The  upper  of  these  formations  con- 

sists of  thin  undulating  layers  of  rock, 
consisting  chiefly  of  quartz  and  mica, 
alternating  occasionally  with   green 
(chlorite)  slates,  common  clay-slates, 
quartz  rock  and  hard  crystalline  lime- 
stones.    The   gneiss   is  a  hard  and 
solid  rock  of  a  similar  nature,  consist- 
ing of  many  thin  layers  distinctly  vi- 
sible, but  firmly  cemented,  and  as  it 
were  half-melted  together. 
Extent, — Two-thirds  of  Scotland,  comprehending  nearly  the  whole  country 
north  and  west  of  the  Grampians,  consist  of  these  rocks.     In  England  there 
is  only  a  small  patch  of  mica  slate  about  Bolt  Head  and  Start  Point  in  South 
Devon,  and  a  somewhat  larger  in  Anglesey  ;  but  in  Ireland,  nearly  the  whole 
of  the  counties  of  Donegal  and  Londonderry  on  the  north,  and  a  large  portion 
of  Mayo,  Connaught,  and  Gal  way,  on  the  west,  are  covered  by  rocks  "belonging 
to  the  mica  slate  system. 

Soils. — These  rocks  are,  in  general,  harder  still  than  those  of  the  Cambrian 
system,  and  still  more  impervious  to  water,  when  not  highly  inclined.  They 
crumble  slowly,  therefore,  and  imperfectly,  and  hence  are  covered  with  thin 
soils,  on  which,  where  good  natural  drainage  exists,  a  coarse  herbage  springs, 
and  from  which  an  occasional  crop  of  corn  may  be  reaped — but  on  which,  where 
the  water  becomes  stagnant,  extensive  heaths  and  bogs  prevail.  That  they 
contain,  when  perfectly  decomposed  and  mellowed,  the  materials  of  a  fertile  soil, 
is  shown  by  the  richness  of  many  little  patches  of  land,  that  occur  m  tiie  shel- 
tered valleys  of  the  Highlands  of  Scotland,  and  by  the  margins  of^  its  jnany 
lakes.  In  general,  however,  the  mica-slate  and  gneiss  country  is  s6  effltated 
that  not  only  does  an  ungenial  climate  assist  its  natural  unproductiveness,  but 
the  frequent  rains  and  rapid  flowing  rivers  bear  down  to  the  bottoms  of  the  yal- 
lies  or  forward  to  the  sea,  much  of  the  fin-r  matter  produced  by  the  decay  of  the 
rocks, — leaving  only  a  poor,  thin,  sari  !y  soil  i),^liii  d. 


256  FERTILITY  DEPENDENT  ON  GEOLOGICAL  STRUCTURE. 

On  these  hard  slate  and  gneiss  rocks  extensive  pine  forests  in  Sweden  and 
Norway  have  long  lived  and  died.  In  these  countries  it  is  customary  in  many 
places  to  burn  down  the  wood,  to  strew  the  ashes  over  the  thin  soil,  to  harrow 
in  the  seed — to  reap  thus  one  or  two  harvests  of  rye,  and  to  abandon  it  aga^n  to 
nature.  A  grove  of  beech  first  springs  up,  which  is  supplanted'by  an  after- 
growth of  pine,  and  finally  disappears. 


Such  is  a  general  description  of  the  nature  and  order  of  succession  of 
the  stratified  rocks,  as  they  occur  in  Great  Britain  and  Ireland — of  the 
relative  areas  over  which  they  severally  appear  at  the  surface — and  of 
the  kind  of  soils  which  they  produce  by  their  natural  decay.  The  con- 
sideration of  the  facts  above  stated,*  shows  how  very  much  the  fertility 
of  each  district  is  dependent  upon  its  geological  structure — how  much  a 
previous  knowledge  of  that  structure  is  fitted  to  enlighten  us  in  regard  to 
the  nature  of  the  soils  to  be  expected  in  any  district — to  explain  anoma- 
lies also  in  regard  to  the  unlike  agricultural  capabilities  of  soils  a{)par- 
ently  similar — to  indicate  to  the  purchaser  where  good  or  better  lands 
are  to  be  expected,  and  to  the  improver,  whether  the  means  of  amelio- 
rating his  soil  by  limeing,  by  marling,  or  by  other  judicious  admixture, 
are  likely  to  be  within  his  reach,  and  in  what  direction  they  are  to  be 
sought  for.  There  still  remain  some  important  branches  of  this  subject 
to  which,  at  the  risk  of  fatiguing  you,  it  will  be  my  duty  briefly  to  draw 
your  attention  in  the  following  lecture. 

*  For  much  of  the  practical  information  contained  in  this  section,  I  have  to  express  my 
obligations  to  the  following  works:— For  the  extreme  soathern  counties,  to  De  La  Deche's 
Geological  Report  on  Cornwall  and  Devon ;  and  to  a  paper  by  Sir  Charles  Lemon,  Bart.,  on 
the  Agricultural  Produce  of  Cornwall ;— for  Wales  and  the  Border  counties,  to  Murchison's 
Silurian  System; — for  the  Midland  counties  of  England,  to  Morton  on  Soils,  a  work  I  have 
in  a  previous  note  recommended  to  the  attention  of  the  reader;  for  Yorkshire,  to  a  paper  by 
Sir  .lohn  Johnston,  Bart.,  in  the  Journal  of  the  Royal  Agricultural  Society  ,•— and  for  the  Old 
Red  Sand-stone  of  the  north  of  Scotland,  to  the  very  interesting  little  work  of  Mr.  Miller  on 
IVie  Old  Red  Sarulstone.  The  reader  would  read  the  above  section  wfth  much  greater 
profit  if  he  were  previously  to  possess  iiimself  of  Phillip's  Outline  Map  of  the  Geology  of  the 
British  Islands. 


LECTURE  XII. 

Composition  of  the  granitic  rocks  and  of  their  constituent  minerals— Cause  ami  made  of 
liieir  degradation— Soils  derived  from  them— Superficial  accumulations— Their  influence 
upon  the  character  of  tlie  soils — Organic  constituents,  ultimate  chemical  constitution,  and 
jiJiysic-al  properties  of  soils. 

It  has  been  stated  in  the  preceding  Lecture,  (§  6,  p.  237),  that  the  rocks 
which  present  themselves  at  the  surface  of  the  earth  arc  of  two  kinds, 
distinguished  by  the  terms  stratified  and  unstratified.  The  former 
crumble  away,  in  general,  more  rapidly  than  the  latter,  and  form  a  va- 
riety of  soils  of  which  the  agricultural  characters  and  capabilities  have 
been  shortly  explained.  The  unstratified  or  crystalline  rocks  form  soils 
of  so  peculiar  a  character  and  possessing  agricultural  capabilities  in 
general  so  different  from  those  of  the  stratified  rocks  which  occur  in  the 
same  neighbourhood,  and  they,  besides,  cover  so^arge  and  hitherto  so 
unfruitful  an  area  in  our  island,  as  to  entitle  them  to  a  separate  and 
somewhat  detailed  consideration. 

§  1.   Composition  of  the  Granitic  Rocks. 

The  name  of  Granite  is  given  by  mineralogists  to  a  rock  consisting  of 
a  mixture  more  or  less  intimate  of  three  simple  minerals — Quartz,  Mica, 
and  Felspar.  When  Mica  is  wanting,  and  Hornblende  occurs  in  its 
stead,  the  rock  is  distinguished  by  the  name  of  Syenite.  This  mineral- 
ogical  distinction  is  often  neglected  by  the  geologist,  who  describes  large 
tracts  of  country  as  covered  by  granitic  rocks,  though  there  may  be 
many  hills  or  mountains  of  syenite.  In  a  geological  sense,  the  distinc- 
tion is  often  of  little  consequence;  in  relation  to  agriculture,  however, 
the  distinction  between  a  granite  and  a  syenite  is  of  considerable  im- 
portance. 

The  minerals  of  which  these  rocks  consist  are  mixed  together  in  very 
variable  proportions.  Sometimes  the  quartz  predominates,  so  as  to  con- 
stitute two-thirds  or  three-fourths  of  the  whole  rock,  sometimes  both 
mica  and  quartz  are  present  in  such  small  quantity  as  to  form  what  is 
then  called  a  felspar  rock.  The  mica  rarely  exceeds  one-sixth  of  the 
whole,  while  the  hornblende  of  the  syenites  sometimes  forms  nearly 
one  half  of  the  entire  rock.  These  differences  also  are  often  overlooked 
by  the  geologist — though  they  necessarily  produce  important  differences 
in  the  composition  and  agricultural  characters  of  the  soils  derived  from 
the  crystalline  rocks. 

A  few  other  minerals  occur  occasionally  among  the  granitic  rocks,  in 
sufficient  quantity  to  affect  the  composition  of  the  soils  to  which  they 
give  rise.  Among  these,  the  different  varieties  of  tourmaline  are  in 
many  places  abundant.  Thus  the  schorl  rock  of  Cornwall  consists  of 
quartz  and  schorl  (a  variety  of  tourmaline),  while  crystals  of  schorl 
are  «o  frequently  found  in  the  granites  of  Devon,  Cornwall,  and  the 


25d  COMPOSITION    OF    GRANITE,    FELSPAR,    AND    ALBITE. 

Scilly  Isles,  as  to  be  considered  characteristic  of  a  very  large  portion  of 
them    (Dr.  Boase). 

These  rocks  decay  with  very  different  degrees  of  rapidity — accord- 
ing to  the  proportions  In'  ti^hich  the  severa.  minerals  are  present  in 
them,  and  to  the  peculiar  state  of  hardness  or  aggregation  in  which  they 
happen  to  occur.  Both  the  mode  of  their  decay,  however,  and  the  cir- 
cumstances under  which  it  takes  place,  as  well  as  the  character  and 
composition  of  the  soils  formed  from  them,  are  materially  dependent 
upon  the  composition  of  the  several  minerals  of  which  the  rocks  consist. 
This  composition,  therefore,  it  will  be  necessary  to  exhibit. 

1^.  Quartz  has  already  been  described  (p.  206),  as  a  variety  of  silica 
— the  substance  of  flints,  and  of  siliceous  sands  and  sand-stones.  In 
granite,  it  often  occurs  in  the  form  of  rock  crystal,  but  it  is  more  frequent- 
ly disseminated  in  small  particles  throughout  the  rocky  mass.  It  is 
hard  enough  to  scratch  glass. 

2*^.  Felspar  is  generally  colourless,  but  is  not  unfrequently  reddish  or 
flesh-coloured.  On  the  colour  of  the  felspar  they  contain,  that  of  the 
granires  most  frequently  depends.  Several  varieties  of  this  mineral  are 
k?io\vn  to  collectors.  Besides  the  common  felspar,  however,  it  is  only 
necessary  to  specify  Albite,  which,  in  appearance,  closely  resembles  fel- 
spar, often  takes  its  place  in  granite  rocks,  and  in  chemical  constitution 
differs  from  it  only  in  containing  soda,  while  the  common  felspar  con- 
tains potash.  These  two  minerals  are  readily  distinguished  from  quartz 
by  their  inferior  hardness.  They  do  not  scratch  glass,  and,  in  general, 
may  easily  be  scratched  by  the  point  of  a  knife. 

They  concitt  respectively  of — 

Felspar.  Albite. 

Silica     ....     65-21  69-09 

Alumina     .     .     .     18-13  19-22 

Potash  ....     16-66  — 

Soda      ....        —  11-69 


100-00  100-00 

It  is  to  be  observed,  however,  that  these  minerals  do  not  generally  oc- 
cur in  nature  in  a  perfectly  pure  state — for  though  they  do  not  essential- 
ly contain  either  lime,  magnesia,  or  oxide  of  iron,  they  are  seldom  found 
without  a  small  admixture  of  one  or  more  of  these  substenees.  It  is  also 
found  that  while  pure  felspar  contains  only  potash,  and  pure  albite  only 
soda,  abundance  of  a  kind  of  intermediate  mineral  occurs  which  contains 
both  potash  and  aoila.  Such  is  the  case  with  the  felspar  of  the  Siebenge- 
hirge,  on  the  right  twrnk  of  the  Rhine  (Berthier),  and  with  those  con- 
tained in  the  lava^  of  Vesuvius  and  the  adjacent  parts  of  Italy  (Abich) 

In  these  two  mmerals  the  silica  is  combined  with  the  potash,  soda, 
and  alumina,  forming  certain  compounds  already  described  under  tlie 
name  o^ silicates  (p.  207). 

Felspar  consists  of  a  silicate  of  alumina  combined  with  a  silicate  of 
potash.  Albite  of  the  same  silicate  of  alumina  combined  with  a  silicate 
of  soda. 

3^.  Mica  generally  occurs  disseminated  through  the  granite  in  smnil 
shining  scales  or  plates,  which,  when  extracted  from  the  rock,  split  rendi- 
ly  into  numerous  inconceivably  thin  layers.     I:  sometimes  occurs  also 


COMPOSITION  OF  MICA  AND    UORNBLENDE.  259 

in  large  masses,  and  is  of  various  colours — white,  grey,  brown,  green, 
and  black.  It  is  soft  and  readily  cut  with  a  knife.  The  thin  shining 
particles  that  occur  in  many  sand  stones,  and  especially  between  the 
partings  of  the  beds,  and  give  them  what  is  called  a  micaceous  charac- 
ter, are  only  more  or  less  weathered  portions  of  this  mineral. 

Mica  also  consists  of  silicates,  though  its  constitution  is  not  always  so 
simple  as  that  of  felspar.  In  some  varieties  magnesia  is  present,  whilst 
in  others  it  is  almost  wholly  wanting,  as  is  shewn  by  the  following  com- 
position of  two  specimens  from  different  localities. 

Potash.  Magnesian. 

Mica.  Mica. 

Silica 46-10  40-00 

Alumina     ....     31-60  12-67 

P rot-Oxide  of  Iron    .       8-65  19.03 

Magnesia   ....       —  15-70 

Potash 8-39  5-61 

Oxide  of  Magnesia   .       1-40  0-63 

Fluoric  Acid   .     .     .       1-12  2-10 

Water    .....       1-00    Titanic  Acid  1-63 

98-26  97-37 

If  we  neglect  the  three  last  substances,  which  are  present  only  in  small 
quantities,  and  recollect  that  the  silica  is  in  combination  with  all  the 
other  substances  which  stand  beneath  it,  we  see  that  these  varieties  of 
mica  consist  of  a  silicate  of  alumina,  combined  in  the  one  with  silicate 
of  iron  and  silicate  of  potash,  and  in  the  other  with  silicate  of  iron  and 
silicate  of  magnesia. 

4°.  Hornhleiide  occurs  of  various  colours,  but  that  which  forms  a  con- 
stituent of  the  syenites  and  of  the  basalts  is  of  a  dark  green  or  brownish 
black  colour,  is  often  in  regular  crystals,  and  is  readily  distinguished 
from  quartz  and  felspar  by  its  colour,  and  from  black  mica  by  not  split- 
ting into  thin  layers,  when  heated  in  the  flame  of  a  candle.  It  consists 
of  silicates  of  alumina,  lime,  magnesia,  and  oxide  of  iron,  or  per  cent, 
f.f— 

Basaltic  Syenitic 

Hornblende.  Hornblende. 

Silica     .....  42-24  45-69 

Alumina    ....  13-92  12-18 

Lime 12-24  13-83 

Magnesia    ....  13-74  18-79 

Prot-Oxide  of  Iron    .  14-59  7-32 

Oxide  of  Manganese  0-33  0-22 

Fluoric  Acid   ...  —  1-50 

97-06  99-53 

A  comparison  of  these  two  analyses  shows  that  the  proportions  of 
magnesia  and  oxide  of  iron  sometimes  vary  considerably,  yet  that  the 
hornblendes  still  maintain  the  same  general  composition.  They  are  re- 
markably distinguished  from  felspar  hy  the  total  absence  of  potash  and 
soda,  and  by  containing  a  large  proportion  of  lime  and  magnesia.  From 
the  potash-mica  they  are  distinguished  by  the  same  chemical  differen- 
ces, and  from  the  magnesian  mica  by  containing  lime  to^the  amount  of 


260  COMPOSITION    OF    SCHORL. 

■|th  part  of  their  whole  weight.  Such  differences  must  materially  af- 
fect the  constitution  and  agricultural  capabilities  of  the  soils  formed  from 
these  several  minerals,  and  they  show  the  correctness  of  what  I  have 
previously  stated  to  you — that  mineraloi^^koai  differences  in  rocks  which 
may  be  neglected  by  the  geologist,  may  be  of  great  importance  in  ex- 
plaining the  appearances  that  present  thtaiiselves  to  the  philosophical 
agriculturist. 

4°.  Schorl  usually  occurs  in  the  form  of  long  black  needles  or  prism.s 
disseminated  through  the  granitic  rock,  and  generally  (in  Cornwall)  at 
the  outskirts  of  the  granite,  where  it  comes  into  contact  with  the  slate 
rocks  that  surround  it  (De  la  Beche).  It  consists  of  a  silicate  of  alumi- 
na in  combination  with  silicates  of  iron  and  of  soda  or  magnesia.     Two 

varieties  gave  by  analysis — 

Schorl  Tourmaline 

from  Devonshire.  from  Sweden. 

Silica, 35-20  37-65 

Alumina,     ....  35-50  33-46 

Magnetic  Oxide  of  Iron,  17-86  9-38 

Magnesia,    ....  0-70  10-98 

Boracic  Acid,  .     .     .  4-11  3-83 

Soda 2-09     Soda  &  potash,  2-53 

Lime, 0-55  0-25 

Oxide  of  Manganese,  0-43  — 

96-44  98-08 

This  mineral,  according  to  these  analyses,  is  characterised  by  con- 
taining from  J  to  ^  of  its  weight  of  magnetic  oxide  of  iron,*  and  some- 
times ~Q  of  magnesia.  The  presence  of  Boracic  acidf  is  also  a  remark- 
able character  of  this  mineral,  but  as  neither  the  presence  of  this  sub- 
stance in  any  soil,  nor  its  effect  upon  vegetation,  have  hitherto  been  ob- 
served, we  can  form  no  opinion  in  regard  to  its  importance  in  an  agri- 
cultural point  of  view. 

§  2.  Q/*  the  degradation  of  the  Granitic  rocJcs,  and  of  the  soils  formed 
from  them. 

The  granites,  in  general,  are  hard  and  durable  rocks,  and  but  little  af- 
fected by  the  weather.  The  quartz  they  contain  is  scarcely  acted  upon  at 
all  by  atmospheric  agents,  and  in  very  many  cases  the  felspar,  mica, 
and  hornblende  yield  with  extreme  slowness  to  their  degrading  power.  It 
is  chiefly  to  the  chemical  decomposition  of  the  felspar  that  the  wearing 
away  of  granite  rocks  is  due,  and  the  formation  of  a  soil  from  their  crum- 
bling substance. 

It  has  been  stated  that  the  felspars  consist  of  a  silicate  of  alumina  in 
combination  with  silicates  of  potash  or  of  soda.  New  these  latter  sili- 
cates are  slowly  decomposed  by  the  carbonic  acid  of  the  air  (see  p.  207), 
which  combines  with  the  potash  and  soda,  and  forms  carbonates  of  these 
alkalies.     These  carbonates  are  very  soluble  in  water,  and  are,  there- 

•  This  oxide  is  composed  of  the^rK  and  second  oxides  of  iron  described  in  p.  210. 

T  Boracic  acid  occurs  in  combination  with  soda  in  the  common  borax  of  the  shops.  It 
combines  wilh  soda,  potash,  lime,  &c.,  and  forms  borates.  In  tho  schorl  it  probably  exists 
In  such  a  slate  of  combination. 


CLAY    FROM    TIIR    FELSPAR    ROCKS.  261 

fore,  washed  away  by  the  first  shower  of  rain  iliat  falls.  The  insoluble 
silica  and  the  silicate  of  alumina  are  either  left  behind  or  are  more  slow- 
ly carried  away  by  the  rains  in  the  form  of  a  fine  powder  (a  fine  porce- 
lain clay),  and  deposited  in  the  valleys  or  borne  into  the  rivers  and  lakes, 
— while  the  particles  of  quartz  and  mica,  having  lost  their  cement  of  fel- 
spar, fall  asunder,  and  form  a  more  or  less  siliceous  sand. 

Granite  soils,  therefore,  on  all  hanging  grounds, — on  the  sides  and 
slopes  of  hills,  that  is — are  poor  and  sandy,  rarely  containing  a  sufficient 
admixture  of  clay  to  enable  them  to  support  crops  of  corn — while  at  the 
bottoms  of  the  hills,  whether  on  flat  or  hollow  grounds,  they  are  com- 
posed, in  great  measure,  of  the  fine  clay  which  has  resulted  from  the 
gradual  decomposition  of  the  felspar. 

This  clay  consists  chiefly  of  the  silicate  of  alumina  contained  natural- 
ly in  the  felspar — it  differs  little,  in  short  from  that  which  has  already 
been  described  (p.  161),  under  the  name  of  pure  or  pipe  clay,  which  is 
too  stiff  and  intractable  to  be  readily  converted  into  a  prolific  soil. 

It  will  readily  be  understood  how  such  soils — decomposed  felspar  soils 
— must  generally  contain  a  considerable  quantity  of  potash  from  the 
presence  of  minute  particles  of  silicate  of  potash  still  undecoraposed ; 
and  it  will  be  as  readily  seen  that  they  can  contain  little  or  no  lime, 
since  neither  in  felspar  nor  in  mica  has  more  than  a  trace  of  this  earth 
been  hitherto  met  with. 

We  have  seen,  however,  that  hornblende  contains  fromi^thto  |thof  its 
weight  of  lime,  and  as  the  same  carbonic  acid  of  the  atmosphere  which 
decomposes  the  felspar,  decomposes  the  silicates  of  the  hornblende  also, 
it  is  clear  that  soils  which  are  derived  from  the  degradatiqsft  of  syenitic 
rocks,  especially  if  the  proportion  of  hornblende  present  in  them  be  lar^e, 
will  contain  lim"^e  as  well  as  clay  and  silica.  Thus  consisting  of  a  great- 
er number  of  the  elements  of  a  fertile  soil,  they  will  be  more  easily 
rendered  fruitful  also — must  naturally  be  more  fruitful — than  those 
which  are  formed  from  the  granites,  correctly  so  called.  It  is  to  the  pre- 
sence of  this  lime  l^at  the  superior  fertility  of  the  soils  derived  from  the 
hornblende  slates  of  Cornwall,  already  adverted  to  (p.  255),  is  mainly 
to  be  ascribed. 

Schorl^  as  above  stated,  contains  much  oxide  of  iron,  and  sometimes 
five  or  six  per  cent,  of  magnesia.  It  decomposes  slowly,  will  give  the 
soil  a  red  colour,  and  though  it  contain  only  a  trace  of  lime,  yet  the  ad- 
mixture of  its  constituents  with  those  of  the  felspar  may  possibly  amelio- 
rate the  quality  of  a  soil  formed  from  the  decay  of  the  felspar  alone. 

It  thus  appears  that  a  knowledge  of  the  constitution  of  the  minerals  of 
which  the  granites  are  composed,  and  of  the  proportions  in  which  these 
minerals  are  mixed  together  in  any  locality,  clearly  indicates  what  the 
nature  of  the  soils  formed  from  them  7nust  be — an  indication  which  per- 
fectly accords  with  observation.  The  same  knowledge,  also,  showing 
that  such  soils  never  have  contained,  and  npver  can,  naturally,  include 
more  than  a  trace  of  lime,  will  satisfy  the  improver,  who  believes  the 
presence  of  lime  to  be  almost  necessary  in  a  fertile  soil,  as  to  the  first 
step  to  be  taken  in  endeavouring  to  rescue  a  granitic  soil  from  a  state  of 
nature — will  explain  to  him  the  reason  why  the  use  of  lime  and  of  shel. 
sand  on  such  soils,  should  so  long  have  been  practised  with  the  best  ef 


262  GRANITE    ROCKS    OF    GRF.AT    BRITAIN'    AND    IRKLAND. 

fects, — and  will  encourage  liim  to  persevere  in  a  course  of  treatment 
which,  while  suggested  by  theory,  is  confirmed  also  by  practice. 

Extent  of  granitic  rocks  in  Great  Britain  and  Ireland. — In  England, 
the  only  extensive  tracts  of  granite  occur  in  Cornwall  and  Devon,  pre- 
senting themselves  here  and  there  in  isolated  patches  from  the  Scilly 
Isles  and  the  Land's  End  to  Dartmoor  in  South  Devon.  In  the  latter 
locality,  the  granite  rocks  cover  an  area  of  about  400  square  miles.  Pro- 
ceeding northward,  various  small  out-bursts*  of  granite  appear  in  the 
Isle  of  Anglesey,  in  Westmoreland,  and  in  Cumberland,  and  north  of 
the  Solway,  in  Kirkcudbright,  it  extends  over  150  or  200  square  miles; 
— but  it  is  at  the  Grampian  Hills  that  these  rocks  begin  to  be  most  ex- 
tensively developed.  With  the  exception,  indeed,  of  the  patches  of  old 
red  sandstone  already  noticed,  nearly  the  whole  of  Scotland,  north  of  the 
Grampians — and  of  the  western  islands,  excluding  Skye  and  Mull,  con- 
sists of  granitic  rocks. 

In  Ireland,  a  range  of  granite  (the  Wicklow)  mountains  runs  south  by 
west  from  Dublin  to  near  New  Ross — the  same  rock  forms  a  consider- 
able portion  of  the  mountainous  districts  in  the  north-west  of  Donegal,  and 
in  the  south  of  Galway — covers  a  less  extensive  area  in  Armagh,  and  pre- 
sents itself  in  the  form  of  an  isolated  patch  in  the  county  of  Cavan. 

Soils  of  the  granitic  rocks. — From  what  has  been  already  stated  in  re- 
gard to  the  composition  of  granite,  it  is  clear  from  theory  that  no  gene- 
rally uniform  quality  of  soil  can  be  expected  to  result  from  its  decompo- 
sition, and  this  deduction  is  confirmed  by  practical  observation.  Where 
quartz  is  more  abundant,  or  where  the  clay  is  washed  out,  the  soil  is 
poor,  hungry,  and  unfruitful — such,  generally,  is  its  character  on  the 
more  exposed  slopes  of  the  hills  in  the  Western  Isles,  and  in  the  north 
of  Scotland. — [Macdonald's  Agricultural  Survey  of  the  Hebrides,  p.  26.] 
In  the  hollows  and  levels,  where  natural  drainage  exists,  stiff  clay  soils 
prevail,  which  are  often  cold  and  unfruitful,  but  are  capable  of  amelio- 
ration where  the  depth  of  earth  is  sufficient,  by  draining  and  abundant 
liming  or  marling.  Where  there  is  no  natural  drainage,  vegetable  mat- 
ter accumulates,  as  we  have  seen  to  be  the  case  on  the  surface  of  all  im- 
pervious rocks — and  bogs  are  formed.  In  the  north  of  Scotland,  and  in 
Ireland,  and  in  the  high  lands  of  Dartmoor  (Devon),  these  are  every- 
where seen  in  such  localities,  and  it  is'said  that  two-thirds  of  the  He- 
brides are  covered  with  peat  bogs  more  or  less  reclaimable. 

In  Cornwall  and  Devon,  the  granitic  soils  {growan  soils,  as  they  are 
there  called)  are  observed  to  be  more  productive  as  the  hills  diminish 
in  height.  Thus  Dartmoor  is  covered  only  with  heath,  coarse  grass, 
and  peat ;  while  in  the  Scilly  Isles  the  growan  land  produces  good  crops 
of  wheat,  potatoes,  barley,  and  grass ;  and  the  same  is  observed  at 
Moreton  Hampstead,  in  Devon,  where  tolerable  crops  of  barley  are  grown, 
and  potatoes,  which  are  highly  esteemed  in  the  Exeter  market  (De  La 
Beche).  No  doubt  the  climate  has  something  to  do  with  these  differ- 
ences ;  but  the  less  the  elevation,  and  the  consequent  washing  of  the 
rains,  the  more  of  the  clay  will  remain  mixed  with  the  siliceous  sand ; 

*  This  expression  is  in  some  measure  theoretical,  and  implies — what  is  the  generally  re« 
ceived  opinion— that  the  granite  rocks  were  forced  up  from  beneath  in  a  fluid  state,  like  the 
lavas  of  existing  volcanoes— that  they,  as  well  as  the  trap  rocks,  are,  in  short,  only  lavas  of 
a  more  ancient  date  (see  p.  237). 


THE  TRAP-ROCKS GREEN-ST()>E.  263 

wrhile  m  aid  of  both  these  causes,  a  small  diflTerence  in  the  composition 
of  its  constituent  minerals,  often  not  to  be  detected  by  the  eye,  may  ma- 
terially affect  the  character  of  the  granitic  soils. 

According  to  Dr.  Paris,  the  presence  of  much  mica  deteriorates  these 
soils;  while  that  which  is  formed  at  the  edges  of  the  granite,  when  it 
comes  in  contact  with  the  slate  rocks,  is  of  a  more  fertile  quality.  The 
latter  remark,  however,  does  not  universally  apply, — especially  where 
the  granite,  as  at  the  edges  of  Dartmoor,  contains  much  scherl,  (De  La 
Beche) — and  the  presence  of  mica,  in  the  richest  soils  of  the  red  marl, 
would  seem  to  imply  that  this  mineral  is  fitted  materially  to  promote 
the  fertility  of  a  soil  in  which  the  other  earthy  ingredients  are  properly 
adjusted. 

The  more  elevated  and  thin  granitic  soils  are  said  to  be  fitted  for  the 
growth  of  larch  ;  the  lower  and  deeper  soils,  which  admit  of  the  use  of 
the  plough,  have  been  found  to  yield  a  three-fold  return  of  corn  by  the 
use  of  lime  alone. 

§  4.  Of  the  trap  rocks,  and  the  soils  formed  from  them. 

Of  the  trap  rocks  there  are  several  varieties,  of  which  the  most  impor- 
tant are  distinguished  by  the  names  of  Greenstone,  Basalt,  and  Ser- 
pentine. 

The  Green-stones  consist  of  a  mixture  more  or  less  intimate  of  felspar 
and  hornblende,  or  of  felspar  and  augite.  They  are  distinguished  from 
the  granites  by  the  absence  of  mica  and  quartz,  and  by  the  presence  of 
the  hornblende  or  augite,  often  in  eijual,  and  not  unfrequently  in  greater 
quantity  than  the  felspar.  In  the  granites,  the  felspar  and  quartz  to- 
gether generally  form  upwards  of  y^^  of  the  whole  mass. 

Augite  is  a  mineral  having  much  resemblance  to  hornblende,  and, 
like  it,  occurring  of  various  colours.  In  the  trap  rocks  it  is  usually  of  a 
dark  green  approaching  to  black.  It  generally  contains  much  lime  and 
oxide  of  iron  in  the  stale  of  silicates.  The  composition  of  two  varieties 
compared  with  that  of  basaltic  hornblende  is  as  follows  : — 

Black  Augite  Augite  from  the  Basaltic 

from  Sweden.  lava  of  Vesuvius.  Hornblende. 

Silica 63-36                 50-90  42-24 

Lime 22-19                 22-96  12-24 

Magnesia 4-99                 14-43  13-74 

P rot-Oxide  of  Iron     .     .     .     17-38                   6-25  ]4-69 

Prot-Oxide  of  Manganese  .       0-09                   —  0-33 

Alumina —                     5-37  13-92 


9S-01  99-91  97-06 

The  predominance  of  this  mineral  (augite)  or  of  hornblende  in  the 
green-stone  rocks  must  necessarily  cause  a  very  material  difference  in 
the  nature  of  the  soils  produced  from  their  decay,  compared  with  those 
which  are  formed  from  the  granitic  rocks  in  which  the  felspars  are  the 
predominating  mineral  ingredient. 

2°.  Basalt  consists  of  a  mixture,  in  variable  proportions,  of  augite, 
magnetic  oxide  of  iron,  and  zeolite.*     It  differs  in  appearance  from  green- 

*  "  Wi7A  or  without  felspar."  In  addition  to  augite,  magnetic  iron,  and  zeolite,  many  ba* 
salts  oontain  also  a  considerable  portion  of  certain  varieties  of  felspar,  especially  of  ODO  to 
which  the  name  oinepheline  has  been  given. 


264  EXTENT  AND  SOIL  OF  THK  TRAP-r.OCKS. 

Stone,  chiefly  by  the  darkness  of  its  colour,  and  by  the  minuteness  of  the 
particles  of  which  it  is  composed,  which,  in  general,  cannot  be  distin- 
guished by  the  naked  eye. 

Zeolite  is  a  generic  term  applied  to  a  great  number  of  mineral  specieg 
which  occur  in  the  basalts,  and  often  intermixed  with  the  green-stone 
rocks.  They  differ  from  felspar  in  their  greater  solubility  in  acids,  and 
by  generally  containing  limey  where  the  latter  contains  potash  or  soda. 

It  may  be  stated,  indeed,  as  the  most  important  agricultural  distinc- 
tion, between  the  granitic  and  the  true*  trap-rocks,  that  the  latter  abound 
in  lime,  while  in  the  former,  it  is  often  entirely  absent.  If  in  a  green- 
stone only  one-fourth  of  its  weight  consist  of  augite,  every  20  tons  of  the 
rock  may  contain  one  ton  of  lime.  If  in  a  basalt  the  augite  and  zeolite 
amount  to  only  two-thirds  of  its  weight,  every  nine  tons  may  contain  a 
ton  of  lime.  The  practical  farmer  cannot  fail  to  conclude  that  a  soil 
f()rmed  from  such  rocks  must  possess  very  different  agricultural  capabil- 
ities from  the  soils  we  have  already  described  as  being  formed  from  the 
decomposition  of  the  granites. 

3°.  Serpentine  is  a  greenish  yellow  mineral,  consisting  of  silica  in 
combination  with  magnesia  and  a  little  iron,  and  occasionally  a  few 
pounds  in  the  hundred  of  lime  or  alumina.  The  distinguishing  ingredi- 
ent is  the  magnesia,  which  generally  approaches  to  40  per  cent,  of  the 
whole  weight  of  the  mineral.  Rocks  of  serpentine  are  generally  mixed 
with  magnetic  iron  ore,  and  with  portions  of  other  minerals  in  greater 
or  less  abundance. 

Extent  of  the  trap  rocks  in  the  British  Isles. — The  serpentine  rock  oc- 
curs to  any  extent  anly  in  Cornwall,  about  the  Lizard  Point,  where  it 
covers  an  area  of  50  square  miles.  The  green-stones  and  basalts  are 
only  met  with  here  and  there  in  small  patches,  until  we  get  so  far  north 
as  the  Cheviot  Hills,  which  consist  of  these  and  other  varieties  of  trap. 
It  is  in  the  low  country  of  Scotland,  however,  intermixed  with  and  sur- 
rounding the  great  coal  district  of  that  part  of  the  island,  that  the  greatest 
breadth  of  trap  is  seen.  It  there  stretches  across  the  island  in  a  south- 
west direction,  and  in  detached  masses,  from  the  Friths  of  Tay  and 
Forth  to  the  island  of  Arran,  covering  an  area  of  800  or  1000  square 
miles.  In  the  prolongation  of  the  same  line  it  re-appears  in  the  north- 
east of  Ireland,  and  extends  over  the  whole  of  the  county  of  Antrim  and 
u  small  part  of  Londonderry  and  Armagh.  In  the  most  northerly  portion 
of  this  tract  the  well-known  columnar  basalt  of  the  Giants'  Cause^yay 
occurs.  On  the  west  coast  of  Scotland  the  trap  rocks  cover  nearly  the 
whole  of  the  islands  of  Mull  and  of  Skye — to  the  west  of  the  former  of 
which  islands  lies  Staflfa  with  its  celebrated  basaltic  caves. 

Soil  of  the  trap  rocks. — The  soil  of  the  serpentine  rocks  at  th«  Lizard 
is  far  from  fertile,  retaining  the  water  and  thus  forming  swamps  and 
marshes.  Even  where  a  natural  drainage  exists  it  rarely^pioduces  good 
grass,  or  average  crops  of  corn.  It  is  remarkable  for  growing  a  pecu- 
liar, very  beautiful  heath — erica  vagans — which  so  strictly  limits  itself 
to  the  serpentine  soil  as  distinctly  to  mark  the  boundary  by  which  the 
serpentine  is  separated  from  other  rocks  (De  La  Beche).     From  the 

*  Serpentine  is  not  generally  included  among  the  trtie  trap  rocks :  It  is  included  among 
tliem  here  as  it  often  is  by  geologists,  because  in  many  places,  as  at  the  Lizard,  it  occurs 
along  with  true  green-stone 


FErvriLlTY    OF    THE    GREEN-STONE    SOILS.  265 

composition  of  serpentine  we  might  be  led  to  suppose  that  tlie  coinpars- 
live  barrenness  of  the  soils  formed  from  it  is  due  to  the  large  quantity 
of  magnesia  which  this  mineral  contains  ;  and  this  may,  in  some  cases, 
be  partly  the  cause.  It  would  appear,  however,  that  these  soils  often 
contain  very  little  magnesia,  the  long  action  of  the  rains  and  of  other 
agents  having  almost  entirely  removed  it  (see  p.  209),  and  yet  they  stiil 
retain  their  barrenness.  But  they  contain  no  lime,  and,,  therefore,  after 
draining,  the  first  great  step  to  take  in  order  to  improve  such  soils,  is  to 
give  them  a  good  dose  of  lime.  How  this  step  is  to  be  followed  up  will 
depend  upon  the  effect  which  this  treatment  is  found  to  produce. 

The  soil  of  the  green-stones  is  generally  fertile,  and  it  is  more  so  in 
proportion  as  the  hornblende  or  augite  predominates — that  is,  generally, 
in  proportion  to  the  darkness  of  its  colour. 

In  Cornwall  and  South  Devon,  where  scattered  masses  of  trap  occur, 
consisting  chiefly  of  hornblende  and  felspar,  they  "afford  the  most  fertile 
soils  of  any  in  the  district  when  their  decomposition  has  taken  place  to 
a  sufficient  depth"  (De  La  Beche).  Wherever  the  trap  rocks  (locally 
dun-stones)  are  observed  at  the  surface,  "  it  is  deemed  a  fortunate  cir- 
cumstance, being  a  certain  indicaiion  of  the  fertility  of  the  incumbent 
soils." — [Worgan's  View  of  the  Agriculture  of  Cornwall,  p.  10.]  The 
Miperior  fertility  of  the  neighbourhood  of  Penzance  is  owing  to  the  pre- 
sence of  these  rocks  (Dr.  Paris),  and  where  their  detritus  has  been  mix- 
ed wiih  that  of  other  rocks — as  with  the  worthless  granite  soils — it  ame- 
liorates and  improves  their  quality. 

.  The  same  general  character  is  exhibited  by  the  trappean  soils  of  other 
districts  of  the  island.  The  height  of  the  Cheviot  Hills  renders  the  cli- 
mate in  many  places  unfavourable  to  arable  culture,  yet  they  produce 
the  sweetest  pasture,*  while  the  low  country  around  them  has  been 
largely  benefitted  by  admixture  with  their  crumbling  fragments.  The 
whole  of  that  lowland  tract  of  Scotland,  over  which  these  rocks  extend — 
comprehending  the  counties  of  Ayr,  Renfrew,  Lanark,  Linlithgow, 
File,  and  portions  of  Perth,  Sterling,  Edinburgh,  and  Haddington, — ex- 
hibit the  fertile  or  fertilizing  character  of  the  decomposing  green-stone. 
In  Cornwall  it  is  dug  up  as  a  marl  and  applied  to  the  land,  and  in  the 
neighbourhood  of  Haddington  I  have  seen  a  farming  tenant  {a  leasehold- 
er) removing  twelve  inches  of  trap  soil  from  the  entire  surface  of  a  field, 
for  the  purpose  of  spreading  a  layer  of  an  inch  in  depth  over  twelve 
limes  the  area  in  another  part  of  his  farm.  There  can  be  no  doubt  that 
this  mode  of  improvement  is  within  the  reach  of  many  proprietors  and 
farmers — especially  along  the  southern  borders  of  Perthshire,  and  near 
the  more  elevated  of  Ayr  and  Lanark. 

To  the  north  of  Ireland,  and  to  the  Western  Islands,  the  above  re- 
marks, with  slight  modifications,  arising  from  local  causes,  will  also  ap- 
ply. For  example,  where  the  surface  is  flat,  and  the  rock  impervious, 
water  will  collect  and  heaths  and  bogs  will  be  produced,  which  only 

*  It  is  a  singular  fact  observed  here  and  there  among  the  Cheviot  Hills  on  the  border,  that 
where  sheep  are  folded  or  pastured  on  hills  of  trap  which  are  covered  with  delicate  herbage, 
they  are  attacked  by  what  is  locally  called  the  pining  iH,— they  pine  away,  become  indolent, 
and  are  unwiUing  to  move.  The  cure  is  to  drive  them  to  a  neighbouring  sandstone  pasture., 
where  they  become  again  active,  and  begin  to  thrive.  T)^e  pining  hills  on  each  farm  are 
well  known,  and  the  tenant  has  no  hesitation  in  pointing  to  this  and  to  that  hill  as  those  Dn 
which  the  sheep  are  sure  to  pine,  if  kept  upon  them  only. 

12 


266  THE    HTPERTHENE  SOILS   OF   SKYE. 

draining  can  remove.  They  apply  also  to  other  conntries  where  trap 
rocks  abound — the  only  fertile  tracts  of  Abyssinia,  for  instance,  being 
found  in  vallies  and  on  mountain  slopes,  where  the  soil  is  com  nosed  of 
the  detritus  of  trappean  rocks  (Dr.  Ruppell., 

Yet  there  are  exceptions  to  this  general  rule. 

Where  the  felspar  is  largely  predominant,  the  soil  formed  from  the 
rock  will  partake  more  or  less  of  the  cold  and  barren  character  of  the 
stiffer  granitic  soils.  Such  appears  to  be  the  case  with  some  of  the  traps 
which  occur  in  the  border  counties  of  England  and  Wales  (Murchison). 

In  the  Isle  of  Skye,  again,  a  local  peculiarity  of  a  different  kind  ob- 
tains, the  effect  of  which  upon  the  soil  is  also  to  render  it  poor  and  un- 
productive. In  that  island  the  singularly  beautiful  ridge^f  the  Cuchul- 
len  Hills  consists  of  a  variety  of  trap  in  which  the  augite  so  far  predomi- 
nates as  to  form  nearly  the  whole  of  the  mountain  masses,  But  the 
augite  in  this  case  is  a  variety  to  which  the  name  of  hypersthene  has 
been  given,  and  which  contains  much  magnesia  and  oxide  of  iron,  but 
scarcely  a  trace  of  either  lime  or  alumina.  The  rock  is  very  hard,  and 
decays  with  extreme  slowness;  yet  however  rapid  its  decay  might  be, 
it  could  never  produce  a  fertile  soil.  We  have  seen  that  the  serpentine 
and  granite  soils  are  essentially  deficient  in  lime,  but  a  hypersthene  soil 
is  in  want  both  of  lime  and  of  clay.  It  would  be  still  more  difficult, 
therefore,  to  render  the  latter  productive — even  supposing,  as  in  the  case 
of  the  serpentine  soils,  that  the  magnesia  of  the  hypersthene*  were  most- 
ly washed  away  by  the  rains. 

Thus  we  perceive  how  eactly  the  study  of  the  composition  of  the  dif- 
ferent varieties  of  the  trap  rocks  explains  the  observed  differences  in  the 
quality  of  the  soils  derived  from  them.  When  the  minerals  they  contain 
abound  in  lime,  the  soils  they  yield  are  fertile — when  those  minerals 
predominate  in  which  lime  is  wanting,  the  soils  are  inferior,  sometimes 
scarcely  capable  of  cultivation.  Again,  the  granites  abound  in  potash; 
but  except  in  the  syenites  they  rarely  contain  lime,  and  their  soils  are 
generally  poor.  Let  them  be  mixed  with  the  trap  soils,  and  they  are 
enriched.  This  would  seem  fairly  and  clearly  to  imply  that  the  fertility 
of  the  one  is  mainly  due  to  the  presence  of  lime,  and  the  barrenness  of 
the  other  to  the  absence  of  this  earth. 

On  this  subject  I  will  only  further  add,  that  the  more  modern  volcanic 
lavas  which  overspread  It-aly,  Sicily,  parts  of  France,  Spain,  and  Ger- 
many, are  closely  related  to  the  trap  rocks  in  their  general  composition 
— aad  the  fertility  which  overspreads  thousands  of  square  miles  of  de- 
composed lava  streams  and  ejections  of  volcanic  ashes  in  Italy  and  Si- 
cily, is  too  well  known  to  require  any  detailed  description. 

§5.0/"  superficial  accumulations  of  foreign  materials^  and  of  the  means 
hy  which  they  have  been  transported. 
Abundant  proof,  I  think,  has  now  been  advanced  that  a  close  relation 

'  The  hypersthene  of  Skye  has  been  found  to  consist  of— 

Silica 51-35  1     Protoxide  of  iron 33-92 

Lime 1-84  I     Water 0-50 

Magnesia 1109  I  

I  98-70 
The  composition  probably  varies  in  different  parts  of  the  rock,  some  containing  more  mag* 
nesia  and  less  iron  than  is  here  represented. 


TRANSPORTED    MATERIALS    OFTEN    MASK    THE    ROCKS.  267 

generally  exists  between  the  soil  and  the  rocks  on  which  it  rests,  and 
that  the  geological  structure  of  a  country,  as  well  as  the  chemical  consti- 
tution of  the  minerals  of  which  its  several  rocky  masses  consist,  have  a 
primary  and  fundamental  influence  upon  the  agricultural  capabilities  of 
its  surface. 

And  yet  I  should  be  leading  you  into  a  serious  error,  were  I  to  permit 
you  tp  suppose  that  this  intimate  and  direct  relation  is  always  to  be  ob- 
served— that  in  whatever  district  you  may  happen  to  be,  you  will  fold 
the  soil  taking  its  general  character  from  the  subjacent  rocks — and  that 
where  the  same  rocks  occur,  similar  soils  are  always  to  be  expected. 
On  the  contrary,  in  very  many  localities  the  soil  is  totally  different  from 
that  which  would  be  produced  by  the  degradation  or  decomposition  of 
the  rocks  on  which  it  rests.  To  infer,  therefore,  or  to  predict,  that  on  a 
given  spot,  where,  according  to  the  geological  map,  red  sand-stone  for 
example  prevails,  a  marly  or  other  red  sand-stone  soil  will  necessarily 
H^  found— or  that  where  the  coal  measures  are  observed,  poor,  ungrate- 
ful land  must  exist — would  be  to  form  or  to  state  opinions  which  a  visit 
to  the  several  localitias  would  in  many  inistances  show  to  be  completely 
erroneous — and  which  would  bring  undeserved  discredit  upon  geologi- 
cal science. 

In  such  cases  as  these  geology  is  not  at  fault.  New  conditions  only 
have  supervened  which  render  the  natural  relation  between  soils  and 
rocks  in  those  places  less  simple,  and  consequently  more  obscure.  Yet 
a  further  study  of  geological  phenomena  removes  the  obscurity — shows 
to  what  cause  it  is  owing  that  in  many  districts  the  soil  is  such  as  could 
never  have  been  formed  from  the  subjacent  rocks — again  places  the  en- 
lightened agriculturist  in  a  condition  to  pronounce  generally  from  what 
rocks  his  soils  have  been  derived — generally  also  what"  their  agricultural 
capabilities  are  likely  to  be,  and  by  what  mode  of  treatment  those  capa- 
bilities may  be  most  fully  developed. 

Of  the  surface  of  Great  Britain  and  Ireland  it  may  indeed  be  truly 
said,  that  it  exhibits  extensive  tracts  in  which  the  character  of  the  soil  is 
directly  influenced  by,  and  may  be  inferred  from,  the  character  and 
composition  of  the  subjacent  rock.  To  these  districts  the  rules  and  ob- 
servations contained  in  the  preceding  sections  directly  and  clearly  apply. 
But  other  extensive  tracts  also  occur  in  which  the  character  of  the  soil  is 
independent  of  that  of  the  rocks  on  which  it  immediately  rests — the 
cause  of  this  apparent  difficulty  we  are  now  to  consider. 

1°.  I  have  already  had  occasion  to  explain  to  you  in  what  way  all 
rocks  crumble  more  or  less  rapidly,  and  give  origin  to  soils  of  various 
kinds.  Were  the  surfaces  of  rocks  uniformly  level,  and  that  of  every 
country  flat,  the  crumbled  materials  would  generally  remain  on  the  spots 
where  they  were  formed.  But  as  already  shown  in  the  diagrams,  in- 
serted in  page  238,  the  rocks  rarely  lie  in  a  horizontal  position, 
but  rest  almost  always  more  or  less  on  their  edges ;  and  the  surface  in 
such  a  country  as  ours  is  often  mountainous  or  hilly,  and  everywhere 
undulating.  Hence  the  rains  ave  continually  washing  off'  the  finer  par- 
ticles from  the  higher,  and  bearing  them  to  the  lower  grounds — and  on 
occasions  of  great  floods,  vast  quantities  even  of  heavy  materials  are 
borne  to  great  distances,  and  spread  sometimes  to  a  great  depth  and  over 
a  great  extent  of  country — [witness  the  still  recent  floods  in  Morayshire.] 


268  EFFECT  OF  RAINS,  UIVERS,  AND  TIDES. 

Thus  the  spoils  of  one  rocky  formation  arc  borne  from  their  native  soil, 
and  are  strewed  over  the  surface  of  other  kinds  of  rock  of  a  totally  dil- 
ferent  character.  The  fragments  of  the  granite,  gneiss,  and  slate  rocks 
of  the  high  lands  are  scattered  over  the  old  red  sand-stones  which  lie  at 
a  lower  level — and  those  of  the  blue  lime-stone  mountains  over  the  mill- 
stone grits,  the  coal  measures,  and  the  new  red  sand-stones,  which  stretch 
away  from  their  feet. 

2°.  But  the  effects  produced  by  this  natural  cause,  though  .they  may 
be  judged  of  in  kind,  can  never  be  estimated  in  degree  by  what  we  per- 
ceive in  our  own  temperate  climates — in  our  country  of  small  rivers  and 
gentle  rains.  How  must  such  effects  exceed  in  magnitude,  in  districts 
where, — as  in  the  Ghauts,  that  separate  the  level  land  of  the  Malabar 
coast  (the  Concan)  from  the  high  table-land  of  the  Deccan, — 120  inches 
of  rain  occasionally  fall  in  a  single  month,  and  240  inches  or  20  feet,  on 
an  average,  every  year  from  June  to  September !  And  to  what  vast 
distances  must  materials  be  transported  by  great  rivers,  such  as  the  Mis- 
sissippi, the  River  of  Amazons,  the  Ganges,  and  the  Indus,  which  main- 
tain a  course  of  thousands  of  miles,  before  they  empty  themselves  into 
ihe  sea  ?  What  necessary  connection  can  the  deposits  of  mud  and  sand 
which  yearly  collect  at  the  mouths  and  in  the  places  overflowed  by  the 
waters  of  these  great  rivers,  have  with  the  nature  of  the  rocks  on  which 
these  transported  materials  may  happen  to  rest? 

3°.  But  the  constant  motion  of  the  waters  of  the  sea  washes  down 
the  cliffs  on  one  coast,  and  carries  away  their  ruins  to  be  deposited,  either 
in  its  own  depths,  or  along  other  more  sheltered  shores.  Hence  sand 
banks  accumulate — as  in  the  centre  of  our  own  North  Sea:  or  the  land 
gains  upon  the  water  in  one  spot  what  it  loses  in  another — as  may  be 
seen  both  on  the  shores  of  our  own  island,  and  on  the  opposite  coasts  of 
Germany  and  France. 

What  necessary  relation  can  the  soils  thus  gained  from  the  sea  have 
to  the  rocks  on  which  they  rest?  Suppose  the  bottom  of  the  North  Sea 
to  become  dry  land,  what  necessary  mineral  relation  would  then  exist 
between  the  soils  which  would  gradually  be  formed  on  its  hundreds  of 
square  miles  of  sand-banks,  and  the  rocks  on  which  those  sand-banks 
immediately  repose? 

4°.  Again,  the  sea,  in  general,  carries  with  it  and  deposhs  in  its  owk 
bosom  the  finest  particles  of  clay,  lime,  and  other  earthy  matters,  and 
leaves  along  its  shores  accumulations  of  fine  siliceous  sand.  This  sand, 
when  dry,  the  sea  winds  bear  before  them  and  strew  over  the  land,  fomi- 
ing  sand  hills  and  downs,  sometimes  of  considerable  height  and  of  great 
extent.  Such  ^re  to  be  seen  here  and  there,  in  our  own  islands,  but  on 
the  Eastern  shores  of  the  Bay  of  Biscay,  and  on  the  coasts  of  Jutland, — 
both  exposed  to  violent  sea  winds, — they  occur  over  much  larger  areas. 
Before  these  winds  the  light^sands  are  continually  drifting,  and,  year  by 
year,  advance  further  and  further  into  the  country,  gradually  driving 
lakes  before  them,  swallowing  up  forests  and  cultivated  fields,  with  the 
houses  of  the  cultivators,  and  burying  alike  the  fertile  soils  and  the  rock* 
from  which  they  were  originally  derived.  [In  the  Landes,  the  ad- 
vance of  the  downs  is  estimated  at  66  to  70  feet  every  year.] 

You  have  all  read  of.  the  fearful  sands  of  the  African  deserts,  and  of 


EFFECTS  OF  WINDS,  AND  OF  GLACIERS.  269 

their  destructive  marc.i  when  the  burning  winds  awaken.  History  tells 
of  populous  cities  and  fertile  plains,  where  nothing  but  blown  sands  are 
now  to  be  seen,  and  geology  easily  leads  us  back  to  still  more  remote 
periods,  when  the  broad  zones  of  sandy  desert  were  but  narrow  stripes 
if  blown  sand  along  the  shores  of  the  sea,  or  beds  of  comparatively  loose 
sand-sfone,  which  here  and  there  came  to  the  surface,  and  which  the 
winds  have  gradually  removed  from  their  original  site,  and  wafted  widely 
over  the  land. 

Wherever  these  sand-drifts  spread,  it  will  also  be  clear  to  you,  that 
there  may  be  no  necessary  similarity  between  the  loose  materials  on 
the  surface  and  the  kind  of  rock  over  which  these  materials  are  strewed. 

5°.  Along  with  these  I  shall  mention  only  one  other  great  agent  by 
^which  loose  materials  are  gradually  transported  to  considerable  dis- 
tances. 

It  is  observed  in  elevated  countries,  where  the  snow  never  entirely 
melts,  and  where  glaciers  or  sheets  of  ice  hang  on  the  mountain  sides, — 
descending  towards  the  plains  as  the  winter's  cold  comes  on,  and  again 
retreating  towards  the  mountain-tops  at  the  approach  of  the  summer's 
heat — that  the  edges  of  the  glaciers  bear  before  them  into  the  valleys,  and 
deposit  along  their  edges,  banks  of  conical  ridges  of  sand  and  gravel 
(Moraines).  These  con^st  of  the  fragments  of  the  rocky  heights,  worn 
atid  rounded  by  the  friction  of  the  sheets  of  ice  beneath  which  they 
have  descended  from  above,  and  from  the  edges  of  which  they  finally 
escape  into  the  plain. 

These  ridges  of  sand  and  gravel  accumulate  till  some  more  sudden 
thaw  than  usual,  or  greater  summer's  heat  arrives,  when  they  are  more 
or  less  completely  broken  up  by  the  rush  of  water  that  ensues,  and  are 
dispersed  over  the  subjacent  tracts  of  level  land. 

When  the  rocks  are  of  a  kind  to  rub  down  so  fine  as  to  form  much 
mud  as  well  as  sand  or  gravel,  the  ridges  are  of  a  more  clayey  charac- 
ter. And  where  the  edges  of  the  glaciers  descend  to  the  borders  of  lakes 
or  seas — as  in  the  Tierra  del  Fuega — this  mud  is  washed  away  and 
widely  spread  by  the  waters,  while  the  gravel  and  sand  remain  nearer 
their  original  site  ;  or,  finally,  when  the  ice  actually  overhangs  the  wa- 
ter, huge  fragments  break  off' now  and  then — loaded  with  masses  of  gra- 
vel and  sand,  or  even  with  rocks  of  large  size, — which  fragments  float 
away  often  to  great  distances  and  drop  their  stony  burdens  here  and 
there,  as  they  gradually  melt  and  disappear. 

To  these  facts,  let  it  be  added,  that  recent  geological  researches,  of  a 
very  interesting  kind,  tend  to  show  that  nearly  all  the  elevated  tracts  of 
country  in  the  temperate  regions  of  Europe  and  America — in  our  own 
island  among  other  localities — have  been  covered  with  glaciers  at  a 
^comparatively  recent  period,  (geologically  speaking,)  and  that  these  gla- 
ciers have  gradually  retreated  step  by  step  to  their  present  altitudes, 
halting  here  for  a  time,  and  lingering  there ; — and  we  shall  find  reason 
to  believe  that  trsi^es  of  transported  materials — moved  from  their  origi- 
nal site  by  this  agent  also — are  to  be  looked  for  on  almost  every  geolo- 
gical formation. 

And  such  the  geological  observer  finds  to  be  in  reality  the  case. 


270  DRIFTS  IN  GREAT  BRITAIN. 

^  S-  Of  the  occurrence  of  such  accumulations  in  Great  Britain^  andoj 
their  influence  in  modifying  the  character  of4he  soil. 

Such  accumulations,  for  example,  present  themselves  over  a  large 
portion  of  our  own  island.  Thus,  in  Devonshire,  the  chalk  and  green 
sand  are  so  completely  covered  by  gravels,  consisting  of  the  fragments 
of  older  rocks  from  the  higher  grounds,  mixed  with  chalk-flints  and 
chert,  that  nearly  the  whole  of  this  tract  possesses  one  common  charac- 
ter of  infertility,  and  is  widely  covered  with  downs  of  furze  and  heath 
(De  La  Beche.)  In  like  manner  the  chalk,  green  sand,  and  plastic  clay 
of  a  large  portion  of  Norfolk  and  Suffolk,  and  of  parts  of  the  counties  of 
Essex,  Cambridge,  Huntingdon,  Bedford,  Hertford,  and  Middlesex,  are 
covered  with  till,  (stiff  unstratified  clay,)  containing  large  stones,  (boul- 
ders,) or  with  gravels,  in  which  are  mixed  fragments  of  rocks  of  various 
ages,  which  must  have  been  brought  from  great  distances,  and  perhaps 
from  different  directions  (Lyell.)  So  over  the  great  plain  of  the  new 
red  sand-stone,  in  the  centre  and  west  of  Eflgland — in  Lancashire, 
Cheshire,  Shropshire,  Staffordshire,  and  Worcestershire — drifted  gra- 
vels of  various  kinds  are  widely  spread.  It  may  indeed  be  generally 
remarked,  that  over  the  bottoms  of  all  our  great  vallies,  such  drifted 
fragments  are  commonly  diffused — that  upon  our  wider  plains,  they  are 
here  and  there  collected  in  great  heaps — and  that  on  the  lower  lands  th-it 
border  either  shore  of  our  island,  extensive  deposits  of  clay,  sand,  or  gra- 
vel, not  unfrequently  cover  to  a  great  depth  the  subjacent  rocks. 

The  practical  agriculturist  will  be  able  to  confirm  this  remark,  in 
whatever  district  almost  he  may  live,  by  facts  which  have  come  within 
his  own  knowledge  and  observation.  I  shall  briefly  explain,  by  way  of 
illustration,  the  mode  in  which  such  accumulations  of  drifted  matter 
overlie  the  eastern  or  lower  half  of  the  county  of  Durham. 

The  eastern  half  of  the  county  of  Durham  reposes,  to  the  north  of  the 
city  of  Durham,  chiefly  upon  the  coal  measures,  (sand-stones  and  shales;) 
to  the  south,  chiefly  on  the  magnesian  lime-stone  and  the  new-red  sand- 
stone. These  coal  measures  rise,  here  and  there,  into  considerable  eleva- 
tions, as  at  Gateshead  Fell  near  Newcastle,  and  Brandon  Hill  near  Dur- 
ham, where  the  rocks  lie  immediately  beneath  the  surface,  and  are  cov- 
ered by  comparatively  little  transported  matter.  The  magnesian  lime- 
stone, also,  in  many  localities,  starts  up  in  the  form  of  round  hills  or  ridges, 
on  which  reposes  only  a  poor  thin  soil,  formed  in  great  measure  by  the 
crumbling  of  the  rock  itself.  Yet,  generally  speaking,  this  entire  dis- 
trict is  overspread  with  a  thick  sheet  of  drifted  matter,  consisting  of 
clays,  sands,  and  gravels. 

This  drift  is  made  up  of  three  separate  layers,  to  be  observed  more  or 
less  distinctly  in  taking  a  general  survey  of  the  county,  though  there  afe 
few  spots  where  they  can  all  be  seen  reposing  immediately  one  over  the 
other. 

1°.  The  upper  layer  consists  of  clays — on  the  higher  grounds,  poor, 
stiff,  yellow — on  the  hill-sides  and  slopes  of  the  valleys,  often  darker  in 
colour — but  almost  everywhere  full  of  rounded  trap  boulders*  from  a  few 

*  In  some  parts  of  Northumberland  these  trap  boulders  are  still  more  numerous.  In  the 
country  which  stretches  between  the  north  and  south  Tyne,  the  old  grass  fields  are  full  of 
them.  A  friend  of  mine  informs  me  that  in  ploughing  out  a  nine-acre  field  on  his  estate  in 
that  district,  there  were  dug  out  and  carried  off  no  less  than  900  tots  of  such  rolled  stonea 
freat  and  small ! 


DRlFr    NEAR    THE    CITT   OF    DURHAM.  271 

pounds  to  many  tons  in  weight.  These  are  generally  dug  up  when  they 
obstruct  the  plough,  and  are  sold  for  mending  the  roads  at  about  5s.  a 
ton.     This  clay  varies  in  depth,  from  one  or  two,  to  fifty  or  sixty  feet. 

2°.  Beneath  the  clay  occurs  an  accumulation  of  fine,  generally  yel- 
low, more  rarely  red,  sand,  intermixed  with  occasional  layers  and 
round  hills  of  gravel — with  frequent  black  streaks  of  rounded  coal  dust, 
and  here  and  there  with  nests  of  rounded  lumps  of  coal,  from  half  an 
inch  to  fiv%or  six  inches  in  diameter.  This  coal  is  sometimes  so  abun- 
dant as  to  be  collected  and  sold  for  burning. 

The  gravels,  where  they  overlie  the  coal  measures,  consist  chiefly  of 
rounded,  and  on  the  upper  part  occasionally  of  large  angular  masses 
of  coal  sand-stones — with  here  and  there  a  fragment  of  trap,  of 
mountain  lime-stone,  or  of  some  of  the  older  rocks  to  be  met  with  in 
the  mountainous  districts  towards  the  west.  Over  the  magnesian  lime- 
stone, however,  in  -the  south-eastern  division  of  the  county,  towards  the 
foot  of  the  south-eastern  slope  of  the  magnesian  lime-stone  hills,  the  gra- 
vels which  exhibit  in  some  places  (Wynyard)  an  irregular  stratification, 
contain  many  rounded  masses  of  magnesian  lime-stone,  and  even  of 
new-red  sand-stone — the  evident  debris  of  adjacent  rodis  long'ago  bro- 
ken up. 

3°.  Tlie  undermost  layer  which  rests  immediately  upon  the  subjacer 
rocks  consists  of  a  stiff  unstratified  blue  clay  often  full  of  trap  boulders 
but  containing  also  occasional  large  rounded  masses  of  blue  lime-stone 
— and  smaller  pebbles  of  quartz,  of  granite,  and  of  the  older  slate  rocks. 
In  many  localities  this  clay  is  wanting,  and  the  sands  or  gravels  rest  im- 
mediately upon  the  carboniferous  or  magnesian  lime-stone  rocks — while 
m  some  tracts,  both  this  and  the  upper  clay  appear  to  degenerate  into  a 
stony  most  unmanageable  clayey  gravel.  I  am  not  aware  that  the 
large  whin  (trap)  boulders  are  ever  met  with  in  the  beds  of  sand. 

The  following  diagram  exhibits  the  mode  in  which  these  drifted  mate- 
rials present  themselves  in  the  neighbourhood  of  the  city  of  Durham. 
The  cross  (I)  indicates  very  nearly  the  site  of  Durham  on  the  banks  of 
the  river  Wear. 


No.  1  represents  the  coal  measures. 

2.  The  lower  new-red  sand-stone,  here  soft  and  pale  yellow. 

3.  The  magnesian  lime-stone  rising  into  a  high  escarpment  from  3  to 
6  miles  south  of  the  city. 

4.  Yellow  loose  sand — with  rolled  sand-stones  and  coal-drift — occa- 
sionally stratified.  It  forms  the  numerous  picturesque  round  hills  in  the 
neighbourhood  of  the  city,  and  varies  from  a  few  feet  to  not  less  than  120 
feet  in  thickness. 

5  is  the  upper  clay,  with  boulders.  N  indicates  Framwellgate 
Moor,  where  it  is  only  a  few  feet  thick.  At  S,  on  the  southern  slope  of 
the  escarpment,  it  some'imes  rests  immediately  on  the  rock  as  here  re- 


272 


THE  SOILS  OFTEN  CHANGE  FROM  SAND  TO  CLAT. 


presented — in  which  case  it  is  difficult  to  decide  whether  it  should  be  con- 
sidered as  the  under  or  tlie  upper  clay — though  in  other  spots  both  sand 
and  clay,  or  gravel  and  clay,  present  themselves. 

It  will  at  once  occur  to  you  from  the  inspection  of  this  diagram,  that 
the  general  character  of  the  soil  in  the  county  of  Durham,  whenever 
such  accumulations  of  drifted  matter  occur,  is  not  to  be  judged  from  the 
nature  of  the  rocks  on  which  they  are  known  to  rest. 

Another  fact,  not  unworthy  of  your  attention,  is  the  rapid  alternations 
of  light  and  heavy  soil,  of  sands  or  gravels  and  clays,  which  present 
themselves  in  the  same  district,  I  may  say  in  the  same  farm,  and  often 
in  the  same  field.  This  arises  from  the  irregular  thickness  of  the  de- 
posit of  sand  or  gravel  over  which  the  upper  clay  rests.  The  surface 
of  this  sand  is  undulating,  as  if  it  had  formed  a  country  of  round  hills 
before  the  clay  was  deposited  upon  it.  This  appears  in  the  following 
diagram,  which  represents  the  way  in  which  the  several  layers  are  seen 
to  occur  in  the  Crindon  cut  on  the  Hartlepool  railway : — 


Here  1  is  the  magnesian  lime-stone,  not  visible ;  2,  the  under  clay, 
with  boulders ;  3,  the  sand  rising  in  round  hills,  and  here  and  there 
piercing  to  the  surface  ;  and  4,  the  upper  boulder  clay. 

In  the  county  of  Durham  it  is  a  very  usual  expression  that  the  tops 
of  the  hills  are  light  turnip  soil — but  that  they  fall  off  to  clay.  Both  the 
meaning  and  the  cause  of  this  are  explained  by  the  above  diagram. 

Nor  is  this  mode  of  occurrence  rare  among  the  alternate  sands  and 
clays  of  which  the  superficial  accumulations  in  various  parts  of  the 
country  consist.  Nearly  the  same  circumstances  give  rise  to  the  rapid 
changes  so  frequently  observed  in  the  character  of  the  soil,  as  we  pass 
from  field  to  field,  not  in  this  county  only,  but  i/i  various  other  parts  ot 
our  island. 

§  7.  How  far  these  accumulations  of  drift  interfere  ivith  the  geiieral 
deductions  of  Agriculcural  Geology. 

Thus  it  appears,  that  over  the  eastern  half  of  the  county  of  Dur- 
ham, and  over  large  portions  of  other  counties,  the  soils  are  found  to 
rest  upon  and  to  ilerive  their  character  from  accumulations  of  drifted 
materials  more  os  lese  different  in  their  nature  from  the  rocks  that  lie 
beneath. 

But  in  the  precedkig  lecture  I  have  endeavoured  to  show  you  that 
soils  are  derived  from  the  rocks  on  which  they  rest,  and  to  impress  upon 
you  the  close  general  relation  which  exists  between  the  kind  of  rocks  of 
which  a  country  is  composed,  and  the  kind  of  soils  by  which  its  surface 
is  overspread. 

How  are  these  apparent  contradictions  to  be  reconciled  ?    How  is  any 


•  DRIFT    MIXED    UP    WITH    THE    DETRITUS    OF    THE    SPOT.  273 

degree  of  order  to  be  evolved  out  of  this  apparent  confusion  ?  Are  the 
general  indications  of  agricultural  geology  (Lecture  xi.,  §8,  )  still,  in  any 
degree,  to  be  relied  upon  ? 

They  are,  and  for  the  following,  among  other  reasons  : 

1°.  It  is  stWl  generally  true  that  where  a  considerable  extent  of  coun- 
try rests  upon  any  known  rock,  th6  soil  in  that  district  derives  its  usual 
character  from  the  nature  of  that  rock.  Thus  though  large  portions  of 
Cheshire  and  Lancashire  are  covered  with  drift,  yet  the  soil  of  these 
counties,  taken  as  a  whole,  has  the  general  characters  of  the  soils  of 
ihe  new-red  sand-stone,  which  in  that  part  of  England  is  so  largely  de- 
veloped. 

2°.  Where  the  drift  overspreads  any  large  area,  it  is  found  to  become 
gradually  mixed  up  with  the  fragments,  large  and  small,  of  the  rocks 
upon  which  it  reposes.  Thus  in  the  neighbourhood  of  Durham,  the 
round  hills  of  sand  and  gravel  with  intermingled  coal  consist  in  great 
part  of  the  ruins  of  the  sand-stones  of  the  country  itself — while  the 
clays,  no  doubt,  are  partly  derived  from  the  shale  beds  which  occur  in- 
termingled with  the  sand-stones  of  tl^  same  coal  measures.  Hence  the 
soils  of  the  northern  half  of  this  county,  in  general,  still  partake  of  the 
usual  qualities  of  those  of  the  coal  measures  and  mill-stone  grit  (pp. 
249  and  250).  In  the  western  and  higher  part  of  the  district  they  lie 
more  immediately  on  the  rocks  from  which  they  have  been  derived, 
while  on  the  eastern  half  they  rest  on  a  mixture  of  the  accumulated 
ruins  of  the  same  rocks,  which  have  been  transported  by  natural  agents 
to  a  greater  or  less  distance  from  their  natural  site. 

It  is  true  that  there  are  mixed  up  with  these  many  portions  of  other 
rocks  brought  from  a  still  greater  distance,  but  these  bear  but  a  small 
proportion  to  the  entire  mass,  and  hence  have,  generally  speaking,  but 
little  influence  in  altering  the  mineral  character  of  the  whole. 

3°.  It  may  indeed  be  staled  as  generally  true,  that  the  greater  propor- 
tion of  the  transported  materials  which  lie  upon  any  spot  has  been 
brought  only  a  comparatively  small  distance.  Thus  the  sands  and  gra- 
vels in  the  county  of  Durham — to  the  west  of  the  magnesian  lime- 
stone— consist  chiefly  of  the  fragments  of  the  coal  measures.  East  and 
south  of  the  magnesian  lime-stone  escarpment  (diagram,  p.  271),  they 
become  mixed  with  rounded  masses  of  this  lime-stone.  On  the  new- 
red  sand -stone  of  the  south-east  of  the  county,  they  consist  chiefly  of 
magnesian  lime-stone  mixed  with  fragments  of  the  red  sand-stone— 
and  on  crossing  the  Tees,  the  debris  of  the  lias  hills  begins  to  appear 
among  them. 

In  countries,  therefore,  where  drifted  sands  and  gravels  prevail  on  the 
surface,  they  generally  consist  of  the  fragments  of  rocks  which  lie  at  no 
great  distance — generally  towards  the  higher  ground — the  natural  ten- 
dency being  for  the  debris  of  one  kind  of  rock,  or  of  one  formation,  to 
overlap  to  a  greater  or  less  extent  the  surface  of  the  adjoining  rock  or 
formation.  By  this  overlapping,  the  geographical  position  of  a  given 
soil  is  removed  to  a  greater  or  less  distance  beyond  the  line  indicated  by 
'the  geological  position  of  the  rocks  from  which  it  is  derived.  Thus,  a 
coal  measure  soil  may  overspread  part  of  the  rhagnesian  lime-stone — 
a  red  sand-stone  soil  may  partially  cover  tiie  lias,  and  so  on — the  general 

12* 


274  GENERAL  DEDUCTIONS   OF  GEOJ.OGY  STILL  TRUE. 

characters  and  distinctions  of  the  soil  peculiar  to  each  rock  being  stil 
preserved  beyond  the  spaces  upon  which  they  have  been  accidentally 
intermingled. 

4°.  To  this,  and  to  each  of  the  other  statements  above  njade,  there  are 
many  local  exceptions.  For  instance,  what  is  true  of  sands  and  gravels, 
will  not  so  well  apply  to  the  fine  mud  of  which  many  clays  are  formed. 
Once  commit  these  to  the  water,  and  if  it  has  any  motion,  they  may  be 
transported  to  very  great  distances  from  their  orii^inal  site.  Rivers, 
lakes,  and  seas,  are  the  agents  by  which  these  extensive  ditfusions  are 
effected.  The  former  produce  what  are  called  alluvial  formations  or  de- 
j)osits ;  which  are  generally  rich  in  all  the  inorganic  substances  that 
plants  require,  and  hence  yield  rich  returns  to  the  agricultural  labourer. 
They  are  usually,  however,  distinguished,  and  their  boundaries  marked, 
by  the  geologist — so  that  the  soils  which  repose  upon  them  do  not  con- 
tradict any  of  the  general  deductions  he  is  prepared  to  draw,  in  regard  to 
the  general  agricultural  capabilities  of  a  country,  from  the  kind  of  rocks 
of  which  it  consists. 

Thus  though  the  occurrence  of^xtensive  fields  of  drift  over  various 
parts  of  almost  every  country,  does  throw  some  further  diflSculty  over 
the  researches  of  the  agricultural  geologist,  and  requires  from  him  the 
application  of  greater  skill  and  caution  before  he  pronounce  with  cer- 
tainty in  regard  to  the  agricultural  capabilties  of  any  spot  before  he  visit 
it— yet  it  neither  contradicts  the  general  deductions  of  the  geologist  nor 
the  special  conclusions  he  would  be  entitled  to  draw  in  regard  to  the 
ability  of  any  country,  when  rightly  cultivated,  to  maintain  in  comfort 
a  more  or  less  numerous  population.  The  political  economist  may  still, 
by  a  survey  of  the  geological  map  of  a  country,  pronounce  with  some 
confidence  to  what  degree  the  agricultural  riches  of  that  country  might 
by  industry  and  skill  be  brought — and  which  districts  of  an  entire  conti- 
nent are  fitted  by  nature  to  maintain  the  most  abundant  population. 
The  intending  emigrant  may  still,  by  the  same  means,  say  in  what  new 
land  he  is  most  likely  to  find  a  propitious  soil  on  which  to  expend  his 
labour — or  such  jnineral  resources  as  will  best  aid  his  agricultural  pur- 
suits ; — while  a  careful  study  of  the  geological  map  of  his  own  cotmtry 
will  still  enable  the  skilful  and  adventurous  /armer  to  determine  in  what 
counties  he  will  meet  with  soils  that  are  suited  to  that  kind  of  practice 
with  which  he  is  most  familiar— or  which  are  likely  best  to  reward 
him  for  the  application  of  the  newest  and  most  approved  methods  of 
culture. 

Still  there  are  some  aids  to  this  kind  of  knowledge  yet  wanting.  We 
have  geological  maps  of  all  our  counties,  in  which  the  boundaries  of  the 
several  rocky  formations  are  more  or  less  accurately  pointed  out,  and 
from  these  maps,  as  we  have  seen,  much  valuable  agricultural  informa- 
tion may  be  fairly  deduced.  "We  have  also  agricultural  maps  of  many 
counties,  compiled  with  less  care,  and  often  with  the  aid  of  little  geolo- 
gical kpDwledge,  as  that  of  Durham  in  Bailey's  '  View  of  the  Agricul- 
ture of  ;he  County  of  Durham,'  published  in  1810.  But  agriculture 
now  requires  geological  maps  of  her  own — which  shall  exhibit  not  only 
the  limits  of  rocky  formations,  but  also  the  nature  and  relative  extent 
of  the  superficial  deposits  (drifts),  on  which  the  soils  so  often  rest,  and 
from  which  they  are  not  unfrequently  formed.     These  would  atTord  a 


AGRICUIiTURAL    MAPS — ACCUMULATIONS    OF    PEAT.  275 

sure  basis  on  which  to  rest  our  opinions  in  regard  to  the  agricultural  ca- 
pabilities of  the  several  parts  of  a  county  in  which,  though  the  rocks  are 
the  same,  the  soils  may^be  very  diflferent.  To  the  study  of  these  drifted 
materials,  in  connection  with  the  action  of  ancient  glaciers  (p.  269),  the 
attention  of  geologists  is  at  present  much  directed,  and  from  their  labours 
agriculture  will  not  fail  to  reap  her  share  of  practical  benefit — the  geolo- 
gical survey,  also,  so  ably  superintended  by  Mr.  De  La  Beche,  is  col- 
lecting and  recording  much  valuable  information  in  regard  to  the  agri- 
cultural geology  of  the  southern  counties — but  it  is  not  unworthy  the  con- 
sideration of  our  leading  agricultural  societies. — whether  some  portion  of 
their  encouragement  might  not  be  beneficially  directed  to  the  preparation 
of  agricultural  maps,  which  should  represent,  by  different  colours,  the  agri- 
cultural capabilities  of  the  several  parts  of  each  county,  based  upon  a 
knowledge  of  the  soils  and  sub-soils  of  each  parish  or  township,  and  of 
the  rocks,  whether  near  or  remote,  from  which  they  have  been  severally 
derived. 

Before  leaving  this  subject,  I  will  call  your  attention  to  one  practi- 
cal application  of  this  knowledge  of  the  extensive  prevalence  of  drifts, 
which  is  not  without  its  value.  Being  acquainted  with  the  nature  of  the 
rocks  in  a  country,  and  with  its  physical  geography — that  is,  which  of 
these  rocks  form  the  hills,  and  which  the  valleys  or  plains — we  can  pre- 
dict, in  general,  that  the  materials  of  the  hills  will  be  strewed  to  a  greater 
or  less  distance  over  the  lower  grounds,  and  that  these  lower  soils  will 
thus  be  more  or  less  altered  in  their  mineral  character.  And  when  the 
debris  of  the  hills  is  of  a  more  fertile  character  than  that  of  the  rocks 
which  form  the  plains,  that  the  soils  will  be  materially  improved  by  this 
covering  : — the  soil  of  the  mill-stone  grit,  for  example,  by  the  debris  of 
the  mountain  lime-stone,  or  of  a  decayed  green-stone  or  a  basalt.  On 
the  other  hand,  where  the  higher  rocks  are  more  unfruitful,  and  the  low 
lands  are  covered  with  sterile  drifted  sands  brought  down  from  the  more 
elevated  grounds — a  knowledge  of  the  nature  of  the  subjacent  rock  may 
at  once  suggest  the  means  of  ameliorating  and  improving  the  unpromis- 
ing surface-drift.  Thus  the  loose  sand  of  Norfolk  is  fertilized  by  the 
subjacent  chalk  marl;  and  even  sterile  heaths  (Hounslow),  on  which 
nothing  grew  before,  have,  by  this  means,  been  made  to  produce  luxu- 
riant crops  of  every  kind  of  grain. 

§  6,  Of  superficial  accumulations  of  Peat. 

Of  superficial  accumulations,  that  of  peat  is  one  which,  in  the  United 
Kingdom,  covers  a  very  large  area.  In  Ireland  alone,  the  extent  of  bog 
is  estimated  at  2,800,000  acres.  None  of  the  drifted  materials  we  have  con- 
sidered, therefore,  would  appear  so  likely  to  falsify  the  predictions  of  the 
geologist,  who  should  judge  of  the  soils  of  such  a  country  from  informa- 
tion in  regard  to  the  rocks  alone  on  which  they  rest — from  a  geological 
map  for  example — as  the  occurrence  of  these  peat  bogs.  Yet  there  are 
certain  facts  connected  with  the  formation  of  peat,  which  place  him  in 
some  measure  on  his  guard  in  reference  even  to  accumulations  of  vege- 
table matter  such  as  these. 

1°.  There  is  a  certain  range  of  temperature  within  which  alone  peal 
seems  capable  of  being  produced.  Thus,  at  the  level  of  the  sea,  it  is 
wove.r  f()und  nearer  the  equator  then  between  the  40°  and  45°  of  latitude; 


276  WHERE    PEAT    IS    TO    BE    EXPECTED. 

while  its  limit  towards  the  poles  appears  to  be  within  the  60th  degree. 
It  is  a  product,  therefore,  chiefly  of  the  temperate  regions. 

Still,  on  the  equator  itself,  at  a  sufficient  altitude  above  the  sea,  the 
temperature  may  be  cool  enough  to  pennit  the  growth  of  peat.  Hence, 
though  on  the  plains  of  Italy  no  peat  is  formed,  yet,  on  the  higher  Ap- 
penines,  it  maybe  here  and  there  met  with,  among  the  marshy  basins, 
and  on  the  undrained  mountain  sides. 

2°.  The  occurrence  of  stagnant  water  is  necessary  for  the  production 
of  peat.  Hence,  on  impervious  beds  of  clay,  through  which  the  rains 
and  springs  can  find  no  outlet,  the  formation  of  peat  may  be  expected. 
Thus  on  the  Oxford  clay  repose  the  fens  of  Lincoln,  Cambridge  and 
Huntingdon  (p.  245).  On  impervious  rocks  also,  peat  bogs  form  for  a 
similar  reason.  The  new-red  sand-stone  is  occasionally  thus  impervi- 
ous, and  on  it,  among  other  examples,  repose  the  Chat  moss,  the  tract  of 
peat,  mostly  in  cultivation,  which  lies  west  of  a  line  drawn  between 
Liverpool  and  Preston,  and  the  large  extent  of  boggy  country  which 
stretches  round  the  head  of  the  Solway  Firth.  On  the  old  red  sand- 
stone, the  mountain  lime-stone,  the  slate,  and  the  granite  rocks,  much 
peat  occurs,  and  it  is  on  these  latter  formations  that  the  extensive  bogs  of 
Scotland  and  Ireland  chiefly  rest. 

But  though  these  two  facts  are  of  some  value  to  the  politician  and  to 
the  geologist  in  indicating  in  what  countries  and  on  what  formations  peat 
may  be  expected  to  occur,  yet  they  are  of  comparatively  little  impor- 
tance to  the  practical  agriculturist.  It  is  of  far  more  consequence  to 
him  that  the  moment  he  casts  his  eye  upon  the  face  of  a  country  he  can 
detect  the  presence  or  absence  of  peat — that  none  of  the  perplexities 
which  beset  the  nature  and  origin  of  other  superficial  accumulations  at- 
tach to  this — that  he  can,  at  once,  judge  both  of  its  source  and  of  its  agri- 
cultural capabilities.  Though  produced  on  a  given  spot,  because  rocks 
of  a  certain  character  exist  there,  yet  its  origin  is  always  the  same — its 
qualities  more  or  less  uniform, — the  improvement  of  which  is  susceptible 
in  some  measure  alike, — and  the  steps  by  which  that  improvement  is  to 
be  effected,  liable  to  variation,  chiefly  according  as  this  or  that  amelio- 
rating substance  can  be  most  readily  obtained. 


LECTURE  XIII. 

Exact  chemical  constitution  of  soils — their  oi^anic  constituents — Analysis  of  soils — Compo* 
sitiou  of  certain  characteristic  soils— Physical  characters  of  soils. 

In  the  two  preceding  lectures  we  have  considered  the  general  consti- 
tuiiuv.  and  origin  of  soils,  and  their  relation  to  the  geological  structure  of 
tiis  country  in  which  they  are  found,  and  to  the  chemical  composition  of 
the  rocks  on  which  they  rest. .  We  have  also  discussed  some  of  the 
causes  of  those  remarkable  differences  which  soils  are  known  to  present 
in  their  relations  to  practical  agriculture.  But  a  more  intimate  and  pre- 
cise acquaintance  with  the  chemical  constitution  of  soils  is  not  unfre- 
quently  necessary  to  a  complete  understanding  of  the  causes  of  these  dif- 
ferences— of  the  exact  effect  which  its  chemical  constitution  has  upon  the 
fertility  of  a  soil — and  of  the  remedy  which  in  any  given  circumstances 
ought  to  be  applied. 

Some  persons  have  been  led  to  expect  too  much  from  the  chemical 
analysis  of  a  soil,  as  if  this  alone  were  necessary  at  once  to  explain  all  its 
qualities,  and  to  indicate  a  ready  method  of  imparting  to  it  every  desir- 
able quality, — while  others  have  as  far  depreciated  their  worth,  and  have 
pronounced  them  in  all  cases  to  be  more  curious  than  useful. — [Boussin- 
gault,  '  Annal.  de  Chim.  et  de  Phys.'  Ixvii.,  p.  9.]  The  truth  here,  as 
on  most  other  subjects,  lies  mthe  middle  between  these  extreme  opinions. 

If  you  have  followed  me  in  the  views  I  have  endeavoured  to  press  upon 
you  in  regard  to  the  necessity  of  inorganic  food  to  plants — which  food 
can  only  be  derived  from  the  soil,  and  which  must  vary  in  kind  and 
quantity  with  the  species  of  crop  to  be  raised, — you  will  at  once  perceive 
that  the  rigorous  analysis  of  a  soil  may  impart  most  valuable  knowledge 
to  the  practical  man  in  the  form  of  useful  suggestions  for  its  improvement. 
It  may  indeed  show  that  to  apply  the  only  available  substances  to  the 
soil  which  are  capable  of  remedying  its  defects,  would  involve  an  expense 
for  Avhich,  in  existing  circumstances,  the  land  could  never  give  an  equiva- 
lent return.  Yet  even  in  this  latter  case  the  results  of  analysis  will  not  be 
withoift  their  value  to  the  prudent  man,  since  they  will  deter  him  from 
addiiig  to  his  soil  what  he  knows  it  already  to  contain,  and  will  set  him 
upon  the  search  after  some  more  economical  source  of  those  ingredients 
which  are  likely  to  benefit  it  most. 

It  will  be  proper,  therefore,  to  turn  our  attention  briefly  to  the  conside- 
ration of  the  exact  chemical  constitution  of  soils. 

§  1.  Of  the  exact  nature  of  the  organic  constituents  of  soils,  and  of  the 
mode  of  separating  them. 
We  have  already  seen  in  Lecture  XL,  p.  229,  that  all  soils  contain  a 
greater  or  less  admixture  of  organic — chiefly  vegetable — matter,  the 
total  amount  of  which  may  be  very  nearly  determined  by  burning  the 
dried  soil  at  a  red  heat  till  all  blackness  disappears  (p.  233).  But  this 
vegetable  matter  consists  of  several  different  chemical  compounds,  the 
nature  and  rela<ive  weights  of  which  it  is  occasionally  of  consequence  to 
be  able  to  determine. 


278  NATURE  OF  THE  ORGANIC  CONSTITUENTS  OF  SOILS. 

1°.  Humus. — The  general  name  of  humus  is  given  to  the  fine,  brown 
light  powder  which  imparts  their  richness  to  vegetable  moulds  and  gar- 
den soils.  It  is  formed  from  the  gradual  decomposition  of  vegetable 
matter,  exists  in  all  soils,  forms  the  substance  of  peat,  and  consists  of  a 
mixture  of  several  different  compounds  which  are  naturally  produced 
during  the  decay  of  the  different  parts  of  plants.  It  is  distinguished  into 
mildy  sour,  and  coaly  humus. 

The  mild  gives  a  brown  colour  to  water,  but  does  not  render  it  sour, 
gives  a  dark  brown  solution  when  boiled  with  carbonate  of  soda,  evolves 
ammonia  when  heated  with  caustic  potash  or  soda  or  with  slaked  lime, 
and  leaves  an  ash  when  burned  which  contains  lime  and  magnesia. 
The  sour  gives,  with  water,  a  brown  solution  of  a  more  or  less  sour 
taste,  [or  reddens  vegetable  blues — see  page  45.]  This  variety  is 
less  favourable  to  vegetation  than  the  former,  and  indicates  a  want  of 
lime  in  the  soil.  The  coaly  humus  gives  little  colour  to  water  or  to  a 
hot  solution  of  carbonate  of  soda,  leaves  an  ash  which  contains  little 
lime,  occurs  generally  on  the  surface  of  very  sandy  soils,  and  is  very  un- 
fruitful. It  is  greatly  ameliorated  by  the  addition  of  lime  or  wood 
ashes. 

2°.  Humic  acid. — When  a  fertile  soil  or  a  piece  of  dry  peat  is  boiled 
with  a  solution  of  the  common  carbonate  of  soda  of  the  shops,  a  brown 
solution,  more^  or  less  dark,  is  obtained,  from  which,  when  diluted  muri- 
atic acid  (spirits  of  salt)  is  added  till  the  liquid  has  a  distinctly  sour 
taste,  brown  flocks  begin  to  fall.     This  brown  flocky  matter  is  humic  acid. 

3°.  Ulmic  acid. — If,  instead  of  a  solution  of  carbonate  of  soda,  one 
of  caustic  ammonia,  (the  hartshorn  of  the  shops,)  be  digested  upon  the  soil 
or  peat  by  a  gentle  heat,  a  more  or  less  dark  brown  solution  is  obtained, 
which,  on  the  addition  of  muriatic  acid,  gives  brown  flocks  as  before, 
but  which  now  consists  of  ulmic  acid. 

These  two  acids  combine  with  lime,  magnesia,  alumina,  and  oxide  of 
iron,  forming  compounds  (salts)  which  are  respectively  distinguished  by 
the  names  of  humates-ax\d  ulmales.  They  probably  both  exist,  ready 
formed,  in  the  soil  in  variable  proportions,  and  in  combination  with  one 
or  more  of  the  earthy  substances  above  mentioned — lime,  alumina,  &c. 
They  are  produced  by  the  decay  of  vegetable  matter  in  the  soil,  which 
decay  is  materially  facilitated  by  the  presence  of  one  or  other  of  these 
substances,  and  by  lime  especially — on  the  principle  that  the  formation 
of  acid  compounds  is  in  all  such  cases  much  promoted  by  the  presence 
of  a  substance  with  which  that  acid  may  combine.  They  2^'''edispose 
organic  substances  to  the  formation  of  such  acids,  and  consequently  to 
the  decomposition  by  which  they  are  to  be  produced.  These  two  acids 
consist  respectively  of 

Humic  acid,  Ulmic  acid. 

Carbon 63  67 

Hydrogen.     ...  .     .       6  4? 

Oxygen 31  38^ 

100  100 

Some  writers  upon  agriculture  have  supposed  that  these  acids  con- 
tribute very  materially  to  the  support  of  growing  plants.     But  Liebig 


CRENIC  AND  APOCRENIC  ACIDS.  279 

has  very  properly  objected  to  this  opinion,*  that  they  are  so  very  sparingly 
soluble  in  water  that  we  cannot  suppose  them  to  enter  directly  into  the 
roots — even  were  all  the  water  they  absorb  to  be  saturated  with  them — 
in  such  quantity  as  to  contribute  in  a  great  degree  to  the  organic  matter 
contained  in  almost  any  crop.f 

We  have  indeed  seen  reason  to  conclude  on  other  grounds,  that  only  a 
small,  though  a  variable,  proportion  of  the  carbon  of  plants  is  derived 
from  the  soil,  yet  of  this  proportion  a  certain  quantity  may  enter  by  the 
roots  in  the  form  of  one  or  other  of  these  acids,  or  of  their  earthy  com- 
pounds. They  are  readily  soluble  in  ammonia ;  and  animal  manures 
which  give  off  this  compound  in  the  soil  may  therefore  facilitate  their 
entrance  into  the  roots  of  those  plants  which  are  cultivated  by  the  aid  of 
such  manures.  They  are  also  soluble  in  carbonate  of  potash  and  car- 
bonate of  soda,  which  are  contained  in  wood  ashes  and  in  the  ash  of 
weeds  and  of  soils  which  are  pared  and  burned.  When  these  substan- 
ces, therefore,  are  applied  to  the  land,  they  may  combine  with,  and, 
among  their  other  beneficial  modes  of  action,  may  serve  to  introduce, 
these  acids  in  larger  quantity  into  the  plant. 

When  exposed  to  the  air,  the  humates  and  ulmates  contained  in  the 
soil  undergo  decomposition,  give  off  carbonic  acid,  and  are  changed  into 
carbonates.  The  admission  of  air  into  the  soil  facilitates  this  decompo- 
sition, which  is  supposed  to  be  continually  going  forward — and  it  is  in  the 
form  of  this  gas  that  plants  are  considered  by  some  to  imbibe  the  largest 
portion  of  that  carbon  for  which  they  are  indebted  to  the  soil. 

4°.  Crenic  and  Aprocrenic  acids. — When  soils  are  digested  or  washed 
with  hot  water,  a  quantity  of  organic  matter  is  not  unfrequently  dissolved, 
which  imparts  to  the  water  a  brownish  yellow  colour.  When  the  solu- 
tion is  evaporated  to  dryness,  there  remains  besides  the  soluble  saline 
substances  of  the  soil,  a  variable  portion  of  brown  extractive  looking 
matter  also,  which  is  a  mixture  of  the  two  acids  here  named,  with  the 
ulmic  and  humic — all  in  combination  with  lime,  alumina,  and  other  bases. 
When  this  residue  is  dried  at  230°  F.,  the  two  latter  acids,  and  their 
compounds,  become  insoluble,  while  the  crenates  and  apocrenates,  more 
esjjecially  the  former,  remain  soluble  in  water,  and  may  be  separated 
by  washing  with  this  liquid. 

These  acids  also  are  formed  in  the  soil  during  the  decay  of  vegetable 
matter.  They  are  distinguished  from  the  two  previously  described  by 
containing  nitrogen  as  an  essential  constituent,  and  by  forming  compounds 
with  lime,  &:c.,  which  are,  for  the  most  part,  readily  soluble  in  water. 
Hence  th^  will  both  prove  more  nourishing  to  plants — in  virtue  of  the 
nitrogen  they  contain — and  in  consequence  of  their  solubility,  will  be  able, 
where  they  exist,  to  enter  more  readily,  and  in  greater  abundance,  into 
the  roots  than  either  the  ulmic  or  the  humic  acid. 

Owing  to  this  solubility,  also,  they  are  more  readily  washed  out  of  the 
soil  by  the  rains,  and  hence  are  rarely  present  in  any  considerable  quan- 

•  Organic  Chemistry  applied  lo  Agriculture,  first  edition,  pp.  11  and  12. 

t  Ulmic  acid  requires  2500  times  its  weiglit  of  water  to  dissolve  it— ulmate  of  lime  2000 
times,  and  ulmate  of  alumina  4200  times — but  all  are  still  less  soluble  after  they  have  been 
perfectly  dried,  or  exposed  to  the  action  of  a  hard  winter's  frost.  The  ulmates  of  potash, 
■oda,  and  alumina,  are  all  dissolved  in  water  with  considerable  ease. 


280  OTHER   ORGANIC    COMPOUNDS    IN    THE   SOIL. 

tity  in  specimens  of  soil  which  are  submitted  to  analysis.  They  are  fre- 
quently, however,  met  with  in  springs  and  in  the  drainings  of  the  land. 
They  have  even  been  found  in  minute  quantity  in  rain-water,*  it  is  prO" 
bable  that  they  ascend  into  the  air  in  very  small  proportion  with  the 
watery  vapour  that  rises.  This  exhibits  another  form,  therefore,  in 
which  the  rains  may  minister  to  the  growth  of  plants  (see  page  36). 

Both  acids  form  insoluble  compounds  with  the  peroxide  of  iron — and 
hence  are  found  in  combination  with  many  of  the  ochrey  deposits  from 
ferruginous  springs,  and  with  the  oxide  of  iron  by  which  so  many  soils 
are  coloured.  The  apocrenic  acid  has  also  a  peculiar  tendency  to  com- 
bine with  alumina,  with  which  it  forms  a  compound  insoluble  in  water, 
and  in  this  state  of  combination  it  probably  exists  not  unfrequently,  espe- 
cially in  clayey  soils. 

When  heated  with  newly  slaked  quick-lime  these  acids  give  off  am- 
monia and  carbonic  acid.  By  the  action  of  the  air,  and  of  lime  in  the 
soil,  they  are  probably  decomposed  in  a  similar  manner,  though  with 
much  less  rapidity. 

5°.  Mudesous  acid  is  another  dark  brown  acid  substance,  which  is  also 
produced  naturally  in  the  soil.  It  resembles  the  apocrenic,  in  having 
a  strong  tendency  to  combine  with  alumina.  In  union  with  this  acid  it 
is  slowly  washed  out  of  the  soil  by  the  rains,  or  filters  through  it  when 
the  water  can  find  an  outlet  beneath.  This  is  seen  to  be  the  case  in  some 
of  the  caves  on  the  Cornish  coast,  where  the  waters  that  trickle  through 
from  above  have  gradually  deposited  on  their  roof  and  sides  a  thick  in- 
crustation of  mudesile  of  alumina.f 

Besides  these  acids,  it  is  known  that  the  malic  and  the  acetic  (vine- 
gar) are  occasionally  produced  in  the  soil  during  the  slow  decay  of  vege- 
table matter  of  different  kinds.  It  is  probable  that  many  other  analo- 
gous compounds  are  likewise  formed — which  are  more  or  less  soluble  in 
water,  and  more  or  less  fitted  to  aid  in  the  nourishment  of  plants.  There 
is  every  reason  to  believe,  indeed,  that  organic  substances  in  the  soil  pass 
through  many  successive  stages  of  decomposition,  at  each  of  which  they 
assume  new  properties,  and  become  more  or  less  capable  of  aiding  in 
the  support  of  living  races.  The  subject  is  difficult  to  investigate,  be- 
cause of  the  obstacles  which  lie  in  the  way  of  exactly  separating  frorri 
each  other  the  small  quantities  of  the  different  organic  compounds  that 
occur  mixed  up  together  in  the  soil.  But  it  seems  quite  clear,  that  while 
some  agricultural  chemists  have  erred  in  describing  the  ulmic  and  hu- 
mic  acids  as  the  immediate  source  of  a  large  portion  of  the  carbon  of 
plants,  others  have  no  less  misstated — as  I  apprehend — the  true  course 
of  nature,  who  deny  any  direct  influence  to  these  and  other  substances 
of  vegetable  origin,  and  limit  their  use  in  the  soil  to  the  supply  of  car- 
bonic acid  only,  which,  on  their  ultimate  decomposition,  they  are  capa- 
ble of  yielding  to  the  roots.  The  resources  of  vegetable  life  are  not  so 
limited ;  but  as  the  human  stomach  can,  and  does,  on  occasion,  convert 
into  nourishment  many  different  compounds  of  the  same  elements, — so, 
no  doubt,  many  of  those  organic  compounds  wH!ch  are  produced  in  the 
soil,  or  in  fermenting  manure  during  the  decay  of  animal  and  vegetable 

*  Fursten  zu  Salm-Horstmar.    Poggend.  Annal.  liv.,  p.  254. 
t  Known  to  mineralogists  under  the  name  of  Pifotite. 


SEPARATION  OF  THESE  ORGANIC  SUBSTANCES.  281 

bodies, — when  once  admitted,  in  consequence  of  their  solubility,  into  the 
circulating  system  of  plants, — are  converted  into  portions  of  their  sub- 
stance, and  really  do  minister  to  their  natural  growth. 

Separation  of  these  Organic  Constituents. — 1°.  When  on  washing 
with  hot  water  a  soil  imparts  a  colour  to  the  solution,  the  liquid  must  be 
filtered  and  evaporated,  to  perfect  dryness.  On  treating  with  water 
what  remains  after  the  evaporation,  the  humic  acid  and  humates  remain 
insoluble,  while  the  crenic  and  apocrenic  acids  are  taken  up  by  the  wa- 
ter along  with  the  soluble  saline  matter  which  the  soil  may  have  con- 
tained. By  evaporating  this  second  solution  to  perfect  dryness,  weigh- 
ing the  residue,  and  then  heating  it  to  dull  redness  in  the  air,  the  loss 
will  indicate  something  more  than  the  quantity  of  these  acids  present  in 
the  soil.  By  burning  the  dried  insoluble  matter,  also,  the  quantity  of 
humic  acid  present  in  it  may  in  like  manner  be  determined. 

2°.  After  being  washed  with  pure  water,  the  soil  is  to  be  boiled  with 
a  solution  of  carbonate  of  soda,  repeated  once  or  twice  as  long  as  a  brown 
solution,  more  or  less  dark,  is  obtained.  Being  filtered,  and  then  ren- 
dered sour  by  muriatic  acid,  brov/n  flocks  fall,  which  being  collected  on 
the  filter,  perfectly  dried  and  weighed,  give  the  quantity  of  humic  acid 
in  the  soil.  As  this  dry  humic  acid  generally  contains  some  earthy 
matter,  it  is  more  correct  to  burn  it,  and  to  deduct  the  weight  of  the  ash 
which  may  be  left. 

3°.  The  insoluble  (coaly)  humus  still  remains  in  the  soil.  On  boiling 
it  now  in  a  solution  of  caustic  potash  for  a  length  of  time,  and  till  a  fresh^ 
solution  ceases  to  become  brown,  the  coaly  humus  is  entirely  dissolved — 
being  converted  according  to  Sprengel  into  humic  acid.  The  addition 
of  muriatic  acid  to  this  solution,  till  it  has  a  sour  taste,  throws  down  the 
humic  acid  in  the  form  of  brown  flocks,  which  may  be  collected,  dried, 
and  weighed  as  before. 

4°.  If  there  be  any  mudesite  of  alumina  in  the  soil,  it  is  also  dis- 
solved by  the  potash,  but  is  not  thrown  down  when  the  solution  is  ren- 
dered sour  by  muriatic  acid.  The  entire  w-eight  of  oi-ganic  matter  in  the 
soil  being  therefore  determined  by  burning  it  in  the  air,  after  being 
perfectly  dried,  the  difference  between  this  weight  and  the  sum  of  those 
of  the  humic  acid  and  insoluble  humus  will  be  the  proportion  of  the 
other  acids  present.  Thus,  if,  by  burning  in  the  air,  the  soil  lose  6  per 
cent.,  and  give  2  per  cent,  of  humic  acid,  and  2  of  insoluble  humus,  there 
remain  2  per  cent,  for  other  organic  substances  in  the  soil. 

In  general,  it  is  considered  sufficient  to  ascertain  only  the  whole  loss 
by  burning,  and  the  quantity  taken  up  by  carbonate  of  soda,  the  propor- 
tion of  the  other  substances  present  being  in  most  cases  so  small  as  to  be 
capable  of  being  precisely  estimated  by  great  precautions  only. 

§  2.  On  the  exact  chemical  constitution  of  the  earthy  part  of  the  soil. 

In  reference  to  the  general  origin  of  soils — to  their  geological  rela  - 
tions — and  to  the  simplest  mode  of  classifying  them, — I  have  shown  yoa 
that  the  earthy  part  of  nearly  all  soils  consists  essentially  of  sand,  clay, 
and  lime  (p.  230).  But  in  reference  to  their  chemical  relations  to  the 
plants  which  grow,  or  may  be  made  to  grow,  upon  them,  it  is  necessary, 
as  you  are  ^w  aware,  to  take  a  more  refined  and  exact  view  of  their 


282  WHY  REFINED  ANALYSES  ARE  NECESSARY. 

constitution.  This  will  appear  by  referring  to  three  important  princi- 
ples established  in  the  preceding  ".lectures. 

l"^.  That  the  ash  of  plants  generally  contains  a  certain  sensible  pro- 
portion of  ten  or  twelve  different  inorganic  substances  (pp.  216  to  221). 

2°.  That  they  can,  in  general,  only  derive  these  substances  from  the 
soil,  which  must,  therefore,  contain  them  (p.  181).     And — 

3°.  That  the  fertility  of  a  soil  depends,  among  other  circumstances, 
upon  its  ability  to  supply  readily  and  in  sufficient  abundance  all  the  in- 
organic substances  which  a  given  crop  requires  (p.  228.) 

Now  the  quantity  of  some  of  these  substances  which  is  necessary  to 
plants  is  so  very  small,  that  nothing  but  a  refined  analysis  of  a  soil  is 
capable,  in  many  cases,  of  determining  whether  they  are  present  in  it  or 
not — much  less  of  explaining  to  what  its  peculiar  defects  or  excellencies 
may  be  owing — what  ought  to  be  added  to  it  in  order  to  render  it  more 
productive — or  why  certain  remarkable  effects  are  produced  upon  it  by 
the  addition  of  mineral  or  animal  manures. 

Thus,  for  example,  half  a  grain  of  gypsum  in  a  pound  of  soil  indicates 
the  presence  of  nearly  two  cwt.  in  an  acre,  where  the  soil  is  a  foot  deep, — 
a  quantity  much  greater  than  need  be  added  to  a  soil  in  which  gypsum 
is  almost  entirely  wanting,  in  order  to  produce  a  remarkable  luxuriance 
in  the  red  clover  crop.  In  100  grains  of  the  soil,  this  quantity  of  gyp- 
sum amounts  only  to  seven-thousandths  of  a  grain-— {j^^^,  or  0-007 
trs.) — a  proportion  which  only  a  very  carefully  ..conducted  analysis 
ould  be  able  to  detect,  and  yet  the  detecting  of  which  may  alone  be  able 
to  explain  the  unlike  effects  which  are  seen  to  follow  the  application  of 
gypsum  to  different  soils. 

Again,  the  phosphoric  acid  is  a  no  less  necessary  constituent  of  the 
soil  than  the  sulphuric  acid  contained  in  gypsum.  This  acid  is  gener- 
ally in  combination  either  with  lime,  with  oxide  of  iron,  or  with  alu- 
mina— and,  as  it  is  much  more  difficult  even  to  detect  than  the  sulphuric 
acid,  requires  more  care  and  skill  to  determine  its  quantity  with  any 
degree  of  accuracy, — and  is  generally  present  even  in  fertile  soils  in  a 
still  smaller  proportion — it  is  obvious  that  safe  and  useful  conclusions  can 
be  drawn  only  from  such  analyses  as  have  been  made  rigorously,  accord- 
ing to  the  best  methods,  and  with  the  greatest  attention  to  accuracy. 

There  are  cases,  no  doubt,  where  a  rough  analysis  may  be  of  use, 
where  the  cause  of  peculiarity  is  at  once  so  obvious  that  further  research 
is  unnecessary — as  where  mere  washing  with  water  dissolves  out  a 
noxious  substance,  such  as  sulphate  of  iron  (green  vitriol).  But  such 
cases  are  comparatively  rare,  and  it  more  frequently  happens,  that  the 
cause  of  the  special  qualities  of  a  soil  only  begins  to  manifest  itself  when 
a  carefully  conducted  analysis  approaches  to  its  close.  I  shall,  therefore, 
briefly  describe  to  you  the  methods  to  be  adopted,  in  order  to-  arrive  at 
these  more  accurate  experimental  results.  [As  these  methods  of  analysis 
involve  considerable  detail,  I  have  transferred  them  to  the  Appendix.— 
See  Appendix,  p.  25.] 


EXACT    CONSTITUTION    OF    SOME    FERTILE    SOILS.  283 

§3.  Of  the  exact  chemical  constitution  of  certain  soils,  and  of  the  results 
to  be  deduced  from  them. 

But  the  importance  of  this  attention  to  rigorous  analysis  will  more 
clearly  appear,  if  I  exhibit  to  you  the  constitution  of  a  few  of  the  nume- 
rous soils  analyzed  by  Sprengel,  in  connection  with  the  agricultural  quali- 
ties and  capabilities  by  which  they  are  severally  distinguished. 

The  following  analyses  are  selected  from  a  much  greater  number  made 
by  Sprengel,  and  embodied  in  his  work  on  soils,  "  Die  Bodenkunde." 

I. — FERTILE    SOILS. 

Soils  are  fertile  which  contain  a  sutficient  supply  of  all  the  mineral 
constituents  which  the  plants  to  be  grown  upon  them  are  likely  to  re- 
quire. 

1°.  Pasture. — The  following  numbers  exhibit  the  constitution  of  the 
surface  soil  in  three  fertile  alluvial  districts  of  Hanover,  where  the  land 
has  been  long  in  pasture. 

Soil  near      From  the  banks  of  the  Weser 
Osterbruch.        near  Hoya.    near  Weserbe 

Silica,  Quartz,  Sand,  and  Silicates.  84-510  71-849  83-318 

Alumina 6-435  9-350  3-085 

Oxides  of  Iron 2-395  5-410  5-840 

Oxide  of  Manganese     ....       0-450  0-925  0-620 

Lime 0-740  0-987  0-720 

Magnesia 0-525  0-245  0-120 

Potash  and  Soda  extracted  by  water  T)-009  0-007  0-005 

.    Phosphoric  Acid 0-120  0-131  0-065 

Sulphuric  Acid        0-046  0-174  0-025 

Chlorine  in  common  Salt       .     .       0-006  0-002  *        0-006 

Humic  Acid 0-780  1-270  0-800 

Insoluble  Humus          ....       2-995  7-550  4-126 

Organic  matters  containing  Nitrogen  0-960  2*000  1-2-20 

Water. 0-029  0-100  0-050 


100  100  100 

These  soils  had  all  been  long  in  pasture,  the  second  is  especially  cele- 
brated for  fattening  cattle  -when  under  grass.  It  will  be  observed  that  in 
none  of  them  is  any  of  the  mineral  ingredients  wholly  wanting,  though 
in  all  the  quantity  of  potash  and  soda  capable  of  being  extracted  by 
water  is  very  small.  This  is  ascribed  to  the  fact  of  their  having  been 
long  in  pasture,  during  which  the  supply  of  these  substances  is  gradually 
withdrawn  by  the  roots  of  the  grasses.  It  is  well  known  how,  in  our  or- 
dinary soils,  grass  is  often  renovated — how  the  mosses,  especially,  are  de- 
stroyed— by  a  dressing  of  wood  ashes,  which  owe  their  effect  to  the  alkali 
they  contain.  In  the  above  soils  the  gradual  decomposition*  of  the  sili- 
cates would  continue  to  supply  a  certain  portion  of  alkaline  matter  for  an 
indefinite  period  of  time. 

You  will  perceive  that  the  soil  which  is  the  most  celebrated  for  its  fat- 
tening power,  is  also  the  richest  in  alumina,  lime,  phosphoric  acid,  sul- 
-phuric  acid,  and  vegetable  matter. 


284 


THE    SOIL   OF    RICH    ARABLE    LAISDS. 


2°.  Arable. — The  following  table  exhibits  the  constitution  of  three 
soils,  celebrated  for  yielding  successive  crops  of  corn  for  a  long  period 
without  manure. 


J.. 
From  Nebtsein, 

From  the  banks  of  the 

o. 
From  the  polde, 

near  Olmutz, 

Ohio,  North  America. 

of  Alt-Arenbergr 

in  Moravia. 

Soil. 

Subsoil. 

in  Belgium 

Silica  and  fine  Sand 

.    77-209 

87-143 

94-261 

64-517 

Alumina 

.     .     8-514 

5-666 

1-376 

4-810 

Oxides  of  Iron 

.     .     6-592 

2-220 

2-336 

8-316 

Oxide  of  Magnesia   . 

.     .     1-520 

0-360 

1-200 

0-800 

Lime 

.     0-927 

0-564 

0-243 

Carbof^   ,^„ 
Lime    9-403 

Carb.of,  _  _  _, 
Mag.  10-361 

Mac^nesia    .     •     •     ^     . 

.      .      1.1  RO 

0-312 

0-310 

Potash   chiefly  combined 

with  Silica   .     . 

.     .     0-140 

0-120  I 
0-025  S 

0-240 

5  0-100 
)  0-013 

Soda,  ditto        .     . 

.     .     0-640 

Phosphoric  Acid  combined 

with  Lime  and  Oxide  of 

Iron     .... 

.     .    0-651 

0-060 

trace 

1-221 

Sulphuric  Acid  in  gypsum  0*011 

0-027 

0-034 

0-009 

Chlorine  in  common 

salt.   0-010 

0-036 

trace 

0-003 

Carbonic  Acid  united  to  the 

Lime     .     . 

0.080 
1.304 

— 

Humic  Acid       .     . 

.     .  0-978 . 

0-447 

Insoluble  Humus  . 

.     .  0-540 

1.072 



__ 

Organic   substances 

con- 

taining  Nitrogen 

.     1-108 

1-011 

— 

— 

100 


100 


100 


100 


Of  these  soils,  the  first  had  been  cropped  for  160  years  successively, 
without  either  manure  or  naked  fallow.  The  second  was  a  virgin  soil, 
celebrated  for  its  fertility.  The  third  had  been  unmanured  for  twelve 
years,  during  the  last  nine  of  which  it  had  been  cropped  with  beans 
—barley — potatoes — winter  barley  and  red  clover — clover — winter  bar- 
ley— wheat — oats — naked  fallow. 

Though  the  above  soils  differ  considerably,  as  you  see,  in  the  propor- 
tions of  some  of  the  constituents,  yet  they  all  agree  in  this — that  they  are 
not  destitute  of  any  one  of  the  mineral  compounds,  which  plants  necessa- 
rily require  in  sensible  quantity.  You  will  also  observe  how  compara- 
tively small  a  proportion  of  vegetable  matter,  less  than  half  a  per  cent., 
is  contained  in  the  fertile  Belgian  soil — a  fact  to  which  I  shall  by-and- 
by  recall  your  attention. 

3°.  Soils  which  have  a  natural  source  of  fertility. — Some  soils,  which 
by  their  constitution  are  not  fitted  to  exhibit  any  great  degree  of  fertility, 
or  for  a  very  long  period,  are  yet,  by  springs  or  otherwise,  so  conslantly 
supplied  with  soluble  saline,  and  other  substances,  as  to  enable  them  to 
jrield  a  succession  of  crops,  without  manure,  and  without  apparent  dete- 
rioration.   Such  is  the  case  with  the  following  soil  from  near  Rotlien- 


SPRINGS    OFTEN    e'nRICH    THE    SOILS.  285 

"elde,  in  Osnabruck,  which  gives  excellent  crops,  though  manured  only 

Mice  in  10  or  12  years. 

Silica  and  coarse  Quartz  Sand      ....  86*200 

Alumina        2-000 

Oxides  of  Iron  and  a  little  Phosphoric  Acid  .  2*900 

Oxide  of  Manganese 0*100 

Carbonate  and  a  little  Phosphate  of  Lime    .  4*160 

Carbonate  of  Magnesia 0*520 

Potash  and  Soda 0*035 

Phosphoric  Acid 0*020 

Sulphuric  Acid 0*021 

Chlorine '...'..  0*010 

Humic  Acid 0*544 

Insoluble  Humus 3*370 

Organic  matter  containing  Nitrogen     .     .     .  0*120 

100 

You  will  see  that,  although  in  this  soil  all  the  inorganic  substances  are 
really  present,  yet  the  potash  and  soda,  the  phosphoric  and  sulphuric 
acids,  and  the  chlorine,  are  not  in  such  abundance  as  to  justify  us  in  ex- 
pecting it  to  grow  any  long  succession  of  crops,  without  exhibiting  the 
usual  evidences  of  exhaustion.  But  it  lies  on  the  side  of  a  hill  which  con- 
tains layers  of  lime-stone  and  marl,  through  which  the  surface  waters 
find  their  way.  These  waters  afterwards  rise  into  the  soil  of  the  field, 
impregnated  with  those  various  substances  of  which  the  soil  is  in  want, 
and  thus,  by  a  natural  manuring,  keep  up  a  constant  supply  for  each  suc- 
ceeding crop. 

This  example  is  deserving  of  your  particular  attention,  inasmuch  as 
there  are  many  soils,  in  climates  such  as  ours,  which  are  yearly  refresh- 
ed from  a  similar  source.  Few  spring  waters  rise  to  the  surface  which 
are  not  fitted  to  impart  to  the  soil  some  valuable  ingredient,  and  which,  if 
employed  for  the  purposes  of  irrigation,  would  not  materially  benefit 
those  lands  especially  on  which  our  pasture  grasses  grow.  The  same 
may  also  be  said  of  the  waters  which  are  carried  off  in  some  places  so 
copiously  by  drains.  Whether  these  waters  rise  from  beneath  in  springs, 
or,  falling  in  rain,  afterwards  sink  through  the  soil,  they  in  either  case 
carry  into  the  brooks  and  rivers  much  soluble  matter,  which  the  plants 
would  gladly  extract  from  them.  On  sloping  grounds  it  would  be  a 
])raiseworthy  economy  to  arrest  these  waters,  and,  before  they  escape, 
to  employ  them  in  irrigation. 

The  fact  that  nature  thus  on  many  spots  brings  up  from  beneath,  or 
down  from  the  higher  grounds,  continual  accessions  of  new  soluble  mat- 
ter to  the  soil,  will  serve  to  explain  many  apparent  anomalies,  and  to  ac- 
count for  the  continued  presence  of  certain  substances  in  small  quantity, 
although  year  by  year  portions  of  them  are  carried  ofT  the  land  in  the 
crops  that  are  reaped,  while  no  return  is  made  in  the  shape  of  artificial 
manure.  It  will  also  in  some  instances  account  for  the  fact  that,  after  a 
hard  cropping,  prolonged  until  the  soil  has  become  exhausted,  a  few 
years'  rest  will  completely  re-invigorate  it,  and  render  it  fit  to  yield 


286 


IMPORTANCE    of    DEPTH    OF    SOIL. 


new  returns  of  abundant  corn.  Other  causes,  as  we  shall  hereafter  see, 
generally  operate  in  bringing  about  this  kind  of  natural  recovery,  but 
there  can  be  no  question  that  in  circumstances  such  as  I  have  now 
adverted  to,  this  recovery  may  be  effected  in  a  much  shorter  period 
of  time. 

4°.  Importance  of  depth  and  uniformity  of  soil, — If  the  surface  soil  be 
of  a  fertile  quality,  ample  returns  will  be  sure  from  many  cijltivated 
crops.  But  where  the  subsoil  is  similar  in  composition  to  that  of  the 
surface — not  only  may  the  fertility  of  the  land  be  considered  as  almost 
inexhaustible,  but  those  crops  also  which  send  their  roots  far  down  will 
be  able  permanently  to  flourish  in  it.  This  fact  is  illustrated  by  the 
composition  of  the  following  soils  from  the  neighbourhood  of  Bruns- 
wick : — 


1. 


2. 


Soil.  Subsoil.  Subsoil. 

Silica  and  fine  Quartz  Sand     .  94-724  97-340  90-035 

Alumina 1*638  0-806  1-976 

Oxides  of  Iron      .     .     .     .      >  ^.q^^  51-126  6-815 

Oxides  of  Manganese     .     .      J  ^  "  J  0-075  0-240 

Lime 1-028  0-296  0-022 

Magnesia trace  0-095  0-115 

Potash  and  Soda 0-077  0-112  .    0-300 

Phosphoric  Acid 0-024  0-015  0-098 

Sulphuric  Acid 0-010  trace  1-399 

Chlorine 0-027  trace  trace 

Humic  Acid 0-302  0-135  — 

Insoluble   Humus       ....  0-210  —  — 

100  100  100 

The  first  of  these  soils  produced  excellent  crops  of  all  deep-roofed 
plants — lucerne,  sainfoin  (esparsette),  hemp,  carrots,  poppies,  &c. — and 
with  the  aid  of  gypsum,  red  clover,  and  leguminous  plants  (vetches, 
peas,  and  beans),  in  great  luxuriance.  The  former  of  these  facts  is  ex- 
plained by  the  great  similarity  in  constitution  which  exists  between  the 
surface  and  the  under  soils.  To  deep-rooted  plants  also  the  magnesia, 
in  which  the  surface  is  deficient,  is  capable  of  being  supplied  by  the  under 
soil.  The  effect  of  the  gypsiim  is  accounted  for  by  the  almost  total  ab- 
sence of  sulphuric  acid  in  the  subsoil,  but  which  the  application  of  gyp- 
sum has  introduced  into  the  upper  soil. 

The  second  soil  was  taken  from  a  field  in  which  sainfoin  died  regu- 
larly in  the  second  or  third  year  after  it  was  planted.  This  was  naturally 
attributed  to  something  in  the  subsoil.  And  by  the  analyses  above 
given,  it  was  found  to  contain  much  sulphuric  acid  in  combination  with 
oxide  of  iron,  forming  sulphate  of  iron  (green  vitriol).  This  salt  being 
noxious  to  plants,  began  to  act  upon  the  crop  of  sainfoin  as  soon  as  the 
roots  had  gone  so  deep  as  to  draw  sufficient  supplies  from  the  subsoil, 
and  it  thus  gradually  poisoned  them,  so  that  they  died  out  in  two  or  three 
years. 


EXACT    CONST -JtOENTS   OF    SOME    UNFRUITFUL    SOtLS.  287 

II. — BARREN    OR    UNFRUITFUL    SOILS. 

Soils  are  unfruiiful  or  altogether  barren,  either  when  they  contain  too 
little  of  one  or  more  of  the  inorganic  constituents  of  plants,  or  when  some 
substance  is  present  in  them  in  such  quantity  as  to  become  hurtful  or 
poisonous  to  vegetation.  The  presence  of  sulphate  of  iron  in  the  subsoil 
just  described  is  an  illustration  of  the  latter  fact.  In  what  way  the  defi- 
ciency o^  ceriaim  substances  really  does  allect  the  agricuhural  capabilities 
of  the  soil  will  appear  from  the  tbllowing  analyses  : — 

1.  2.  3.  4. 

Moor  land  soil,         Another  Sandy     Soil  on  the 

near  Aurich,  soil  from      soil  from    Muschel- 

East  Friesland.        the  same  Wettingen        kalk, 

neighbour-  in  Liine-    near  Mlihl- 
Soil.        Subsoil.         hood.  burg-         hausen. 

Silica  and  auartz Sand  .     .  70-576— 95190  61576  96000  77780 

Alumina 1050—  2520  0450  0500  9  490 

Oxides  of  Iron 0-252—  1-460  0-524  2000  5  800 

Oxide  of  Manganese  .     .     .  trace —  0048  trace  trace  01 05 

Lime do.—  0-336  0320  0001  0866 

Magnesia 0012—  0125  0130  trace  0728 

Potash trace —  0072  trace  do.  trace 

Soda do.  —  0-180  do.  do.  do. 

Phosphoric  Acid    ....  do.        0034  do.  do.  0003 

Sulphuric  Acid do.        0020  do.  do.  trace 

Carbonic  Acid —           —  —  —  0200 

Chlorine trace —  0015  trace  trace  trace 

HumicAcid 11-910-    —  11-470  0200  0732 

Insoluble  Humus  ....  16-200—    —  26530  1-299  0-200 

Water _          _  _  _  4096 

100         100  100  100  100 

Each  of  these  analyses  is  deserving  of  attention. 

1°.  That  the  barrenness  of  the  moor-land  soils  (1  and  2)  is  to  be  at- 
tributed to  their  deficiency  in  the  numerous  substances  of  which  they 
contain  only  traces,  may  almost  be  said  to  be  proved  by  the  fact — one 
long  recognised  and  acknowledged  on  many  of  our  own  moor-lands  and 
peaty  soils — that  when  dressed  with  a  covering  of  the  subsoil  they  be- 
come capable  of  successful  cultivation.  The  analysis  of  the  sub.soil  in 
the  second  column  shows  that  it  contains  all  those  mineral  constituents  in 
which  the  soil  itself  is  deficient — and  to  the  eflect  of  these,  therefore,  the 
improvement  produced  upon  the  soil  by  bringing  it  to  the  surface  is  alto- 
gether to  be  attributed. 

2°.  The  sandy  soil,  No.  3,  is  evidently  barren  for  the  same  reason  as 
the  moorland  soils,  1  and  2.  The  soil  No.  4  rests  on  lime-stone,  and 
was  mixed  with  7  percent,  of  lime-stone  gravel,  and  contains  a  great 
number  of  the  substances  which  plants  require — but  its  unfruitfulness  is 
to  be  ascribed  to  the  want  of  potash  and  soda,  of  sulphuric  acid  and  of 
chlorine.  Wood  ashes  and  a  mixture  of  common  salt  with  gj'^psum  or 
sulphate  of  soda,  would  probably  have  remedied  these  defects. 

3°.  Among  the  fertile  soils  to  which  I  recently  directed  your  attention 
(p.^284)  was  one  frpm  Belgium,  in  which  the  proportion  of  organic 
matter  was  less  than  half  a  per  cent,  of  its  whole  weight.  In  the  above 
table,  on  the  other  band,  we  have  two  nearly  barren  soils,  containing 


288  WHAT  RENDERS  A  SOIL  EERTILE. 

each  11  per  cent  of  humic  acid,  besides  a  much  larger  proportion  of  in- 
soluble organic  matter.  It  is  obvious,  therefore,  that  the  fertility  of  a 
soil  is  not  dependent  upon  its  containing  this  or  that  proportion  of  vege- 
table matter,  either  in  a  soluble  or  an  insoluble  form.  It  is  certaiflly 
true  that  many  very  fertile  soils  do  contain  a  considerable  quantity  of 
organic  matter,  in  a  form  in  which  it  may  readily  yield  nourishment  to 
the  roots  of  plants.  Yet  such  soils  are  not  fertile  merely  in  consequence 
of  the  presence  of  this  organic  matter,  as  a  source  o{  organic  food  to  the 
plant.  It  may  be  present,  and  yet  the  soils,  like  those  above-mentioned, 
may  remain  barren.  Where  soils  become  fertile  apparently  by  the 
long  accumulation  of  such  vegetable  matter  in  the  soil,  it  is  not  merely 
because  of  the  increase  of  pujely  organic  substances,  such  as  the  humic 
and  ulmic  acids,  but,  because,  as  I  have  already  had  occasion  to  mention 
to  you,  the  decaying  vegetable  matter  which  produces  them  contains 
also,  and  yields  to  the  soil,  a  considerable  abundance  of  some  of  those 
inorganic  substances  which  plants  necessarily  require.  The  organic 
matter  is  an  indication  of  their  presence  in  such  soils.  But  they  may 
be  present  without  the  organic  matter.  They  may  either  be  duly  pro- 
portioned in  the  soil  by  nature — or  they  may  be  artificially  mixed  with 
it,  and  then  this  use  of  the  organic  matter  may  be  dispensed  with.  It  is 
of  more  importance  to  bear  this  in  mind,  because  not  only  vegetable 
physiologists,  but  some  zealous  chemists  also,  have  laid  great  stress  upon 
the  quantity  of  soluble  and  insoluble  organic  matter  contained  in  a  soil, 
and  have  been  led  to  consider  it  as  a  safe  index  of  the  relative  fertility 
of  different  soils. 

The  history  of  science  shows,  by  many  examples,  that  those  men 
who  adopt  extreme  views, — who  attempt  to  explain  all  phenomena  of  a 
given  kind,  by  reference  to  a  single  specific  cause — have  ever  been  of 
very  great  use  in  the  advancement  of  certain  knowledge.  Their  argu- 
ments, whether  well  or  ill  founded,  lead  to  discussion,  to  further  investi- 
gation, to  the  discovery  of  exceptional  cases,  and,  finally,  to  the  general 
adoption  of  modified  views  which  recognise  the  action  of  each  special 
cause  in  certain  special  cases,  but  all  in  subordination  to  some  more  ge- 
neral principle. 

Thus,  if  some  ascribe  the  fertility  of  the  soil  to  the  presence  of  the 
alkalies  in  great  abundance,  others  to  that  of  the  phosphates,  others  to 
that  of  lime,  others  to  that  of  alumina,  and  others,  finally,  to  that  of  ve- 
getable matter  in  a  soluble  state — all  these  extreme  opinions  are  recon- 
ciled, and  their  partial  truths  recognised,  in  one  general  principle,  that 
a  soil  to  he  fertile  must  contain  all  the  substances  which  the  plant  we  de- 
sire to  grow  can  only  obtain  from  the  soil,  and  in  such  abundance  as 
readily  to  supply  all  its  wards ;  while  at  the  same  time  it  must  contain 
nothing  hurtful  to  vegetable  life. 

III. SOILS  CAPABLE  OF  IMPROVEMENT  BT  THE  ADDITION  OF 

MINERAL  MATTER. 

On  the  principle  above  stated  depends  in  very  many  cases  the  mode 
of  improving  soils  by  the  addition  of  mineral  substances,  as  well  as  the 
method  of  explaining  the  remarkable  effects  occasionally  pcoduce*  by 
their  mixture  with  the  land.  The  following  analyses  wUi  place  this 
matter  in  a  clearer  light : — 


COMPOSITION  or  READILI   IMFROVEABLE  S0IL3. 


S89 


1. 

2. 

3. 

4. 

Soil  near  Pa- 

Near  Draken- 

Near  Ganders- 

Near 

dingbiittel,  on 

burjr,  on  the 

helm,  in 

Bruns- 

the Weser. 

Weser. 

Brunswick, 

wick. 

Silica  and  Quartz  Sand 

.  93-720 

92-014 

90-221 

95-698 

Alumina    . 

.     1-740 

2-652 

2-106 

0-504 

Oxide  of  Iron     . 

.     2-060 

3-192 

3-951 

2-496 

Oxide  of  Manganese  . 

.     0-320 

0-480 

0-960 

trace 

Lime 

.     0-121 

0-243 

0-539 

0-038 

Magnesia  . 

.     0-700 

0-700 

0-730 

0-147 

Potash  (chiefly  in  combina- 

tion with  Silica) 
Soda    (do.) 

.     0-062 
.     0-109 

0-125 
0-026 

0-066  ? 
0-010  s 

0-090 

Phosphoric  Acid 

.     0-103 

0  078 

0-367 

0-164 

Sulphuric  Acid 

.     0-005 

trace 

trace 

0-007 

Chlorine  in  common  Salt 

.     0-050 

trace 

0-010 

0-010 

Huraic  Acid  .    . 

.     0-890 

0-340 

0-900 

0-626 

Other  Organic  matter 

.     0-120 

0-150 

0-140 

0-220 

100 


100 


100 


100 


The  first  of  these  soils  produces  naturally  beautiful  red  clover — the 
second  produces  very  bad  red  clover.  On  comparing  the  constitution  of 
the  two  soils,  we  see  the  second  to  be  deficient  in  sulphuric  acid  and 
chlorine.  A  dressing  of  gypsum  and  common  salt  would  supply  these 
deficiencies,  and  render  it  capable  of  producing  this  kind  of  clover.  The 
third  soil  is  remarkable  for  growing  luxuriant  crops  of  pulse,  when  ma- 
nured with  gypsum.  The  almost  total  absence  of  sulphuric  acid  ex- 
plains this  effect.  The  fourth  soil  was  greatly  improved  by  soap-boiler's 
ash,  which  supplied  it  with  lime,  magnesia,  manganese,  and  other  sub- 
stances. 


I  need  not  further  multiply  examples  to  show  you  how  much  real 
knowledge  is  to  be  derived  from  a  rigidly  accurate  analysis,  not  only  in 
regard  to  the  agricultural  capabilities  of  a  soil,  but  also  in  regard  to  the 
natural  and  necessary  food  of  plants,  and  to  the  manner  in  which 
mineral  manures  act  in  promoting  and  increasing  their  growth.  The 
illustrations  I  have  already  presented  will  satisfy  you — 

1°.  That  a  fertile  soil  must  contain  all  the  inorganic  constituents  which 
the  plant  requires,  and  none  that  are  likely  to  do  it  an  injury. 

2°.  That  if  the  addition  of  a  given  manure  to  the  soil  render  it  more 
fertile — it  is  because  the  soil  was  defective  in  one  or  more  of  those  sub- 
stances which  the  manure  contained. 

3°.  That  if  a  given  application  to  the  land  fail  to  improve  k — of  gyp- 
sum, of  bone-dust,  of  common  salt,  for  example — it  is  because  enough  of 
the  substance  applied  is  already  present,  or  because  something  else  is 
still  wanting  to  render  the  previous  additions  available. 

4°.  That  the  result  of  extended  experience  in  our  country,  that  the 
clay  soils  are  best  for  wheat,  and  sandy  soils,  such  as  that  of  Nor- 
folk, for  barley,  is  not  to  be  considered  as  anything  like  a  law  of  nature, 
setting  aside  the  clay  land  for  the  special  growth  of  wheat,  and  denying 

13 


290  PHi:SlCAL    PROPERTIES    OF    SOILS. 

to  the  sandy  soils  the  power  of  yielding  abundant  crops  of  this  kind  of 
grain.  Almost  every  district  can  present  examples  of  well  cultivaled 
fields,  where  the  contrary  is  proved — and  the  wheat  crops  w'hich  are 
yearly  reaped  from  the  sandy  plains  of  Belgium,  demonstrate  it  on  a 
more  extended  scale. 

Chemically  speaking,  a  soil  will  produce  any  crop  abundantly,  pro- 
vided it  contain  an  ample  supply  of  all  that  the  crop  we  wish  to  raise 
may  happen  to  require.  But,  in  practice,  soils  which  do  not  contain  all 
these  substances  plentifulljs  are  yet  found  to  differ  in  their  power  of 
yielding  plentiful  returns  to  the  husbandman.  Such  differences  arise 
from  the  climate,  the  exposure,  the  colour,  the  fineness  of  the  particles, 
the  lightness  or  porosity  of  the  soil — from  the  quantity  of  moisture  it  is 
capable  of  retaining,  or  from  some  other  of  its  numerous  physical  pro- 
perties. These  physical  properties,  therefore,  it  is  necessary  shortly  to 
consider. 

§  4.   Of  the  physical  properties  of  soils. 

To  the  physical  properties  of  soils  was  formerly  ascribed  a  mudi 
more  fundamental  importance  than  we  can  now  attach  to  them.  Crome 
and  Schiibler  regarded  the  fertility  of  a  soil  as  entirely  dependent  upon 
its  physical  properties.  Influenced  by  this  opinion,  the  former  published 
the  results  of  an  examination  of  numerous  soils  in  the  Prussian  provin- 
ces, which  are  now  possessed  of  no  scientific  interest;  because  they 
merely  indicate  the  amount  of  clay,  sand,  and  vegetable  matter  which 
these  soils  severally  contained.*  The  latter  completed  a  very  elaborate 
examination  of  the  physical  properties  of  soils,  which  is  very  useful  and 
instructive  ;f  but  the  defective  nature  of  which,  in  accounting  for  their 
agricultural  capabilities,  became  evident  to  the  author  himself,  when  the 
more  correct  and  scientific  views  of  Sprengel,  illustrated  in  the  preced- 
ing section,  afterwards  became  known  to  him.  In  giving,  therefore, 
their  due  weight  to  the  physical  properties,  we  must  not  forget  that  in 
nature  they  are  subordinate  to  the  chemical  constitution  of  soils.  Plants 
may  grow  upon  a  soil,  whatever  its  physical  condition — if  all  the  fo(xJ 
they  require  be  within  their  reach — while,  howevej  t^yourable  the  phy- 
sical condition  may  be,  nothing  can  vegetate  in  a  heallhy  manner,  if  the 
soil  be  deficient  in  some  necessary  kind  of  food,  or  contain  what  is  de- 
structive to  vegetable  life. 

Of  the  physical  properties  of  soils  the  most  impQ«tant  are  their  den- 
sity, their  power  of  absorbing  and  retaining  water  ancfair,  their  capillary 
action,  their  colour,  and  their  consistence  or  adhesive  power.  There 
are  one  or  two  others,  however,  to  which  it  will  be  necessary  shortly  to 
advert. 

I. MECHANICAL  RELATIONS  OF  SOILS. 

1°.  The  density  and  absolute  weight  of  a  soil. — Some  soils  are  much 
heavier  than  others,  not  merely  in  the  ordinary  sense  of  heavy  and  light, 
as  denoting  clayey  and  sandy  soils,  but  in  reference  to  the  absolute  weight 
of  equal  bulks. 

*  Recorded  in  his  Grunda'dize  der  AgricuUur  Chemie. 
t  /»«r  Boden  und  aein  verhdltniss  zu  den  Gewdchsen. 


ABSOLUTE  WEIGHT  AND   FIRMNESS  OF  SOILS.  291 

Thu8^  cubic  foot  of  dry 

Siliceous  or  Calcareous  Sand — weighs  about    .     1 10  lbs. 

Half  Sand  and  half  Clay 95 

Of  common  arable  Land,  from  .  .  .  .  80  to  90 
Of  pure  agricultural  Clay  (page  231)  ...  75 
Of  garden  Mould,  richer  in  vegetable  matter  .  70 
Of  a  peaty  Soil,  from 30  to  50 

Sandy  soils,  therefore,  are  the  heaviest.  The  weight  diminishes  with 
the  increase  of  clay,  and  lessens  still  further  as  the  quantity  of  vegetable 
matter  augments. 

In  practice,  the  denser  a  soil  is,  the  less  injury  ■w'ill  be  done  to  the 
land  by  the  passage  of  carts  and  the  treading  of  cattle  in  the  ordinary 
operations  of  husbandry.  In  a  theoretical  point  of  view  it  is  of  conse- 
quence to  vegetation,  chiefly  in  so  far  as,  according  to  the  experiments 
of  Schiibler,  the  denser  soils  retain  their  warmth  for  a  longer  period  when 
the  sun  goes  down,  or  a  cold  wind  comes  on.  Thus  a  peaty  soil  will 
cool  as  much  in  an  hour  and  a  half  as  a  pure  clay  in  two,  or  a  sand  in 
three  hours. 

2°.  Of  the  state  of  division  of  the  constituent  parts  of  the  soil. — 
With  the  relative  weight  of  different  soils,  their  state  of  division  is  in 
some  degree  connected.  Some  soils  consist  of  an  admixture  of  exceed- 
ingly fine  particles  both  of  sand  and  clay — while  in  others,  coarse  sand, 
stones  and  gravels,  largely  predominate.  There  can  be  no  doubt  that  the 
state  of  the  soil  in  this  respect  has  a  material  influence  upon  its  produc- 
tive character,  and  consequently  upon  its  money  value,  since  the  labours 
of  the  husbandman  in  lands  of  a  stiffer  and  more  coherent  nature  are 
chiefly  expended  in  bringing  them  into  this  more  favourable  powdery  con- 
dition. In  the  description  and  examination  of  a  soil,  therefore,  this  pro- 
perty ought  by  no  means  to  be  passed  lightly  over — since  it  is  one  in 
regard  to  which  a  mere  chemical  analysis  gives  us  little  or  no  informa- 
tion. 

In  some  parts  of  the  country,  the  farmer  diligently  gathers  th^. 
stones  off'  his  land,  while  in  others  the  practice  is  condemned  as  hurtful 
to  the  arable  crops.  The  latter  fact  is  explained  by  supposing  that 
these  stones  in  winter  afford  shelter  to  the  winter-corn,  and  in  warmer 
seasons  protect  the  ground  in  some  degree  from  the  drying  winds,  and 
retain  beneath  them  a  supply  of  moisture  of  which  the  neighbouring 
roots  can  readily  avail  themselves. 

3°.  Firmness  and  adhesive  power  of  soils. — When  soils  dry  in  the 
air  they  cohere  and  become  hard  and  stiff"in  a  greater  or  less  degree. 
Pure  siliceous  sands,  alone,  do  not  at  all  cohere  when  dry — while  pure 
clays  become  hard  and  very  difficult  to  pulverize.  In  proportion  to  the 
quantity  of  sand  with  which  the  latter  are  mixed,  do  their  tenacity  and 
hardness  diminish.  The  diffici^  of  reducing  clays  to  a  fine  powder  in 
the  open  field,  or  of  bringing  them  into  a  good  tilth,  may  be  overcome, 
therefore,  by  an  admixture  of  sand  or  gravel,  but  there  are  few  localities 
where  the  expense  of  such  an  operation  does  not  present  an  insur- 
mountable obstacle.  Thorough  draining,  however,  subsoil  ploughing, 
and  careful  tillage,  will  gradually  bring  the  most  refractory  soils  of  this 
character  into  a  condition  in  which  they  can  be  more  perfectly  and  more 
economically  worked. 


292  ADUK3;o.\  ov  soils  to  the  plough. 

Soils  also  adhere  to  the  ploug'i  in  different  degrees,  and,  therefore,  pre- 
sent a  more  or  less  [)o%verfLil  obstruction  to  its  passage.  All  soils  present 
a  greater  resistance  when  wet  than  when  dry,  and  all  considerably  more 
to  a  wooden  than  to  an  iron  plough.  A.  sandy  soil  when  wet  offers  a  re- 
sistance to  the  passage  of  agricultural  implements,  ecpial  to  about  4  lbs. 
to  the  square  foot  of  the  surface  which  passes  through  it — a  fertile  vege- 
table soil  or  rich  garden  mould  about  6  lbs.,  and  a  clay  from  8  to  25  lbs. 
to  the  square  foot.  These  differences  will  naturally  form  no  inconsider- 
able items  in  the  calculations  of  the  intelligent  farmer  when  he  estimates 
the  cost  of  working,  and  the  consequent  rent  he  can  afford  to  pay  for  this 
or  that  soil,  otherwise  equal  in  value. 

II. RELATIONS    OF  SOILS  TO  WATER. 

1°.  Power  of  imbibing  moisture  from  the  air. — When  a  portion  of  soil 
is  dried  carefully  over  boiling  water,  or  in  an  oven,  and  is  then  spread 
out  upon  a  sheet  of  paper  in  the  open  air,  it  will  gradually  drink  in  watery 
vapour  from  the  atmosphere,  and  will  thus  increase  in  weight.  In  hot 
climates  and  in  dry  seasons  this  property  is  of  great  importance,  restoring 
as  it  does,  to  the  thirsty  soil,  and  bringing  within  the  reach  of  plants,  a 
portion  of  the  moisture  which  during  the  day  they  had  so  copiously  ex- 
haled. 

Different  soils  possess  this  property  in  unequal  degrees.  During  a 
night  of  12  hours,  and  when  the  air  is  moist,  according  to  Schiibler,  1000 
lbs.  of  a  perfectly  dry 


Clay  Loam     ...      25  lbs. 
Pure  Agricultural  Clay  27 


Quartz  Sand  will  gain     0  lbs. 
Calcareous  Sand.     .       2 
Loamy  Soil         .     .     21 
and  peaty  soils,  or  such  as  are  rich  in  vegetable  matter,  a  still  larger 
quantity. 

Sir  Humphry  Davy  found  this  property  to  be  possessed  in  the  highest 
degree  by  the  most  fertile  soils.  Thus,  when  made  perfectly  dry,  1000 
lbs.  of  a 

Very  fertile  Soil  from  East  Lothian  gained  in  an  hour   18  lbs. 

Very  fertile  Soil  from   Somersetshire 16 

Soil  worth  45s.  per  acre  from  Mersea,  in  Essex  .     .       13 
Sandy  Soil  worth  28s.,  from  Essex   ......       11 

Coarse  Sand  worth  only  15s 8 

Soil  of  Bagshot  Heath      . 3* 

Fertile  soils,  therefore,  possess  this  property  in  a  very  considerable  de- 
gree, and,  though  we  cannot,  by  determining  this  property  alone,  infer 
with  safety  what  the  fertility  of  a  soil  is  likely  to  prove — since  peaty 
soils  and  very  strong  clays  are  still  more  absorbent  of  moisture,  and 
since  this  property  is  only  remotely  connected  with  the  special  chemical 
constitution  of  a  soil — yet  among  arable,  sandy,  and  loamy  lands,  it  cer- 
tainly does,  as  Sir  Humphry  Davy  mkes,  afford  one  means  of  judging 
of  their  relative  agricultural  capabilities. 

2°.  Power  of  containing  or  holding  water. — If  water  be  poured  drop 
by  drop  upon  a  piece  of  chalk  or  of  pipe-clay,  it  will  sink  in  and  disap- 
pear, but  if  the  dropping  be  continued,  the  pores  of  the  earth  will  by  de- 

•  Sir  H.  Davy's  Works,  vol.  vii.,  p.  326. 


RELATIONS   CT   SOILS   TO   WATKR.  293 

grees  become  filled  with  water,  and  it  will  at  length  begin  to  drop  out 
from  the  under  part  as  it  is  added  above.  This  property  is  exhibited  in 
a  certain  degree  by  all  soils.  The  rain  falls  and  is  drunk  in,  the  dew 
also  descends,  and  is  thus  taken  possession  of  by  the  soil.  But  after  much 
rain  has  fallen,  the  earth  becomes  saturated,  and  the  rest  either  runs  off 
from  the  surface  or  sinks  through  to  the  drains.  This  happens  more 
speedily  in  some  soils  than  in  others.  Thus  from  106  lbs.  of  dry  soil, 
water  will  begin  to  drop — if  it  be  a 

Quartz  Sand,  when  it  has  absorbed 25  lbs. 

Calcareous  Sand 29 

Loamy  Soil       40 

English  Chalk 45— J. 

Clay  Loam       50 

Pure   Clay        70 

but  a  dry  peaty  soil  will  absorb  a  very  much  larger  proportion  (Schii- 
bler),  before  it  suffers  any  to  escape.  Useful  arable  soils  are  found  to  be 
capable  of  thus  containing  from  40  to  70percent.  of  their  weight  of  water. 
If  the  quantity  be  less  than  this,  the  soils  are  said  to  be  best  adapted  for 
pine  plantations, — if  greater,  for  laying  down  to  grass. 

In  dry  climates  this  power  of  holding  water  must  render  a  soil  more 
valuable,  whereas  in  climates  such  as  ours,  where  rains  rather  over- 
abound,  a  simple  determination  of  this  property  will  serve  to  indicate 
to  the  practical  farmer  on  which  of  his  fields  it  is  most  important  to  him, 
in  reference  to  surface  water,  that  the  operation  of  draining  should  be 
first  and  most  effectually  performed.  The  more  water  the  soil  contains 
within  its  pores,  the  more  it  has  to  part  with  by  subsequent  evaporation  ; 
and,  therefore,  the  colder  it  is  likely  to  be.  The  presence  of  this  water  also 
excludes  the  air  in  a  great  degree,  so  that  for  these,  as  well  as  for  other 
reasons,  it  is  desirable  to  afford  every  facility  for  the  speedy  removal  of 
the  excess  of  water  from  such  soils  as  absorb  it,  and  are  capable  of  con- 
taining it,  in  a  very  large  proportion. 

3°.  Power  of  retaining  water  when  exposed  to  the  air. — Unless  when 
rain  or  dew  are  falling,  or  when  the  air  is  perfectly  saturated  with  mois- 
ture, watery  vapour  is  constantly  rising  from  the  surface  of  the  earth. 
The  fields,  after  the  heaviest  rains  and  floods,  gradually  become  dry, 
though  this,  as  every  farmer  has  observed,  takes  place  in  some  of  his 
fields  with  much  greater  rapidity  than  in  others.  Generally  speaking, 
those  soils  which  are  capable  of  arresting  and  containing  the  largest  por- 
tion of  the  rain  that  falls,  retain  it  also  with  the  greatest  obstinacy,  and  take 
the  longest  time  to  dry.  Thus  a  sand  will  become  as  dry  in  one  hour  as  a 
pure  clay  in  three,  or  a  piece  of  peat  in  four  hours.  This,  therefore,  not 
only  explains,  and  shows  the  correctness  of,  the  well-known  distinctions 
of  warm  and  cold  soils,  but  exhibits  another  strong  argument  in  favour 
of  a  perfect  drainage  of  stiff  soils  and  of  such  as  contain  a  large  proportion 
of  decaying  vegetable  matter. 

4°.  Capillary  power  of  the  soil. — When  water  is  poured  into  the  sole 
of  a  flower-pot,  the  soil  gradually  sucks  it  in  and  becomes  moist  even  to 
the  surface.  The  same  takes  place  in  the  soil  of  the  open  fields.  The 
water  from  beneath — that  contained  in  the  subsoil — is  gradually  sucked 
up  to  the  surface.  Where  water  is  present  in  excess,  this  capillary  action, 
as  it  is  called,  keeps  the  soil  always  moist  and  cold. 


294  CAPILLARY    PDWER   OF    THE    SOIL. 

The  tendency  of  the  water  to  ascend,  however,  is  not  the  same  in  all 
soils.  In  those  which,  like  sandy  soils  and  such  as  contain  much  vege- 
table matter,  are  open  and  porous,  it  probably  ascends  most  freely,  while 
stiff  clays  will  transmit  it  with  less  rapidity.  No  precise  experiments, 
however,  have  yet  been  made  upon  this  subject,  chiefly,  I  believe,  be- 
cause this  property  of  the  soil  has  not  hitherto  been  considered  of  such 
importance  as  it  really  is,  to  the  general  vegetation  of  the  globe.  Let  us 
attend  a  little  to  this  point. 

I  have  already  drawn  your  attention  to  the  fact,  that  the  specimens  of 
soil  which  are  submitted  to  analysis  generally  contain  very  little  saline 
matter,  and  yet  that  in  a  crop  reaped  from  the  same  soil  a  very  consider- 
able proportion  exists.  This  I  have  attributed  to  the  action  of  the 
rains  which  dissolve  out  the  soluble  saline  matter  from  the  surface 
soil,  and  as  they  sink,  carry  it  with  them  into  the  subsoil;  or  from 
sloping  grounds,  and  during  very  heavy  rains,  partly  wash  it  into  the 
brooks.  Hence  from  the  proportion  of  soluble  matter  present  at  any  one 
time  in  the  surface  soil,  we  cannot  safely  pronounce  as  to  the  quantity 
which  the  whole  soil  is  capable  of  yielding  to  the  crop  that  may  be  grown 
upon  it.  For  when  warm  weather  comes  and  the  surface  soil  dries 
rapidly,  then  by  capillary  action  the  water  rises  from  beneath,  bringing 
with  it  the  soluble  substances  that  exist  in  the  subsoil  through  which  it 
ascends.  Successive  portions  of  this  water  evaporate  from  the  surface, 
leaving  their  saline  matter  behind  them.  And  as  this  ascent  and  eva- 
poration go  on  as  long  as  the  dry  weather  continues,  the  saline  matter 
accumulates  about  the  roots  of  the  plants  so  as  to  put  within  their  reach 
an  ample  supply  of  every  soluble  substance  which  is  not  really  defective 
in  the  soil.  I  believe  that  in  sandy  soils,  and  generally  in  all  light  soils, 
of  which  the  particles  are  very  fine,  this  capillary  action  is  of  great  im- 
portance, and  is  intimately  connected  with  their  power  of  producing 
remunerating  crops.  They  absorb  the  falling  rains  with  great  rapidity, 
and  these  carry  down  the  soluble  matters  as  they  descend — so  that  when 
the  soil  becomes  soaked,  and  the  water  begins  to  flow  over  its  surface, 
the  saline  matter  being  already  buried  deep,  is  in  little  danger  of  being 
washed  away.  On  the  return  of  dry  weather,  the  water  re-ascends  from 
beneath  and  again  diffuses  the  soluble  ingredients  through  the  upper  soil. 

In  climates  such  as  ours,  where  rains  and  heavy  dews  frequently  fall, 
and  where  the  soil  is  seldom  exposed  for  any  long  period  to  hot  summer 
weather  unaccompanied  by  rain,  we  rarely  see  the  full  effect  of  (his  ca- 
pillary action  of  the  soil.  But  in  warm  climates,  where  rain  seldom  or 
never  falls,  the  ascent  of  water  from  beneath,  where  springs  happen  to 
exist  in  the  subsoil,  goes  on  without  intermission.  And  as  each  new 
particle  of  water  that  ascends  brings  with  it  a  particle,  however  small, 
of  saline  matter  (for  such  waters  are  never  pure),  which  it  leaves  behind 
when  it  rises  into  the  air  in  the  form  of  vapour,  a  crust,  at  first  thin,  but 
thickening  as  time  goes  on,  is  gradually  formed  on  the  surface  of  the  soil. 
Such  crusts  are  seen  in  the  dry  season — in  India,  in  Egypt,  and  in  many 
parts  of  Africa  and  America.  In  hot,  protracted  summers  they  may  be 
seen  on  the  surface  of  our  own  fields,  but  they  disappear  again*  with  the 
first  rains  that  fall.  Not  so  where  rains  are  unknown.  And  thus  on  the 
arid  plains  of  Peru,  and  on  extensive  tracts  in  Africa,  a  deposit  of  saline 
matter,  sometimes  many  feet  in  thickness,  is  met  with  on  the  surface  of 


ITS  IMPORTANCE  TO  VEGETATION.  296 

wide  plains,  in  the  hollows  of  deep  valleys,  and  on  the  bottoms  of  ancient 
lakes.  Such  an  incrustation,  probably  so  formed,  is  the  bed  of  nitrate  of 
soda  in  Peru,  from  which  all  our  supplies  of  that  salt  are  drawn — such 
are  the  deposits  of  carbonate  of  soda  (urao)  extracted  from  the  soil  in  the 
South  American  State  of  Colombia. 

5°.  Contraction  of  the  soil  on  drying. — Some  soils  in  dry  weather  di- 
minish very  much  in  bulk,  shrink  in,  and  crack.  Thus,  after  being 
soaked  by  rain,  pure  clay  and  peaty  soils  diminish  in  bulk  about  one- 
fifth  when  they  are  again  made  perfectly  dry — while  sand  has  the  same 
bulk  in  either  state.  The  more  clay  or  vegetable  matter,  therefore,  a 
soil  contains,  the  more  it  swells  and  contracts  in  alternate  wet  and  dry 
weather.  This  contraction  in  stiff  clays  can  scarcely  fail  to  be  occa- 
sionally injurious  to  young  roots  from  the  pressure  upon  the  tender  fibres 
to  which  it  must  give  rise,  while  in  light  and  sandy  soils  the  compres- 
sion of  the  roots  is  nearly  uniform  in  all  weathers,  and  they  are  undis- 
turbed in  their  natural  tendency  to  throw  out  off-shoots  in  every  direction. 
Hence  another  good  quality  of  light  soils,  and  a  less  obvious  benefit 
which  must  necessarily  result  from  rendering  soils  less  tenacious  by  ad- 
mixture or  otherwise. 

III. RELATIONS    OF    THE    SOIL    TO    THE    ATMOSPHERE. 

Power  of  absorbing  oxygen  and  other  gaseous  substances  from  the 
air. — 1°.  The  importance  of  the  oxygen  of  the  atmosphere,  first  to  the 
germination  of  the  seed,  and  afterwards  to  the  growth  of  the  ])lant,  Ihave 
already  sufficiently  insisted  upon.  It  is  of  consequence,  therefore,  that 
this  oxygen  should  gain  access  to  every  part  of  the  soil,  and  thus  to  all 
the  roots  of  the  plant.  This  access  can  be  facilitated  by  artificially 
working  the  land,  and  thus  rendering  it  more  porous.  But  some  soils, 
in  whatever  state  they  may  be  in  this  respect,  have  been  found  to  absorb 
oxygen  with  more  rapidity,  and  in  larger  quantity,  than  others.  Thus 
clays  absorb  more  oxygen  than  sandy  soils,  and  vegetable  moulds  or 
peats  more  than  clays.  This  difference  depends  in  part  upon  the  natural 
porosity  of  these  different  soils,  and  in  part  also  upon  the  chemical  con- 
stitution of  each.  If  the  clay  contain  iron  or  manganese  in  the  state  of 
first  or  ^ro^-oxides,  these  will  naturally  absorb  oxygen  for  the  purpose  of 
combining  with  it, — while  the  decaying  vegetable  matter  will  in  like 
manner,  in  such  as  contain  it  largely,  drink  in  much  oxygen  to  aid  their 
natural  decomposition. 

2°.  Besides  the  gases,  oxygen  and  nitrogen,  of  which  the  air  princi- 
pally consists,  the  soil  absorbs  also  carbonic  acid  from  the  atmosphere, 
and  portions  of  those  various  vapours, — whether  of  ammonia  and  other 
effluvia  which  rise  from  the  earth,  or  of  nitric  acid  formed  in  the  air,— 
and  these,  in  the  opinion  of  some  chemists,  contribute  very  materially  to 
its  natural  fertility.  This,  however,  is  very  much  a  matter  of  conjec- 
ture, and  no  experiments  have  been  made  as  to  the  relative  capabilities 
of  different  soils  thus  to  extract  vegetable  food  from  the  surrounding  air. 
One  fact,  however,  seems  to  be  clearly  ascertained,  that  all  soils,  namely, 
absorb  gaseous  substances  of  every  kind  most  easily  and  in  the  greatest 
abundance  when  they  are  in  a  moist  state. .  The  fall  of  rains,  or  the  de- 
scent of  dew,  therefore,  will  favour  this  absorption  in  dry  seasons,  and  it 
will  also  be  greatest  in  those  soils  which  have  the  power  of  most  readily 


296  POWER   OF    SOILS    TO    RETAIN    HEAT, 

extracting  watery  vapour  from  the  air  during  the  absence  of  the  sun 
Hence  the  influence  of  the  dews  and  of  gentle  showers  on  the  progress 
of  vegetation,  is  not  limited  to  the  mere  supply  of  water  to  the  thirsty 
ground,  and  of  those  vapours  which  they  bring  with  them  as  they  descend 
to  the  earth,  but  is  partly  due  also  to  the  power  which  they  impart  to  the 
moistened  soil,  of  extracting  for  itself  new  supplies  of  gaseous  matter 
from  the  surrounding  atmosphere. 

IV. RELATIONS  OF  THE  SOIL  TO  HEAT. 

There  are  some  of  the  relations  of  soils  to  heat,  which  have  considera- 
ble influence  upon  their  power  of  promoting  vegetation.  These  are  the 
rapidity  with  which  they  absorJa  heat  from  the  air,  the  temperature  they 
are  capable  of  attaining  under  the  direct  action  of  the  sun's  rays,  and  the 
length  of  time  during  which  they  are  able  to  retain  this  heat. 

1°.  Power  of  absorbing  heat. — It  is  an  important  fact,  in  reference  to 
thegrowthof  plants,  that  during  sunshine,  when  the  sun's  rays  beat  upon 
it,  the  earth  acquires  a  much  higher  temperature  than  the  surrounding 
air.  This  temperature  very  often  amounts  to  110°,  and  sometimes  to 
nearly  150°,  while  the  air  in  the  shade  is  between  70°  and  80°  only. 
Thus  the  roots  of  plants  are  supplied  with  that  amount  of  warmth  which 
is  most  favourable  to  their  rapid  growth. 

Dark-coloured — such  as  black  and  brownish  red — soils  absorb  the 
heat  of  the  sun  most  rapidly,  and  therefore  become  warm  the  soonest. 
They  also  attain  a  higher  temperature — by  a  few  degrees  only,  how-^ 
ever  (3°  to  8°), — ^than  soils  of  other  colours,  and  thus,  under  the  action 
of  the  same  sun,  will  more  rapidly  promote  vegetation.  In  climates, 
such  as  ours,  where  the  presence  of  the  sun  is  often  wished  for  in  vain 
in  time  of  harvest,  this  property  of  the  soil  possesses  a  considerable  eco- 
nomical value.  In  other  parts  of  the  world,  where  sunshine  abounds, 
it  becomes  of  less  importance. 

Every  one  will  understand  that  the  above  differences  are  observed 
among  such  soils  only  as  are  exposed  to  the  same  sun  under  the  same 
circumstances.  "Where  the  exposure  or  aspect  of  the  soil  is  such  as  to 
give  it  the  prolonged  benefit  of  the  sun's  rays,  or  to  shelter  it  from  cold 
winds,  it  will  prove  more  propitious  to  vegetation  than  many  others  less 
favourably  situated,  though  darker  in  colour  and  more  free  from  super- 
fluous moisture. 

2°.  Power  of  retaining  heat. — But  soils  differ  more  in  their  power  of 
retaining  the  heat  they  have  thus  absorbed.  You  know  that  all  hot  bodies, 
when  exposed  to  the  air,  gradually  become  cool.  So  do  all  soils  ;  but  a 
sandy  soil  will  cool  more  slowly  than  a  clay,  and  the  latter  than  a  soil 
which  is  rich  in  vegetable  matter.  The  difference,  according  to  Schiib- 
ler,  is  so  great,  that  a  peaty  soil  cools  as  much  in  one  hour  as  the  same 
bulk  of  clay  in  two,  or  of  sand  in  three  hours.  This  may  no  doubt  have 
considerable  influence  upon  growing  crops,  inasmuch  as,  after  the  sun 
goes  down,  the  sandy  soil  will  be  three  hours  in  cooling,  while  the  clavs 
will  cool  to  the  same  temperature  in  two,  and  rich  vegetable  mould  in 
one  hour.  But  on  those  soils  which  cool  the  soonest,  dew  will  first  l)(i:i  i 
to  be  deposited,  and  it  is  doubtful,  where  the  soils  are  equally  drninod, 
whether,  in  summer  weather,  the  greater  proportion  of  dew  deposited  oi 
the  clays  and  vegetable  moulds  mnv  not  more  than  compensate  to  t:.tj 


POWER    OF    MODIFTINQ    THE    PHYSICAL    CHARACTERS.  297 

parched  soil — for  the  less  prolonged  duration  of  the  elevated  tempera- 
ture derived  from  the  action  of  the  sun's  rays.  It  is  also  to  be  remem- 
bered, that  vegetable  soils  at  least  absorb  the  sun's  heat  more  rapidly 
tlian  the  lighter  coloured  sandy  soils,  and  thus  the  plants  which  grow  in 
the  former,  which  is  sooner  heated,  may  in  reality  be  exposed  to  the 
highest  influence  of  the  sun's  warmth — for  at  least  as  long  a  period  as 
those  which  are  planted  in  the  latter. 

The  only  power  we  possess  over  these  relations  of  soils  to  heat,  ap- 
pears to  be,  that  by  top-dressing  with  charcoal,  with  soot,  or  with  dark- 
coloured  composts,  we  may  render  it  more  capable  of  rapidly  absorbing 
the  sun's  heat,  and  by  admixture  with  sand,  more  capable  of  retaining 
the  heat  which  it  has  thus  obtained. 


Sucn  are  the  most  important  of  the  physical  properties  of  soils.  Over 
some  of  them,  the  skilful  farmer  possesses  a  ready  control.  He  can 
drain  his  land,  and  thus  render  it  cheaper  to  work  and  more  easy  to  re- 
duce to  a  fine  powder.  He  can  plough,  subsoil,  and  otherwise  work  it 
well,,  and  thus  can  make  it  more  open  and  porous,  more  accessible  both 
to  air  and  water.  When  it  is  light  and  peaty,  he  can  lay  heavy  matter 
over  it — clay,  and  sand,  and  lime-stone  rubble — and  can  thus  increase 
its  density.  He  can  darken  its  colour  in  some  localities  with  peat  com- 
posts, and  can  thus  make  it  more  absorbent  of  heat  and  moisture,  as  well 
as  more  retentive  of  the  rain  that  falls.  But  here  his  power  ends,  and 
how  far  any  of  the  changes  within  his  power  can  be  'prudently  attempted 
will  depend  upon  the  expense  which,  in  any  given  locality,  the  operation 
would  involve.  And  even  after  he  has  done  all  which  mere  mechanical 
skill  can  suggest,  the  soil  may  still  disappoint  his  hopes,  and  refuse  to 
yield  him  remunerating  crops  of  corn. 

"  A  soil,"  says  Sprengel,  "  is  often  neither  too  heavy  nor  too  light, 
neither  too  wet  nor  too  dry,  neither  too  cold  nor  too  warm,  neither  too 
fine  nor  too  coarse ; — lies  neither  too  high  nor  too  low,  is  situated  in  a 
propitious  climate,  is  found  to  consist  of  a  well-proportioned  mixture  of 
clayey  and  sandy  particles,  contains  an  average  quantity  of  vegetable 
matter,  and  has  the  benefit  of  a  warm  aspect  and  favouring  slope." — 
I'BodenJcunde,  p.  203.]  It  has  all  the  advantages,  in  short,  which 
physical  condition  and  climate  can  give  it,  and  yet  it  is  unproductive. 
And  why  ?  Because,  answers  chemical  analysis,  it  is  destitute  of  cer- 
tain mineral  constituents  which  plants  require  for  their  daily  food.  The 
physical  properties,  therefore,  are  only  accessory  to  the  chemical  consti- 
tution. They  bring  into  favourable  circumstances,  and  thus  give  free 
scope  to  the  operation,  upon  the  seeds  and  roots  of  plants,  of  those  che- 
mical substances  which  Nature  has  kindly  placed  in  most  of  our  soils,  or 
by  the  lessons  of  daily  experience  is  teaching  the  skilful  labourer  in  her 
fields  to  supply  by  art. 

And  yet  the  study  of  the  physical  properties  of  soils  is  not  without  its 
use,  even  in  a  theoretical  point  of  view.  It  shows  both  the  use  of  the 
fundamental  admixture  of  sand,  clay,  and  vegetable  matter,  of  which 
our  soils  consist,  and  for  what  special  end  all  the  mechanical  labours  Oi 
the  husbandman  are  undertaken,  and  why  they  are  so  necessary.     Plants 

13* 


298  GENERAL    FUNCTIONS    OF    THE    SOIL. 

must  be  firmly  fixed,  therefore  the  soil  must  have  a  certain  consistency, 
— -their  roots  must  find  a  ready  passage  in  every  direction  ;  therefore  the 
soils  must  be  somewhat  loose  and  open.  Except  for  these  purposes,  we 
see  linle  immediate  use  for  the  sand  and  alumina  whicli  form  so  much 
oi  -ne  substance  of  soils — till  we  come  to  study  their  physical  properties. 
The  siliceous  sand  is  insoluble,  and  the  alumina  exists  in  plants  In  very 
minute  quantity  only,  while  during  the  progress  of  natural  vegetation, 
the  proportion  of  vegetable  matter  in  the  soil  actually  increases.  The 
immediate  agency,  therefore,  of  these  substances  is  not  chemical  but 
physical. 

The  alumina  of  the  clays  is  of  immediate  use  in  absorbing  and  retain- 
ing both  water  and  air  for  the  use  of  the  roots — while  the  vegetable  mat- 
ter is  advantageous  in  reference  to  the  same  ends,  as  well  as  to  the  power 
of  absorbing  quickly  and  largely  the  warmth  of  the  sun's  rays.  The 
soil,  in  short,  in  reference  to  vegetation,  performs  the  four  following  dis- 
tinct and  separate,  but  each  of  them  important  and  necessary,  func- 
tions : — 

1°.  It  upholds  and  sustains  the  plant,  affording  it  a  sure  and  safe  an- 
chorage. 

2°.  It  absorbs  water,  air,  and  heat,  to  promote  its  growth 

These  are  its  mechanical  and  physical  functions. 

3°.  It  contains  and  supplies  to  the  plant  botli  organic  and  inorganic 
food  as  its  wants  require  ;  and 

4°.  It  is  a  workshop  in  which,  by  the  aid  of  air  and  moisture,  cliemi 
cal  changes  are  continually  going  on  ;  by  which  changes  these  several 
kinds  of  food  are  prepared  for  admission  into  the  living  roots. 

These  are  its  chemical  functions. 

All  the  operations  of  the  husbandman  are  intended  to  aid  the  soil  in  the 
performance  of  one  or  other  of  these  functions.  To  the  most  important 
of  these  operations — tlie  methods  adopted  by  the  practical  farmer  for 
improving  the  soil — it  is  my  intention,  in  the  following  division  of  these 
Lectures,  briefly  to  direct  your  attention. 


LECTURES 

ON  THE 

APPLICATIONS  OF  CHEMISTRY  AND  GEOLOGY 

TO 

AGRICULTURE. 


ON  THE  IMPROVEMENT  OF  THE  SOIL  BY  ME- 
CHANICAL AND  CHEMICAL  MEANS. 


LECTURE   XIV. 


The  physical  qualities  and  chemical  constitution  of  a  soil  may  be  changed  by  art.— Nature 
of  the' plants  dependent  upon  that  of  the  soil  on  which  they  grow.— Mechanical  methods 
of  improving  the  soil.— Effects  produced  by  draining.— Theory  of  springs.— Effect  of 
ploughing,  subsoiling,  deep  ploughing  and  trenching.-^Artificial  improvement  by  mixing 
with  clay,  sand,  or  marl. 

The  facts  detailed  in  the  preceding  lecture  may  be  considered  as  af- 
fording sufficient  proof  that  the  abiUty  of  the  farmer  to  grow  this  or  that 
crop  upon  his  land,  is  very  much  restrained  by  its  natural  character  and 
constitution.  Each  soil  establishes  upon  itself — so  to  speak — a  vegeta- 
tion suited  to  its  own  nature,  one  that  requires  most  abundantly  those 
substances  which  actually  abound  in  the  soil — and  the  art  of  man  can- 
not long  change  this  natural  connection  between  the  living  plant  and  the 
kind  of  land  in  which  it  delights  to  grow. 

But  he  can  change  the  character  of  the  land  itself.  He  can  alter 
both  its  physical  qualities  and  its  chemical  constitution,  and  thus  can  fit 
it  for  growing  other  races  of  plants  than  those  it  naturally  bears — or,  if  he 
choose,  the  same  races  in  greater  abundance,  and  with  increased  luxuri- 
ance. It  is,  in  fact,  in  the  production  of  such  changes,  that  nearly  all  the 
labour  and  practical  skill  of  the  husbandman — apart  from  local  peculiari- 
ties of  climate,  &c. — is  constantly  expended.  For  the  attainment  of 
this  end  he  drains,  ploughs,  subsoil- ploughs,  and  otherwise  works  his 
land.  For  this  end  he  clays,  sands,  marls,  and  manures  it.  By  these 
and  similar  operations  the  land  is  so  changed  as  to  become  both  able  and 
willing  to  nourish  and  ripen  those  peculiar  plants  which  the  agriculturist 
wishes  to  raise.  On  this  practical  department  of  the  art  of  culture, 
the  principles  explained  and  illustrated  in  the  preceding  parts  of  these 
lectures,  throw  much  light.  They  not  only  explain  the  reason  why  cer- 
tain practices  always  succeed  in  the  hands  of  the  intelligent  farmer,  but 
why  others  also  occasionally  and  inevitably  fail — they  tell  him  which 
practices  of  his  neighbours  he  ought  to  adopt,  and  which  of  them  he  had 
better  modify  or  wholly  reject, — and  they  direct  him  to  such  new  modes 
of  improving  his  land  as  are  likely  to  add  the  most  to  its  permanent 
productive  value. 

The  operations  of  the  husbandman  in  producing  changes  upon  the 
land,  are  either  mechanical  or  chemical.  When  he  drains,  ploughs, 
and  subsoils,  he  alters  chiefly  the  physical  characters  of  his  soil — when 
he  limes  and  manures  it,  he  alters  its  chemical  constitution.  These  two 
classes  of  operations,  therefore,  are  perfectly  distinct.  Where  a  soil  con- 
tains all  that  the  crops  we  desire  to  grow  are  likely  to  require,  mere  me- 
chanical operations  may  suffice  to  render  it  fertile — but  where  one  or 
more  of  the  inorganic  constituents  of  plants  are  wanting,  draining  may 
prepare  the  land  to  benefit  by  further  operations,  but  it  will  not  be  alone 
sufficient  to  remove  its  comparative  sterility.  I  shall,  therefore,  con- 
sider in  succession  these  two  classes  of  practical  operations : — 

1°.  Mechanical  methods  of  improving  the  soil,  including  draining, 
ploughing,  mixing  with  clay,  sand,  &c. 


301  PLANTS     PECULIAR    TO    CERTAIN    SOILS. 

2°  Chemical  methods,  including  llmeing,  marling,  and  the  application 
of  vegetable,  animal,  and  mineral  manures. 

To  satisfy  you  fully,  however,  in  regard  to  the  absolute  necessity 
for  such  changes,  if  we  would  render  the  land  fit  to  produce  any  given 
crop,  let  me  illustrate,  by  a  few  brief  examples,  the  intimate  relation 
observed  in  nature  between  the  kind  of  soil  and  the  kind  of  plants  that 
grow  upon  it. 

§  1.  0«  the  connection  between  the  kind  of  soil  and  the  land  of  plants 
that  grow  uj)on  it. 

That  a  general  connection  exists  between  the  kind  of  soil  and  the 
kind  of  plants  that  grow  upon  it,  is  familiar  to  all  practical  men.  Thus 
clay  soils  are  generally  acknowledged  to  be  best  adapted  for  wheat — 
loamy  soils  for  barley — sandy  loams  for  oals  or  barley — such  as  are  more 
sandy  s^ll  for  oats  or  rye — and  those  which  are  almost  pure  sand,  for 
rye  alone  of  all  the  corn-bearing  crops. 

But  in  a  state  of  nature,  we  find  special  differences  among  the  spon- 
taneous produce  of  the  soil,  which  are  more  or  less  readily  traceable  to 
its  cheruical  constitution  in  the  spots  where  the  plants  are  seen  to 
grow.     Thus — 

1°.  On  the  sandy  soils  of  the  sea  shores,  and  oh  the  salt  steppes  ol 
Hungary  and  Russia,  the  sand- worts,  salt- worts,  glass-worts,  and  other 
salt-loving  plants  abound.  When  these  sands  are  inclosed  and  drained, 
the  excess  of  the  salt  is  gradually  washed  out  by  the  rains,  or  in  some 
countries  is  removed  by  reaping  the  saline  plants  annually,  and  burning 
them  for  soda  (barilla),  when  wholesome  and  nutritive  grasses  take  their 
place ;  but  the  white  clover  and  the  daisy,  and  the  dandelion,  must  first 
appear,  before,  as  a  general  rule,  it  can  be  profitably  ploughed  up  and 
sown  with  corn. 

2°.  The  dry  drifted  sands,  more  or  less  remote  from  the  sea,  produce 
no  such  plants.  They  are  distinguished  by  their  own  coarse  grasses, 
among  which  the  clymus  arenarius  (upright  sea lyme-grass)  often,  in  our 
latitudes,  occupies  a  conspicuous  place.  On  the  downs  of  North  Jut- 
land, it  was  formerly  almost  the  orly  plant  which  the  traveller  could 
meet  with  over  an  area  of  many  nl  es. 

3°.  On  ordinary  sandy  soils,  legummous  plants  are  rare,  and  the  herb- 
age often  scanty  and  void  of  nourishment.  With  the  presence  of  marl 
in  such  soils,  the  natural  growth  of  leguminous  plants  increases.  The 
colt's-foot  also,  and  the  butter-bur,  not  only  grow  naturally  where  the 
subsoil  is  marly,  but  infest  it  sometimes  to  such  a  degree  as  to  be  with 
great  difficulty  extirpated.  So  true  is  this  indication  of  the  nature  of 
the  soil,  that  in  the  lower  vallies  of  Switzerland  these  plants  are  said  to 
indicate  to  the  natives  where  they  may  successfully  dig  for  marl,  (Prize 
Essays  of  the  Highland  Society,  I.,  p.  134).  On  calcareous  soils,  again, 
or  such  as  abound  in  lime,  the  quicken  or  couch-grass  is  seldom  seen  as 
a  weed,  (Sprengel,  Bodenkunde,  p.  201 ),  while  the  poppy,  the  vetch,  and 
the  darnel  abound. 

4°.  So  peaty  soils,  when  laid  down  to  grass,  slowly  select  for  them- 
selves a  peculiar  tribe  of  grasses,  especially  suited  to  their  own  nature, 
among  which  the  holcus  lanatus  (meadow  soft-grass)  is  remarkably 
abundant.     Alter  their  constitution  by  heavy  limeing,  and  they  produce 


NATURAL    ROTAT^^  N    AMONG    FOREST    TREES.  305 

luxuriant  green  crops  and  a  great  bulk  of  straw,  but  give  a  coarse  thick- 
skinned  grain,  more  or  less  imperfectly  filled.  Alter  them  further  by  a 
dressing  of  clay,  or  keep  them  in  arable  culture,  and  stiffen  them  with 
composts,  and  they  will  be  converted  into  rich  and  sound  corn-bearing 
lands. 

5°.  In  the  waters  that  gush  from  the  sides  of  lime-stone  hills — on  the 
bottoms  of  ditches  that  are  formed  of  lime-stones  or  marls — and  in  the 
springs  ihat  have  their  rise  in  many  trap  rocks,  the  water-cress  appears 
and  accompanies  the  running  waters,  sometimes  for  miles  on  their 
course.  The  mare's-tail  {equisetum),  on  the  other  hand,  attains  its  largest 
size  by  the  marshy  banks  of  rivulets  in  which  not  lime  but  silica  is 
more  abundantly  present.  So  the  Cornish  heath  {erica  vagans)  is  found 
only  o!%r  the  serpentine  soils  of  Cornwall,  and  the  red  broom  rape 
{orobanche  rubra,  Hooker's  Flora  Scotica),  only  on  decayed  traps  in 
Scotland  and  Ireland. 

These  facts  all  point  to  the  same  natural  law,  that  where  other  circum- 
stances of  climate,  moisture,  &c.,  are  equal,  the  natural  vegetation — that 
which  grows  best  on  a  given  spot — is  entirely  dependent  upon  the  chemical 
constitution  of  the  soil. 

But  both  the  soil  and  the  vegetation  it  willingly  nourishes,  are  seen 
to  undergo  slow  but  natural  changes.  Lay  down  a  piece  of  land  to  grass, 
and,  after  a  lapse  of  years,  the  surface  soil — originally,  perhaps,  of  the 
stitfest  clay — is  found  to  have  become  a  rich,  light,  vegetable  mould, 
bearing  a  thick  sward  of  nourishing  grasses,  almost  totally  different  from 
those  which  naturally  grew  upon  it  when  first  converted  into  pasture. 
So  in  a  wider  field,  and  on  a  larger  scale,  the  same  slow  changes  aYe 
exhibited  in  the  vast  natural  forests  that  are  known  to  have  long  covered 
extensive  tracts  in  various  countries  of  Europe. 

Thus  it  is  a  matter  of  history  that  Charlemagne  hunted  in  the  forest 
of  Gerardmer,  then  consisting  of  oak  and  beech — though  now  the  same 
forest  contains  only  pines  of  various  species.  On  the  Rhine,  between 
Landau  and  Kaiserlautern,  oak  forests,  of  several  centuries  old,  are  seen 
to  be  gradually  giving  way  to  (he  beech,  while  others  of  oak  and  beech 
are  yielding  to  the  encroachments  of  the  pine.  In  the  Palatinate,  the 
Scotch  fir  {pinus  sylvestris)  is  also  succeeding  to  the  oak.  In  the  Jura, 
and  in  the  Tyrol,  the  beech  and  the  pine  are  seen  mutually  to  replace 
each  other — and  the  same  is  seen  in  many  other  districts.  When  the 
time  for  a  change  of  crop  arrives,  the  existing  trees  begin  to  languish 
one  after  another,  their  branches  die,  and  finally  their  dry  and  naked 
tops  are  seen  surrounded  by  the  luxuriant  foliage  of  other  races  [Le  Ba- 
ron de  Mortema*t  de  Boisse,  Voyage  dans  les  Landes,  p.  189.1  These 
facts  not  only  show  how  much  the  vegetable  tribes  are  dependent  upon 
the  chemical  nature  of  the  soil — they  indicate,  likewise,  the  existence 
of  slow  natural  changes  in  the  constitution  of  the  soil,  which  lead  neces- 
sarily to  a  change  of  vegetation  also. 

We  can  ourselves,  in  the  case  of  ancient  i^rests,  eflfect  such  changes. 
When  in  the  United  States  a  forest  of  oak  or  maple  is  cut  down,  one  of 
pine  springs  up  in  its  place  ;  while  on  the  site  of  a  pine  forest,  oak  and 
other  broad-leaved  trees  speedily  appear. 

But  if  the  full  time  for  such  changes  has  not  come,  the  new  vegeta- 
tion may  bej^yp^^^^^en,  and  smothered  by  the  original  tribes.  ..Ti|^i% 


306  OF    DRAINING,    AND    ITS    EFFECTS. 

when  the  pine  forests  of  Sweden  are  burned  down,  a  young  growth  of 
birch  succeeds,  but  after  a  time  the  pines  again  appear  and  usurp  their 
former  dominion.  The  soil  remains,  still,  more  propitious  to  the  growth 
of  the  latter  than  of  the  former  kind  of  tree. 

We  may,  therefore,  take  a  practical  lesson  from  the  book  of  nature. 
If  we  wish  to  have  a  luxuriant  vegetation  upon  a  given  spot,  we  must 
either  select  such  kinds  of  seeds  to  sow  upon  it  as  are  fitted  to  the  kind 
of  soil,  or  we  must  change  the  nature  of  the  land  so  as  adapt  it  to  our 
crop.  And,  even  when  we  have  once  prepared  it  to  yield  abundant  re- 
turns of  a  particular  kind,  the  changes  we  have  produced  can  only  be 
more  or  less  of  a  temporary  nature.  Our  care  and  attention  must  still 
be  bestowed  upon  it,  that  it  may  be  enabled  to  resist  the  slow^iatural 
causes  of  alteration,  by  which  it  is  gradually  unfitted  to  nouriSli  those 
vegetable  tribes  which  it  appears  now  to  delight  in  maintaining 

Let  us  now  turn  our  attention,  therefore,  to  the  methods  by  which 
these  beneficial  changes  are  to  be  effected  and  maintained. 

§  2.   Of  draining,  and  its  effects. 

Among  the  merely  mechanical  methods  by  which  those  changes  are 
to  be  produced  upon  the  soil,  that  are  to  fit  it  for  the  better  growth  of 
valuable  crops,  draining  is  now  allowed  to  hold  the  first  place.  That  it 
is  an  important  step  in  heavy  clay  lands,  and  that  it  must  be  xha  jirst  step 
in  all  cases  where  water  abounds  in  the  surface  soil,  will  be  readily  con- 
ceded ;  but  that  it  can  be  beneficial  also  in  situations  where  the  soils  are 
of  a  sandy  nature — where  the  subsoil  is  light  and  porous — or  where  the 
inclination  of  the  field  appears  sufficient  to  allow  a  ready  escape  to  the 
water,  does  not  appear  so  evident,  and  is  not  unfrequently,  therefore,  a 
matter  of  considerable  doubt  and  difficulty.  It  may  be  useful,  then, 
briefly  to  state  the  several  effects  which  in  different  localities  are  likely 
to  follow  an  efficient  drainage  of  the  land  : — 

1°.  It  carries  off"  all  stagnant  water,  and  gives  a  ready  escape  to  the 
excess  of  what  falls  in  rain. 

2°.  It  arrests  the  ascent  of  water  from  beneath,  whether  by  capillary 
afition  or  by  the  force  of  springs — and  thus  not  only  preserves  the  sur- 
face soil  from  undue  moisture,  but  also  frees  the  subsoil  from  the  linger- 
ing presence  of  those  noxious  substances,  which  in  undrained  land  so  fre- 
quently lodge  in  it  and  impair  the  growth  of  deep-rooted  plants. 

3°.  It  allows  the  water  of  the  rains,  instead  of  merely  running  over 
and  often  injuriously  washing  the  surface,  to  make  its  way  easily 
through  the  soil.  And  thus,  while  filtering  through,  not  only  does  the 
rain-water  impart  to  the  soil  those  substances  useful  to  vegetation,  which, 
as  we  have  seen,  [see  Lecture  II.,  p.  37,  Lecture  IV.,  p.  69,  and  Lecture 
VIII.,  p.  159,]  it  always  contains  in  greater  or  less  abundance  ;  but  it 
washes  out  of  the  upper  soil,  and,  when  the  drains  are  deep  enough, 
out  of  the  subsoil  also,  such  Hoxious  substances  as  naturally  collect  and 
may  have  been  long  accumulating  there — rendering  it  unsound  and 
hurtful  to  the  roots.  The  latter  is  one  of  those  benefits  which  gradually 
follow  the  draining  of  land.  When  once  thoroughly  effected,  it  consti- 
tutes a  most  important  permanent  improvement,  and  one  which  can  be 
fully  produced  by  no  other  available  means.  It  will  be  permanent, 
however,  only  so  long  as  the  drains  are  kept  in  good  condition.     The 


SECURES    A    DRY    SEED-TIME    AI^D    AN    EARLl     HARVEST.  307 

same  openness  of  the  soil  which  enables  the  rains  tc  wash  out  those  so- 
luble noxious  substances,  whicli  have  been  long  collecting,  permits  them 
to  carry  off  also  such  as  are  gradually  formed,  and  thus  to  keep  it  in  a 
sound  and  healthy  state ;  but  let  this  openness  be  more  or  less  impaired 
by  a  neglect  of  the  drainage,  and  the  original  state  of  the  land  will  again 
gradually  return. 

4°.  This  constant  descent  of  water  through  the  soil  causes  a  similar 
constant  descent  of  fresh  air  through  its  pores,  from  the  surface  to  the 
depth  of  the  drains.  When  the  rain  falls,  it  enters  the  soil  and  more  or 
less  completely  displaces  the  air  which  is  contained  within  its  pores. 
T^his  air  either  descends  to  the  drains  or  rises  into  the  atmosphere. 
When  the  rain  ceases,  the  water,  as  it  sinks,  again  leaves  the  pores  of 
tiie  upper  soil  open,  and  fresh  air  consequently  follows.  It  is  in  fact 
sucked  in  after  the  water,  as  the  latter  gradually  passes  down  to  the 
drains.  Thus,  where  a  good  drainage  exists,  not  only  is  the  land  re- 
freslied  by  every  shower  that  falls — not  only  does  it  derive  from  the 
rains  those  important  substances  which  occasionally,  at  least,  are  brought 
down  by  them  from  the  atmosphere,  and  which  are  in  a  great  measure 
lost  where  the  waters  must  flow  over  the  surface — but  it  is  supplied  also 
with  renewed  accessions  of  fresh  air,  which  experience  has  shown  to  be 
so  valuable  in  promoting  the  healthy  growtli  of  all  our  cultivated  crops. 

5°.  But  other  consequences  of  great  practical  importance  follow  from 
these  immediate  effects.  When  thus  readily  freed  from  the  constant 
presence  of  water,  the  soil  gradually  becomes  drier,  sweeter,  looser,  and 
more  friable.  The  hard  lumps  of  the  stiff'  clay  lands  more  or  less  dis- 
appear. They  crumble  more  freely,  offer  less  resistance  to  the  plough, 
and  are  in  consequence  more  easily  and  economically  worked.  These 
are  practical  benefits,  equivalent  to  a  change  of  soil,  which  only  the 
farmer  of  stubborn  clays  can  adequately  appreciate. 

6°.  With  the  permanent  state  of  moisture,  the  coldness  of  many  soils 
also  rapidly  disappears.  The  backwardness  of  the  crops  iri  sprjng,  and 
the  lateness  of  the  harvests  in  autumn,  are  less  frequently  complained 
of— for  the  drainage  in  many  localities  produces  effects  which  are  equi- 
valent to  a  change  of  climate.  "  In  consequence  of  the  drainage  which 
has  taken  place  in  the  parish  of  Peterhead,  in  Aberdeenshire,  during  the 
last  20  years,  the  crops  arrive  at  maturity  ten  or  fourteen  days  sooner 
than  they  formerly  did  ;"*  and  the  same  is  true  to  a  still  greater  extent 
in  many  other  localities. 

7°.  On  stiff'  clay  lands,  well  adapted  for  wheat,  wet  weather  in  au- 
tumn not  unfrequently  retards  the  sowing  of  winter  corn — in  undrained 
lands,  often  completely  prevents  it — compelling  the  farmer  to  change  his 
system  of  cropping,  and  to  sow  some  other  grain,  if  the  weather  permit 
him,  when  the  spring  comes  round.  An  efficient  drainage  carries  off"  the 
water  so  rapidly  as  to  bring  the  land  into  a  workable  state  soon  after  the 
rain  has  ceased,  and  thus,  to  a  certain  extent,  it  rescues  the  farmer  from 
the  fickle  dominion  of  the  uncertain  seasons.f     To  the  skilful  and  in- 

*  Mr.  Gray,  in  the  Prize  Essays  of  the  Highland  and  Agricultural  Society,  U.,  ■p.  171 
This  opinion  was  given  in  1830,  since  which  time  many  other  extensive  improvements  have 
been  made  in  tliat  part  of  the  island. 

1  "Formerly,"  says  Mr.  Wilson,  of  Cumledge,  in  his  account  of  the  drainage  of  a  farm 
in  Berwiclcshire,  "  this  part  of  the  farm  was  so  wet,  that — though  better  adapted  for  wheat 
than  any  other  crop— the  season  for  sowing  waa  frequently  lost,  and  after  an  experisive  fat 


308  IS    EqUIVALE.NT    TO    A    I  EEPENING    OF    THE    SOIL. 

telligcnl  farmer,  who  applies  every  available  means  to  the  successful 
prosecution  of  his  art,  the  promise  even  in  our  age  and  country  is  sure 
— "that  seed-time  and  harvest  shall  never  fail." 

8°.  But  on  lands  of  every  kind  this  removal  of  the  superfluous  wafer 
is  productive  of  another  practical  benefit.  In  its  consequences  it  is  equi- 
valent to  an  actual  deepening  of  the  soil. 

When  land  on  which  the  surface  water  is  in  the  habit  of  resting,  be- 
comes dry  enough  to  admit  the  labours  of  the  husbandman,  it  is  still 
found  to  be  wet  beneath,  and  the  waters,  even  in  dry  seasons,  not  unfre- 
quently  remain  where  the  roots  of  the  crops  w^ould  otherwise  be  inclined 
to  come.  Or,  if  the  surface  soil  permit  a  ready  passage  to  the  rains,  and 
waters  linger  only  in  the  moist  subsoil,  still — though  the  farmer  may 
not  be  delayed  in  his  labours — the  subsoil  repels  the  approach  of  the 
roots  of  his  grain,  and  compels  them  to  seek  their  nourishment  from  the 
surface  soil  only.  But  remove  the  waters,  and  the  soil  becomes  dry  to 
a  greater  depth.  The  air  penetrates  and  diffuses  itself  wherever  the 
waters  have  been.  The  roots  now  freely  and  safely  descend  into  the 
almost  virgin  soil  beneath.  And  not  only  have  they  a  larger  space 
through  which  to  send  their  fibres  in  search  of  food,  but  in  this  hitherto 
ungenial  soil  they  find  a  store  of  substances — but  sparingly  present,  it  may 
be,  in  the  soil  above — which  the  long- continued  washing  of  the  rains, 
or  the  demands  of  frequent  crops,  may  have  removed,  but  which  may 
have  been  all  the  time  accumulating  in  the  subsoil,  into  which  the 
roots  of  cultivated  plants  could  rarely  with  safety  descend.  It  is  not 
wonderful  then  that  the  economical  effects  of  draining  should  be  found 
by  practical  men  to  be  not  only  a  diminution  in  the  cost  of  cultivation, 
but  a  considerably  augmented  produce  also  both  in  corn  and  grass;  or 
that  this  increased  produce  should  alone  be  found  sufficient  to  repay  the 
entire  cost  of  thorough-draining  in  two  or  three  yeBxs. 

An  obvious  practical  suggestion  arises  out  of  the  knowledge  of  this 
fact.  The  deeper  the  drains,  provided  the  water  have  still  a.  ready  escape^ 
the  greater  the  depth  of  soil  which  is  rendered  available  for  the  purposes 
of  vegetable  nutiition.  Deep-rooted  plants,  such  as  lucerne,  often  fail, 
even  in  moderately  deep  soils,  because  an  excess  of  water  or  the 
presence  of  some  noxious  ingredient  which  deep  drains  would  remove, 
prevents  their  natural  descent  in  search  of  food.  Even  plants,  which, 
like  that  of  wheat  or  clover,  do  not  usually  send  down  their  roots  so  far, 
will  yet,  where  the  subsoil  is  sound  and  dry,  extend  their  fibres  for  three 
or  more  feet  in  depth,  in  quest  of  more  abundant  tiourishment. 

Not  only,  then,  do  deep  drains  permit  the  use  of  the  subsoil  plough 
without  the  chance  tii  injury, — not  only  are  they  less  liable  to  be  choked 
up  by  the  accumulated  roots  of  plants  which  naturally  make  their  way 
into  them  in  search  of  water, — but  they  also  increase  the  value  and  per- 
manent fertility  of  the  land,  by  increasing  its  available  depth.  In  other 
words,  that  kind  of  drainage  which  is  most  efficiently  perforrned,  with  a 
regard  to  the  greatest  number  of  contingencies,  will  not  only  be  the  most 
permanent,  but  will  also  be  followed  by  the  greatest  number  of  eccnomi- 
cal  advantages. 

lowing  and  limeing,  it  was  sown  with  oats  in  spring,  of  which  it  always  produced  very  poor 
crops.  It  is  now  so  dry  as  to  grow  very  good  crops  of  turnip  or  rape,  and  except  in  two 
instances,  I  have  always  sown  my  wheat  in  capital  order." — Prize  Essays  of  the  Highland 
and  Agrictdtural  Society,  I.,  p.  243. 


EFFECT  OF  A  GENERAL  DRAINAGE  OF  THE  SOIL.  309 

9°.  Nor  do  the  immediate  and  practical  benefits  of  draining  end  with 
•vhe  attainment  of  these  beneficial  results.  It  is  not  till  the  land  is  ren- 
dered dry  tliat  the  skilful  and  enterprising  farmer  has  a  Mr  field  on 
which  to  expend  his  exertions.  In  wet  soils,  bones,  wood-ashes,  rape- 
dui5t,  nitrate  of  soda,  and  other  artificial  manures,  are  almost  thrown 
away.  Even  lime  exhibits  but  one-half  of  its  fertilizing  virtue,  where 
water  is  allowed  to  stagnate  in  the  soil.  Give  him  dry  fields  to  work 
upon,  and  the  well-instructed  agriculturist  can  bring  all  the  resources, 
as  well  of  modern  science  as  of  old  experience,  to  bear  upon  them,  with 
a  fair  chance  of  success.  The  disappointments  which  the  holder  of  un- 
drained  lands  so  often  meets  with,  he  will  less  frequently  experience. 
An  adequate  return  will  generally  be  obtained  for  his  expenditure  ia 
manuring  and  otherwise  improving  his  soil,  and  he  will  thus  be  encour* 
aged  to  proceed  in  devoting  his  capital  to  the  permanent  amelioration  of 
his  farm — not  less  for  his  own  than  for  his  landlord's  benefit. 

Viewed  in  this  light,  draining  is  only  the  first  of  a  long  series  of  im- 
provements, or  rather  it  is  a  necessary  preparative  to  the  numerous  im- 
provements of  which  the  soil  of  islands  is  susceptible — which  improve- 
ments it  would  be  a  waste  of  money  to  attempt,  until  an  efficient  system 
of  drainage  is  established.  And  when  we  consider  how  great  a  national 
benefit  this  mere  preparatory  measure  alone  is  fitted  directly  to  confer 
upon  the  country,  you  will  agree  with  me  in  thinking  that  every  good 
citizen  ought  to  exercise  his  influence  in  endeavouring,  in  his  own  district, 
more  or  less  rapidly  to  promote  it.  It  has  been  calculated  that  the  drain- 
age of  those  lands  only,  which  are  at  present  in  arable  culture  (10  mil- 
lions of  acres),  would  at  once  increase  their  produce  by  10  millions  of 
quarters  of  tlie  various  kinds  of  grain  now  grown  upon  them  ; — and  that 
a  similar  drainage  of  the  uncultivated  lands  (15  millions  of  acres) 
would  yield  a  further  increased  produce  of  twice  as  much  more.  This 
increase  of  30  millions  of  quarters  is  equal  to  nearly  one-half  of  our  pre- 
sent consumption*  o^  all  kinds  of  grain — so  that  were  it  possible  to  effect 
at  once  this  general  drainage,  a  large  superfluity  of  corn  would  be  raised 
from  the  British  soil. 

This  general  drainage,  however,  cannot  possibly  be  eflfected  in  any 
given  time.  The  individual  resources  of  the  land-owners  are  not  suffi- 
cient to  meet  the  expense, f  and  such  calculations  as  the  above  are  use- 
ful, mainly,  in  stimulating  the  exertions  of  those  who  have  capital  to 
spare,  or  such  an  excess  of  income  as  can  permit  them  to  invest  an  an- 
nual portion  permanentlyj  in  the  soil. 

10°.  He  who  drains  and  thus  improves  his  oyn  land,  confers  a 
benefit  upon  his  neighbours  also.     In  the  vicinity  of  wet  and  boggy 

•  65  millions  of  qnarters.  See  an  excellent  paper  on  this  subject  in  the  Quarterly  Agri- 
euUuralJournal,  xii,  p.  505,  by  Mr.  Dudgeon,  of  Spyelaw,  in  Roxburghshire,  a  county  in 
which  the  practical  benefits  of  draining  have  been  extensively  experienced,  and  are  therefore 
well  understood. 

t  To  drain  25  millions  of  acres,  at  j66  an  acre,  would  cost  150  millions  sterling,  a  sum  equal, 
probably,  to  the  whole  capital  at  present  invested  in  farming  the  land. 

X  By  an  efficient  drainage  the  soil  is  permanently  benefitted,  but  it  is  not  so  clear  that  the 
money  it  costs  is  permanently  invested  or  hnried  in  the  soil.  If  the  cost  be  repaid  by  the 
increase  of  produce,  in  three  years,  the  money  is  not  invested,  it  is  only  lent  for  this  period 
to  the  soil  *'  I  drain  so  many  acres  every  year,"  said  the  holder  of  a  large  Berwickshire 
farm  to  me,  "  and  I  find  myself  always  repaid  by  the  end  of  the  third  season.  If  I  have 
spare  capital  enough,  therefore,  to  go  on  for  three  years,  I  can  gradually  drain  any  extent  of 
land,  by  the  repeated  use  of  the  same  sum  of  money." 


310  RENDERS  A  COUKTRT    >IORE  SALUBRIOUS. 

lands  the  hopes  of  the  industrious  farmer  are  often  disappointed.  Mi«T« 
are  frequent  and  rains  more  abundant  on  the  edges  of  the  moor,  and 
mill-dews  retard  the  maturity,  and  often  seriously  injure  the  c^ops.  Of 
undrained  land,  in  general,  the  same  is  true  to  a  less  extent,  and  tVie 
presence  of  one  unimproved  property  in  the  centre  of  an  enterprising 
district,  may  long  withhold  from  the  adjoinhig  farms  that  full  measure 
of  benefit  which  the  money  and  skill  expended  upon  them  would  in 
other  circumstances  have  immediately  secured. 

So  true  is  it  in  regard  to  every  new  exercise  of  human  skill  and  in 
every  walk  of  life,  that  we  are  all  mutually  dependent,  every  one  upon 
every  other ;  and  that  the  kindly  co-operation  of  all  can  alone  secure 
that  ample  return  of  good,  which  the  culture  either  of  the  dead  earth 
or  of  the  living  intellect  appears  willing,  and  we  may  hope  is  ultimately 
destined,  to  confer  upon  our  entire  race. 

11°.  I  would  not  here  willingly  neglect  to  call  your  attention  to  a 
higher  benefit  still,  which  the  skilful  drainage  of  an  extensive  district  is 
fitted  to  confer  upon  its  whole  population.  Not  only  is  this  drainage 
equivalent,  as  above  stated,  to  a  change  of  climate  in  reference  to  the 
growth  and  ripening  of  plants,  but  it  is  so  also  in  reference  to  the  gene- 
ral health  of  the  people,  and  to  the  number  and  kind  of  the  diseases  to 
which  they  are  observed  to  be  exposed. 

I  may  quote  in  illustration  of  this  fact  the  interesting  observations  of 
Dr.  Wilson  on  the  comparative  state  of  health  of  the  labouring  popula- 
tion in  the  district  of  Kelso  during  the  last  two  periods  of  ten  years.  In 
his  excellent  paper  on  this  subject,  in  the  Quarterly  Journal  of  Agricul- 
ture, (volume  xii.,  p.  317),  he  has  shown  that  fever  and  ague,  which 
formed  nearly  one-half  of  all  the  diseases  of  the  population  during  the 
former  ten  years,  have  almost  wholly  disappeared  during  the  latter  ten, 
in  consequence  of  the  general  extension  of  an  efficient  drainage  through- 
out the  country  ;  while,  at  the  same  time,  the  fatality  of  disease,  or  the 
comparative  number  of  deaths  from  every  hundred  cases  of  serious  ail- 
ment, has  diminished  in  proportion  of  4*6  to  2*59.  Such  beneficial  re- 
sults, though  not  immediately  sought  for  by  the  practical  farmer,  yet 
are  the  inevitable  consequence  of  his  successful  exertions.  Apart,  there- 
fore, from  mere  considerations  of  pecuniary  profit,  a  desire  to  promote 
the  general  comfort  and  happiness  of  the  entire  inhabitants  of  a  district 
may  fairly  influence  the  possessors  of  land  to  promote  this  method  of 
ameliorating  the  soil ;  while  the  whole  people,  on  the  other  hand,  of 
whatever  class,  ought  "gratefully  to  acknowledge  the  value  of  those  im- 
provements which  at  once  render  our  homes  more  salubrious  and  our 
fields  more  fruitful.'^ 


The  practical  benefits  of  draining,  therefore,  may  be  stated  generally 
as  follows  : — 

A.  It  is  equivalent  not  only  to  a  change  of  soil,  but  also  to  a  change 
of  climate,  both  in  reference  to  the  growth  of  plants  and  to  the  health 
of  the  population. 

B.  It  is  equivalent  also  to  a  deepening  of  the  soil,  both  by  removing 
the  water  and  by  allowing  those  noxious  ingredients  to  be  washed  out 


BENEFITS  POROUS  SOILS. — ORIGIN  OF  MOOR-LAND.  31*1 

of  the  subsoil  which  had  previously  prevented  the  roots  from  descend- 
ing. 

C.  It  is  a  necessary  preparation  to  the  many  other  means  of  improve- 
ment which  may  be  applied  to  the  land. 

You  will  now  be  able  to  perceive  in  what  way  it  is  possible  that 
even  light  and  sandy  soils,  or  such  as  lie  on  a  sloping  surface,  may  be 
greatly  benefitted  by  draining.  Where  no  open  outlet  exists  under  a 
loamy  or  sandy  surface  soil,  any  noxious  matters  that  either  sink  from 
above,  or  ooze  up  from  beneath,  will  long  remain  in  the  subsoil,  and 
render  it  more  or  less  unwholesome  to  valuable  cultivated  plants.  But 
let  such  an  outlet  be  made  by  the  establishment  of  drains,  and  that 
which  rises  from  beneath  will  be  arrested,  while  that  which  descends 
from  above  will  escape.  The  rain-waters  passing  through  will  wash 
the  whole  soil  also  as  deep  as  the  bottom  of  the  drains,  and  the  atmos- 
pheric air  will  accompany  or  follow  them. 

The  same  remarks  apply  to  lands  which  p^sess  so  great  a  natural 
inclination  as  to  allow  the  surface  water  readily  to  flow  away.  Such  a 
sloping  surface  does  not  necessarily  dry  the  subsoil,  free  it  from  noxious 
substances,  or  permit  the  constant  access  of  the  air.  Small  feeders  of 
water  occasionally  make  their  way  near  to  the  surface,  and  linger  long 
in  the  subsoil  before  they  make  their  escape.  This  is  in  itself  an  evil ; 
but  wben  such  springs  are  impregnated  with  iron  the  evil  is  greatly 
augmented,  and  from  such  a  cause  alone  a  more  or  less  perfect  barren- 
ness not  unfrequently  ensues.  To  bring  such  lands  by  degrees  to  a 
sound  and  healthy  state,  a  mere  outlet  beneath  is  often  alone  sufficient. 

It  is  to  this  lingering  of  unwholesome  waters  beneath,  that  the  origin 
of  many  of  our  moor-lands,  especially  on  higher  grounds,  is  in  a  great 
measure  to  be  attributed.  A  calcareous  or  a  ferruginous  spring  sends  up 
its  waters  into  the  subsoil.  The  slow  access  of  air  from  above,  or  it 
may  be  the  escape  of  air  from  water  itself,  causes  a  more  or  less  ochrey 
deposit,*  which  adheres  to  and  gradually  cements  the  stones  or  earthy 
particles,  among  which  the  water  is  lodged.  Thus  a  layer  of  solid 
stone  is  gradually  formed — the  moor-land  fan  of  many  districts — which 
neither  allows  the  roots  of  plants  to  descend  nor  the  surface  water  to  es- 
cape. Hopeless  barrenness,  therefore,  slowly  ensues.  Coarse  grasses, 
mosses,  and  heath,  grow  and  accumulate  upon  soils  not  originally  in- 
clined to  nourish  them,  and  by  which  a  better  herbage  had  previously 
been  long  sustained.  Of  such  lands  many  tracts  have  been  reclaimed 
by  breaking  up  this  moor-land  pavement,  but  such  an  improvement, 
unless  preceded  by  a  skilful  drainage,  can  only  be  temporary.  The 
same  natural  process  will  again  begin,  and  the  same  result  will  follow, 
unless  an  outlet  be  provided  for  the  waters  from  which  the  petrifying 
deposit  proceeds. 

It  ought  to  be  mentioned,  however,  that  where  a  ready  passage  and 
escape  for  the  water  is  provided  by  an  efficient  drainage,  and  especially 
in  light  and  porous  soils,  the  saline  and  other  soluble  substances  they 

•  If  the  wafer  contain  8M//)^afe  of  iron,  the  air  from  above  will  impart  to  its  iron  an  ad- 
ditional quantity  of  oxygen,  and  cause  a  portion  of  it  to  fall  in  the  slate  of  peroxide.  If  the 
iron  or  lime  be  present  in  the  state  of  fticarbonate,  the  escape  of  carbonic  acid  from  the 
water  will  cause  a  deposit  of  carbonate  of  iron  or  of  lime.  Any  of  these  deposits  will 
cement  the  earthy  or  stony  particles  together.  Iron,  however,  is  sometimes  held  in  solu- 
tion by  an  orgaxiic  acid  (wentc),  which  becomes  insoluble,  and  falls  along  with  the  iron 
when  the  latter  has  absorbed  more  oxygen  from  the  atmosphere. 


312  THEORY  OF  SPRINGS. 

contain  will  be  liable,  in  periods  of  heavy  rain,  to  be  more  or  less  com- 
pletely washed  out  and  carried  otf  by  the  water  that  trickles  through 
them.  While,  therefore,  the  establishment  of  drains  on  all  soils  may 
adapt  and  ])repare  them  for  further  improvements,  and  may  make  them 
more  grateful  for  every  labour  or  attention  that  may  be  bestowed  upon 
them — yet  after  drainage  they  must  be  more  liberally  dealt  with  than 
before,  if  the  increased  fertility  they  at  first  exhibit  is  to  be  permanently 
maintained  or  increased. 

§  3.   Of  the  theory  of  Springs. 

In  the  general  drainage  of  the  land  a  double  object  is  sought  to  be  at- 
tained. In  very  rainy  districts,  the  first  wish  of  the  farmer  is  to  carry 
off  the  surface  water  from  his  fields — but  where  less  rain  falls,  that 
which  ascends  from  beneath  in  springs,  attracts  at  least  an  equal  share 
of  the  husbandman's  regard.  In  draining,  with  a  view  to  the  removal 
of  this  latter  source  of  llperfluous  moisture,  a  knowledge  of  the  true 
theory  of  springs,  as  indicated  by  an  examination  of  certain  geological 
phenomena,  is  of  the  greatest  possible  service  to  the  practical  man,  in 
pointing  out  the  sources  from  which  the  water  that  injures  his  land  pro- 
ceeds, as  well  as  the  lines  along  which  it  may  be  most  etiiciently  and 
most  economically  carried  off". 

1°.  The  rain  which  falls  on  the  surface  of  an  extensive  tract  of  country 
partly  escapes  into  the  rivers,  and  partly  sinks  into  the  earth.  This 
latter  portion  descends  through  the  covering  of  soil  and  other  loose  ma- 
terials till  it  reaches  the  rocks  on  which  they  rest.  If  these  rocks  are 
porous,  like  many  sand-stones,  or  are  traversed  by  cracks  and  vertical 
fissures,  as  many  sand-stones  and  lime-stones  are,  it  descends  through 
them  also  till  it  reaches  a  bed,  such  as  one  of  indurated  clay,  so  close  and 
compact  as  to  resist  its  further  passage.  By  this  impervious  bed  the  wa- 
ter is  arrested,  and  is,  therefore,  compelled  to  spread  itself  laterally,  and 
gradually  to  accumulate  in  the  beds  that  lie  above  it.     Thus,  if  the 


outline  from  A  to  C  in  the  annexed  diagram  represent  the  surface  of  an 
undulating  country,  «  which  the  subjacent  rocks  (1,  2,  3,  4)  are  covered 
by  a  considerable  thickness  of  loose  materials,  the  rain  which  falls  from 
A  to  B  will  sink  more  or  less  rapidly  to  the  bed  (1),  and,  if  this  be  im- 
l)ermoable  to  water,  will  rest  there,  or  will  slowly  drain  off'  in  the  di- 
rection of  B  and  C  along  the  inclined  surface  of  the  rock.  But  if  (1) 
be  porous,  it  will  sink  through  it  to  the  surface  of  the  bed  (2),  and 
through  this  also,  if  permeable,  to  (3)  or  (4),  until  it  reaches  the  stratum 
through  which  it  cannot  pass.  On  the  surface  of  this  latter  bed,  or 
among  the  rocks  above  it,  the  water  will  accumulate  until,  flowing 
downwards  towards  C,  it  is  enabled  either  to  sink  among  the  deeper 
rocks  or  to  make  its  escape  again  to  the  surface. 

But  if  the  rocks  beneath,  as  is  shown  in  the  same  diagram  from  E  to 
F,  be  traversed  by  vertical  fissures  passing  through  two  or  more,  or,  like 
the  one  represented  from  B  to  E,  through  a  great  number  of  beds,  tha 


WATER  IS  AR-tLESTED  BY  IMPERVIOUS  BEDS. 


313 


water  that  falls  on  the  surface  will  readily  find  a  passage  downwards  to 
a  considerable  depth,  and  to  the  same  cracks  the  water  that  lodges 
among  the  un  fissured  rocks  from  D  to  E  will  also  gradually  make  its  way. 

The  practical  effects  of  these  several  conditions  on  the  drainage  of  a 
country  are  very  obvious.  If  the  stratum  (1)  be  impervious  to  wafer, 
the  surface  from  A  to  B  may  be  full  of  water,  and  may  urgently  de- 
mand the  introduction  of  drains,  whereas  if  (1)  and  (2)  be  porous,  tho 
surface  water  will  gradually  sink,  and  the  apparent  necessity  for  artifi- 
cial drainage  will  become  much  less  striking.  On  tlie  other  hand, 
where  ihe  rocks  are  filled  with  frequent  cracks<  as  from  B  to  C,  the 
surface  water  may  descend  and  disappear  so  rapidly,  as  to  render 
useless  the  sinking  of  wells — and,  as  in  dry  summers,  greatly  to  retard 
the  progress  of  the  crops,  or  even  seriously  to  injure  the  produce  of  the 
harvest.  Tn  such  a  fissured  state  are  the  magnesian  lime-stone  rocks  in 
some  parts  of  the  county  of  Durham — and  such  is  the  consequent  scar- 
city of  water,  on  some  farms,  that  when,  in  long  droughts,  the  supply 
})reserved  in  artificial  tanks  begins  to  fail,  the  cattle  must  be  driven  to 
water  sometimes  for  miles,  to  the  nearest  living  brook. 

2^.  But  water  often  finds  its  way  to  greater  depths  without  passing 
through  the  superior  strata,  and  even  where  they  are  absolutely  impervi- 
ous to  the  rains  that  fall  upon  them.  Thus  along  the  country  from  A  to 
B,  and  especially  towards  A,  the  surface  soil  rests  upon  the  upper  edges 


of  ihe  strata.  Suppose  now  the  beds  1,  2,  3,  to  be  impervious  to  water, 
the  rain  tliat  falls  wherever  these  rocks  lie  immediately  beneath  the  sur- 
fnce  will  either  remain  stagnant,  or  will  flow  off" by  some  natural  drain- 
age. Thus  from  the  highest  point  C  in  the  above  diagram,  the  water 
will  descend  on  either  hand  towards  a  and  b.  At  h  it  may  remain  stag- 
nant, for  it  cannot  descend  through  the  bed  (2),  which  forms  the  bottom 
of  the  valley,  and  the  same  is  true  of  the  hollow  c,  in  which  other  por- 
tions of  the  water  will  rest.  All  this  tract  of  country,  therefore,  will  be 
m-ore  or  less  cold,  wet,  and  consequently  unproductive.  But  let  the  bed 
(4),  the  edge  (or  outcrop)  of  which  forms  the  surface  at  a,  be  porous  or 
permeable,  then  the  water  which  falls  upon  that  spot  or  which  descends 
from  the  higher  grounds  about  C  and  A,  will  readily  sink  and  drain  ofT, 
descending  from  a  towards  d  along  the  inclined  bed  till  it  finds  an  outlet 
'n  the  latter  direction. 

Thus  it  may  readily  happen  that  a  naturally  dry  and  fertile  valley,  as 
at  rt,  may  exist  at  no  great  distance  from  others,  h  and  c,  which  are 
marshy  and  insalubrious,  and  in  which  artificial  drainage  alone  can  de- 
velope  the  agricultural  capabilities  of  the  soil.  It  appears  also  that, 
though  in  any  district  the  rocks  which  lie  immediaiely  beneath  the  sur- 
face may  contain  no  water,  and  may  allow  none  to  pass  through  them, 
yet  that  other  beds,  perhaps  at  a  great  depth  beneath,  may  contain  much. 
It  is,  in  fact,  this  accumulation  of  water  beneath  impervious  beds  that 


314 


SPRINGS  PRODUCED  BY   VALLEYS  AND  SLIPS. 


gives  rise  to  so  many  natural  springs,  and  enables  us  by  artiBcial  wells 
to  bring  water  to  the  surface — often  where  the  land  would  otherwise  be 
wholly  uninhabitable.  ♦ 

3°.  Thus  in  undulating  countries,  where  hill-sides  frequently  pre- 
sent themselves,  or  valleys  are  scooped  out  among  the  rocks,  as  in  the 
following  wood-cut,  the  water  that  has  fallen  over  the  high  grounds  to- 


wards A,  and  has  entered  as  above  described,  or  has  sunk  down  to  the 
several  strata  1,  2,  3,  &c.,  will  find  a  ready  outlet  along  the  slojje  of  tlie 
valley,  and  will  give  rise  to  springs  at  a,  b,  c,  or  d,  according  as  the  wa- 
ter has  lodged  in  the  one  or  the  other  of  these  beds.  These  springs  will 
fill  the  surface  soil  with  water,  which  will  also  descend  into  the  botiom  of 
the  valley,  and,  if  no  sufficient  outlet  be  provided  for  it,  will,  according 
to  its  quantity,  give  rise  to  a  lake,  a  bog,  or  a  morass.  On  the  slope  to- 
wards B  the  same  springs  are  not  to  be  expected,  since  the  rains  which 
sink  through  the  surface  on  this  side  of  the  valley,  and  lodge  in  the  po- 
rous rocks  beneath,  will,  by  the  inclination  of  the  beds,  be  drawn  off  in 
the  opposite  direction,  till  a  second  valley  or  some  other  available  outlet, 
present  itself  for  their  escape.  This  explains  why  the  land  on  one  side 
of  a  valley  or  of  a  hill  is  often  much  drier  than  on  the  other,  and  why, 
even  in  the  absence  of  the  improver's  skill,  an  apparently  more  fertile 
soil  may  exist,  and  betler  crops.be  reaped. 

4°.  Again,  such  an  outlet  for  the  waters  that  rest  among  inclined  strata 
is  not  unfrequently  afibrded,  without  the  intervention  of  valleys,  and 
even  in  level  or  hilly  countries,  by  the  existence  of  slips  or  faults  in  the 
rocks  beneath.     Such  a  slip  or  shifting  of  the  beds  is  represented  in  the 


annexed  diagram,  in  which  B  D  is  a  crack,  along  which  the  strata  from 
B  to  C  appear  to  have  slipped  downwards,  so  that  the  thin  bed  (2),  for 
example,  which  terminates  at  b  on  the  one  side  of  the  crack,  begins  again 
at  a  lower  level  c  on  the  other  side,  and  so  with  the  other  beds  that  lie 
above  and  below  it.  None  of  them  is  exactly  continuous  on  the  oppo- 
site sides  of  the  slip.  From  such  cracks  or  faults  in  the  beds,  springs  of 
water  often  rise  to  the  surface,  even  on  hill  tops,  as  at  B,  and  they  may 
be  thus  thrown  or  forced  out  from  either  of  two  causes — 

1.  These  slips  are  often  of  considerable  width,  and  arfe  usually  found 
to  be  filled  with  impervious  clay.  This  is  the  case  at  least  among  the 
coal  measures,  which  have  beeu  the  most  extensively  explored.  The 
effect  of  this  wall  of  clay  is  to  dam  back  at  B  D  the  water  which  de- 


SLIPS   ARREST   AND    THROW    UP    THE    WATER. 


315 


scends  along  the  inclined  beds  towards  C  from  the  country  beyond  A, 
and  thus  to  arrest  its  further  progress.  But  the  pressure  of  the  water 
behind  forces  that  which  has  reached  the  fault  B  D  to  seek,  a  way  up- 
wards, and,  as  spaces  not  unfrequently  exist  between  the  wall  of  clay 
and  the  rocks  between  which  it  stands,  the  water  jfinds  a  more  or  less 
ready  outlet  at  the  surface  B,  and  either  gushes  forth  as  a  living  and 
welcome  spring,  or  oozes  out  unseen  among  the  soil,  rendering  it  cold, 
wet,  and  unproductive.  Thus  from  6  the  water  accumulated  in  the  bed 
(2)  may  rise  to  the  surface,  or  from/ that  which  exists  in  (4),  or  from 
any  other  bed  in  which  water  exists,  and  from  almost  any  depth. 

2.  But  even  where  no  such  wall  of  clay  exists,  the  waters  may  still 
find  their  way  to  the  surface  along  lines  of  fault,  and  from  great  depths. 
Thus  suppose  the  thin  bed  (2)  to  be  full  of  water,  and  that  it  is  covered 
by  an  impervious  bed  (1),  then  the  water  which  tends  downwards  from 
a  to  b  will  be  arrested  at  the  fault,  and  dammed  back  by  the  impervious 
extremity  of  (1)  against  which  it  now  rests.  If  an  outlet  can  be  found, 
it  will  therefore  rise  towards  the  surface.  And  as  the  rocks  incline  up- 
wards in  the  direction  of  A,  the  pressure  from  behind  may  easily  cause 
the  water  to  ascend  to  the  summit  of  the  hill  at  B,  and  to  gush  out  in  a 
more  or  less  copioas  spring. 

5°.  Where  no  natural  outlets  of  the  kind  above  described  exist  in^a 
district,  there  may  be  a  great  scarcity  of  water  on  the  surface,  while 
abundance,  as  we  have  already  seen  (2°),  may  exist  in  the  rocks  be- 
neath, ready  and  willing  to  rise  if  a  passage  be  opened  for  it.  Such  is 
the  case  with  the  site  of  the  city  of  London,  represented  below  : — 


St.  Alban's. 


Hampstead.         London.  Thames.    Sydenham. 


Knockholt. 


SECTION  ACROSS  THE  LONDON  BASIN  FROM  ST.  ALBAN'S  TO  KNOCKHOLT. 

iBiickland's  Bridgewater  Treatise,  plate  69.) 
1.  Marine  Sand.     2.  London  Clay  (almost    impermeable).    3.  Plastic  Clay  and  Sand. 
4.  Chalk,  both  full  of  water. 

The  rain-water  which  falls  between  a  and  A  on  the  one  hand,  and 
upon  the  plastic  clay  and  chalk  between  d  and  B  on  the  other,  sinks  into 
these  two  beds  and  rests  in  them  till  it  finds  an  escape.  It  cannot  rise 
through  the  great  thickness  of  impervious  clay  on  which  London  and  its 
neighborhood  stands,  unless  where  wells  are  sunk,  as  above  represented 
at  a,  6,  c,  d,  either  into  the  plastic  clay  (3),  or  into  the  chalk  (4),  when 
the  water  ascends  copiously  till  it  reaches  the  general  level  of  the  country 
about  St.  Alban's,  the  lowest  part  of  the  basin  where  the  permeable  beds 
form  the  surface.  Hence  in  the  vale  of  the  Thames  at  &,  it  rises  above 
the  surface,  and  forms  a  living  spring,  while  at  other  places,  as  at  a,  c,  </, 
it  has  still  to  be  pumped  up  from  a  greater  or  less  depth.*     It  is  the  ex- 

*  In  January  1840,  there  were  stated  to  be  in  the  London  clay  upwards  of  200  such  wells, 
of  which  174  were  in  London,  and  of  which  latter  30  taken  together  were  known  to  yield  30 
14 


316      ARTESIAN  WELLS. SPRINGS  IN  DESERTS  AND  PARCHiHD  PLAINS. 

istence  of  water  beneath  the  surface  where  the  soils  rest  on  impermea 
ble  beds,  and  the  known  tendency  of  these  waters  to  rise  when  a  boring 
is  sunk  to  them,  that  have  given  rise  to  the  establishment j?f  Artesi(m* 
wells,  so  frequently  executed,  and  with^o  much  success,  in  recent  times. 
There  is  probably  no  geological  fact  that  promises  hereafter  to  be  of  more 
practical  value  to  mankind,  when  good  government  and  the  arts  of  peace 
shall  obtain  a  permanent  resting-place  in  those  countries  where,  without 
irrigation,  the  soil  remians  hopelessly  barren.  Wherever  a  living  spring 
bursts  out  in  the  sands  of  Arabia,  in  the  African  deserts,  or  in  the  parched 
plains  of  South  America,  an  island  of  perennial  verdure  delights  the  eye 
of  the  weary  traveller,  and  wherever  in  such  countries  the  labour  of  man 
has  been  expended  in  digging  wells,  and  in  raising  water  from  them  for 
artificial  irrigation,  the  same  beauty  and  fertility  always  appear.  It 
has  recently  been  found  that  the  oases  of  Thebes  and  Garba,  in  Upper 
Egypt,  where  the  blown  sands  now  hold  a  scarcely  disputed  dominion, 
are  almost  riddled  with  wells  sunk  by  the  ancient  Egyptians,  but  for  the 
greater  part  long  since  filled  up.  The  re-opening  of  such  wells  might 
restore  to  these  regions  their  long-lost  fertility,  as  the  sinking  of  new 
ones  by  our  easier  and  more  economical  methods  might  reclaim  many 
other  wide  tracts,  and  convert  them  to  the  use  of  man.  In  contemplating 
what  man  may  do,  when  his  angry  passions  and  his  prejudices  do  not 
interfere  with  the  exercise  of  his  natural  dominion  over  dead  matter,  it  is 
not  unreasonable  to  hope  that,  guided  by  such  indications  of  natural 
science,  human  industry  may  hereafter,  by  slow  degrees,  re-establish  its 
power  in  long-deserted  regions  of  country,  spreading  abundance  over  the 
broad  wilderness,  staying  the  Arab's  wandering  foot,  and  fixing  his 
household  in  a  permanent  and  plenteous  home. 

6°.  It  not  unfrequently  happens  that  alternate  layers  of  sand  and  clay 
overspread  the  rocks  of  a  country,  and  act  in  arresting  or  in  throwing  out 
the  surface  water  in  the  same  manner  as  the  solid  strata  beneath.     Thus 


under  the  surface  A  B  here  represented,  alternate  layers  of  sand  and  clay 
overspread  the  inclined  beds  of  rock,  and  alone  affect  not  only  the  qual- 
ity but  the  state  of  dryness  also  of  the  soil. 

The  rain  which  falls  on  the  upper  bed  of  sand  will  sink  no  further 
than  the  first  bed  of  clay,  and  will  appear  as  a  spring,  or  will  form  a 
wet  band  along  the  side  of  the  hill,  at  a.  That  which  falls  or  exists  in 
the  second  bed  of  sand  will  in  like  manner   ome  to  day  at  6,  c,  and  d,  e, 

millions  of  gallons  weefely.  "Ais  number  of  wella  has  since  been  increased,  and  is  still 
increasing.  Tiie  borings  are  generally  carried  down  into  the  chalk,  because  the  water  which 
ascends  from  the  plastic  clay  has  been  found  to  bring  with  it  much  sand,  which  both  ob« 
structs  the  pipes  and  is  injurious  to  the  pumps. 

*  So  called  from  the  district  of  Jr/ots,  in  France,  in  which  it  was  formerly  sapposed  that 
such  borings  had  been  longest  or  most  extensively  practised. 


EFFECT    OF    ALTERNATE    LAYERS    OF    SAND    AND    CLAY.  317 

filling  the  two  vallies  more,  or  less  with  water,  and  forming  wet  tracts  of 
country  resting  upon  a  lower  bed  of  impervious  clay. 

In  endeavouring  to  form  a  satisfactory  opinion  as  to  the  best  mode  of 
draining  a  piece  of  land,  it  is  of  great  importance  to  be  able  to  determine 
not  only  the  immediate  natural  source  of  the  water  we  are  desirous  tore- 
move,  but  also  the  probable  quantity  it  may  be  necessary  to  carry  off, 
and  the  'permanence  of  the  supply.  It  is  well  known,  for  example,  that 
in  many  spots,  when  the  accumulated  waters  are  once  carried  off,  there 
remains  only  a  small  and  probably  intermitting  supply,  for  wjwch  an 
outlet  is  afterwards  to  be  left  and  kept  open  ;  while  in  other  localities  a 
constant  stream  of  water  is  seen  to  pass  along  the  drains.  In  connection 
with  this  point  it  is  of  consequence  to  make  out  whether  the  water  is 
thrown  out  by  surface  clays,  as  in  this  latter  diagram,  or  flows  from 
among  the  solid  rocks  at  a  greater  or  less  depth — as  shown  in  the  prece- 
ding wood-cuts.  That  which  is  thrown  out  by  beds  of  clay  is  in  most 
cases  derived  only  from  the  rains  that  fall,  and  is,  therefore,  liable  to  in- 
termit, to  cease  altogether,  or  to  become  more  copious,  according  as  the 
season  is  dry  or  otherwise  ;  while  that  which  escapes  from  a  bed  of  rock, 
being  independent  of  the  seasons,  will  seldom  vary  in  quantity.  Thus 
it  happens  that  where  surface  water  only  stagnates  in  the  soil  of  a  district, 
a  warm,  dry,  and  long  continued  summer  may  cause  it  to  yield  a  crop 
of  unusual  excellence,  while  other  soils  fed  by  springs  from  beneath  may, 
even  in  such  seasons,  still  retain  moisture  enough  to  render  them  unfit  to 
rear  and  ripen  a  profitable  crop  of  corn. 

7°.  There  remains  one  other  interesting  principle  connected  with  this 
subject,  which  I  must  briefly  explain  to  you.     Let  C  and  D  in  the  ac- 


companying wood-cut  be  two  impervious  beds  through  which  tjjie  water 
finds  noescape,  and  from  which  the  rains  pass  oflTonly  by  the  natural  in- 
clination of  the  ground,  and  let  E  be  a  porous  bed  from  which  the  water 
finds  a  ready  escape  somewhere  towards  the  right.  Then  if  a  boring 
be  sunk  through  C  and  D  in  any  part  of  this  tract  of  country,  the  wa- 
ter will  descend,  and.  will  be  absorbed  by  the  bed  E.  Such  dry,  porous 
or  absorbent  beds  exist  in  many  localities,  and  the  skilful  drainer  may 
occasionally  avail  himself  of  their  aid  in  easily  and  effectually  freeing 
land  from  water,  which  could  not  without  great  cost  be  permanently 
drained  by  any  other  method.  Where  water  collects  on  a  surface  rest- 
ing upon  chalk,  or  upon  the  loose  sands  beneath  it,  this  method  of  boring 
is  frequently  had  recourse  to  in  some  of  our  southern  counties.  One  dan- 
ger, however,  is  to  be  guarded  against  in  trying  this  method,  that  the 
bore-rod,  namely,  may  enter  a  bed  which  is  full  of  water,  and  from 
which,  as  in  Artesian  wells,  it  may  readily,  and  in  considerable  quantity, 
ascend.  Such  a  boring  it  is  obvious  would  only  add  to  the  evil,  and 
might  render  necessary  a  larger  outlay  in  establishing  an  efficient  syg- 


318 


PLOUGHING    AND    SUBSOILINO. 


tern  of  drainage  by  the  ordinary  method,  than  would  otherwise  have  been 
required.* 

I  do  not  enter  into  any  further  details  in  regard  to  the  application  of 
these  principles  to  the  practice  of  draining,  being  satisfied  that  when  you 
have  once  mastered  the  principles  themselves,  the  applications  will 
readily  suggest  themselves  to  your  own  minds  when  circumstances  re- 
quire it. 

§  4.  Of  ploughing  and  suhsoiling. 

I.  jrloughing. — Apart  from  the  obvious  effect  of  ploughing  the  land, 
in  destroying  weeds  and  insects,  the  immediate  advantage  sought  for 
by  the  farmer  is  the  reduction  of  his  soil  to  a  state  of  minute  division. 
In  this  state  it  is  not  only  more  pervious  to  the  roots  of  his  corn,  but  it 
also  gives  a  more  ready  admission  to  the  air  and  to  water. 

Of  the  good  effects  produced  by  the  easy  descent  and  escape  of  water 
from  the  surface,  I  have  already  spoken  (p.  306),  but  the  permeability 
of  tlie  soil  to  air  is  no  less  useful  in  developing  its  natural  powers  of  pro- 
duction. How  important  the  presence  of  the  air  is  both  to  the  mainten- 
ance of  animal  and  to  the  support  of  vegetable  life,  we  have  had  fre- 
quent occasion  to  observe.  By  its  oxygen  the  breathing  of  animals  is 
sustained,  and  by  its  carbonic  acid  the  living  plant  is  fed.  On  the  earthy 
particles,  of  which  the  soil  consists  also,  the  influence  of  these  gaseous 
substances,  though  not  so  visible  and  striking,  is  of  almost  equal  conse- 
quence in  the  economy  of  nature.  Among  other  immediate  benefits 
derived  from  the  free  access  of  air  into  the  soil,  we  may  enumerate  the 
following : — 

1°.  The  presence  of  oxygen  in  the  soil  is  necessary  to  the  healthy 
germination  of  all  seeds  (page  132),  and  it  is  chiefly  because  they  are 
placed  beyond  its  reach,  that  those  of  many  plants  remain  buried  for 
years  without  signs  of  life,  though  they  freely  sprout  when  again  brought 
to  the  surface  and  exposed  to  the  air.  We  have  also  seen  reason  "to  be- 
lieve (page  77),  that  the  roots  of  living  plants  require  a  supply  of 
oxygen  in  order  that  they  may  be  maintained  in  a  healthy  condition. 
Such  a  supply  can  only  be  obtained  where  the  soil  is  sufficiently  open 
to  perrrfft'the  free  circulation  of  the  air  among  its  pores. 


•  It  sometimes  happens  that  in  sinking  an  old  well  deeper 
for  the  purpose  of  obtaining  a  better  supply  of  water,  the 
original  springs  disappear  altogether.  This  is  owing  to  the 
occurrerice  at  this  greater  depth,  of  an  absorbent  bed,  in 
which  the  water  disappears.  By  descending  still  farther,  a 
second  supply  of  water  may  often  be  found,  but  which  will 
naturally  ascend  uo  further  than  the  absorbent  bed,  by  which 
the  whole  supply  will  be  drunk  np,  if  not  prevented  by  the 
insertion  of  a  nietal  pipe.  Advantage  is  sometimes  taken  of 
the  known  existence  of  such  absorbent  strata,  not  only  for  the 
purposes  of  draining,  but  also  for  removing  "vaste  water  of 
various  kinds.  An  interestine  example  ofsucrj  application  is 
to  be  seen  at  St.  Denis,  in thePlace aux  Gueldres,  where  the 
water  from  the  bed /at  the  depth  of  200  feet  ascends  through 
the  inner  tube  a— from  another  bed  c,  at  160  feet,  through  the 
tube  b — while  between  it  and  the  outermost  tube,  through  the 
space  c,  it  is  sent  down  again  after  it  has  been  employed  in 
washing  the  square,  and  disappears  in  the  absorbent  stra- 
iumd 


— f-^Tpl 

a      

e        c 

^ Vl ^ 

e        ~        e 

•y— 


DECOMPOSITION    OF    ROCKF    MOUNTAINS.  31% 

4 

2°.  In  the  presence  of  air  the  decomposition  of  the  vegetable  matter 
of  the  soil  proceeds  more  rapidly — it  is  more  speedily  resolved  into  those 
simpler  forms  of  matter,  carbonic  acid  and  water  chiefly  (page  152), 
which  are  fitted  to  minister  to  the  growth  of  new  vegetable  races.  In 
the  absence  of  the  air  also,  not  only  does  this  decomposition  proceed 
more  slowly,  but  the  substances  immediately  produced  by  it  are  fre- 
quently unwholesome  to  the  plant,  and  therefore  fitted  to  injure,  or  ma- 
terially to  retard,  its  growth. 

3°.  When  the  oxygen  of  the  air  is  more  or  less  excluded,  the  vege- 
table matter  of  the  soil  takes  this  element  from  such  of  the  earthy  sub- 
stances as  it  is  capable  of  decomposing,  and  reduces  them  to  a  lower 
state  of  oxidation.  Thus  it  converts  the  red  or  per-oxide  of  iron  into 
the  ^ro^-oxide  (p.  211),  and  it  acts  in  a  similar  manner  upon  the  oxides 
of  manganese  (p.  213).  Jtalso  takes  their  oxygen  from  the  sulphates  (as 
from  gypsum),  and  converts  them  into  sulphurets.  These  lower  oxides 
of  iron  and  manganese  are  injurious  to  vegetation,  and  it  is  one  of  the 
beneficial  purposes  served  by  turning  up  the  soil  in  ploughing,  or  by 
otherwise  loosening  it  so  as  to  allow  the  free  admission  of  atmospheric 
air,  that  the  natural  production  of  these  oxides  is  either  in  a  great  mea- 
sure prevented,  or  that  when  produced  they  speedily  become  harmless 
again  by  the  absorption  of  an  additional  dose  of  oxygen. 

4°.  Further,  there  are  few  soils  which  do  not  contain,  in  some  quan- 
tity, fragments  of  one  or  other  of  those  compound  mineral  substances  of 
which,  in  a  previous  lecture,  (xii.,  p.  257,)  we  have  seen  the  crystalline 
rocks  to  consist — of  hornblende,  of  mica,  of  felspar,  &c.,  in  a  decom- 
posing state.  From  these  minerals,  as  they  decompose,  the  soil,  and 
therefore  the  plants  that  grow  in  it,  derive  new  supplies  of  several  of 
those  inorganic  substances  which  are  necessary  to  the  healthy  nourish- 
ment of  cultivated  crops.  The  continued  decomposition  of  these  mine- 
ral fragments  is  aided  by  the  access  of  air,  and  near  its  surface,  in  an  es- 
pecial manner,  by  the  carbonic  acid  which  the  air  contains.  A  state  of 
porosity,  therefore,  or  a  frequent  exposure  to  the  air,  is  favourable  to  the 
growth  of  the  plant,  by  presenting  to  its  roots  a  larger  abundance  not  only 
of  organic  but  also  of  inorganic  food. 

5^.  Again,  that  production  of  ammonia  and  of  nitric  acid  in  the  soil, 
to  which  I  drew  your  especial  attention  on  a  former  occasion  (pages  157 
and  160),  as  apparently  of  so  much  consequence  to  vegetable  life,  takes 
place  more  rapidly,  and  in  larger  quantity,  the  more  frequently  the  land 
is  turned  by  the  plough,  broken  by  the  clod-crusher,  or  stirred  up  by  the 
liarrow.  Whatever  amount  of  either  of  these  compounds,  also,  the  sur- 
face soil  is  capable  of  extracting  from  the  atmosphere,  the  entire  quan- 
tity thus  absorbed  will  evidently  be  greater,  and  its  distribution  more 
uniform,  the  more  completely  the  whole  soil  has  been  exposed  to  its  in- 
fluence. It  is  for  this,  among  other  reasons,  that,  as  every  farmer  knows, 
the  better  he  can  plough  and  pulverise  his  land,  the  more  abundant  in 
general  are  the  crops  he  is  likely  to  reap. 

6°.  Nor  lastly,  though  in  great  part  a  mechanical  benefit,  is  it  one  of 
little  moment  that  when  thus  every  where  pervious  to  the  air,  the  roots 
also  can  penetrate  the  soil  in  every  direction.  None  of  the  food  around 
them  is  shut  up  from  the  approach  of  their  numerous  fibres,  nor  are  they 
prevented,  by  the  presence  of  noxious  substances,  from  throwing  out 


320  ErFECT    OF    THE   SUBSOIL-PLOUGH. 

branches  in  every  direction.  A  deep  soil  is  not  absolutely  necessary  fo 
the  production  of  valuable  crops.  A  well-pulverised  and  mellow  soil, 
to  which  the  air  and  the  roots  have  every  where  ready  access,  will, 
though  shallow,  less  frequently  disappoint  the  hopes  of  the  husbandman, 
— than  where  a  greater  depth  prevails,  less  permeable  to  the  air,  and 
therefore  less  wholesome  to  the  growing  roots. 

II.  Subsoil  Ploughing. — And  yet,  as  a  general  rule,  it  cannot  be  de- 
nied that  a  deep  soil  is  greatly  superior  in  value  to  a  shallow  soil  of  the 
same  nature.  It  is  so  both  to  the  owner  and  to  the  occupier,  though  m 
too  many  cases  the  available  qualities  of  deep  Sf*''ls  have  hitherto  been 
more  or  less  overlooked  and  neglected. 

The  general  theoretical  priHciple  on  this  subjet  ': — that  the  deeper  the 
soil  the  longer  it  may  be  cropped  without  the  risk  of  exhaustion,  and  the 
greater  the  variety  of  crops,  deep  as  well  as  shallow-rooted,  which  may 
be  grown  upon  it — is  so  reasonable  in  itself,  as  to  command  a  ready  ac- 
quiescence. But  a  soil  is  virtually  shallow  where  a  few  inches  of  porous 
earth,  often  turned  by  the  plough,  rest  upon  a  subsoil,  hard,  stiffs  and  al- 
most impervious, — and  the  practical  farmer  will  rarely  be  willing  to 
allow  the  depth  of  the  latter  to  influence  his  opinion  in  regard  to  the  gene- 
ral value  of  the  land.  And  in  this  he  is  so  far  correct,  that  a  subsoil 
must  be  dried,  opened  up,  mellowed  by  the  air,  and  rendered  at  once 
pervious  and  wholesome  to  the  roots  of  plants,  before  it  can  be  made 
available  for  the  growth  of  corn.  This  may  be  effected,  after  draining, 
by  the  use  of  the  subsoil  plough,  an  instrument  at  present,  I  believe, 
imequalled  for  giving  a  real,  practical,  and  money-value  to  stiff"  and 
hitherto  almost  worthless  clayey  subsoils.  It  is  an  auxiliary  both  to  the 
surface  plough  and  to  the  drain,  and  the  source  of  its  efficacy  will  appear 
from  the  following  considerations  : 

1°.  The  surface  plough  turns  over  and  loosens  the  soil  to  the  depth  of 
6  to  10  inches — the  subsoil  plough  tears  open  and  loosens  it  to  a  further 
depth  of  8  or  10  inches.  Thus  the  water  obtains  a  more  easy  descent, 
and  the  air  penetrates,  and  roots  more  readily  make  their  way  among 
the  particles  of  the  under-soil.  So  far  it  is  an  auxiliary  to  the  common 
plough,  and  assists  it  in  aerating  and  mellowing  the  soil. 

2°.  But  though  it  opens  up  the  soil  for  a  time  to  a  greater  depth,  the 
subsoil  plough  will  in  most  cases  afford  no  permanent  cure  for  the  defi- 
ciencies of  the  subsoil,  if  unaided  hy  the  drain.  If  the  soil  rest  upon 
an  indurated  substratum — upon  a  calcareous  or  ochrey  j^an — this  plough 
may  tear  it  up,  may  thus  allow  the  surface  water  to  sink,  and  may  great- 
ly benefit  the  land  ;  but  the  same  petrifyiDg  action  will  again  recur,  and 
I'he  benefit  of  the  subsoiling  will  slowly  disappear.  Or,  if  the  subsoil 
contain  some  noxious  ingredients,  such  as  salts  of  iron,  which  the  ad- 
mission of  air  is- fitted  to  render  harmless,  then  the  use  of  this  plough 
may  afford  a  partial  amelioration.  But  in  this  case,  also,  the  efl^ect  will 
be  only  temporary  ;  since  the  source  of  the  evil  has  not  been  removed, 
the  same  noxious  compounds  will  again  be  naturally  produced,  or  will 
again,  in  fresh  supplies,  be  conveyed  into  the  soil  by  springs.  Or,  if  the 
subsoil  be  a  sliff'clay,  containing  no  noxious  ingredient,  it  may  be  cut,  or 
for  the  time  torn  asunder,  but  scarcely  will  the  plough  have  passed  over 
it  till  the  particles  will  be  again  cemented  together,  and  probably,  by  the 


PREVIOUS  DRYNESS  OF  THE  SUBSOIL  NECESSARY.  321 

end  of  a  single  season  at  the  furthest,  the  under-soil  may  be  as  solid  and 
impermeable  as  ever. 

It  is  as  the  follower  of  the  drain,  therefore,  in  the  course  of  improve- 
ment, that  the  subsoil  plough  finds  its  most  beneficial  and  most  economi- 
cal use.  After  land  has  been  drained,  the  water  may  still  too  slowly 
pass  away,  or  the  air  may  have  too  imperfect  an  entrance  into  the  sub- 
soil from  which  the  drains  have  removed  the  vi'ater.  In  the  former  case, 
the  subsoil  plough  must  be  employed,  in  order  that  the  drains  may  be- 
come fully  efficient;  in  the  latter,  that  the  under-layers  may  be  opened 
up  to  all  the  beneficial  influences  which  the  atmosphere  is  fitted  to  exert 
upon  them.  In  this  respect  it  is  an  auxiliary  to  the  drain.  But  as  the 
full  eflect  which  the  subsoil  plough  is  capable  of  producing  upon  stiff" 
and  clayey  subsoils,  can  only  be  obtained  after  they  have  been  brought  to 
such  a  state  of  dryness  that  the  sides  of  the  cut  or  tear,  which  the  plough 
has  made,  will  not  again  readily  cohere,  it  is  of  importance  that  the 
drains  should  be  allowed  a  considerable  time  to  operate  before  the  use  of 
this  plough  is  attempted.  The  expense  of  the  process  is  comparatively 
great,  and  this  expense  will  be  in  a  great  measure  thrown  away  upon 
clay  lands,  which  are  undrained,  or  from  which  the  water,  either  through 
defective  draining,  or  from  the  want  of  sufficient  time,  has  not  been  able 
fully  to  flow  away.  There  are  few  kinds  of  clay  land  on  which  the  ju- 
dicious use  of  this  valuable  instrument  will  not  prove  both  actually  and 
economically  useful,  thougli  from  the  neglect  of  the  above  necessary  pre- 
caution, it  has  been  found  to  fail  in  the  hands  of  some.  Such  failures, 
however,  do  not  justify  us  in  ascribing  to  some  fancied  defect  in  the  in 
strument,  or  in  the  theory  upon  which  its  use  is  recommended,  what  ne- 
cessarily arose,  and  could  have  been  predicted,  from  our  own  neglect  of 
an  indispensable  preliminary  observation.  The  sanguine  anticipations 
of  its  inventor,  Mr.  Smith,  of  Deanston,  may  not  be  fully  realized,  yet 
the  value  of  the  subsoil  plough  itself,  and  the  benefits  it  is  fitted  to  confer, 
when  rightly  used,  appear  to  me  to  be  both  theoretically  and  practically 
established. 

§  5.  Of  deep-ploughing  and  trenching. 

Deep-ploughing  and  trenching diflfer  from  ordinary  and  subsoil  plough- 
ing in  this, — that  their  special  object  is  to  bring  to  the  surface  and  to  mix 
with  the  upper-soil  a  portion  of  that  which  has  lain  long  at  a  consider- 
able depth,  and  has  been  more  or  less  undisturbed. 

The  benefit  of  such  an  admixture  of  fresh  soil  is  in  many  localities  un- 
doubted, while  in  others  the  practical  farmer  is  decidedly  opposed  to  it. 
On  what  principle  does  its  beneficial  action  depend,  and  in  what  circum- 
stances is  it  likely  to  be  attended  with  disadvantage  ? 

1°.  It  is  known  that  when  a  heavy  shower  of  rain  falls  it  sinks  into 
the  soil,  and  carries  down  with  it  such  readily  soluble  substances  as  it 
meets  with  on  the  surface.  But  other  substances  also,  which  are  more 
sparingly  soluble,  slowlj'  and  gradually  find  their  way  into  the  subsoil, 
and  there  more  or  less  permanently  remain.  Among  these  may  be 
reckoned  gypsum,  and  especially  those  silicates  of  potash  and  soda  al- 
ready spoken  of  (page  206),  as  apparently  so  useful  to  corn-growing 
plants.  Such  substances  as  these  naturally  accumulate  beyond  the 
reach  of  the  ordinary  plough.     Insoluble   substances  likewise  slowly 


sua  OBJECT  AM)  KFFKCT  OF  J)r:i:r-PLOUGIIIPSO. 

sink.  This  is  well  known  to  be  the  case  with  lime,  when  laid  upon  or 
ploughed  into  the  land.  So  it  is  with  clay,  when  mixed  with  a  surface 
soil  of  sand  or  peat.  They  all  descend  till  they  get  beyond  the  reach  of 
the  common  plough — and  more  rapidly  it  is  said  (in  Lincolnshire) 
when  laid  down  to  grass,  than  when  they  are  constantly  brought  to 
the  surface  again  in  arable  culture.  Thus  it  happens  that  after  the  sur- 
face soil  becomes  exhausted  of  one  or  other  of  those  inorganic  compounds 
which  the  crops  require,  an  ample  supply  of  it  may  be  still  present  in 
the  subsoil,  though,  until  turned  up,  unavailable  for  the  promotion  of  ve- 
getable growth. 

There  can  be  little  question,  I  think,  that  the  greater  success  which 
attends  the  introduction  of  new  implements  in  the  hands  of  better  in- 
structed men,  upon  farms  long  held  in  arable  culture,  it'  to  be  ascribed  in 
part  to  this  cause.  One  tenant,  during  a  long  lease,  has  been  in  the 
habit  of  ploughing  to  a  depth  of  three,  or  at  most,  perhaps,  of  four 
inches — and  from  this  surface  the  crops  he  has  planted  have  derived  their 
chief  supplies  of  inorganic  food.  He  has  Hmed  his  land  in  the  customary 
manner,  and  has  laid  upon  it  all  the  manure  he  could  raise,  but  his  crops 
have  been  usually  indifferent,  and  he  considers  th.e  land  of  comparative- 
ly little  value.  But  another  tenant  comes,  and  with  better  implements 
turns  up  the  land  to  a  depth  of  7  or  8  inches.  He  thus  brings  to  the  sur- 
face the  lime  and  the  accumulated  manures  which  have  naturally  sunk, 
and  which  his  predecessor  had  permitted  year  after  year  to  bury  them- 
selves in  his  subsoil.  He  thus  has  a  new,  often  a  rich,  and  almost  always 
a  virgin  soil  to  work  upon — one  which,  from  being  long  buried,  may  re- 
quire a  winter's  exposure  and  nriellowing  in  the  air,  but  which  in  most 
cases  is  sure  to  repay  him  for  any  extra  cost.  The  deep  ploughing 
which  descends  to  14  inches,  or  the  trenching  wliich  brings  up  a  new 
soil  from  the  depth  of  20  or  30  inches,  is  only  an  extension  of  the  same 
practice.  It  is  justified  and  recommended  upon  precisely  the  same 
principle.  It  not  only  brings  a  new  soil,  containing  ample  nourishment, 
to  the  immediate  roots  of  plants,  but  it  affords  them  also  a  deeper  and 
more  open  subsoil,  through  which  their  fibres  may  proceed  in  every  di- 
rection in  search  of  food.  The  full  benefits  of  this  deepening  of  the  soil, 
however,  can  only  be  expected  where  the  subsoil  has  previously  been 
laid  dry  by  drains  ;  for  it  matters  not  how  deep  the  loosened  and  perme- 
able soils  may  be,  if  the  accumulation  of  water  prevent  the  roots  from 
descending. 

2°.  Two  practical  observations,  however,  may  here  be  added,  which 
the  intelligent  farmer  will  always  weigh  well  before  he  hastily  applies 
t!iis  theoretical  principle — sound  though  it  undoubtedly  be — in  a  district 
with  which  he  has  no  ])revious  acquaintance.  It  is  possible  that  the 
deeper  soil  may  contain  some  substance  decidedly  noxious  to  vegetation. 
In  such  a  case  it  would  be  improper  at  once  to  mix  it  with  the  upper 
soil.  Good  drains  must  be  established,  they  must  be  allowed  some  time 
to  act,  and  the  subsoil  plough  will  be  used  with  advantage,  before  any 
portion  of  such  an  under-soil  can  be  safely  brought  to  the  surface.  The 
subsoil  plough  and  the  drain,  indeed,  as  I  have  already  mentioned,  are 
the  most  certain  available  remedies  for  such  a  state  of  the  subsoil.  In 
many  localities,  however,  the  exposure  Df  such  an  under-soil  to  a  winter's 
frost,  or  to  a  summer  fallow,  will  so  faV  'mprove  and  mellow  it,  as  to  ren- 


EFFECT  OF  IISfSECTS. — IMPROVEMENT  OF  THE  SOIL.  323 

der  it  capable  of  being  safely  mixed  with  the  surface  soil.  Unless,  how- 
ever, tliis  ?nellowing  be  effected  at  once,  and  before  admixture,  a  long 
time  may  elapse  ere  the  entire  soil  attain  to  its  most  perfect  condition.* 

Again,  it  is  known  that  some  districts,  for  reasons  perhaps  not  well  un- 
derstood, are  more  infested  than  others  with  insects  that  attack  the  corn 
or  other  crops.  These  insects,  their  eggs,  or  their  larvae,  generally  bury 
themselves  in  the  undisturbed  soil,  immediately  beyond  the  ordinary 
reach  of  the  plough.  If  they  remain  wholly  undisturbed  during  the 
preparation  of  the  soil,  some  species  remain  in  a  dormant  state,  and  the 
subsequent  crop  may  in  a  great  measure  escape.  Plough  the  land  deep- 
er than  usual,  and  you  bring  them  all  to  the  surface.  Do  this  in  the 
autumn,  and  leave  your  land  unsown,  and  the  frost  of  a  severe  winter 
may  kill  the  greater  part,  so  that  your  crops  may  thereafter  growin  safety. 
But  cover  them  up  again  along  with  your  winter  corn,  or  let  this 
deep  ploughing  be  done  in  the  spring,  and  you  bring  all  these  insects 
within  reach  of  the  early  sun,  and  thus  call  them  to  life  in  such  num- 
bers as  almost  to  ensure  the  destruction  of  your  coming  crop.  It  is  to 
something  of  this  kind  that  I  am  inclined  to  attribute  the  immediate  fail- 
ures which  have  attended  the  trial  of  deep  ploughing  in  certain  parts  of 
England.  Thus  in  Berkshire,  certain  soils  which  are  usually  ploughed 
to  a  depth  of  only  two  inches,  yielded  almost  nothing  when  deeper  plough- 
ing was  more  lately  tried  upon  them — the  crop  was  almost  entirely  de- 
stroyed by  insects.  So  also  in  the  north  of  Yorkshire,  where  deep 
ploughing  has  recently  been  attempted,  the  wheat  crop  on  land  so  treated 
was  observed  to  sufler  more  from  the  worm  than  on  any  other  spot. 
Such  facts  as  these,  therefore,  show  the  necessity  of  caution  on  the  part 
of  the  practical  man,  and  especially  of  the  land  agent  or  steward,  how- 
ever correct  may  be  the  principles  on  which  his  general  practice  is 
founded.  Failures  such  as  the  above  do  not  show  the  principle  on  which 
deep  ploughing  is  recommended  to  be  false,  or  the  practice  to  be  in  any 
case  reprehended :  but  it  does  show  that  a  knowledge  of  natural  local 
peculiarities,  and  some  study  of  ancient  local  practice,  may,  in  an  im- 
portant degree,  influence  our  mode  of  procedure  in  introducing  more 
improved  methods  of  husbandry  into  any  old  agricultural  district. 

§  C.  Improvement  of  the  soil  by  mixing. 
There  are  some  soils  so  obviously  defective  in  constitution,  that  the 
most  common  observer  can  at  once  pronounce  them  likely  to  be  improved 
by  mechanical  admixtures  of  various  kinds.  Thus  peaty  soils  aboujid 
too  much  in  vegetable  matter;  a  mixture  of  earthy  substances,  there- 
fore, of  almost  any  common  kind,  is  readily  indicated  as  a  means  of  im- 
provement.    In  like  manner  we  naturally  impart  consistence  to  a  sandy 

*  Ttie  Marquis  of  Tweedale,  in  his  home-farm  at  Yeslers.  has  raised  his  land  in  value 
eight  times  (horn  5s.  to  40s.  per  acre),  by  draining  and  deep  ploughing.  After  draining,  the 
fields  of  stiff  clay,  with  streaks  of  sand  in  the  subsoil,  are  turned  over  to  a  depth  of  12  or  14 
inches,  by  two  ploughs  (two  hor.ses  each)  following  one  another,  the  under  6  inches  being 
thrown  on  the  top.  hi  this  state  it  is  left  to  the  winter's  frost,  when  it  falls  to  a  yellow  marly 
looking  soil  Ii  is  now  ploughed  again  to  a  depth  of  9  or  10  inches,  by  which  half  the  origi- 
nal soil  is  lirought  ajrain  to  the  surface.  By  a  cross  ploughing  this  is  mixed  with  the  new 
goil,  after  which  the  field  is  prepared  in  the  usual  way  for  turnips.  But  it  is  observed  that  if 
the  ploughing  has  been  so  late  that  the  subsoil  has  not  had  a  proper  exposure  to  the  winter's 
cold,  the  land  on  such  spots  does  not  for  many  years  equal  that  which  was  earlier  ploughed. 
The  reason  is,  that  when  once  mixed  up  with  the  other  soil,  the  air  has  no  longer  the  same 
easy  access  ioto  its  pores. 

14* 


324  EFFECTS    OF  CLAY  AND  MARL. 

soil  by  an  admixture  of  clay,  and  openness  and  porosity  to  stiff' clays  by 
the  addition  of  sand. 

Th^  first  and  obvious  effect  of  such  additions  is  to  alter  the  physical 
qualities  of  the  soil — to  consolidate  the  peats  and  sands,  and  to  loosen 
the  clays.  But  we  have  already  seen  that  the  fertility  of  a  soil,  or  its 
power  of  producing  a  profitable  return  of  this  or  that  crop,  depends  in 
the  first  place  on  its  chemical  constitution.  It  must  contain  in  sufficient 
abundance  all  the  inorganic  substances  which  that  crop  requires  for 
its  daily  food.  Where  this  is  already  the  case,  as  in  a  rich  stiff" clay,  a 
decided  improvement  may  be  produced  by  an  admixture  with  siliceous 
sand,  which  merely  separates  the  particles  mechanically,  and  renders 
the  whole  more  porous.  But  let  the  clay  be  deficient  in  some  necessary 
constituent  of  a  fertile  soil,  and  such  an  addition  of  siliceous  sand  would 
not  produce  by  any  means  an  equal  benefit.  It  may  be  proper  to  add 
this  sand  with  the  view  of  producing  the  mere  physical  alteration,  but 
we  must  add  some  other  substance  also  for  the  purpose  of  producing  the 
necessary  chemical  change. 

The  good  eflfects  which  almost  invariably  follow  from  the  addition  of 
clay  to  peaty  or  sandy  soils  are  due  to  the  production  at  one  and  the  same 
time  of  a  physical  and  of  a  chemical  change.  They  are  not  only  ren- 
dered firmer  or  more  solid  by  the  admixture  of  clay,  but  they  derive 
from  this  clay  at  the  same  time  some  of  those  mineral  substances  which 
they  previously  contained  in  less  abundance. 

The  addition  of  marl  to  the  land  acts  often  in  a  similar  two-fold  capa- 
city. It  renders  clay  lands  more  open  and  friable,  and  to  all  soils  brings 
an  addition  of  carbonate,  and  generally  of  phosphate  of  lime,  both  of 
which  are  proved  by  experience  to  be  not  only  very  influential,  but  to  be 
absolutely  necessary  to  healthy  vegetation. 

That  much  benefit  to  the  land  would  in  many  instances  accrue  from 
such  simple  admixtures  as  those  above  adverted  to,  where  the  means 
are  available,  will  be  readily  granted.  The  only  question  on  the  sub- 
ject that  ought  to  arise  in  the  mind  of  a  prudent  man,  is  that  which  is 
connected  with  the  economy  of  the  case.  Is  this  the  most  profitable  way 
in  which  I  can  spend  my  money  ?  Can  I  employ  the  spare  labour  of 
my  men  and  horses  in  any  other  way  which  will  yield  me  a  larger 
return  ?  It  is  obvious  that  tlie  answer  to  these  questions  will  be  modi- 
fied by  the  circumstances  of  the  district  in  which  he  lives.  It  may  be 
more  profitable  to  drain, — or  labour  may  be  in  great  request  and  at  a 
high  premium, — or  a  larger  return  may  be  obtained  by  the  investment 
of  money  in  purchasing  new  than  in  improving  old  lands.  It  is  quite 
true  that  the  country  at  large  is  no  gainer  by  the  mere  transfer  of  land 
from  the  hands  of  A  to  those  of  B,  and  that  he  is  undoubtedly  the  most 
meritorious  citizen  who,  by  expending  his  money  in  improving  the  soil, 
virtually  adds  to  the  breadth  of  the  land,  in  causing  it  to  yield  a  larger 
produce.  Yet  it  is  no  less  true  that  the  employment  of  individual  capi- 
tal in  such  improvement  is  not  to  be  expected  generally  to  take  place, 
unless  it  be  made  to  appear  that  such  an  investment  is  likely  to  be  as 
profitable  as  any  other  within  the  reach  of  its  possessor.  It  seems  to  be 
established  beyond  a  doubt,  that  in  very  many  districts  no  money  is  more 
profitably  invested,  or  yields  a  quicker  return,  than  that  which  is  ex- 
pended in  draining  and  subsoiling — and  yet  in  reality  one  main  obstacle 


CLAr  AND  SAND. — SPECIAL  MIXTURES. 


325 


to  a  more  rapid  increase  in  the  general  produce  of  the  British  soil  is  the 
practical  difficulty  which  exists  in  convincing  the  owners  and  occupiers 
(}f  the  soil  that  such  is  the  case,  or  would  be  the  case,  in  regard  to  their 
own  holdings.  The  more  widely  a  knowledge  of  the  entire  subject,  in 
all  its  bearings,  becomes  diffused,  the  less  it  is  to  be  hoped  will  this  diffi- 
culty become — for  the  economist,  who  regards  the  question  of  improve- 
ment as  a  mere  matter  of  profit  and  loss,  cannot  strike  a  fair  balance 
unless  he  knows  the  several  items  he  may  prudently  introduce  into  each 
side  of  his  account. 

Thus  in  reference  to  the  special  point  now  before  us,  it  seems  re.ason- 
able  to  believe  that,  in  a  country  such  as  that  here  represented,  where 
alternate  hilU  of  sand  (3),  and  hollows,  and  flats  of  clay  (4)  occur,  there 


^^^g^s^;^^^ 


may  be  many  spots  where  both  kinds  of  soil — being  near  each  other- 
might  be  improved  by  mutual  admixture,  at  a  cost  of  labour  which  the 
alteration  in  the  quality  of  the  land  might  be  well  expected  to  repay. 
In  this  condiiion  i«  a  considerable  portion  of  the  eastern  half  of  the 
county  of  Durham,  and,  especially,  I  may  mention  the  neighbourhood 
of  Castle  Eden,  where  a  cold,  stiff,  at  present  often  poor  clay,  rests  upon 
red,  rich-looking,  loamy  sand,  in  many  places  easily  accessible,  and  by 
admixture  with  which  its  agricultural  capabilities  may  be  expected  to 
improve.  In  this  locality,  and  in  many  others  besides,  those  having  a 
pecuniary  interest  in  the  land  rest  satisfied  that  their  fields  are  incapable 
of  such  improvement,  or  would  gk^  no  adequate  return  for  the  outlay 
required,  without  troubling  themselves  to  collect  and  compare  all  the 
facts  from  which  a  true  solution  of  the  question  can  alone  be  drawn. 

Besides  such  general  admixtures  for  the  improvement  of  land,  the 
geological  formation  of  certain  districts  places  within  the  reach  of  its  in- 
ielligent  farmers  means  of  improvement  of  a  special  kind,  of  which  they 
may  often  profitably  avail  themselves.  Thus  both  in  Europe  and  Ame- 
rica, the  green-sand  soils  (p.  243)  are  found  to  be  very  fertile,  and 
the  sandy  portions  of  this  formation  are  often  within  easy  distance  of  the 
stiff-clays  of  the  gault,  and  of  the  poor  soils  of  the  chalk  with  either  of 
which  they  might  be  mixed  with  most  beneficial  effects.  The  soils  that 
rest  on  the  new,  and  even  on  some  parts  of  the  old  red  sandstone,  are 
in  like  manner  often  within  an  available  distance  of  beds  of  red  marl  of 
a  very  fertilizing  character  (p.  248),  while  in  the  granitic  and  trap 
districts  the  materials  of  which  these  rocks  consist,  if  mixed  with  judg- 
ment, maybe  made  materially  to  benefit  some  of  the  neighbouring  soils. 
To  this  point,  however,  I  shall  draw  your  attention  again  in  my  next  lec- 
ture, when  treating  of  mineral  manures. 


LECTURE  XV. 

Improvement  of  the  soil  by  chemical  means.— Principles  on  which  all  manuring  depends. 
—Mineral,  vegetable,  and  animal  manures.— Saline  manures.-Carbonates.— Pearl-ash. 
—Sulphates.— Glauber   salts.— Chlorides.— Common  Salt.— Nitrates.— Nitrate  of  soda.— 

Phosphates.— Phosphate   of  lime.— Sihcates.     SiUcate  of  potash.— Saline   mixtures 

Vegetable  ashes.— Prepared  granite.— Use  of  lime. 

The  mechanical  methods  of  improving  the  soil,  described  in  the  pre- 
ceding section,  are  few  in  number  and  simple  in  theory.  They  are  so 
important,  however,  to  the  general  fertility  of  the  land,  that  were  they 
judiciously  employed  over  the  entire  surface  of  our  islands,  they  would 
alone  greatly  increase  the  average  produce  of  the  British  and  Irish  soils. 
1  may,  indeed,  repeat  what  was  stated  in  reference  to  draining  (p.  308), 
that  the  full  effect  of  every  other  means  of  improving  the  soil  will  be 
obtained  in  those  districts  only  where  these  mechanical  methods  have 
already  been  had  recourse  to. 

The  chemical  methods  of  improving  the  soil  are  founded  upon  the 
following  principles,  already  discussed  and  established  : — 

1°.  That  plants  obtain  from  a  fertile  soil  a  variable  proportion  of  their 
organic  food  ; — of  their  nitrogen  probably  the  greatest  part. 

2°.  That  they  require  inorganic  food  also  of  various  kinds,  and  that 
this  they  procure  solely  from  the  soil. 

3°.  That  different  species  of  plants  require  a  special  supply  of  dif- 
ferent kinds  of  inorganic  food,  or  of  the  same  kinds,  in  different  pro- 
portions. 

4°.  That  of  these  inorganic  substances  one  soil  may  abound  or  be 
deficient  in  one,  and  another  soil  in  an()ther ;  and  that,  therefore,  this  or 
that  plant  will  prefer  to  grow  on  the  me  or  the  other  accordingly. 

On  these  few  principles  the  whole  art  of  improving  the  soil  by  che- 
mical means — in  other  words,  of  beneficially  manuring  the  soil — is 
founded. 

It  must  at  the  same  time  be  borne  in  mind,  that  there  are  three  dis- 
tinct methods  of  operation  by   which  a  soil  may  be  improved  : — 

1°.  By  removing  from  it  some  noxious  ingredient.  The  only  method 
by  which  this  can  be  effected  is  by  draining, — providing  an  outlet  by 
which  it  may  escape,  or  by  which  the  rains  of  heaven,  or  water  applied 
in  artificial  irrigation,  may  wash  it  away. 

2°.  By  changing  the  nature  or  state  of  combination  of  some  noxious 
ingredient,  which  we  cannot  soon  remove  in  this  way ;  or  of  stjme  inert 
ingredient  which,  in  its  existing  condition,  is  unfit  to  become  food  for 
plants.  These  are  purely  chemical  processes,  and  we  put  them  re- 
spectively in  practice  when  we  add  lime  to  peaty  soils,  or  to  such  as 
abound  in  sulphate  of  iron  (p.  212),  when  by  admitting  the  air 
into  the  subsoil  we  change  the  prot-oxide  into  the  per-oxide  of  iron, 
(p.  210,)  or  when  by  adding  certain  known  chemical  compounds  we 
produce  similar  beneficial  chemical  alterations  upon  other  compounds 
^Iready  existing  in  the  soil. 


ACTION  OF  CHEMICAL  SUBSTANCES  IN  THE    SOIL.  327 

3°.  By  adding  to  the  soil  those  substances  which  are  fitted  to  become 
the  food  of  plants.  This  is  what  we  do  in  strictly  manuring  the  soil — 
though  we  are  as  yet  unable  in  many  cases  to  say  whether  that  which 
we  add  promotes  vegetation  by  actually  feeding  the  plant  and  entering 
into  its  substance — or  only  by  preparing  food  for  it.  There  is  reason  to 
believe,  however,  that  many  substances,  such  as  potash,  soda,  &c.,  act 
in  several  capacities, — now  preparing  food  for  the  plant  in  the  soil,  now 
bearing  it  into  the  living  circulation,  and  now  actually  entering  into  the 
perfecf  substance  of  the  growing  vegetable.  In  order  to  steer  clear  of 
the  difficulty  which  this  circumstance  throws  in  the  way  of  an  exact 
classification  of  the  chemical  substances  applied  to  the  soil,  I  shall  con- 
sider generally  under  the  name  oi  manures^  all  those  substances  which  are 
usually  applied  to  the  land  for  the  purpose  of  promoting  vegetable  growth ; 
whether  those  substances  be  supposed  to  do  so  directly  by  feeding  the 
plants,  or  only  indirectly,  by  preparing  their  food,  or  by  conveying  it  into 
their  circulation. 

Manures,  then,  in  this  sense,  are  either  simple,  like  common  salt  and 
nitrate  of  soda,  or  they  are  mixed,  like  farm-yard  manure  and  the  nu- 
merous artificial  manures  now  on  sale.  Or,  again,  they  consist  of  sub- 
stances of  mineral,  of  vegetable,  or  of  animal  origin.  The  latter  is  the 
more  natural,  and  is  by  far  the  most  useful,  classificati9n.  We  shall, 
therefore,  consider  the  various  substances  employed  in  improving  the 
soil — or  what  is  in  substance  the  same  thing,  in  promoting  vegetation,— 
in  the  following  order  : — 

1°.  Mineral  manures — including  those  substances,  whether  simple  or 
mixed,  which  are  of  mineral  origin,  or  which  consist  entirely  of  inor- 
ganic or  mineral  matter.  Under  this  head  the  use  of  lime  and  of  the 
ashes  of  plants  will  fall  to  be  considered. 

2°.  Vegetable  manures. — These  are  all  of  natural  origin,  and  are  all 
mixtures  of  organic  and  inorganic  matter. 

3°.  Animal  manures,  which  are  also  mixtures,  but,  owing  to  their  im- 
mediate origin,  dilTer  remarkably  in  constitution  from  vegetable  sub- 
stances. 

§  1.   Of  mineral  manures. 

Mineral  manures  may  be  conveniently  considered  under  the  two  heads 
of  saline  and  earthy  manures. 

A. SALINE  MANURES. 

1^.  Carbonate  of  potash. — This  substance,  in  the  form  either  of  crude 
potash  or  of  the  pearl-ash  of  the  shops,  has  hitherto  been  considered  too 
nigh  in  price  to  admit  of  its  extensive  application  in  the  culture  of  tlie 
land. 

2°.  Carbonate  of  soda. — This  remark,  however,  does  not  apply  to 
the  carbonate  of  soda  (corhmon  soda  of  the  shops), 'which  is  sufficiently 
low  in  price  (dfill  a  ton)  to  allow  of  its  being  applied  with  advantage 
under  many  circumstances.  In  the  case  of  grass-lands,  which  are  over- 
run with  moss — of  such  as  abound  largely  in  vegetable  matter  or  in 
noxious  sulphate  of  iron — a  weak  solution  applied  with  a  water-cart 
might  be  expected  to  produce  good  results.  It  might  be  applied  in  the 
sai«e  way  to  fields  of  sprouting  corn,  or  in  fine  powder  as  a  top-dressing 


328  QUANTITY  OF  SALINE  MANURES  USEFUL  TO  THE  SOIL. 

in  moist  weather — and  generally  wherever  wood  ashes  are  found  useful 
to  vegetation. 

Many  experiments  have  shown  that  both  of  these  substances  may  be 
employed  in  the  field  with  advantage  to  the  growing  crop — but  further 
trials  are  necessary  to  show  how  far  the  practical  farmer  may  safely  use 
then!  with  the  hope  of  profit.  In  gardening,  they  greatly  hasten  the 
growth  and  increase  the  produce  of  the  strawberry,*  and  in  garden  cul- 
ture, generally,  where  the  cost  of  the  manure  employed  is  of  less  con- 
sequence, more  extended  trials  would,  no  doubt,  lead  to  useful  results. 

The  quantity  of  these  substances  which  ought  to  be  applied  to  our 
fields,  in  order  to  produce  the  beneficial  effect  which  theory  and  practice 
both  lead  us  to  expect,  will  depend  much  upon  the  natureof  the  soil  in 
each  locaHty  and  on  the  kind  of  manuring  to  which  it  has  previously 
been  subjected.  By  referring  to  our  previous  calculations  (page  222,) 
it  will  be  seen  that  upwards  of  800  lbs.  of  these  carbonatesf  would 
be  necessary  to  replace  all  that  is  extracted  from  the  soil  by  the  entire 
crops  during  a  four  years'  rotation.  But  in  good  husbandry  every  thing 
is  returned  to  the  soil  in  the  form  of  manure  which  is  not  actually 
sent  to  market  aud  sold  for  money.  That  is — the  grain  only  of  the  corn 
crops,  the  dairy  produce,  and  the  live  stock,  are  carried  off  the  land.J 
Less  than  40  lbs.  per  acre  of  the  mixed  carbonates  would  replace  all  thai 
is  contained  in  the  grain,  and  if  we  suppose  as  much  to  be  present  in  the 
other  produce  sold,  we  have  80  lbs.  for  the  quantity  necessary  to  be  re- 
stored to  the  land  by  the  good  husbandman  every  four  years,  in  order  to 
keep  his  farm  permanently  in  the  same  condition.  There  are,  however, 
in  most  soils,  certain  natural  sources  of  supply  (pp.  207,  208)  by  which 
new  portions  of  these  alkahes  are  continually  conveyed  to  them.  Hence 
it  is  seldom  necessary  to  add  to  the  land  as  much  of  these  substances  as 
we  carry  off';  and  therefore  from  40  to  60  lbs.  per  acre,  of  either  of 
them,  may  be  considered  as  about  the  largest  quantity  which,  in  a  well- 
managed  farm,  need  be  added  in  order  to  give  a  fair  trial  to  their  agri- 
cultural value.  Half  acwt.  of  tl  e  potash  will  cost  less  than  15s.,  and 
of  the  soda  less  than  6s.,  or  of  a  m  xture,  in  equal  quantities,  less  than 
21s.  at  their  present  prices. 

Theory  of  the  action  of  potash  and  soda. 

But  upon  what  theoretical  grounds  is  the  beneficial  action  of  potash 
and  soda  upon  vegetation  explained?  This  question,  to  which  I  have 
already  more  than  once  drawn  your  attention  (pp.  83  and  187),  it  will 
be  proper  here  briefly  to  consider. 

a.  The  first  and  most  obvious  purpose,  served  by  the  presence  of  these 
alkalies  in  the  soil,  is  that  of  yielding  readily  to  the  growing  plant  such 
a  full  supply  of  each  as  may  be  essential  to  its  healthy  growth.  If  the 
roots  can  collect  them  from  the  soil  slowly  only,  and  with  difficulty,  the 
growth  of  the  plant  will  necessarily  be  retarded  ;  while  in  situations 

'  Mr  Fleming,  of  Barochan,  has  informed  me  that  he  found  this  to  be  the  case  with  the 
common  potash  ;  and  Mr.  Campbell,  of  Islay,  with  the  common  soda  of  the  shops.  They 
should  be  applied  early  in  the  spring,  and  in  the  state  of  a  very  weak  solution.  Wocd- 
ashes  would  probably  produce  a  similar  eflfect, 

1 390  lbs.  of  dry  pearl  ash  and  440  lbs.  of  crystallized  carbonate  of  soda. 

X  In  bad  husbandry  much  more  is  carried  off  the  land  by  the  waste  of  liquid  and  other 
manure.—See  the  succeeding  chapter,  "  On  aninud  manures.'' 


POTASH  AND  SODA  PREPARE  THE  FOOD  OF    PLANTS.  329 

where  they  naturally  abound,  or  are  artificially  supplied,  the  crops  will 
as  certainly  ])rove  both  more  early  and  more  abundant — provided  no 
other  essential  food  be  deficient  in  the  soil. 

In  reference  to  this  mode  of  action  i.;  will  occur  to  you  that  potash  is 
the  more  likely  of  the  two  to  be  beneficial  to  our  cultivated  crops,  inas- 
much as  the  ash  of  those  plants  which  are  raised  for  food  is  generally 
much  more  rich  in  potash  than  in  soda.  [Seethe  tabular  details  given  in 
Lecture  X.,  §  3.,  p.  216  et  seq.']  But  this  may  possibly  arise  from  the 
more  abundant  presence  of  potash  in  the  soil  generally,  since  some 
chemists  are  of  opinion  that  soda  may  take  the  place  of  potash  in  the  in- 
terior of  plants,  without  materially  affecting  their  growth,  [Berzelius 
Chimie,  VI.,  p.  733,  edit.  1832.]  This  hypothesis,  whatever  may  be 
its  theoretical  value,  will  prove  useful  to  practical  agriculture  if  it  lead  to 
experiments  from  which  the  relative  action  of  each  of  these  carbonates, 
in  tlie  same  circumstances,  may  be  deduced, — and  the  specific  influ- 
ence of  each,  in  promoting  the  growth  of  particular  plants,  in  some  de- 
gree determined.  Potash  (or  wood-ashes)  aids  the  growth  of  corn  after 
turnips  or  potatoes  (Lampadius) — would  soda  do  the  same  ?  Carbon- 
ate of  soda  assists  in  a  remarkable  manner  the  growth  of  buck-wheat 
(Sprengel) — wouldthe  same  good  effects  follow  from  the  use  of  potash  ? 

h.  Another  purpose  which  these  carbonates  are  supposed  to  serve,  is 
that  of  combining  with,  and  rendering  soluble,  the  vegetable  matter  of 
the  soil,  so  as  to  bring  it  into  a  state  in  which  it  may  be  readily  con- 
veyed into  the  roots  of  plants.  They  may  in  this  case  be  said  to  pre- 
pare the  food  of  plants.  That  they  are  really  capable  of  forming 
readily  soluble  compounds  with  the  humic  acid,  and  with  certain  other 
organic  substances  which  exist  in  the  soil,  is  certain.  Those,  however, 
who  maintain  with  Liebig  that  plants  imbibe  all  their  carbon  in  the 
form  of  carbonic  acid,  will  not  be  willing  to  admit  that  this  property  of 
the  above  carbonates  can  either  render  them  useful  to  vegetation,  or  ac- 
count for  the  beneficial  action  they  have  so  often  been  observed  to  exer- 
cise. From  this  opinion  we  have  already  seen  reason  (pp.  63  and  64,) 
to  dissent,  and  we  are  prepared,  therefore,  to  concede  that  potash  and 
soda,  in  the  form  of  carbonates,  may  act  beneficially  upon  vegetation — 
by  preparing  the  organic  matter  of  the  soil  for  entering  into  the  roots  of 
j)Iants,  and  thus  administering  to  their  growth. 

This  preparation  also  may  be  effected  either  by  their  directly  com- 
bining with  the  organic  matter,  as  they  are  known  to  do  with  the  humic 
and  other  acids  which  exist  in  the  soil  ;  or  by  their  disposing  this  or- 
ganic matter,  at  the  expense  of  the  air  and  of  moisture,  to  form  new 
chemical  compounds  whicli  shall  be  capable  of  entering  into  the  vege- 
table circulation.  This  disposing  influence  of  the  alkalies,  and  even  of 
lime,  is  familiar  to  chemists  under  many  other  circumstances. 

This  mode  of  action  of  the  carbonates  of  potash  and  soda  can  be  ex 
ercised  in  its  fullest  extent  only  where  vegetable  matter  abounds  in  the 
soil.  It  is  stated  by  Sprengel  [Lehre  vom  Diinger,  p.  402,]  according- 
ly, ^s  the  result  of  experiment,  that  they  are  most  useful  where  vegeta- 
ble matter  is  plentiful,  and  that  they  ought  to  be  employed  more  spar- 
ingly, and  with  some  degree  of  hesitation,  where  such  organic  matter  is 
deficient. 

c.  We  have  already  seen,  during  our  study  of  the  composition  of  the 


330  rOTASU  AND  SODA  RENDER  SILICA  SOLUBLE,  ETC. 

ash  of  plants  (page  216  et  seq.)  how  very  important  a  substance  silica  is, 
especially  to  the  grasses  and  the  stems  of  our  various  corn-bearing  plants. 
Tliis  silica  exists  very  frequently  in  the  soil  in  a  state  in  which  it  is  insol- 
uble in  pure  water,  and  yet  is  more  or  less  readily  taken  up  by  water 
containing  carbonate  of  potash  or  carbonate  of  soda;  and  as  there  is  eve- 
ry reason  to  believe  that  nearly  all  the  silica  they  contain  is  actually  con- 
veyed into  the  circulation  of  plants  by  the  agency  of  potash  and  soda,  (in 
the  state  of  silicates — see  pp.  83  and  207,)  it  is  not  unlikely  that  a  portion 
of  the  beneficial  action  of  these  substances,  especially  upon  the  grass  and 
corn  crops,  may  be  due  to  the  quantity  of  silica  they  are  the  means  of 
conveying  into  the  interior  of  the  growing  plants. 

d.  Another  mode  in  which  these  substances  act,  more  obscurely,  per- 
haps, though  not  less  certainly,  is  by  disposing  the  organic  matters  con- 
tained in  the  sap  of  the  plant  to  form  such  new  combinations  as  may  be 
re(]ulred  for  the  production  of  the  several  parts  of  the  living  vegetable.  1 
have  on  a  former  occasion  illustrated  (  pp.  112-114,)  to  you  the  very  re- 
markable changes  which  starch  may  be  made  to  undergo,  without  any 
essential  alteration  in  its  chemical  composition — how  gum  and  sugar 
may  be  successively  produced  from  it,  without  either  ^oss  or  gain  in  respect 
of  its  original  elementary  constitution.  We  have  seen  also  how  the 
presence  of  a  comparatively  minute  quantity  of  diastase  (p.  118)  or  of 
sulphuric  acid  (p.  113)  is  capable  of  inducing  such  changes,  first  rendering 
the  starch  soluble,  and  then  converting  it  into  gum  and  into  sugar.  Ana- 
logous, though  somewhat  different  changes,  are  induced  by  the  presence 
in  certain  solutions  of  small  quantities  of  potash*  or  soda,  as,  for  example, 
in  milk — the  addition  of  carbonate  of  soda  to  which  gradually  causes  (per- 
suades?) the  whole  of  the  sugar  it  contains  to  be  converted  into  the  acid  of 
milk.  Such  changes  also  must  be  produced  or  facilitated  by  the  presence 
of  acid  and  of  alkaline  substances  in  the  sap  of  plants  ;  and  though  we 
can  as  yet  only  guess  at  the  precise  nature  of  these  changes,  yet  there 
seems  good  ground  for  believing  that  to  facilitate  their  production  is  one  of 
the  many  purposes  served  by  the  constant  presence  of  inorganic  substances 
in  the  sap  of  plants,  indeed  so  important  is  this  function  considered  by 
some  writers  upon  the  nourishment  of  plants,  (see  especially  Hlubeck's 
Erndkrung  der  Pjianzen  und  Statik  desLandbaues,)  that  they  are  inclined 
to  ascribe  to  it,  erroneously  however,  as  I  believe,  the  main  influence  upon 
vegetation,  of  nearly  all  the  inorganic  substances  which  are  found  in  the 
ash  of  plants,  and  therefore  are  known  to  enter  into  their  circulation. 

€.  I  only  allude  to  one  other  way  in  which  these  substances  may  be  sup- 
posed to  have  an  influence  upon  vegetation.  We  have  already  seen  (Lee. 
Vin,  §  5,  6,  7,  pp.159  to  167,)  how  important  a  part  the  nitric  acid  produ- 
ced in  the  atmosphere  or  in  the  soil  may  be  supposed  to  perform  in  the  gen- 
eral vegetation  of  the  globe.  This  acid  is  observed  to  be  more  abundantly 
— either  fixed  or  actually  produced  in  the  soils  or  composts  which  contain 
much  potash  or  soda.  It  may  be,  therefore,  that  in  adding  either  of  these 
to  our  fields,  we  give  to  the  soil  the  means  of  bringing  within  the  reach 
of  the  roots  of  our  crops  a  more  ready  supply  of  nitric  acid,  and  l^ence 
of  nitrogen,  so  necessary  a  part  of  their  daily  food. 

3°.  Sulphates  of  Potash  and  Soda. — It  is  nearly  100  years  since  Dr. 

•  It  is  also  shown  ^.  112,)  that,  by  means  of  potas^.,  woody  fibre  may  be  converted 
into  starch. 


EFFECTS  PRODUCED    BY  SULPHATE  OF  SODA.  331 

Home,  of  Edinburgh,  observed  that  these  salts  produced  a  beneficial 
effect  upon  vegetation.  Applied  to  growing  corn,  they  increased  the 
produce  by  one-fourth.  Other  experiments,  since  made  in  Germ-any, 
have  shown  that  they  may  be  applied  with  manifest  advantage  both  to 
field  crops  and  to  fruit  trees  (Sprengel),  but  the  price  has  hitherto  been 
considered  too  high  to  admit  of  their  being  economically  used  in  ordinary 
husbandry. 

The  manufacture  of  sulphate  of  soda  in  England,  however,  has  of 
late  years  become  so  much  extended,  and  the  price  in  consequence  so 
much  reduced,  that  I  was  induced  in  the  spring  of  the  year  1841,  (when 
the  publication  of  these  lectures  was  commenced,)  again  to  recommend 
it  to  the  attention  of  the  practical  agriculturists  of  the  country — as  likely, 
either  alone  or  mixed  with  other  substances,  to  increase  in  many  locali- 
ties not  only  the  produce  but  the  profit  also  to  be  derived  from  the  land. 
(See  Appendix,  also  published  at  the  end  of  this  volume, — "  Suggestions 
for  Experiments  in  Practical  Agriculture,"  No.  I.)  Many  experiments 
were  in  consequence  made  in  various  parts  of  the  country,  the  details  of 
some  of  which  are  given  in  the  Appendix.  When  applied  at  the  rate  of 
half  a  cwt.  of  the  dry  salt  (or  one  cwt.  of  crystals)  per  acre,  it  produced 
little  effect  upon  the  hay  crop,  the  quantity  being  probably  too  small. 
Apphed  to  hay  and  rye,  at  the  rate  of  84  lbs.  of  the  dry  salt,  and  to  pota- 
toes at  the  rate  of  100  lbs.,  it  gave  per  imperial  acre,  with 

Hay     .     . 
Winter  Rye 
Potatoes     . 

The  grain  of  the  dressed  rye  was  much  heavier  than  that  of  the  other, 
and,  though  nitrate  of  soda  and  sal-ammoniac  applied  to  other  parts  of 
the  same  field  caused  a  larger  increase  in  the  crop  of  rye,  yet  the  increase 
obtained  by  the  use  of  the  sulphate  was  cheaper  per  bushel  than  that  ob- 
tained by  the  use  of  either  of  the  other  substances. 

On  beans  and  peas  also  the  effect  produced  by  it  (Appendix,  page  23,) 
was  very  striking — its  action  being  exerted  not  upon  the  straw  but  upon 
the  pods,  increasing  their  number  and  enlarging  their  size. 

The  results  of  these  experiments,  therefore,  are  such  as  to  encourage 
further  trials.  The  quantity  applied  should  not  be  less  than  one  cwt. 
of  the  dry  salt  per  acre,  and  it  should  be  put  on  either  in  the  state  of  a 
very  weak  solution  witli  a  water-cart,  or  sprinkled  on  the  young  crop 
when  the  ground  is  moist  or  when  rain  is  soon  expected. 

4°.  Sulphate  of  Magnesia  {Epsom  Salts)  was  found  by  Dr.  Home  to 
promote  vegetation  almost  in  anequaldegree  with  the  sulphates  of  potash 
and  soda,  but  the  usually  high  price  of  this  compound,  among  other 
causes,  has  hitherto  prevented  it  from  being  tried  upon  an  extensive 
scale.  The  manufacture  of  thiS  article  also  has  of  late  years,  however, 
been  so  much  extended  and  simplified,  that  the  refined  salts  for  medi- 
cinal purposes  may  be  purchased  as  low  as  8s.  a  cwt.  (at  Messrs  Cook- 
son's,  Jarrow  Alkali  Works,  near  Newcastle,)  and  the  impure  salts  of  the 
Yorkshire  and  other  alum  works  at  a  much  lower  rate.  So  much  capi- 
tal indeed  has  now  been  embarked  in  the  manufacture  of  the  sulphates 
and  (arbonates  of  soda  and  magnesia  (p.  192),  and  i:  is  so  desirable 


Undressed. 

Dressed  with  Sulphate. 

Increase. 

.     .     .    4480    lbs. 

5288    lbs. 

808    lbs. 

grain,       640    lbs. 

896    lbs. 

256    lbs. 

straw,     4096    lbs. 

4608    lbs. 

512    lbs. 

.     .            16  j  tons. 

18^  tons. 

1|  tons. 

332-  USE  CF  SULPHATE  OF  LIME  OR  GYPSUM. 

on  many  accounts  to  discover  new  outlets  for  the  products  of  these  impor- 
tant manufactories,  that  were  there  only  theoretical  reasons  for  believing 
them  likely  to  benefit  practical  agriculture,  it  would  be  desirable  to  make 
trial  of  their  effects  upon  the  land.  But  their  favorable  influence  has 
already  been  shown,  and  it  remains,  therefore,  only  to  work  out  the  de- 
tails by  which  their  application  to  this  or  that  soil  or  crop  shall  be  so 
regulated  as  to  yield  a  fair  and  constant  profit  to  the  farmer  who  em- 
ploys them. 

1  have  elsewhere  (Appendix,  p.  4,)  recommended  the  application  of 
sulphatie  of  soda  at  the  rate  of  1  cwt.  of  the  dry  salt,  or  of  2  cwt.  of  crys- 
tals (cost  10s.  or  lis.)  per  acre.  The  Epsom  salts  are  only  sold  in  crys- 
tals, and  l-i-  cwt.  (cost  12s.)  in  this  form,  should  be  nearly  equal  in  efl[i- 
cacy  upon  the  land  to  2  cwt.  of  crystallized  sulphate  of  soda.  In  this 
proportion,  therefore,  it  would  be  proper  to  apply  it  to  the  young  crops, 
esj)ecially  of  wheat,  clover,  peas,  beans,  and  other  leguminous  plants. 

5°.  Sulphate  of  Lime  {Gypsum)  has  been  long  and  extensively  applied 
to  the  land  in  various  countries  and  to  various  crops.  In  Germany  its  influ- 
ence has  been  most  generally  beneficial  upon  grass  and  red  clover,  while 
in  many  parts  of  the  United  States  it  is  apphed  with  advantage  to  almost 
every  crop.  In  the  former  country  and  in  England,  it  is  usually  dusted 
over  the  young  plants  in  early  spring  ;  in  America  it  is  frequently  sown 
with  the  seed,  or,  in  the  case  of  potatoes,  put  into  the  drills  or  holes 
along  with  the  manure.  The  propriety  of  adopting  the  one  rather  than 
the  other  of  these  methods  will  depend  upon  the  nature  of  the  soil  and 
upon  the  climate.  Gypsum  requires  much  water  to  dissolve  it,  and  in 
dry  soils,  climates  or  seasons,  it  might  readily  fail  to  influence  the  crop 
at  all,  if  applied  in  the  form  of  a  top-dressing  only. 

It  would  appear  that  the  time  and  mode  of  its  application  has  more 
influence  upon  its  activity  than  we  might  suppose — siuce,  according  to 
Professor  Korte,  when  appli'ed  to  clover  at  different  periods  in  thesyiring, 
the  produce  of  different  parts  of  the  same  field  was  in  the  following 
proportions : — 

Undressed, 1 00  lbs. 

Top-dressed  on  the  30th  of  March, 132  lbs. 

13th  of  April, 140  lbs. 

27th  of  April 156  lbs.* 

The  effect  of  a  top  dressing  of  gypsum  seems  therefore  to  be  greatest 
when  it  is  applied  after  the  leaves  have  been  pretty  well  developed. f 

Theory  of  the  action  of  these  sulphates. 

a.  It  does  not  seem  diflflcult  now  to  account  for  the  general  action  of 
these  several  sulphates  of  potash,  soda,  magnesia,  and  lime.  The  ex- 
planation may  be  deduced  partly  from  recent  chemical  analyses,  and 
partly  from  agricultural  experiments  more  lately  made  by  practical  men. 

It  has  been  found,  for  example,  that  Sulphur  is  a  constant  and  appa- 
rently necessary  constituent  of  the  glyten  and  albumen  of  the  several 
varieties  of  grain,  and   of  the  legumin,  which   forms  the  largest  part 

t  Mdglinscke  Jahrbv-cher,  I,  p.  85,  quoted  in  Hlubek's  PJlanzenndhrung. 

I  Cau  the  result  here  mentioned  have  any  connection  with  the  fact  observed  by  Peschier. 
that  gypsum  laid  upou  the  leaves  of  plants  is  gradually,  converted  into  carbonate,  its  sulphuric 
acid  being  absorbed  ? 


THEORY   OF    THE  ACTION  OF  THESE    SULPHATES.  33J 

of  the  substance  of  the  pea,  the  bean,  the  vetch,  and  of  the  seeds  of 
other  leguminous  plants.  This  sulphur  they  must  obtain  from  the  soil, 
and  one  cause  of  the  efficacy  of  the  above  sulphates  is  unquestionably 
tliat  they  are  fitted  easily  to  yield  to  the  growing  plant  the  supply 
of  sulphur  they  necessarily  require — while,  if  they  are  more  efficacious 
upon  the  leguminous  than  upon  other  kinds  of  plants,  it  is  because 
the  latter  produce  a  larger  proportion  of  that  kind  of  organic  matter  in 
which  sulphur  is  constantly  pre^^nt. 

That  such  is  really  the  true  explanation  of  their  general  action  is 
proved  by  the  observation — that  sulphuri:  acid  applied  to  the  land  in  a 
very  diluted  state  exerts  an  influence  upon  the  crops  precisely  similar  to 
that  observed  when  jjypsum  or  sulphate  of  soda  is  used.  (See  Appendix, 
Nos.  I.  and  II.) 

In  reference  to  this  mode  of  action  it  is  of  consequence  to  know  the 
relative  efficiency  of  the  several  salts.  This  will  obviously  depend  upon 
the  relative  proportions  of  sulphur  or  sulphuric  acid  they  contain — sup- 
posing the  circumstances  in  which  they  are  apphed  to  be  equally  favour- 
able to  the  introduction  of  each  into  the  circulation  of  the  plant.  Their 
relative  value  upon  this  view  is  as  follow^s  : — 

100  lbs.  of  burned  gypsum  are  equal  to,  or  contain  as  much  sulphuric 
acid,  as 

126  lbs.  of  common  or  unburned  gypsum. 

128  lbs.  of  sulphate  of  [)otash. 

104  lbs.  of  sulphate  of  soda — dry. 

235  lbs.  of  sulphate  of  soda — crystallized. 

180  lbs.  of  sulphate  of  magnesia — crystallized. 
And  as  of  all  these  the  gypsum  is  by  far  the  cheapest,  it  should  form,  in 
reference  to  this  general  action  of  the  above  sulphates,  in  all  cases,  the 
most  economical  application  to  the  land. 

h.  But  they  have  each  also  their  special  a-Ciion  dependent  partly  upon 
their  physical  properties,  and  partly  on  their  chemical  constitution. 

Thusit  will  be  of  little  use  mixing  any  of  them  with  the  soil,  unless 
they  become  capable  of  entering  into  the  roots  of  the  plants  which  are 
growing  upon  it.  The  facility  with  which  this  can  be  effected  depends 
upon  their  solubility  in  water,  which  is  very  unlike.  Thus  an  imperial 
gallon  of  pure  water  at  the  ordinary  temperature  will  dissolve  of 

Gypsum  (burned,) about     \  lb. 

Gypsum  (unburned,) 1  lb. 

Sulphate  of  Potash, IJ  lbs. 

Sulphate  of  Soda,  t^ry, l|  lbs. 

Sulphate  of  Soda,  crystallized, 3|  lbs. 

Sulphate  of  Magnesia, 4    lbs. 

In  rainy  weather,  therefore,  and  in  moist  climates,  it  would  still  be 
most  economical  to  apply  the  gypsum,  since,  though  very  sparingly 
soluble,  water  would  be  sufficiently  abundant  to  dissolve  as  much  as  the 
plant  might  retjuire.  But  in  times  of  only  moderate  rain,  and  especially 
in  dry  seasons,  the  use  of  the  sulphates  of  soda  and  magnesia,  which 
are  also  low  in  price,  is  recommended  by  the  comparative  ease  with 
which  they  may  be  taken  up  by  water  and  conveyed  to  the  roots. 

c.  Again,  the  chemical  constitution  of  these  sulphates — the  nature  of 
the  substance  with  which  the  sulphuri:  acid  is  combined — determines  in 


334  SPECIAL  ACTION  UPON  GRASSES  AND  CLOVERS, 

a  still  greater  degree  the  nature  and  extent  of  their  special  action.  If 
the  soil  already  abound  in  potash,  in  soda,  in  lime,  or  in  magnesia,  then 
the  influenee  of  these  compounds  may  depend  entirely  upon  the  sul- 
phuric acid  they  contain.  But  suppose  the  land  to  be  deficient  in  lime, 
then  the  gypsum  we  add  will  act  not  only  in  virtue  of  the  sulphuric  acid, 
but  of  the  lime  also  which  it  contains,  and  thus  its  apparent  effect  will 
be  much  more  striking  than  when  the  land  is  naturally  calcareous,  or 
has  been  previously  dressed  with  hnie.  So  if  it  be  deficient  in  potash, 
the  sulphate  of  potash  will  be  more  efficient  than  it  could  be  expected  to 
prove  upon  a  soil  in  which  sulphuric  acid  alone  is  wanting.  And  so 
also,  if  lime  and  potash  abound,  and  soda  or  magnesia  be  deficient,  the 
sulphates  of  these  latter  bases  will  exercise  a  special  action  upon  the 
soil,  by  supplying  it  at  the  same  time  with  sulphuric  acid  and  with  soda 
or  magnesia  also.  Thus  on  land  to  which  lime  has  been  abundantly 
added,  according  to  the  ordinary  practice  of  husbandry,  the  sulphate  of 
soda  has  the  best  chance  of  proving  useful  to  vegetation,  not  only  because 
it  is  more  soluble,  and  is,  therefore,  more  independent  of  the  seasons, 
but  because  it  is  capable  of  supplying  two  different  substances — sulphuric 
acid  and  soda — neither  of  which  are  directly  added  in  the  ordinary 
manuring  of  the  land,  but  both  of  which  the  plants  may  find  difficulty 
in  obtaining. 

d.  Another  consideration  will  indicate  further  special  applications  of 
these  several  sulphates,  independent  of  the  sulphuric  acid  which  they 
in  common  contain.  If  we  refer  to  the  table  (p.  220,  )  in  which  is  exhibit- 
ed the  constitution  of  the  ash  of  the  several  clovers  and  grasses,  we  find 
the  constituents  of  our  sulphates  to  be  present  in  3  00  parts  of  the  ash  in 
the  following  proportions  : — 

^^'n/yf'    Red  Clover.      ^hUe  Lucerne.      Sainfoin. 

Potash 8-81         19-95        31-05        13-40         20-57 

Soda 3-94  5-29  5-79  6-15  4-37 

Lime 7-34         27-80        23-48        48-31         21-95 

Magnesia     ....        0-90  3-33  3-05  3-48  2-88 

Sulphuric  Acid      .     .        3-53  4-47  3-53  4-04  3-41 

Of  the  two  clovers  the  red  contains  more  lime  and  much  less  potash, 
therefore  the  sulphate  of  lime  is  more  likely  to  benefit  the  red  clover, 
and  the  sulphate  of  potash  the  white,  which  is  consistent  with  the  results 
of  experiment.  A  similar  difference  exists  between  lucerne  and  sainfoin, 
to  the  former  of  which  lime  and  soda  are  more  necessary  than  the  latter. 
The  first  column  under  rye  grass  shows,  on  the  other  hand,  how  very 
much  smaller  a  proportion  of  all  the  four — potash,  soda,  lime,  and  mag- 
nesia— is  required  by  this  green  crop  than  by  the  others;  and  therefore 
that  the  same  weight  of  any  one  of  these  sulphates,  which,  when  applied 
as  a  top  dressing  to  one  crop  (rye  grass),  would  cause  it  to  thrive  luxuri- 
antly, may  be  insufficient  to  supply  the  most  necessary  wants  of  another 
crop  (clover  or  sainfoin.)  Not  only  the  kind  of  mineral  manure,  there- 
fore, which  we  mix  with  the  soil,  but  the  quantity  also,  must  be  deter- 
mined by  the  kind  of  crop  we  intend  to  raise.  (For  the  theoretical  opinions 
of  other  authors  in  regard  to  the  action  of  gypsum,  see  Appendix,  No.  VI.) 

6°.  Nitrates  of  Potash  and  Soda. — The  efficacy  of  these  ttvo  substan- 
ces as  manures  in  certain  circumstances  is  now  generally  acknowledged, 


THEY  AFFECT    THE  GROWTH  OF  THE  STEM.  335 

though  the  disappoiriifnents  which  have  ocasionally  attended  their  use 
naturally  cause  the  practical  iarmer  to  hesitate  stifl,  before  he  applies 
them  in  any  quantity  to  his  land.  As  these  salts,  especially  the  nitrate 
of  soda,  are  comparatively  abundant  in  nature, — as  they  are  really  be- 
neficial in  many  cases,  and  can  be  employed  with  a  profit, — as  their  use 
in  practical  agriculture  has  recently  excited  considerable  interest — and 
as  many  eKperiments  fiave  in  consequence  been  made  with  them  upon 
various  cropsT — I  shall  briefly  direct  your  attention  to  the  most  impor- 
tant facts  which  have  yet  been  established  in  regard  to  their  action  upon 
the  growing  plant. 

a.  Apparent  effects  of  the  Nitrates. — The  first  visible  effect  of  the  ni- 
trates upon  every  crop  is  to  impart  a  dark  green  colour  to  the  leaves  and 
stems.  2^.  They  then  hasten,  increase,  and  not  unfrequently  prolong 
the  growth  of  the  plant.  3°.  They  generally  cause  an  increase  both  in 
the  weight  of  hay  or  straw,  and  of  corn — though  the  colour  and  growth 
are  occasionally  affected  without  any  sensible  increase  of  the  crop.  4°. 
The  hay  or  grass  produced  is  always  more  greedily  eaten  by  the  cattle 
than  that  which  has  not  been  dressed,  even  when  the  quantity  is  not 
affected  ; — but  the  grain  is  usually  of  inferior  quality,  bringing  a  some- 
what less  price  in  the  market,  and  yielding  a  smaller  produce  of  flour. 

Its  principal  action  seems  to  be  expended  in  promoting  the  growth— 
that  is,  increasing  the  production  of  woody  fibre,  either  in  the  stem  or  the 
ear,  without  so  much  affecting,  except  indirectly,  the  quantity  of  seed. 

lllustration.s. — 1°.  Mr.  Pusey  observed  that  the  increase  of  his  wheat 
crop,  on  the  Oxford  clay,  where  nitrate  of  soda  was  applied,  arose  from 
there  being  no  underling  straws  with  short  ears  as  in  the  undressed,  but 
all  were  of  equal  length  and  consequent  fullness  and  ripeness.  The 
nitrate  had  merely  promoted  the  growth.  (See  Royal  Agricultural  Jour- 
nal, IL,  p.  120.) 

2°.  "It  affected  the  tops  of  the  potatoes,  but  the  produce  of  bulbs  was 
less  both  by  weight  and  measure"  (Mr.  Grey,  of  Dilston).  "On  peas, 
in  a  thin  sandy  soil,  subsoil  gravel,  it  had  much  effect  on  the  colour  and 
strength  of  the  stems,  and  on  the  state  of  forwardness,  but  when  ripe, 
though  the  straw  was  stronger,  there  was  no  diflTerence  in  the  crop  of 
peas"  (Colonel  Campbell,  of  Rozelle).  "  On  land  in  high  condition  it 
did  harm  by  forcing  the  straw  at  the  expense  of  the  ear"  (Mr.  Barclay). 
"  It  appeared  to  act  strongly,  and  there  was  a  greater  bulk  of  straw,  but 
the  increase  of  grain  was  only  50  lbs.  per  acre"  (Sir  Robert  Throckmor- 
ton). In  another  experiment  of  Mr.  Barclay's  the  straw  was  vei^ strong, 
and  much  of  the  wheat  laid,  but  the  undressed  sold  for  4s.  a  bushel  more, 
and  there  was  no  profit. 

In  all  these  cases  the  nitrate  promoted  chiefly  the  growth  of  the  stem, 
or  the  production  of  woody  fibre.  The  inferior  quality  of  the  grain  and 
yield  of  flour  was  owing  to  this  action.  The  grain  was  enveloped  in  a 
thicker  covering  of  the  woody  matter  which  forms  the  skin  or  bran. 

3°.  "  The  turnips  after  the  nitrated  wheat  are  decidedly  better,  the  lops 
are  still  growing  and  luxuriant,  while  on  the  other  part  they  are  begin- 
ing  to  fall"  (Hon.  H.  Wilson).  They  seem,  therefore,  in  some  cases,  at 
least,  to  prolong  the  growth. 

From  the  above  statements  we  seem  to  derive  an  explanation  why  the 
effects  of  the  nitrate  should  have  been  so  universally  observed  upon  the 


336 


EFFECT  UPON  THE  aUANTITY  OF  THE  CROP. 


grasses  and  clovers — while  ia  regard  to  its  application  to  com  crops, 
they  indicate  this  important — 

Practical  Rule. — Not  to  apply  the  nitrates  upon  land  or  under  cir- 
cumstances where  there  is  already  a  sufficient  tendency  to  produce 
straw. 

b.  Effects  of  the  nitrates  upon  tlie  quantity  of  the  crop. — Cases  have 
occurred  where  the  nitrates  have  failed  to  produce  any  apparent  effect 
at  all — others  where  the  color  was  affected  and  the  growth  promoted 
without  any  ultimate  increase  of  crop— and  others  again,  where  the  ap- 
plication of  these  salts  was  decidedly  injurious.  These  failures  are  de- 
serving of  a  close  consideration,  but  let  us  first  attend  to  the  amount  of 
benefit  derived  from  their  use  where  it  has  been  attended  with  success. 

I. — Effect  on  Common  and  Clover  Hay. 


Locality. 

Produce  per  acre. 

Quantity  of  Nitrate  of  Soda  applied  p/»r  acre, 
and  nature  of  soil. 

Undressed. 

DreeseJ. 

Aske  Hall,  Earl  of 
Zetlaiid 

At  Erskine,  Lord 
Blantyre 

Barochan,     Mr. 
Fleming 

Dilston,  Mr.  Grey. 

Farnham,  Suffolk, 
Mr,  Muskett 

Methven    Castle, 
Mr.  Bishop 

tons.    cwt. 

|2  12 

,2    OJ 

2    1 

^2  11 
2  10 
|2    4J 

1- 

tons.    cwt. 

3    4    \ 

3    01 

2  10 

2  4i 
2l9jJ 

3  18 

3   n 

2    2  J 

1  cwt.,  on  a  thin  light  soil,  subsoil' 
clay  upon  limestone. 

120  lbs.,  good  lightsoil,  subsoil  gravel. 
Do.     clay  soil  on  clay  subsoil. 

160  lbs.,  stiff  clay,  after  wheat. 
Do.     light  clay  loam,  drained,  after 
barley. 

1  cwt.,  meadow  hay,  soil  not  stated. 

150  lbs.,  clover  hay,  soil  not  stated. 

Icwt.  nitrate  of  potash  and  U  of  ni- 
trate of  soda,  had  each  the  same  ef- 
fect on  a  heavy  damp  loam,  partially 
drained. 

On  the  other  hand,  Mr.  Barclay  says  that,  on  his  heavy  clay  lands 
(plastic  clay),  in  Surrey,  near  the  edge  of  the  chalk,  it  is  almost  al- 
ways a  failure  ;  and  the  Messrs.  Drewitt,  of  Guildford,  that  on  their 
chalk  soils,  the  additional  produce  of  hay,  whether  on  upland  or  mea- 
dow, does  not  repay  the  expense. 

•  II. — On  Barley. 


Locality. 

Produce. 

Undressed. 

Dressed. 

Quantify  per  acre,  and  kind  of  soil. 

Grain. 

Straw. 

Grain. 

Straw 

Surry,  Mr.Barclay 
Newton  Hall,  Nor- 
thumberland, Mr. 
Jobhng  

Suffolk,  Hon.  H. 
Wilson 

bsl.ls. 

44i 
{47 

|X8 

cwt. 

16i 
26 

bshls. 

59 
32 

cwt. 

20J 
36 

i 

I  cwt,  on  light  soil, with  chalk  subsoil. 

1  cwt.,  on  strong  turnip  land. 

1  cwt.,  on  a  poor  sandy  soil,  where 
the  turnips  the  preceding  year  were 
nearly  destroyed  by  the  land  blowing. 

EFFECT    ON    WINTER    RYE   AND    OATS. 


3C7 


In  Berkshire,  on  the  other  hand,  it  failed  (1839),  for  barley  on  the 
light  lands,  causing  them  in  some  cases  to  be  burned  up  (Mr.  Pusey), 
but  the  season  was  droughty. 

III. — On  Winter  Rye. 

Mr.  Fleming,  of  Barochan,  applied  160  lbs.  per  acre  to  rye,  upon  a 
strong  clay,  after  potatoes,  and  obtained — 

Undressed.  /Dressed. 

Grain        .        ,         14  bushels.  .         .        26  bushels.- 

Straw        .        ,  1  ton  7^  cwt.      .        .  2  tons,  19i  cwt. 


IV. — Upon   Oats. 


f     ■ 

Locality. 

PRODUCE. 

Gluantity  per  acre 
and  kind  of  soil. 

Undressed. 

Dres 

sed. 

grain. 

straw. 

grain. 

straw. 

Bakewell  Derbyshire, 
Mr.  Greaves    .     .     . 

Court  Farms,  Hayes, 

Mr.  Neioman  .... 

Leatherhead,  Surrey, 

Mr.  Barclay  .... 

bush. 

481 

46 
40 

cwt. 
251 

31 

61 

bush. 
64 

60| 

60 

bush. 
38| 

46i 

90 

I  cwt. ;  heavy  soil, 
clay  subsoil. 

1  cwt. ;  land  satu- 
rated with  water, 
and  out  of  condi- 
tion. 

1  cwt.;  a  loam  con- 
taining flints,  on  a 
subsoil  of  chalk. 

Mr.  Everett,  in  Norfolk,  obtained  an  increase  of  15  bushels  per  acre, 
by  the  use  of  |  cwt.  per  acre  ;  and  Mr.  Calvert,  of  Ockley  Court,  of  20 
bushels  of  grain,  and  9i  cwt.  of  straw,  by  applying  1^  cwt.  of  nitrate 
of  soda.  At  Kirkleatham  (North  Yorkshire),  it  had  an  excellent  effect 
upon  oats,  on  strong  land — and  on  the  strong  clays  of  the  Weald  of  Sur- 
rey and  Sussex,  it  is  said  by  Mr.  Dewdney,  of  Dorking,  to  be  universally 
beneficial,  particularly  when  sown  on  ley  ground — paying  the  grower 
27s.  to  30s.  per  acre.  "  When  it  has  failed,  the  nitrate  has  been  sown 
early,  and  when  the  land  was  in  a  dry  state.  In  these  instances  the 
crop  was  more  or  less  blighted."  On  the  other  hand,  Mr.  Barclay 
states  that,  on  his  strong  heavy  land  (plastic  clay),  near  the  edge  of  the 
chalk,  in  Surrey,  it  gave  no  profit. 

In  most  cases,  therefore,  the  nitrate  of  soda  seems  capable  of  pro- 
ducing a  large  increase  in  the  oat  crop^the  few  failures  which  are  noted 
must  be  due  either  to  the  state  of  the  weather  or  to  some  peculiarities  in 
the  physical  condition  or  chemical  constitution  of  the  soils  on  which  they 
were  observed. 


938 


EFFECT,. OF    THE    NITRATES    ON    WHEAT. 


V. — On  Wheat. 


Locality. 


grain  straw  grain  straw 


Farnham,  Suffolk,  i 
Mr.  MusMt,     .    \ 

Painswick,  Glou-  \ 
cester, Mr. Hyett,    \ 

Fairford  Park,  do.  i 
Mr. Raym.  Barker  ) 
Mr.Dugdale,  .     . 


Do. 


CourtFarm,  Hayes 
Mr.  Newman, 

Brandon,  Suffolk, 
Hon.  Mr.  Wilson, 

Surrey,  Mr.  Bar- 
clay,   

Faringdon,    Mr. 
Pusey,  .... 

Ockley  Court,  Mr. 

Calvert,  .  .  .  I 
Newton  Hall,  Mr.  | 

Jobling,  ...  J 
Cirencester,  Dr.      X 

Daubeny,    .     .     .  ( 

Rozelle,  near  Ayr,  < 

Col.  Campbell,     .  \ 


Undressed.     Dressed. 


ush\< 

cwt  t 

1 

33i 

26 

15 

42 

34 

32 

— 

141 

m 

21h 

30i 

331 

31 

27 

211 

201 

20 
24i 

241 
2()i 
20i 

33 

251 

30 

271 

29i 
16 

35 

3U 

27 
43«^ 

33i 

54 

36i 
20 

32 

36 
39i 
331 
391 

24^ 
45f 

36 
311 

47 
42 


211 

381 

251 


23 

27| 
341 
251 
24  i 

37i 


Quantity  per  acre,  and  kind  of  soil. 


1^  cwt. ;   a  poor  spongy  sandy  soil. 

1  cwt. ;  a  stone-brask  soil  abounding 
in  carbonate  of  lime. 

I  cwt. ;  on  a  light  stone-brash  poor 
thin  soil. 

1  cwt.  nitr.  of  soda,  on  SLgravelly  soil ; 
an  equal  weight  riUrate  of  potash  pro- 
duced only  I  bushel  of  increase  (1). 

I  cwt.  nit.  of  soda  on  a  strong  clay. 
Both  portions  previously  limed. 

1  cwt.;  on  a  very  thin  crop,  inj'd  by  an 
unfavorable  autumn.  Soil  not  stated. 

I  cwt. ;  on  a  fair  light  soil. 

Do.,  loamy,  better  land. 

I  cwt. ;  soil  loamy,  resting  on  chalk, 
straw  strong,and  much  wheat  laid.* 

Do.  on  heavy  soil,  resting  on  the  Ox- 
ford clay.  But  all  these  very  different 
resvZts  were  obtain^  in  the  same  field. 

Do.;  corn  generally  laid;  soil  not 
mentioned. 


35j  1  cwt. ;  soil  not  mentioned. 

20j  1  cwt.  nitrate  of  potash. 

15^  Do.  nitrate  of  soda,  soil  and  subsoil 

clay,  resting  on  the  corn-brash. 
52  1180  lbs.  nitrate  of  soda. 
76  JDo.  nit,  of  potash.  Soil  not  stated.t 


VI. — On  Turnips. 

At  Rozelle  the  Swedes  were  improved  several  tons  an  acre  by  the 
use  of  the  nitrate  of  soda  (Mr.  Campbell).  At  Dorking  it  was  very  be- 
neficial as  a  top-dressing  to  the  Swedes  and  white  turnips,  when  sown 
broad-cast  at  the  rate  of  1|  cwt.  per  acre  (Mr.  Dewdney).  In  neither 
of  these  cases  is  the  soil  described.  On  thin  stony  land  upon  chalk  at 
Filmshurst,  Bucks,  turnips  manured  with  nitrate  alone,  were  very  su- 
perior to  those  to  which  10  loads  an  acre  of  farm-yard  manure  had  been 
applied  (Mr.  Burgess).  The  only  numerical  results  with  which  1  am 
acquainted  are  those  of  Mr.  Barclay  on  a  loamy  soil  resting  on  chalk. 
His  crop  of  turnips  was 

•  The  dressed  grain  sold  at  4s.  less  than  the  undressed,  and  there  was  no  profit ;  the  nitrate 
failed  on  heavy  land,  and  on  land  in  high  condition. 

t  The  produce  of  etraw,  especially  from  saltpetre,  is  very  surprising.  It  is  stated  at  518 
and  764  stones  for  the  two  lots  respectively.  1  auppose  the  acres  to  be  Scotch,  and  the 
stones  14  lbs. 


EFFECT  UPON  TURNIPS,  AND  THE  QUALITY  OF  THE  CROP.   339 

30i  cwt.  when  dressed  with  bones  and  wood  ashes,  each  15  bushels. 
31  cwt.  when  dressed  with  1  cwt.  of  nitrate  of  soda,  drilled  in. 
35  cwt.  when  seed  and  nitrate  were  both  broad-cast. 
38  cwt.  when  the  seed  was  drilled  and  the  nitrate  broad-cast. 

On  the  other  hand,  Lord  Zetland  thought  it  did  no  good  to  turnips  ; 
Mr.  Vansittart,  that  on  strong  land  well  dunged  it  did  harm  ;  and  the 
Messrs.  Drewitt,  that  on  their  dry  rubbly  chalk  it  had  no  effect  on  this 
crop,  though  it  improved  in  a  remarkable  degree  the  succeeding  crop 
of  barley. 

We  are  obviously  in  want  of  more  numerous  and  better  observations, 
especially  in  regard  to  turnips.  The  above  discordancies  will  either 
vanish  when  we  obtain  a  2  larger  collection  of  results,  or  they  will  find  an 
exjolanation  in  the  more  accurate  observations  we  may  expect  to  obtain 
in  regard  to  the  climate,  soil,  and  geological  position  of  the  locality  in 
which  each  experiment  is  made.  Those  practical  men  who  are  really 
desirous  of  aiding  the  progress  of  scientific  agriculture, — by  which  pro- 
gress not  only  the  national  welfare,  but  their  own  individual  interests 
also  are  likely  to  be  promoted, — will  do  more  towards  this  end  by  one 
single  experiment  in  which  weights  and  measures  are  carefully  deter- 
mined, and  the  soil,  the  climate,  the  geological  position  and  the  lie  of 
the  land,  accurately  described,  than  by  any  number  of  mere  general 
statements,  such  as  those  I  have  here  laid  before  you  in  regard  to  the 
effect  of  the  nitrates  upon  the  turnip  crop. 

c.  Effect  of  the  nitrates  on  the  quality  of  the  crop. — This  I  have 
already  in  some  measure  alluded  to.  It  so  affects  the  grass  and  clover 
as  to  make  it  more  relished  by  the  cattle.  This  is  usually  expressed 
by  saying  that  the  crop  is  sweeter,  but  since  cattle  are  known  to  be  fond 
of  saline  substances,  it  may  be  that  the  grasses  are,  by  these  salts,  only 
rendered  more  savoury.  It  generally  also  gives  a  grain  (of  wheat) 
of  an  inferior  quality— ^which  has  a  thicker  skin,  and  yields  more  bran. 
This  may  possibly  arise  from  its  having  been  generally  allowed  to  ripen 
too  long.  [See  Mr.  John  Hannam's  valuable  experiments  on  the 
orer- ripening  of  corn  in  the  Quarterly  Journal  of  Agriculture.]  A 
question  still  undetermined  is,  whether  the  flour  of  nitrated  corn  is  more 
nutritive  than  that  obtained  from  corn  which  has  been  undressed. 

It  is  generally  supposed  that  those  samples  of  flour  which  contain  the 
most  gluten  are  also  the  most  nutritive.  But  hitherto  the  only  experi  • 
ments  which  have  been  made  with  the  view  of  determining  the  relative 
quantities  of  gluten  in  samples  of  grain  from  the  same  field,  one  por- 
tion of  which  had  been  nitrated,  and  the  other  not,  are,  one  made  by 
Mr.  Daubeny,  and  one  reported  by  Mr.  Hyett,  to  the  latter  of  which  1 
have  already  had  occasion,  for  another  purpose,  to  direct  your  attention. 
[See  note,  p.  167.] 

In  these  experiments  the  flour  of  the  several  wheats  gave — 

In  Dr.  Daubeny 's  In  Mr.  Hyett'ft 

Experiment.  Experiment. 

Nitrated 15  per  cent,  of  gluten    23^  per  cent. 

CJnnitrated 13  per  cent,  of  gluten     19    per  cent. 

Excess  of  gluten  in  the  nitrated,    2  per  cent.  4^  per  cent. 

X5 


340  AFTER-EFFECTS    OF    THE    NITRATES. 

both  of  which  results  favour  the  supposition  that  one  effect  of  the  ni- 
trates upon  the  quality  of  the  grain  is  to  increase  the  proportion  of  gluten, 
and  thus  to  render  them,  as  is  generally  believed,  n-iore  nutritive.  This 
is  a  result  which  theoretically  we  might  be  led  to  anticipate,  were  there 
no  large  increase  in  the  quantity  of  the  produce — for  then  we  might 
naturally  expect  the  nitrogen  of  the  nitric  acid  to  be  expended  solely  in 
enriching  the  grain  with  gluten.  But  the  increase  of  crop  contains  in 
many  cases  more  nitrogen  than  we  add  to  the  soil  when  we  dress  it  with 
one  cwt.  of  nitrate  of  soda  per  acre ;  there  is,  therefore,  no  excess  of  ni- 
trogen which  we  can  suppose  to  go  to  such  an  enriching  of  the  more 
abundant  crop  of  grain.  For  this  reason,  among  others,  I  am  inchned 
to  doubt  whether  further  careful  examination  will  prove  the  flour  from 
nitrated  grain  to  be  always  richer  in  gluten,  and,  therefore,  more  nutri- 
tious. At  all  events  increased  experiments  are  to  be  wished  for. 
.  d.  After-effects  of  these  nitrates. — It  is  comparatively  seldom  that 
any  good  effects  have  been  observed  upon  the  crop  which  succeeds  that 
to  which  the  nitrate  of  soda  has  been  applied.  Where  they  have  been 
noticed  it  has  been  chiefly  in  cases  where  from  some  cause  (drought  or 
dryness  of  soil  chiefly)  the  salt  has  been  prevented  from  exerting  its  full 
and  legitimate  action  upon  its  first  application.     Thus, 

1°.  Failing  to  improve  turnips  on  a  rubbly  chalk  soil,  it  greatly  be- 
nefitted the  succeeding  crop  of  barley  (Mr.  Drewitt,  Guildford,  Surrey). 

Producing  little  effect  on  tares  (upon  a  clay  soil  ?)  it  improved  very 
much  the  turnip  crop  which  followed  (Mr.Barclay,L8atherhead,Surrey.) 

2°.  In  the  following  instances  the  benefit  was  seen  on  successive 
crops  :— 

After  producing  an  increase  of  one-sixth  in  the  wheat  crop,  both 
grain  and  straw,  on  a  light  sandy  soil  (subsoil?),  the  turnips  of  the  fol- 
lowing year  were  decidedly  better  where  the  nitrate  had  been  sown  (Hon. 
H.  Wilson,  Brandon,  Suffolk.) 

After  improving  the  crop  of  wheat,  the  after-crop  of  hay  was  also 
better  (Mr.  Grey,  of  Dilston.) 

At  Upleatham,  the  second  cut  of  clover  was  nearly  as  much  im- 
proved as  the  first  (Mr.  Vansittart),  and  at  Dilston  the  aftermath  hay 
was  greater  in  quantity,  and  better  relished  by  the  cattle  (Mr.  Grey). 

3°.  A  curious  effect  is  noted  by  Mr.  Rod  well,  of  Alderton,  Wood-  - 
bridge — the  white  clover  failed  after  barley  on  which  nitrate  had  been 
used  ! 

The  solubility  of  these  nitrates  is  so  great,  that  in  our  climate,  in  sea- 
sons of  ordinary  rain,  and  on  lands  having  a  moderate  degree  ofincli-^ 
nation,  we  should  expect  that  they  would  be  in  a  great  measure  washed 
out  of  the  land  in  a  single  year.  Hence  one  reason — even  supposing 
little  of  the  salt  to  have  entered  into  the  roots  of  the  growing  crop — why 
we  are  not  entitled  generally  to  expect  any  marked  effect  from  it  upon 
a  second  crop.  But  let  the  season  be  so  dry,  or  the  soil  so  retentive, 
§rid  the  land  so  level,  as  to  prevent  its  being  all  taken  up  by  the  roots, 
or  washed  away  by  the  rains  during  one  year,  and  we  may  then  look 
for  after-effects,  such  as  those  above  described, 

e.  Circumstances  necessary  to  ensure  the  success  of  iKesc  saline  ma- 
nures,— This  explanation  will  appear  more  satisfactory  if  we  glance  for 


THEIR    ACTION    AFFECTED    BY    CIRCUMSTANCES.  341 

a  moment  at  the  general  conditions  which  are  necessary  to  ensure  the 
success  of  these  or  any  other  saline  manures. 

1°.  They  must  contain  one  or  more  substances  which  are  necessary 
to  the  growth  of  the  plant. 

2°.  The  soil  must  be  more  or  less  deficient  in  these  substances. 

3°.  The  weather  must  prove  so  moist  or  the  soil  be  so  springy  as  to 
admit  of  their  being  dissolved,  and  conveyed  to  the  roots. 

4°.  They  must  not  be  applied  in  too  large  a  quantity,  or  allowed  to 
come  in  contact  with  the  young  shoots  in  too  concentrated  a  form — the 
water  that  reaches  the  roots  or  young  leaves  must  never  be  too  strongly 
impregnated  with  the  salt,  or  if  the  weather  be  dry,  the  plant  will  be 
blighted  or  burned  up. 

5°.  The  soil  must  be  sufficiently  light  to  permit  the  salt  easily  to 
penetrate  to  the  roots,  and  yet  not  so  open  as  to  allow  it  to  be  readily 
washed  away  by  the  rains.  In  reference  to  this  point  the  nature  of  the 
subsoil  is  of  much  importance.  A  retentive  subsoil  will  prevent  the 
total  escape  of  that  which  readily  passes  through  a  sandy  or  gravelly 
soil,  while  an  open  subsoil  again  will  retain  nothing  that  has  once  made 
its  way  through  the  surface. 

/.  Cases  in  which  the  nitrates  have  failed. — A  knowledge  of  the 
above  conditions  will  enable  us  in  many  cases  to  explain  why  the  ni- 
trates, and  other  generally  useful  substances,  have  failed  to  exhibit  any 
beneficial  e.Tect. 

1°.  Thus  on  the  light  soils  of  Berkshire  the  nitrate  of  soda  failed  for 
barley,  causing  it  often  to  be  blighted  or  burned  up.  This,  no  doubt, 
arose  from  the  drought  which  may  act  in  one  or  other  of  several  ways. 
Either  it  may  prevent  the  salt  from  being  dissolved  at  all,  and  thus  hin- 
der its  action  altogether  for  the  time,— -or  it  may  retard  the  solution  till 
the  plant  has  attained  such  a  state  of  maturiry,  that  it  is  no  longer  ca- 
pable of  being  equally  benefitted  by  the  introduction  of  the  salt  into  its 
roots— or  after  being  dissolved,  and  having  partially  descended  into  the 
soil,  the  drought  may  cause  it  to  ascend  again  with  the  water  which 
rises  to  the  surface  in  consequence  of  the  evaporation,  and  may  thus 
present  it  to  the  plant  in  so  concentrated  a  form  as  to  injure  the  young 
shoots — or,  finally,  the  action  of  the  sun  upon  the  green  leaf,  into  which 
a  portion  of  the  salt  has  already  been  conveyed  by  the  roots,  may  be  so 
powerful  as  to  concentrate  the  saline  solution,  or  to  increase  its  decom- 
position to  such  an  extent  as  to  cause  injury,  and  consequent  blight  to 
the  leaf  itself. 

2'^.  Again,  at  Cheadale,  in  Cheshire,  {Mr.  Austin),  the  nitrate  of  soda 
is  said  to  have  had  a  good  effect  on  wheat  and  grass  where  the  subsoil 
was  clay,  but  none  where  the  subsoil  was  gravel,  or  the  soil  light  and 
sandy.  Here  the  supply  of  water  in.  the  soil  may  have  been  such  as  to 
fit  it  for  entering  readily  into  the  roots  in  a  proper  state  of  dilution,  when 
the  retentive  subsoil  kept  it  within  reach  of  the  roots, — and  yet  sufficient, 
at  the  same  time,  to  wash  it  away  altogether  where  the  soil  and  sub- 
soil were  too  open  to  be  able  to  retard  its  passage. 

3°.  But  the  occasional  occurrence  of  droughts  or  the  mere  physical 
distinctions  of  lands  as  light  or  heavy,  are  not  sufficient  to  account  for  all 
the  recorded  differences  in  the  effect  of  the  nitrates.     Thus  on  the  clays 


342  WHEN    THE    USE    OF    NITRATES    IS    BENEFICIAL. 

of  the  Weald  in  Sussex  (Mr.  Dewdney),  and  on  the  Oxford  clay  in 
Berkshire  (Mr.  Pusey),  the  use  of  the  nitrate  has  heen  attended  with 
general  benefit  upon  oats  and  wheat,  while  on  the  plastic  clay  in  Sur- 
rey (Mr.  Barclay),  it  has  been  uniformly  unsuccessful.  The  cause  of 
these  differences  is  to  be  sought  for,  most  probably,  in  the  chemical  con- 
stitution of  the  several  clays,  which  are  known  to  be  very  unlike.  The 
"Weald  clay  is  a  fresh- water  formation,  contains  much  fine  grained 
siliceous  matter  (page  244),  and  is,  therefore,  comparatively  per- 
vious to  water.  The  Oxford  clay  soils  in  Berkshire  abound  in  lime, 
and  must,  therefore,  be  in  some  degree  pervious,  while  the  plastic  clay 
of  Surrey,  where  they  are  stiffest,  contain  little  lime  and  partake  more 
of  the  impervious  character  of  pipe  clays.  It  may  possibly  be  in  such 
differences  as  these  that  we  are  to  find  an  explanation  of  the  discordant 
results  of  different  experimenters,  but  much  further  observation  is  still 
wanting  before  we  can  si)eak  with  any  degree  of  confidence  upon  the 
subject. 

To  some  an  explanation  may  appear  to  be  most  easily  given  by  sup- 
posing the  one  soil  to  have  been  rich  in  soda,  while  the  other  was  de- 
fective in  this  substance.  I  shall  advert  to  this  point  in  explaining  the 
theory  of  the  action  of  the  nitrates  of  potash  and  soda. 

g.  Circumstances  in  which  the  employment  of  the  nitrates  is  most  hene- 
Hcial. — 1°.  It  appears  to  succeed  most  invariably  in  lands  which  are 
poor — or  out  of  condition— or  on  which  the  corn  is  thin.  Every  farmer 
knows  that  the  most  critical  time  with  his  crop,  as  wdth  his  cattle,  is 
during  the  earliest  stage  of  its  growtli.  If  it  come  away  quickly  and 
strong  during  the  first  few  weeks,  his  hopes  are  justly  high,  but  if  it 
droop  and  linger  after  it  is  above  the  ground,  his  fears  are  as  justly  ex- 
cited. It  is  in  this  latter  condition  of  things  that  an  addition  of  nitrate 
comes  to  the  aid  of  the  feeble  plant,  re-animating  the  pining  shoots,  and 
making  the  thin  corn  tiller.  On  rich  lands  and  thickly  growing  crops  it 
only  causes  an  over-growth  of  already  abundant  straw.  According  to 
the  experiments  of  Mr.  Barclay,  it  is  most  advantageous  when  sown 
Droad-cast.* 

2°.  Whatever  may  be  the  chemical  nature  of  the  surface  soil,  the 
success  of  the  nitrate  seems  to  be  most  sure  where  the  land  is  not  wholly 
destitute  of  water,  where  the  soil  is  open  enough  to  allow  it  readily  to 
descend,  and  yet  the  subsoil  sufficiently  retentive  to  prevent  it  from 
being  readily  waslied  away. 

3°.  I  throw  it  out  as  a  suggestion  which  has  occurred  to  me  from  a 
comparison  of  the  results  contained  in  tlie  above  tables,  with  the  kind 
of  soils  on  which  the  experiments  were  made — that  probably  the  pre- 
sence of  lime  in  the  soil  may  tend  to  insure  the  success  of  the  nitrate. 
In  many  of  the  instances  of  large  crops  obtained  by  its  aid  the  land  was 
either  naturally  rich  in  lime,  or  it  had,  in  the  ordinary  course  of  hus- 
bandry, been  previously  marled  or  limed. 

h.   Theory  of  the  action  of  the  iiitrates. — The  nitric  acid  of  these  salts 

'  A  valuable  precept  also  is,  to  proceed  cautiously  in  the  use  of  theso  expenaive  Bub- 
etances — making  small  trials  at  first,  and  increasing  the  quantities  employed  as  success 
may  warrant.  By  this  mode  of  procedure,  large  lessee,  of  which  I  have  heard,  would 
have  been  avoided. 


THEORY    OF    THE    ACTION    OF    THE    NITRATES.  343 

contains  26  per  cent,  of  its  weight  of  nitrogen—or  one  cwt.  of  pure  dry 
nitrate  of  soda  contains  about  19  lbs.  of  nitrogen.  This  nitrogen  we 
know  to  be  a  necessary  constituent  of  plants— one  which  they  obtain 
almost  wholly  from  the  soil — ^but  v  hich  nevertheless  is  generally  pre- 
sent in  the  soil  in  small  quantity  on.y.  "We  have  already  seen  reason 
(Lee.  VIII.,  p.  159,)  to  believe  that  nitric  acid  exists  naturally  in  the 
soil,  and  is  the  form  in  which  a  large  portion  of  their  nitrogen  is  con- 
veyed into  the  roots  of  plants ; — when  we  add  it  to  our  fields,  therefore, 
we  only  aid  nature  in  supplying  a  compound  by  which  vegetables  are 
usually  sustained.  And  as  the  young  plant  will  necessarily  languish 
in  the  absence  of  one  essential  kind  of  food,  although  every  other  kind 
it  may  require  be  present  in  abundance,  it  is  easy  to  see  how  the 
growth  of  a  crop — languidly  proceeding  upon  a  soil  deficient  in  nitrogen 
— may  be  suddenly  re-animated  by  an  application  of  nitrate  of  soda  to 
its  roots.  That  this  is  the  true  way  in  which  the  nitrates  generally  act 
is  supported  by  the  oUseivation  that  it  is  in  the  poorest  soils  that  they 
are  most  useful  to  the  husbandman. 

We  have  already  seen,  also,  that  one  function  of  the  leaf  in  the  pre- 
sence of  the  sun  is  to  decompose  carbonic  acid,  and  give  off  its  oxygen 
(Lee.  v.,  sec.  5.)  It  exerts  a  similar  action  upon  the  nitric  acid  of  the 
nitrates,  and  upon  the  sulphuric  acid  of  the  sulphates,  discharging  their 
oxygen  into  the  air,  and  thus  leaving  the  nitrogen  and  sulphur  at  liberty 
to  unite  with  the  other  elementary  substances  contained  in  the  sap — for 
the  production  of  the  several  compounds  of  which  the  parts  of  the 
growing  plant  consist. 

Nor,  as  shown  in  a  previous  lecture,  (VIII. ,  sec.  8,)  is  the  good  effect 
of  these  nitrates  upon  the  crop  limited  to  the  supply  of  that  quantity  of 
nitrogen  only  which  they  themselves  contain.  The  excess  of  crop 
raised  by  their  aid  often  contains  very  much  more  nitrogen  than  they 
have  been  the  means  of  conveying  to  the  roots,  even  supposing  it  all 
to  have  been  absorbed  and  appropriated  by  the  plant.  This  arises  from 
the  circumstance  that  the  more  the  plant  is  made  to  thrive,  the  more 
numerous  and  extended  become  its  roots  also,  and  these  roots  are  thus 
enabled  to  gather  from  the  deeper  and  more  distant  soil  those  supplies 
of  nitrogenous  and  other  necessary  food,  which  would  have  remained 
beyond  their  reach  had  the  plant  been  allowed  to  remain  in  its  pre- 
viously feeble  or  more  languid  condition.  This  has  been  called  the 
stimulating  effect  of  manures,  and  some  substances  have  been  said  to 
act  only  in  this  way  upon  vegetation.  This,  however,  appears  to  me  to 
be  a  mistake.  The  supposed  stimulating  is  always  a  secondary  effect, 
and  necessarily  follows  from  the  use  o^ every  kind  of  manure,  which  by 
feeding  the  plant  gives  it  greater  strength,  and  thus  enables  it  to  appro- 
priate other  supplies  of  food  which  were  previously  beyond  its  reach,  or 
which  from  the  absence  of  one  necessary  constituent  it  could  not  render 
available  to  its  natural  growtff. 

In  this  way  the  nitrates  act  as  such — in  contra-distinction  to  the  sul- 
phates and  other  salts  of  potash  and  soda.  But  there  is  every  reason  to 
believe  that  the  potash  and  soda  themselves  often  aid  the  effect  of  the 
nitric  acid  with  which  they  are  associated.  In  soils  deficient  in  these 
alkalies  the  nitrates  would  act  beneficially,  even  though  nitric  acid 


344  COMPARATIVE    EFFECTS    OF    THESE    TWC    NITRATES. 

were  already  present  in  abundance, — while,  on  the  other  hand,  a  field 
that  is  defective  in  both  constituents  of  the  salt  (nitric  acid  and  potash 
or  soda),  will  be  more  grateful  for  the  same  addition  of  it  than  one  in 
which  either  of  them  already  abounds.  In  this  way,  it  is  not  unlikely 
that  the  discordant  results  of  experiments,  even  on  the  same  farm,  and 
especially  when  the  soils  are  different,  may  occasionally  be  explained. 

i.  Special  ejects  of  the  nitrates  of  potash  and  soda. — On  this  alka- 
line constituent  of  the  two  nitrates  will  depend  the  special  action  of  each 
when  applied  to  the  same  soil  under  the  same  circumstances.  It  has 
rot  yet  been  clearly  made  out  that  any  definite  special  action  can  be 
ascribed  to  them,  yet  some  experiments  bearing  upon  this  point  liave 
already  been  published,  to  which  it  will  be  proper  to  advert.  From 
the  study  of  the  special  action  of  given  manures  upon  given  crops, 
practical  agriculture  has  much  good  to  expect. 

1°.  At  Rozelle,  near  Ayr  (1840),  nitrate  of  potash  caused  oats  to 
coine  away  darker  and  stronger,  and  give  a  heavy  crop,  w^hile  in  the 
same  field  nitrate  of  soda  produced  no  benefit.  The  soil  was  inferior, 
light,  and  sandy,  with  a  red  irony  subsoil  (Capt.  Hamilton).  It  is  add- 
ed that  the  crop  was  injured  by  the  early  drought,  from  which  it  never 
recovered.  This  fact  renders  the  special  effect  of  the  nitrate  of  potash 
in  this  case  doubtful. 

2°.  In  the  experiments  upon  wheat,  made  by  the  same  gentleman 
on  the  same  farm, — it  is  to  be  presumed  upon  a  similar  soil, — 

Nitrate  of  soda  gave     .     .  46  bush,  grain,  and  52  cwt.  straw  ; 

Nitrate  of  potash  gave  .     .  42  bush,  grain,  and  76  cwt.  straw ; 

the  produce  of  straw  being  here  also  greatly  in  favour  of  the  potash  salt. 

3°.  Dr.  Daubeny  also,  in  the  experiment  upon  wheat  above  detailed, 
found  the  nitrate  of  potash  to  increase  the  produce  considerably,  while 
the  nitrate  of  soda  caused  no  increase  whatever.  The  soil  was  stiff"  clay 
upon  the  corn-brash. 

These  superior  effects  of  the  potash  salt  may  certainly  be  ascribed  to 
the  greater  deficiency  of  the  several  soils  in  potash  than  in  soda,  a  sup- 
position which  in  the  case  of  the  Rozelle  experiment  is  consistent  with 
the  fact,  that  common  salt,  when  tried  upon  the  same  land,  produced 
no  good  effect.  If  however,  as  some  suppose,  (p.  328),  potash  and  soda 
are  capable  of  re-placing  each  other  in  the  living  vegetable  without  ma- 
terially affecting  its  growth,  this  explanation  cannot  be  the  true  one. 
Further  experiments,  however,  if  carefully  conducted,  will  not  fail  to 
clear  up  this  question. 

4°.  On  a  gravelly  soil  Mr.  Dugdale  obtained  an  increase  of  12  bush- 
els of  wheat  by  the  use  of  nitrate  of  soda,  while  nitrate  of  potash  in- 
creased the  crop  by  only  half  a  bushel. 

This  result  may  be  explained  after  the  same  manner  as  the  preceding 
— the  soil  may  have  already  abounded  in  potash. 

5°.  In  Perthshire,  upon  a  moist  loam,  Mr.  Bishop  obtained  an  equal 
increase  of  hay  from  the  use  of  both  nitrates;  each  having  caused  the 
production  of  a  double  crop. 

The  equality  in  this  case  may  have  risen  from  the  effects  being 
wholly  due  to  the  nitric  acid,  both  potash  and  soda  being  already  abun- 
dant in  the  soil.     This  is  consistent  with  the  situation  of  the  locality  in 


USE   OF    COMMON    SALT    AS   A   MANURE. 


345 


a  granite  country,  and  is  further  supported  by  the  fact,  that  on  the  same 
soil  and  field,  ammoniacal  liquor,  which  contains  no  alkali,  produced  a 
still  larger  increase  of  produce. 

You  will  ucderstand,  however,  that  all  these  attempted  explanations 
proceed  upon  the  supposition  that  the  experiments  have  been  both 
carefully  made  and  faithfully  recorded. 

7°.  Chloride  of  Sodium  or  Common  Salt. — The  use  of  common  salt 
as  a  manure  has  been  long  recommended.  In  some  districts  it  has  been 
highly  esteemed,  and  is  still  extensively  and  profitably  applied  to  the 
land.  It  has,  like  many  other  substances,  however,  suffered  in  gene- 
ral estimation  fjjpm  the  unqualified  terms  in  which  its  merits  have  been 
occasionally  extolled.  About  a  century  ago  (1748J,  Brownrigg*  main- 
tained that  the  whole  kingdom  might  be  enriched  by  the  application  of 
common  salt  to  the  soil,  and  since  his  time  its  use  has  been  at  intervals 
recommended  in  terms  of  almost  equal  praise.  But  these  warm  re- 
commendations have  led  sanguine  men  to  make  large  trials,  which 
have  occasionally  ended  in  disappointment,  and  hence  the  use  of  salt 
has  repeatedly  fallen  into  undeserved  neglect. 

It  is  certain  that  common  salt  has  in  very  many  cases  been  advanta- 
geous to  the  growing  croj).  Some  of  the  'more  carefully  observed  re- 
sults which  have  hitherto  been  published,  are  contained  in  the  follow- 
ing table  : 


Produce  per  acre. 

Locality. 

Quantity  applied  per  acre,  and  kind  of  soil. 

Unsalted. 

Salted. 

UPON  WHEAT. 

bushels. 

bushels. 

' 

16i 

m 

11  bushels,  after  barley. 

111 

21 

6|    do.,      after  beans. 

16 

171 

Do.  sown  with  the  seed,    )  after 
Do.  dug  in  with  the  seed,  \  peas. 

Mr.  G.  Sinclair. . . .  ] 



23i 

12 

281 

5^  do.  }  appied  before  sowing,  after 
11  do.  S      turnips. 

■ 

— 

281 

Great  Totham,  Essex,  ) 
Mr.  Cuth.  Johnson .  K 

13§ 

26i 

5  bushels,  light  gravelly  soil. 

Barochan,  Paisley,       * 
Mr.  Fleming ) 

25 

32 

160  lbs.,  heavy  loam,  after  potatoes. 

ON    BARLEY. 

Suffolk,  Mr.  Rati&ovi. . . 

30 

51 

16  bushels. 

ON    HAY. 

tons,  cwt 

tons,  cwt 

At  Aske  Hall,  near) 
Richmond S 

2    10 

3     12 

6  bushels,  thin  light  soil,  clay  subsoil. 

At  Erskine,  near  Ren-  t 

2      0 

2    12 

5  bushels,  li^ht  soil  on  gravel. 

frew {  1  2      1 

2      8 

Do.,  clay  soil  on  clay. 

But  it  is  as  certain  that  in  many  cases,  when  applied  to  the  land, 
common  salt  has  failed  to  produce  any  sensible  improvement  of  the 
growing  crop.  And  as  failures  are  long  remembered,  and  more  gene- 
rally made  known  than  successful  experiments,  the  fact  of  their  fre- 
quent occurrence  has  prevented  the  use  of  salt  in  many  cases  where  it 
might  have  been  the  means  of  much  good. 

"  On  the  art  of  making  coffvnon  salt,  p.  158  (London,  1748). 


346  CAUSES    OF    THK    FAILURE    OF   COMMON    SALT. 

Cause  of  these  failures. — It  is  not,  indeed,  to  be  wondered  at,  that 
amid  conflicting  statements  as  to  its  value,  the  practical  farmer  should 
have  hesitated  to  incur  the  trouble  and  expense  of  applying  it — so  long 
as  no  principle  was  made  known  to  him  by  which  its  application  to  this 
soil  rather  than  to  that,  and  in  this  rather  than  the  other  locality,  was  to 
be  regulated. 

1°.  We  know  that  plants  require  for  their  sustenance  and  growth  a 
certain  supply  of  each  of  the  constituents  of  common  salt,  which  supply, 
in  general,  they  must  obtain  from  the  soil.  If  the  soil  in  any  field 
contain  naturally  a  sufficient  quantity  of  common  salt — or  of  chlorinv'i 
and  soda,  in  any  other  state  of  combination — it  will  b^nnecessary  to 
add  this  substance,  or,  if  added,  it  will  produce  no  benencial  effect.  If, 
on  the  other  hand,  the  soil  contain  little,  and  has  no  natural  source  of 
supply,  the  addition  of  salt  may  cause  a  considerable  increase  in  the  crop. 

Now  there  are  certain  localities  in  which  we  can  say  beforehand  that 
common  salt  is  likely  to  be  abundant  in  the  soil.  Such  are  the  lands 
that  lie  along  the  sea  coast,  or  which  are  exposed  to  the  action  of  pre- 
vailing sea  winds.  Over  such  districts  the  spray  of  the  sea  is  constantly 
borne  by  the  winds  and  strewed  upon  the  land,  or  is  lifted  high  in  the 
air,  from  which  it  descends  afterwards  in  the  rains.*  This  considera- 
tion, therefore,  affords  us  the  important  practical  rule  in  regard  to  the 
application  of  common  salt — that  it  is  most  likely  to  he  beneficial  in 
spots  which  are  remote  from  the  sea  or  are  sheltered  from  the  prevailing 
sea  winds. 

It  is  an  interesting  confirmation  of  this  practical  rule,  that  nearly  all 
the  successful  experiments  above  detailed  were  made  in  localities  more 
or  less  remote  from  the  sea,  while  most  of  the  failures  on  record  were 
experienced  near  the  coast.  This  consideration,  it  may  be  hoped,  will 
induce  many  practical  men  to  proceed  with  more  confidence  in  making 
trial  of  its  effects  on  inland  situations.  It  is  very  desirable  that  the 
value  of  this  practical  rule,  which  I  suggested  to  you  in  a  former  lec- 
ture (see  p.  190),  should  be  put  to  a  rigorous  test.f 

2°.  But  some  plants  are  more  likely  to  be  benefitted  by  the  applica- 
tion of  common  salt  than  others.  This  may  be  inferred  from  the  fact 
that  certain  species  are  known  to  flourish  by  the  sea-shore,  and  where 
they  grow  inland  to  select  such  soils  only  as  are  naturally  impregnated 
with  much  saline  matter.  Observations  are  still  wanting  to  show  which 
of  our  cultivated  crops  is  most  favoured  by  common  salt.  It  is  known, 
however,  that  the  gas  of  salt  marshes  is  peculiarly  nourishing,  and  is 
much  relished  by  cattle,  and  that  the  grass  lands  along  various  parts  of 
our  coast  produce  a  herbage  which  possesses  similar  properties.  It  is 
also  said  that  the  long  tussaclc  grass  which  covers  the  Falkland  Islands, 

*  Dr.  Madden  has  calculated  that  the  quantity  of  rain  which  falls  at  Penicuick  in  a  year, 
brings  down  upon  each  acre  of  land  in  that  neighborhood  more  than  COO  lbs.  weight  of  com- 
mon salt.  This  would  be  an  enormous  dressing  were  it  all  to  remain  upon  the  land. 
Heavy  rains,  however,  probably  carry  off  more  from  the  soil  than  they  impart  to  it.  It  is 
the  gentle  showers  that  most  enrich  the  fields  with  the  saline  and  other  matters  they  con- 
tain. 

t  A  number  of  failures  are  described  in  the  sixth  volume  of  the  "  Transactions  of  the 
Highland  and  Agricultural  Society."  Dr.  Madden  has  recently  shown  that  to  nearly  all 
these  cases  the  above  principle  applies— the  farms  on  whic  ■,  they  were  tried  being  more  or 
less  freely  exposed  to  the  \tiviis  from  the  east  or  west  sea  —Quarterly  Journal  of  Agri- 
culture,  Sept.  1842,  p.  574. 


WHEN    APPLIED    AS    A    MANURE.  347 

luxuriates  most  when  it  is  within  the  immediate  reach  of  the  driving 
spray  of  the  southern  sea.  It  may  well  be,  therefore,  that  among  our 
cultivated  crops  one  may  delight  more  in  common  s^U  than  another, — 
and  if  we  consider  how  much  alkaline  matter  is  contained  in  the  tops 
and  bulbs  of  the  turnip  and  the  potatoe,  we  are  almost  justified  in  con- 
cluding that  generally  common  salt  will  benefit  green  crops  more  than 
crops  of  corn,  and  that  it  will  promote  more  the  developement  of  the 
leaf  and  stem  than  the  filling  of  the  ear. 

If  this  be  so,  we  can  readily  understand  how  a  soil  may  already  con- 
tain abundance  of  salt  to  supply  with  ease  the  wants  of  one  crop,  and 
yet  too  little  to  meet  readily  the  demands  of  another  crop.  The  appli- 
cation of  salt  to  such  a  soil  will  prove  a  failure  or  otherwise,  according 
to  the  kind  of  crop  we  wish  to  raise. 

3°.  Failures  have  sometimes  been  experienced  also  on  repeating  the 
application  of  salt  to  fields  on  which  its  first  effects  were  very  favour- 
able. In  such  cases  it  may  be  presumed  that  the  land  has  been  already 
supplied  with  salt,  sufficient  perhaps  for  many  years'  consumption  — 
and  that  it  now  requires  the  application  of  some  other  substance. 

If  it  be  desired,  experimentally,  to  ascertain  whether  the  land  already 
contains  a  sufficient  supply  of  common  salt,  the  readiest  method  is  to 
collect  half  a  pound  of  the  soil  in  dry  weather,  to  wash  it  well  with  a 
pint  or  two  of  cold  distilled  water,  and  then  to  filter  through  paper,  or 
carefully  to  pour  off*  the  clear  liquid  after  the  whole  of  the  soil  has  been 
allowed  to  subside.  A  solution  of  nitrate  of  silver  (common  lunar-caus- 
tic of  the  shops)  will  throw  down  a  white  precipitate,  becoming  purple 
in  the  sun,  which  will  be  more  or  less  copious  according  to  the  quantity 
of  salt  in  the  soil.  If  this  precipitate  be  collected,  dried  in  an  oven, 
and  weighed,  every  10  grains  will  indicate  very  nearly  the  presence  of 
4  grains  of  common  salt.  The  quantity  of  this  precipitate  to  be  expect- 
ed, even  from  a  soil  rich  in  common  salt,  is,  however,  very  small.  If 
half  a  pound  of  the  drj"-  soil  yield  a  single  grain  of  salt,  an  acre  should 
contain  about  1000  lbs.  of  salt  where  the  soil  is  12  inches  deep — where 
it  has  depth  of  only  6  inches,  it  will  contain  nearly  500  lbs.  in  every 
acre. 

8°.  Chlorides  of  Calcium  and  Magnesium. — These  compounds  are 
rejected  in  large  quantities  as  a  refuse  in  some  of  our  chemical  manu- 
factories— and  tbey  are  contained,  especially  the  latter,  in  considerable 
abundance  in  the  refuse  liquor  of  our  salt  pans.  They  have  both  been 
shown  to  be  useful  to  vegetation  (see  Appendix),  and  where  they  are 
easily  to  'be  obtained,  they  are  deserving  of  further  trials.  Like  com- 
mon salt,  it  is  generally  in  inland  situations  that  they  are  fitted  to  be 
the  most  useful.  Where  salt  springs  are  found  in  the  interior  of  Ger 
many,  the  refuse  obtained  by  boiling  down  the  mother  liquors  after  the 
separation  of  the  salt  has  been  often  applied  with  advantage  to  the  land. 

Theory  of  the  action  of  these  chlorides. — Common  salt  and  the  chlo- 
rides of  calcium  are  not  unfrequenily  found  in  the  sap  of  plants — they 
may  be  supposed,  therefore,  to  enter  into  the  roots  without  necessarily 
undergoing  any  previous  decomposition.  But  we  have  already  seen 
(Lee.  v.,  §  5),  that  the  green  leaves  under  the  influence  of  the  sun, 
have  the  power  of  decomposing  common  salt — and  no  doubt  the  other 
15* 


348  PHOSPHATE  OF  LIME  AND  EARTH  OF  BOKES. 

chlorides  also — and  of  giving  ofT  their  chlorine  into  the  surrounding  air. 
When  they  have  been  introduced  into  the  sap  therefore,  by  the  roots,  the 
plant  first  appropsiates  so  much  of  the  chlorine  they  contain  as  is  neces- 
sary for  the  supply  of  its  natural  wants,  and  evolves  the  rest.  When 
common  salt  is  thus  decomposed,  soda  remains  behind  in  the  sap,  and 
this  is  either  worked  up  into  the  substance  of  the  plant,  or  performs  one 
or  other  of  those  indirect  functions  1  have  already  explained  to  you 
(p.  328)  when  illustrating  the  probable  action  of  potash  and  soda  upon 
the  vegetable  economy.  When  the  other  chlorides  (of  calcium  or  mag- 
nesium) are  decomposed,  lime  or  magnesia  remains  in  the  sap,  and  is 
in  like  manner  either  used  up  directly  in  the  formation  of  the  young 
stem  and  seed,  or  is  employed  indirectly  in  promoting  the  chemical 
changes  that  are  continually  going  on  in  the  sap.  The  living  plant, 
when  in  a  healthy  state,  is  probably  endowed  with  the  power  of  admit- 
ting into  its  circulation,  and  of  then  decomposing  and  retaining,  so  much 
only  of  these  several  chlorides,  or  of  their  constituents,  as  is  fitted  to 
'enable  its  several  organs  to  perform  their  functions  in  the  most  perfect 
manner. 

In  the  soil  itself,  in  the  presence  of  organic  matter  of  animal  and 
vegetable  origin,  common  salt  is  fitted  to  promote  certain  chemical 
changes,  such  as  the  production  of  alkaline  nitrates — and  probably  sili- 
cates— by  which  the  growth  of  various  kinds  of  plants  is  in  a  greater 
or  less  degree  increased.  In  the  soil,  also,  from  thek  tendency  to  deli- 
quesce, or  run  into  a  liquid,  all  these  chlorides  attract  water  from  the 
air,  and  thus  help  to  keep  the  soil  in  a  moister  state.  When  applied  in 
sufficient  quantity  they  destroy  both  animal  and  vegetable  life,  and 
have,  in  consequence,  been  often  used  with  advantage  for  the  extirpa- 
tion of  weeds,  and  for  the  destruction  of  grubs  and  other  vermin  that 
infest  the  land. 

9°.  Phosphate  of  Lime  and  Earth  of  Bones. — The  cattle  that  graze 
in  our  fields  derive,  as  you  know,  all  the  earthy  materials  of  which  cer- 
tain parts  of  their  bodies  consist  from  the  vegetables  on  which  they  feed. 
These  vegetables  again  must  derive  them  from  the  soil.  Thus  the 
earth  of  bones,  or  the  phosphoric  acid  and  lime  of  which  it  consists 
(p.  196),  must  exist  in  the  soil  on  which  nutritive  plants  grow,  and  it 
must  occasionally  occur  that  a  soil  will  be  deficient  in  these  substances, 
and  will,  therefore,  supply  them  with  difficulty  lo  the  crops  it  rears. 
The  benefit  which  in  this  country  is  so  often  experienced  from  the  use 
of  bones  as  a  manure,  has  been  ascribed,  in  part,  to  the  supply  of  bone- 
earth,  with  which  it  enriches  the  land.  (See  Appendix,  No.  I.)  It 
is  not,  however,  to  be  inferred  from  this,  that  wherever  bones  are  use- 
ful, the  application  of  bone-earth  alone — in  the  form  of  burned  bones, 
or  of  the  native  phosphate  of  lime,  (p.  199,)  will  necessarily  prove 
advantageous  also.  Burned  bones  were  formerly  employed  in  Eng- 
land, but  the  practice  has  gradually  fallen  into  disuse,  and  the  same  is, 
I  believe,  the  case  in  Germany.  This  is  no  proof,  however,  that  the 
native  phosphate  of  Estremadura — already,  it  is  said,  imported  into 
Ireland  for  agricultural  purposes, — would  not  benefit  many  soils  if  ap- 
plied in  the  state  of  a  sufficiently  fine  powder.  Until  carefully  con- 
ducted experunents,  however,  shall  have  been  made,  and  the  numerical 


USE  OF  SULPHATE  OF  AMMONIA.  34D 

results  precisely  ascertained,  it  would  be  improper  to  incur  much  risk 
either  in  bringing  this  substance  to  our  shores  or  in  applying  it  to  our 
fields. 

10°.  Silicates  of  Potash  and  Soda. — These  compounds,  which  have 
been  already  described  (p.  206),  are  supposed  to  act  an  important 
part  in  the  growth  of  the  grasses,  and  of  the  corn-bearing  plants,  by 
supplying,  in  a  soluble  state  to  the  roots,  the  silica  which  is  so  necessary 
to  the  strength  of  their  stems.  This  supposition  has  been  strengthened 
by  the  results  of  some  experiments  made  by  Lampadius,  who  found  a 
solution  of  silicate  of  potash  to  produce  remarkable  effects  upon  Indian 
corn  and  upon  rye.  {Lehre  von  den  mineralischen  Dungmitteln,  p.  25, 
1833.)  It  is  possible  to  manufacture  them  at  a  cheap  rate,  and  it  would 
be  desirable  to  ascertain  by  further  trials  how  far  the  employipent  of 
these  compounds,  as  artificial  manures,  can  be  safely  recommended  or 
adopted  with  the  hope  of  remuneration.* 

11°.  Salts  of  Ammonia, — There  is  reason  tobelieve  that  ammonia  in 
every  state  of  combination  is  fitted,  in  a  greater  or  less  degree,  to  pro- 
mote the  growth  of  cultivated  plants.  None  of  its  compounds,  how- 
ever, are  known  to  occur  anywhere  in  nature  in  such  quantity  as  to  be 
directly  available  in  practical  agriculture,  and  only  a  very  few  can  be 
produced  by  art  at  so  low  a  price  as  to  admit  of  their  being  used  with 
profit. 

a.  Sulphate  of  Ammonia. — An  impure  sulphate  is  manufactured  by 
adding  sulphuric  acid  to  fermented  urine,  or  to  the  ammoniacal  liquor 
of  the  gas  works,  and  evaporating  to  dryness.  When  prepared  from 
urine,  it  contains  a  mixture  of  those  phosphates  which  exist  in  urine, 
and  which  ought  to  render  it  more  valuable  as  a  manure.  The  gas 
liquor  yields  a  sulphate  which  is  blackened  ^y  coal  tar — a  substance 
which,  while  not  injurious  to  vegetation,  is  said  to  be  noxious  to  the 
insects  that  infest  our  corn  fields.  In  any  of  these  economical  forms  this 
salt  has  been  found  to  promote  vegetation ;  but  accurate  experiments 
are  yet  wanting  to  show  in  what  way  it  acts — whether  in  promoting  the 
growth  of  the  green  parts  or  in  filling  the  ear,  or  in  both — to  what  kind 
ol"  crops  it  may  be  applied  with  the  greatest  advantage — and  what 
amount  of  increase  may  be  expected  from  the  application  of  a  given 
weight  of  the  salt.  It  is  from  the  rigorous  .determination  of  such  points 
that  I  he  practical  farmer  will  be  able  to  deduce  the  soundest  practical 
precepts,  and  at  the  same  time  to  assist  most  in  the  advancement  of 
theoretical  agriculture. 

The  crystallized  sulphate  of  ammonia  is  soluble  in  its  own  weight  of 
water.  100  lbs.  contain  about  35  lbs.  of  ammonia,  53  lbs.  of  acid,  and 
1 2  lbs.  of  water.  It  may  be  applied  at  the  rate  of  from  30  lbs.  to  60  lbs. 
per  acre. 

b.  Sal- Ammoniac  or  Muriate  of  Ammonia. — This  salt,  in  the  pure 
state  in  which  it  is  sold  in  the  shops,  is  too  high  in  price  to  be  economi- 
cally employed  by  the  practical  farmer.  An  impure  salt  might,  how- 
ever, be  prepared  from  the  gas  liquor,  which  could  be  sold  at  a  sufficiently 

•  I  have  been  informed  by  Dr.  Playfair  that  a  number  of  experiments  with  a  soluble 
silicate  of  soda,  manufactured  at  Manchester,  have  this  summer  (1842)  been  made  at  his 
suggestion,  the  results  of  which  will,  no  doubt,  prove  very  interesting. 


350  SAL-AMMONIAC  AND  CARBONATE  OF  AMMONIA. 

cheap  rate  to  admit  of  an  extensive  application  to  the  land.*  The  only 
numerical  results  from  the  use  of  this  salt  with  which  I  am  acquainted, 
are  those  given  hy  Mr.  Fleming,  who  applied  it  at  the  rate  of  20  lbs. 
per  acre  to  wheat  on  a  heavy  loam,  and  to  winter  rye,  on  a  tilly  clay, 
both  after  potatoes,  and  obtained  the  following  increase  of  produce  per 
acre  : — 

Grain.  Straw. 

Rye,  undressed     .     14     bushels  36|  cwt. 

Do.  dressed    ♦.     .     19         do.  43^    do. 

Increase  ...       5     bushels.  7     cwt. 

Wheat,  undressed    25     bushels,  each  61  lbs. 
Do.  dressed  .     26^  bushels,  each  62  lbs. 

Increase  -     .     .       Ij  bushels. 

The  increase  of  these  experiments  was  not  very  large,  but  the  quan- 
tity of  sal-ammoniac  employed  was  probably  not  great  enough  to  pro- 
duce a  decided  effect.  It  is  a  valuable  fact  for  the  farmer,  however,  and 
not  uninteresting  in  a  theoretical  point  of  view,  that  a  part  of  the  same 
wheat  field,  dressed  with  li  cwt.  of  common  salt  per  acre,  gave  a  pro- 
duce of  40  bushels  of  grain  (see  Appendix,  p.  19.) 

c.  Carbonate  of  Ammonia — is  obtained  in  an  impure  form  by  the  dis- 
tillation of  horns,  hoofs,  anl  even  bones.  In  this  impure  form  it  is  not 
generally  brought  into  the  market,  but  in  this  state  it  might  possibly  be 
afforded  at  so  low  a  price  as  to  place  it  within  the  reach  of  the  practical 
farmer^  It  is  supposed  by  some  that  this  carbonate  is  too. volatile — or 
rises  too  readily  in  the  forni  of  vapour — to  be  economically  applied  to 
the  land.  In  the  form  of  a  weak  solution,  however,  put  on  by  a  water 
cart,  or  in  moist  showery  weather  simply  as  a  top-dressing,  especially 
to  grass  lands  and  on  light  soils,  it  may  be  safely  recommended  where 
it  can  be  cheaply  procured. 

d.  Ammoniacai  Liquor. — This  is  proved  by  the  success  which  has  in 
many  localities  been  found  to  attend  the  application  of  the  ammoniacai 
liquor  of  the  gas  works.  This  liquid  holds  in  solution  a  variable  quan- 
tity of  sulphate  of  ammonia  and  sal-ammoniac, f  but  in  general  it  is 
richest  in  the  carbonate  of  ammonia. 

The  strength  of  the  liquor  varies  in  different  gas  works;  chiefly  ac- 
cording to  the  kind  of  coal  employed  for  the  manufacture  of  the  gas. 
One  hundred  gallons  may  contain  from  20  lbs.  to  40  lbs.  of  ammonia, 
in  one  or  other  of  the  above  states  of  combination.  No  precise  rule, 
therefore,  can  be  given  for  the  quantity  which  ought  to  be  applied  to  the 
acre  of  land,  but  as  the  application  of  a  larger  quantity  can  do  no  harm, 
provided  it  be  sufficiently  diluted  with  water,  one  hundred  gallons  may 
be  safely  put  on  at  first,  and  more  if  experience  should  afterwards  prove 
it  to  be  useful. 

On  grass  and  clover,  upon  a  heavy  moist  loam,  Mr.  Bishop  applied 

*  By  mixing,  for  example,  the  waste  muriatic  acid,  or  the  waste  chloride  of  calcium, 
with  ga3  liquor,  and  evaporating  the  mixture  to  dryness. 

t  Each  gallon  of  the  ammoniacai  liquor  of  the  Manchester  gas-works  is  said  to  contain 
9  ounces  of  Sql  Ammoniae.    In  theM  works  the  Canoel  coal  of  Wigan  is  employed. 


SPECIAL    ACTIOIN    OF  THE  SULPHATE  AND    NITRATE.  351 

105  galloiis  an  acre,  diluted  with  500  gallons  of  water,  and  obtained,  of 
..ay,  from  the 

Undressed  ...     ^  lb.  per  square  yard,  or  20i  cwt.  per  acre. 

Dressed    ....  Ij^  lb.  do.  or  61i  cwt.      do. 


Increase  ...  1     lb.  do.  or  41    cwt.*    do. 

The  increase  herh  is  so  very  great  that  further  trials  with  this  liquor — 
hitherto,  in  most  country  towns  at  least,  allowed  to  run  to  waste — can- 
not be  too  strongly  recommended.  On  the  dressed  part,  according  to 
Mr.  Bishop,  the  Timothy  grass  was  particularly  luxuriant. 

These  experiments  with  the  gas  liquor  show,  as  I  have  said,  that  im- 
pure carbonate  of  ammonia  may  be  safely  applied  to  the  land  without 
any  previous  preparation.  If  it  is  wished,  however,  to  fix  it  or  to  ren- 
der it  less  volatile — which  in  warm  and  dry  seasons  may  sometimes  be 
desirable — this  may  be  effected  by  mixing  it  with  powdered  gypsum,  in 
the  proportion  of  Tib.  to  each  gallon  of  the  ammoniacal  liquor,  or  by 
adding  directly  sulphuric  acid,  or  the  waste  of  muriatic  acid  of  the  al- 
kali works.  + 

e.  Nitrate  of  Ammonia. — If  it  be  correct  that  those  substances  act 
most  powerfully  as  manures  which  are  capable  of  yielding  the  largest 
quantity  of  nitrogen  to  plants,  the  nitrate  of  ammonia  ought  to  promote 
vegetation  in  a  greater  degree  than  almost  any  other  saline  substance  we 
could  employ.  According  to  the  experiments  of 'Sir  H.  Davy,  (Davy's 
Agricultural  Chemistry^  Lecture  VII.)  however,  this  does  not  appear 
to  be  the  case,  though  Sprengel  has  found  it  more  efficacious  than  the 
nitrates  either  of  potash  or  of  soda.  This  question  as  to  the  relative 
action  of  the  nitrate  of  ammonia  is  very  interesting  theoretically,  but  it 
directly  concerns  practical  agriculture  very  little,  since  the  high  price 
of  this  salt  is  likely  to  prevent  its  being  ever  employed  in  the  ordinary 
operations  of  husbandry. 

/.  Special  action  of  the  different  Salts  of  Ammonia. — The  theory  of 
the  action  of  ammonia  itself  upon  vegetation  I  have  in  a  former  lecture 
(p.  164)  endeavoured  to  explain  to  you.  But  the  special  action  of  the 
several  saline  compounds  of  ammonia  above  described  will  depend  upon 
the  qualities  of  the  acid  with  which  it  may  be  in  combination. 

The  sulphate  will  partake  of  the  action  of  the  sulphates  of  potash, 
soda,  or  lime  (gypsum), — in  so  far  as  it  may  be  expected  to  exhibit  a 
more  marked'effect  upon  the  leguminous  than  upon  the  corn  crops,  and 
upon  the  produce  of  grain  than  on  the  growth  of  the  leaves  and  the 
stem.  This  special  action  may  be  anticipated  from  the  sulphuric  .acid 
it  contains.  And  if  this  reasoning  from  analogy  be  correct,  we  should 
expect  the  sulphate  of  ammonia  to  rank  among  the  most  useful  of  ma- 
nures— since  the  one  constituent  (ammonia)  will  promote  the  general 
growth  of  the  plant,  while  the  other  will  expend  its  influence  more  in 
the  filling  of  the  ear. 

The  nitrate  again  has  been  found  to  ac^  more  upon  the  crops  of  corn 
than  upon  the  leguminous  plants  and  clovers  (Sprengel) — a  result  which 

•  Prize  Essays  of  the  Highland  Society,  xiv.,  p.  359. 

t  100  gallons  thus  saturated  with  acid  will  convey  to  the  soil  a^xmt  ICO  -bs.  of  salphate  of 
ammonia  or  of  sal-ammoniac. 


362  MIXTURE   OF    NITRATE    WITH    SULPHATE    OF    SODA. 

is  to  be  explained  by  the  absence  of  sulphuric  acid,  which  appears  to 
aid  especially  in  the  development  of  the  latter  class  of  plants. 

On  this  subject,  however,  experiments  are  too  limited  in  number,  in 
general  too  inaccurately  made,  and  our  information  in  consequence  too 
scanty,  to  enable  us  as  yet  to  arrive  at  satisfactory  conclusions. 

12°.  Mixed  Saline  Manures. — The  principle  already  so  frequently 
illustrated,  that  plants  require  for  their  rapid  and  perfect  development 
a  sufficient  supply  of  a  considerable  number  of  different  inorganic  sub- 
stances, will  naturally  suggest  to  yon  that  in  our  endeavours  to  render 
a  soil  productive,  or  to  increase  its  fertility,  we  are  more  likely  to  suc- 
ceed if  we  add  to  it  a  mixture  of  several  of  those  substances,  than  if  we 
dress  it  or  mix  it  up  with  one  of  them  only.  This  theoretical  conclu- 
sion is  confirmed  b^'  universal  experience. 

Nearly  all  the  natural  manures,  whether  animal  or  vegetable,  which 
are  applied  to  the  land,  contain  a  mixture  of  saline  substances,  each  of 
which  exercises  its  special  effect  upon  the  after-crop — so  that  the  final 
increase  of  produce  obtained  by  the  aid  of  these  manures,  must  be  as- 
cribed not  to  the  single  action  of  one  of  their  constituents,  but  to  the 
joint  action  of  all.  An  important  practical  problem,  therefore,  pro- 
pounded by  scientific  agriculture  in  its  present  state,  is — what  mixtures 
of  saline  substances  are  most  likely  to  be  generally  useful,  what  others 
specially  useful,  to  this  or  to  that  crop  ?  The  complete  solution  of  this 
problem  will  require  the  joint  aid  of  chemical  theory  and  of  agricultu- 
ral experiment, — of  experiments  often  varied  and  probably  long  con- 
tinued. But  that  we  may  finally  expect  to  solve  it,  will  appear  from 
what  has  already  been  accurately  observed  in  regard  to  the  effect  of 
certain  artificial  mixtures  upon  some  of  our  cultivated  crops.     Thus — 

a.  Mixture  of  Nitrate  with  Sulphate  of  Soda. — If,  instead  of  dressing 
young  potatoes  with  nitrate  or  with  sulphate  of,  soda  alone  (page  331|, 
we  employ  a  mixture  of  the  two,  the  growth  of  the  plant  is  much  more 
promoted  and  the  crop  of  potatoes  much  more  largely  increased.  Thus 
Mr.  Fleming  (in  1841)  applied  to  his  potatoe  crop  a  mixture  of  equal 
weights  of  nitrate  and  of  dry  sulphate  of  soda,  in  the  proportion  of  200 
lbs.  of  the  mixture  to  the  imperial  acre,  with  the  following  remarkable 
result : — 

Undressed,     .     .     .     66  bolls,  each  5  cwt.,  per  acre. 
Dressed,    ....  107  bolls. 

Increase,    ...     41  bolls,*  or  10  tons  per  acre  ! 

The  stems  also  were  six  and  seven  feet  high.  The  addition  of  nitrate 
of  soda  to  a  portion  of  the  same  field  gave  a  produce  of  only  80  bolls. 
Similar  effects,  of  which,  however,  I  have  not  yet  obtained  the  numeri- 
cal results,  have  been  observed  on  the  same  crop  in  various  localities 
during  the  present  season  (1842). 

The  effect  of  this  one  artificial  mixture  holds  out  the  promise  of 
much  good  hereafter  to  be  ob^ined  by  the  judicious  trial  of  other  mix- 
tures— probably  of  a  greater  number  of  substances — upon  all  the  crops 
we  are  in  the  habit  of  raising  for  food. 

b.  Wood  ashes. — This  opinion  is  strengthened  by  the  effects  which 

'  See  Appendix,  p.  20. 


COMPOSITION    OF    WOOD    ASHES,    AND    USE   AS    A    MANURE.        363 

have  almost  universally  been  found  to  follow  the  use  of  wood  ashes  and 
of  the  ash  of  other  vegetables  in  the  cultivation  of  the  land. 

The  quality  of  the  ash  left  by  plants  when  burned  varies,  as  we  have 
already  had  occasion  to  remark  (p.  216),  with  a  variety  of  circum- 
stances. It  always  consists,  however,  of  a  mixture  in  variable  propor- 
tions of  carbonates,  silicates,  sulphates,  and  phosphates  of  potash,  soda, 
lime,  and  magnesia,  with  certain  other  substances  present  in  smaller 
quantity,  yet  more  or  less  necessary,  it  may  be  presumed,  to  vegetable 
growth.  Thus,  according  to  Sprengel,  the  ash  of  the  red  beech,  the  oak 
and  the  Scotch  fir  (  pinus  sylvestris),  consists  of 

Bo/i  n^^v^K      r»,i,  Scotch     Pitch  Pine. 

Red  Beech.     Oak.  p^         (Berthier.) 

Silica 5-52  2695  659  750 

Alumina 2-33 

Oxide  of  Iron.     .    .     .  377  814  1703  IMO 

Oxide  of  Manganese    .  3.85  —  —  275 

Lime 25  00  1738  2318  13-60 

Magnesia 500  1'44  502  435 

Potash 22-11  16  20  2-20  14-10 

Soda 3-32  6-73  2  22  20-75 

Sulphuric  Acid    ...  7-64  336  2-23  3-45 

Phosphoric  Acid.    .     .  5-62  1-92  2-75  0-90 

Chlorine 1-84  241  230 

Carbonic  Acid    .    .    .  1400  1547  36-48  1750 

100  10^  100  960 

The  composition  of  these  different  kinds  t  f  ash  is  very  unlike — that 
of  the  pitch  pine,  for  example,  being  greatly  richer  in  potash  and  soda, 
and  poorer  in  lime  and  phosphoric  acid,  than  that  of  the  Scotch  fir — 
while  the  beech  is  richer  than  any  of  the  others  in  potash  and  lime  and 
in  the  sulphuric  and  phosphoric  acids.  The  several  effects  of  different 
kinds  of  wood  ashes  when  applied  to  the  land  will  therefore  be  different- 
also. 

In  England,  wood  ashes  are  largely  employed  in  many  districts, 
mixed  with  bone  dust,  os  a  manure  for  turnips,  and  often  with  great 
success.  4s  much  as  15  bushels  (7i  cwt.)  of  ashes  are  drilled  in  per 
acre  with  15  bushels  (6  cwt.)  of  bones.  The  large  quantity  of  alkali 
present  in  the  turnip  crop  (p.  219)  may  be  supposed  to  explain  the 
good  effects  which  wood  ashes  have  upon  it,  and  may  lead  us  to  expect 
that  they  would  in  a  similar  degree  increase  the  produce  of  the  carrot 
and  of  the  potatoe.* 

The  immediate  benefit  of  wood  ash  is  said  to  be  most  perceptible  upon 
leguminous  plants  (Sprengel),  such  as  lucerne,  clover,  peas,  beans,  and 
vetches.  As  a  top-dressing  to  grass  lands  it  roots  out  the  moss  and  pro- 
motes the  growth  of  white  clover.  Upon  red  clover  its  effects  will  be 
more  certain  if  previously  mixed  with  one  fourth  of  its  weight  of  gyp- 
sum. In  small  doses  of  two  or  three  hundred  weight  (4  to  6  bushels) 
it  may  be  safely  applied  even  to  poor  and  thin  soils,  but  in  large  and 
repeated  doses  its  effects  will  be  too  exhausting,  unless  the  soil  be  either 

*  This  inference  has  been  verified  by  Mr.  Wharton,  of  Dryburn,  who  has  obtained  an 
excellent  crop  of  potatoes  from  newly  ploughed-out  land  by  manuring  with  wood  ashes 
only. 


354  SPONTANEOUS    COMBUSTION    OF    WOOD    ASHES. 

naturally  rich  in  vegetable  matter,  or  be  mixed  from  year  to  year  with  a 
sufficient  quantity  of  animal  or  vegetable  manure. 

In  so  far  as  the  immediate  effect  of  wood  ashes  is  dependent  upon  the 
soluble  saline  matter  they  contain,  their  effect  may  be  imitated  by  a 
mixture  of  crude  potash  with  carbonate  and  sulphate  of  soda,  and  a  lit- 
tle common  salt.  The  wood  ash  of  this  country  contains  only  about 
one-fifteenth  of  its  weight  of  soluble  matter  (Bishop  Watson),  so  that 
the  following  quantity  of  such  a  mixture  would  be  nearly  equal  in  effi- 
cacy to  the  saline  matter  of  one  ton  of  wood  ash. 

Crude  of  Potash 60  lbs.  at  a  cost  of  15s, 

Crsytallized  Carbonate  of  Soda      .        .  60    "        "         "       7s. 

Sulphate  of  Soda 20    "    )   „        .«      Oc 

Common  Salt 20    "    $  "'^• 

160  24s. 

Where  the  wood  ash  costs  only  a  shilling  a  bushel  (or  662  a  ton),  it 
would  obviously  be  more  economical  to  employ  this  mixture,  were  the 
efficacy  of  wood  ashes  dependent  solely  upon  the  soluble  saline  matter 
they  are  capable  of  yielding  on  the  first  washing  with  water.  But  they 
contain  also  a  greater  or  less  quantity  of  imperfectly  burned  carbonace- 
ous matter,  the  effect  of  which  upon  vegetation  cannot  be  precisely 
estimated,  and  a  large  proportion — nine-tenths,  perhaps,  of  their  whole 
weight — of  insoluble  carbonates,  silicates,  and  phosphates  of  potash, 
lime,  and  magnesia,  which  are  known  more  permanently  to  influence 
the  fertility  of  the  land  to  which  they  are  applied.* 

c.  Washed  or  lixiviated  wood-ashes. — fn  countries  where  wood  ashes 
are  washed  for  the  manufacture  of  the  pot  and  pearl  ash  of  commerce 

'  Some  discussion  has  lately  arisen  in  America  (Silliman's  Journal,  xlii.  p.  165,  and 
xliii.  p.  80),  in  regard  to  the  fact,  in  itself  sufficiently  interesting,  that  wood  ashes,  when 
thrown  together  in  heap',  not  unfrequently  take  fire,  becoming  red  hot  throTjghout  their 
whole  mass,  and  sometimes  occasioning  serious  accidents.  Such  ashes  always  contain  a 
quantity  of  minutely  divided  carbonaceous  matter,  which,  like  the  impalpable  charcoal 
powder  of  the  gunpowder  manufactories,  may  have  the  property  of  absorbing  much  air 
mto  its  pores,  and  of  thus  undergoing-a  spontaneous  elevation  of  temperature.  I  throw  it 
out,  however,  as  a  more  probable  conjecture,  (hat  during  the  combustion  of  the  wood  a 
portion  of  the  potash  has  been  decomposed  by  the  charcoal,  and  converted  into  potassium 
(potash  consisting  of  potassium  and  oxygen,  p.  1S7.  When  exposed  to  tHfe  air  and  to 
moisture  this  potassium  gradually  absorbs  oxygen  and  spontaneously  burns,  again  form- 
ing potash.  That  such  a  decomposition  may  take  place  where  wood  or  other  vegetable 
matter  is  burned  with  little  access  of  air  will,  readily  be  granted,  but  it  is  not  so  obvious 
that  it  can  take  place  in  an  open  fire.  But  even  in  an  open  fire,  or  in  an  open  capsule,  par- 
ticles of  potassium  may  remain  in  the  pores  of  the  unburned  charcoal,  or  more  frequently 
may  be  covered  over  with  a  glaze  of  melted  potash,  by  which  further  combustion  will  be 
prevented.  That  this  really  does  happen,  any  one  must  have  satisfied  himself  who  has 
been  in  the  habit  of  burning  vegetable  substances  for  the  purpose  of  determining  the  pro- 
portion of  ash  they  leave.  The  glaze  of  melted  alkaline  matter  often  renders  the  com- 
plete combustion  a  very  difficult  and  tedious  matter.  That  potassium  is  formed  during  this 
process  is  rendered  further  probable  by  the  observation  that  the  quantity  of  potash  ob- 
tained from  wood  or  other  vegetable  ash  is  less  when  the  wood  has  been  burned  at  a  high 
than  a  low  temperature.  The  potassium,  which  is  volatile,  may  have  been  dissipated  in 
vapour. 

It  is  probable  that  a  spontaneous  combustion  similar  to  that  observed  in  America  may 
occasionally  take  place  in  the  heaps  of  ashes  left  f«n  stand  upon  our  fields  af>er  paring  and 
burning— and  hence  probably  has  arisen  the  practical  rule,  to  sprea<l  the  ashes  as  soon  as 
possible  after  the  burning  is  finished.  If  allowed  to  remain,  they  are  .'aid  "/o  take  hold  of 
the  land,"  and  when  it  is  of  clay,  to  burn  it  into  brick.  An  instance  of  such  combustion  is 
mentioned  as  having  occurred  at  Chatteris,  in  the  Isle  of  Ely,  where  an  entire  common 
was  burned  16  or  18  inches  deep,  down  to  the  very  gravel.— See  British  Husbandry,  II.  j 
p.  350. 


COMPOSITION    OF    LIXIVIATED    WOOD    ASHES.  355 

(p.  187),  this  insoluble  portion  collects  in  large  quantities.  It  is  also 
present  in  the  refuse  of  the  soap  maliers,  where  wood  ash  is  em- 
ployed for  the  manufacture  of  soft  soap.  The  composition  of  this  inso- 
luble matter  varies  very  much,  not  only  with  the  kind  of  wood  from 
which  the  ash  is  made,  but  also  with  the  temperature  it  is  allowed  to 
attain  in  burning.  The  former  fact  is  illustrated  by  the  following  analy- 
sis made  by  Berthier,  of  the  insoluble  matter  left  by  the  ash  of  five  dif- 
ferent species  of  wood  carefully  burned  by  himself: — 

Oak.  Lime.        Birch.    Pitch  Pine.    Scotch  Fir.    Beech. 


Silica 3-8 

20 

55 

130 

4-6 

5-8 

Lime 54  8 

51-8 

52-2 

27-2 

423 

426 

Magnesia ....     06 

2-2 

30 

87 

10-5 

70 

Oxide  of  Iron     .     .    — 

01 

0-5 

22-3 

01 

15 

Oxide  of  Manganese  — 

0-6 

35 

5-5 

0-4 

4-5 

Phosphoric  Acid     .    0  8 

2-8 

4-3 

1-8 

10 

57 

Carbonic  Acid    .     .  396 

398 

310 

21-5 

360 

32-9 

Carbon      ....  — 

— 

— 

— 

4-8 

— 

99-6 

100 

100 

100 

99  7 

100 

The  numbers  in  these  several  columns  differ  very  much  from  each 
other,  but  the  constitution  of  the  insoluble  part  of  the  ash  he  obtained 
probably  differed  in  every  case  from  that  which  would  have  been  left 
by  the  use  of  the  same  wood  burned  on  the  large  scale,  and  in  the  open 
air.  This  is  to  be  inferred  from  the  total  absence  of  potash  and  soda  in 
the  lixiviated  ash — while  it  is  well  known  that  common  lixiviated  wood 
ash  contains  a  notable  quantity  of  both.  This  arises  from  the  high  tem- 
perature at  which  wood  is  commonly  burned,  causing  a  greater  or  less 
portion  of  the  potash  and  soda  to  combine  with  the  silica,  and  to  form 
insoluble  silicates,  which  remain  behind  along  with  the  lime  and  other 
earthy  matter,  when  the  ash  is  washed  with  water.  It  is  to  these  sili- 
cates, as  well  as  to  the  large  quantity  of  lime,  magnesia,  and  phosphoric 
acid  it  contains,  that  common  wood  ash  owes  the  xnoxe  permanent  effects 
upon  the  land,  which  it  is  known  to  have  produced.  When  the  rains 
have  washed  out  or  the  crops  carried  off  the  more  soluble  part  from  the 
soil,  these  insoluble  compounds  still  remain  to  exercise  a  more  slow  and 
enduring  influence  upon  the  after-produce. 

Still  from  the  absence  of  this  soluble  portion,  the  action  of  lixiviated 
wood  ash  is  not  so  apparent  and  energetic,  and  it  may  therefore  be  safely 
added  to  the  land  in  much  larger  quantity.  Applied  at  the  rate  of  two 
tons  an  acre,  its  effects  have  been  observed  to  continue  for  15  or  20 
years.  It  is  most  beneficial  upon  clay  soils,  and  it  is  said  especially  to 
promote  the  growth  of  oats. 

I  am  not  aware  that  in  any  part  of  the  British  Islands  this  refuse  ash 
is  to  be  obtained  in  large  quantity,  but  in  North  America  much  of  it  is 
thrown  away  in  waste,  which  might  be  advantageously  restored  to  the 
land  on  which  the  wood  had  grown. 

d.  Kelp  is  the  name  given  in  this  country*  to  the  ash  left  by  marine 
plants  when  burned.     It  used  to  be  extensively  prepared  in  the  Western 

*  In  Brittany  and  Normandy  it  is  called  varec^  while  that  of  Spain  is  known  by  the  name 
of  barilla. 


356  COMPOSITION    AND    USE    OF    KELP. 

Islands,  but  the  low  price  at  which  carbonate  of  soda  can  now  be  maa« 
ufactured  has  so  reduced  the  price  and  the  demand  for  kelp  as  almost 
to  drive  it  from  the  market.  As  a  natural  mixture,  however,  which 
can  now  be  obtained  at  a  cheap  rate  (about  c5£3  a  ton),  and  which  has 
been  proved  to  be  useful  to  vegetation  in  a  high  degree,  (Prize  Essays 
ot'  the  Highland  Society,  vols.  1  and  4,)  it  is  very  desirable  that  accu- 
rate experiments  should  be  instituted  with  the  view  of  determining  the 
precise  extent  of  its  action,  as  well  as 'the  crops  and  soils  to  which  it  can 
be  most  advantageously  and  most  economically  applied. 

Like  wood  ashes,  kelp  varies  in  composition  with  the  species  and  age 
of  the  marine-  plants  (sea  weeds)  from  which  it  is  prepared,  and  like 
them  also  it  consists  of  a  soluble  and  insoluble  portion.  Two  samples 
from  different  localities  in  the  Isle  of  Skye,  analyzed  by  Dr.  Ure,  (Dic- 
tionary of  Arts  and  Manufactures,  p.  726),  consisted  of — 

Normandy, 
Soluble  Portion.  Heisker.    Rona.    Gay-Lussac. 

Carbonate  of  Soda  with  Sulphuret  of  Sodium  .        85  5-5  — 

Sulphate  of  Soda 80        190  — 

Common  Salt ^  qc  f;         ii  r,     5^^'^ 

Chloride  of  Potassium $  "^^  ^''^     {250 

530  620 
Insoluble  Portion. 

Carbonate  of  Lime 240  100  — 

Silica 8-0  —  — 

Alumina  and  Oxide  of  Iron     .        .        .        .  9  0  100  — 

Gypsum —  95  — 

Sulphur  and  loss 60  8-5  — 

100         100 

Besides  these  constituents,  however,  the  soluble  portion  contains 
iodide  of  potasium  or  sodium  in  variable  quantity,  and  the  insoluble 
more  or  less  of  potash  and  soda  in  the  state  ot  silicates. 

Kelp  may  be  applied  to  the  land  in  nearly  the  same  circumstances  as 
wood-ash — but  for  this  purpose  it  would  probably  be  better  to  burn  the 
sea  weed  at  a  lower  temperature  than  is  usually  employed.  By  this 
means,  being  prevented  from  melting,  it  would  be  obtained  at  once  in 
the  state  of  a  fine  powder,  and  would  be  richer  in  potash  and  soda. 

It  might  lead  to  important  results  of  a  practical  nature,  were  a  series 
o^ precise  experiments  made  with  this  finely  divided  kelp  as  a  manure* 
— especially  in  inland  situations — for  though  the  variable  proportion  of 
its  constituents  will  always  cause  a  degree  of  uncertainty  in  regard  to 
the  action  of  the  ash  of  marine  plants — yet  if  the  quantity  of  chloride 
of  potassium  it  contains  to  be  on  an  average  nearly  as  great  as  is  stated 
above  in  the  analysis  of  Gay-Lussac — kelp  will  really  be  the  cheapest 
form  in  which  we  can  at  present  apply  potash  to  the  land. 

e.  Straiv  ashes. — The  ashes  obtained  by  burning  the  straw  of  oats, 
barley,  wheat,  and  rye,  contain  a  natural  mixture  of  saline  substances, 
which  is  exceedingly  valuable  as  a  manure  to  almost  every  crop.     The 

'  For  some  other  suggestions  on  this  subject,  I  beg  to  refer  the  reader  to  the  Prize  Et- 
tays  and  Transactions  of  the  Highland  and  Agricultural  Society,  xiv.,  p.  503. 


SOILS    ON    WHICH    STRAW    ASH    MAT    BE    USED.  357 

proportion  of  the  several  constituents  of  this  mixture,  however,  is  differ- 
ent, according  as  the  one  or  the  other  kind  of  straw  is  burned.  Thus, 
100  parts  of  each  variety  of  ash — in  the  samples  analyzed  by  Sprengel 
{Cliemie^  II.) — consisted  of — 


Oats. 

Barley. 

Wheat. 

Rye. 

Rape. 

Potash      . 

.      152 

34 

06 

12 

18-8 

Soda 

.    trace. 

09 

0-8 

04 

11-2 

Lime 

.        2-6 

10-5 

6-8 

6-4 

16  9 

Magnesia 

.        04 

1-4 

0-9 

0-4 

31 

Silica 

.      800 

73-5 

81-6 

82-2 

21 

Alumina 

.       01 

2-8) 

Oxide  of  Iron  . 

.     trace. 

02  . 

26 

0.9 

2-3 

Oxide  of  Manganese 

.     trace. 

0-3) 

Phosphoric  Acid 

.        02 

35 

4-8 

1-8 

99 

Sulphuric  Acid 

.        14 

22 

10 

61 

133 

Chlorine  . 

.        01 

1-3 

09 

0-6 

11-4 

Carbonic  Acid 

— 

— 

— 

— 

110 

100  100  100  100  100 

The  most  striking  differences  in  the  above  table  are  the  comparatively 
large  quantity  of  potash  in  the  oat  straw — of  lime  in  that  of  barley — 
of  phosphoric  acid  in  that  of  wheat — of  sulphuric  acid  in  that  of  rye — 
and  of  all  the  saline  substances  in  rape  straw.  These  differences  are 
not  to  be  considered  as  constant,  nor  will  the  numbers  in  any  of  the 
above  columns  represent  correctly  the  composition  of  the  ash  of  any 
variety  of  straw  we  may  happen  to  burn  (see  p.  183),  but  they  may 
be  safely  depended  upon  as  showing  the  general  composition  of  such 
ashes,  as  well  as  the  general  differences  which  may  be  expected  to  pre- 
vail among  them. 

That  such  ashes  should  prove  useful  to  vegetation  might  be  inferred 
not  only  from  their  containing  many  saline  substances  which  are  known 
to  act  beneficially  when  applied  to  the  land,  but  from  the  fact  that  they 
have  actually  been  obtained  from  vegetable  substances.  If  inorganic 
matter  be  necessary  to  the  growth  of  wheat,  then  surely  the  mixture  of 
such  matters  contained  in  the  ash  of  wheat  straw  is  more  likely  than 
any  other  we  can  apply  to  promote  the  growth  of  the  young  wheat 
plant.  A  question  might  even  be  raised,  whether  or  not  in  some  soils, 
rich  in  vegetable  matter,  the  ash  alone  would  not  produce  as  visible  an 
effect  upon  the  coming  crop,  as  the  direct  application  of  the  straw,  either 
iri  the  dry  state  or  in  the  form  of  rotted  fa<-m-yard  manure.  And  this 
question  would  seem  to  be  answered  in  the  affirmative,  by  the  result 
of  many  trials  of  straw  ashes  which  have  been  made  in  Lincolnshire. 
In  this  county  the  ash  of  five  tons  of  straw  has  been  found  superior  in 
efficacy  to  ten  tons  farm-yard  manure,  (Survey  of  Lincolnshire,  p. 
304,  quoted  in  British  Husbandry,  II.,  p.  334.)  This  is  perfectly  con- 
sistent with  theory,  yet  as  vegetable  matter  appears  really  essential  to  a 
fertile  soil,  and  as  the  quantity  of  this  vegetable  matter  is  lessened  in 
some  degree  by  every  corn  crop  we  raise,  it  cannot  be  good  husbandry 
to  manure  for  a  succession  of  rotatiDns  with  saline  substances  only. 
The  richest  soil  by  this  procedure  must  ultimately  be  exhausted.  On 
the  other  hand,  where  much  vegetable  matter  exists,  and  especially 
what  is  usually  called  inert  vegetable  matter,  it  may  be  an  evidence  of 


358  COMPARATIVE   EFFECTS    OF    STRAW   AND    STRAW   ASH. 

great  skill  in  the  practical  farmer  to  apply  for  a  time  the  ashes  only  of 
his  stravs"- — or  some  other  saline  mixture  to  his  land. 

The  practice  of  burning  the  stubble  on  a  windy  day  has  been  found 
in  the  East  Riding  of  Yorkshire  to  produce  better  clover,  and  to  cause 
a  larger  return  of  wheat,  (British  Husbandry,  ii.,  p.  333) — for  this 
purpose,  however,  the  stubble  must  be  left  of  considerable  length.  In 
Germany,  rape  straw — which  the  above  table  shows  to  be  rich  in  saline 
and  earthy  matter,  and,  therefore,  exhausting  to  the  land — is  spread 
over  the  field  and  burned  in  a  similar  maimer.  The  destruction  of 
weeds  and  insects  which  attends  this  practice,  is  mentioned  as  one  of  its 
collateral  advantages,  (Sprengel,  Lehre  vom  Diinger,  p.  355.) 

In  the  United  States,  where,  according  to  Captain  Barclay,  the  sti:aw 
is  burned  merely  in  order  that  it  may  be  got  rid  of,  (Agricultural  Tour 
in  the  United  States,  pp.  42  and  54,)  it  would  cost  little  labour  to  apply 
the  ash  to  the  soil  from  which  the  straw  was  reaped,  while  it  would 
certainly  enlarge  the  future  produce — and  in  Little  Russia,  where  from 
the  absence  of  wood  the  straw  is  universally  burned  for  fuel,  and  the 
ashes  afterwards  consigned  to  the  nearest  river,  the  same  practice 
might  be  beneficially  adopted.  However  fertile,  and  apparently  inex- 
haustible, the  soils  in  this  country  may  appear,  the  time  must  come 
when  the  present  mode  of  treatment  will  have  more  or  less  exhausted 
their  productive  powers. 

It  is  not  advisable,  as  I  have  already  said,  wholly  to  substitute  the 
ash  for  the  straw  in  ordinary  soils,  or  in  any  soils  for  a  length  of  time, 
yet  that  it  may  be  partially  so  substituted  with  good  effect — or  that  straw 
ashes  will  alone  give  a  large  increase  of  the  corn  crop,  and  therefore 
should  never  be  wasted — is  shown  by  the  following  comparative  experi- 
ments, conducted  as  such  experiments  should  be,  during  an  entire  rota- 
tion of  four  years.  The  quantity  of  manure  applied,  and  the  produce 
per  imperial  acre,  were  as  follows : 

15  cwt.    barley       3  tons  stable  dung       2  tons  of  rotten 
No  manure.  straw  burned  in     the    straw  dung      eight 

on  the  ground.  state.  months  old. 

1°.   Turnips,  22  lbs.  8^  cwt.  18|  cwt.  \^%  cwt. 

2°.   Barley,     14f  bush.  30i  bush.  30^  bush.  30f  bush. 

3°.   Clover,      8  cwt.  18    cwt.  20    cwt.  21    cwt. 

4°.   Oats,        32  bush.  18    bush.  38    bush.  40  bush. 

The  kind  of  soil  on  which  this  experiment  was  made  is  not  stated, 
(British  Husbandry,  ii.,  p.  248,)  but  it  appears  to  show,  as  we  should 
expect,  that  the  effects  of  straw  ash  are  particularly  exerted  in  promot- 
ing the  growth  of  the  corn  plants  and  grasses  which  contain  much  sili- 
ceous matter  in  their  stems — in  short,  of  plants  similar  to  those  from 
which  the  ash  has  been  derived. 

Theory  of  the  action  of  straw  ash. — That  it  should  especially  pro- 
mote the  growth  of  such  plants  appears  most  natural,  if  we  consider 
only  the  source  from  which  it  has  been  obtained,  but  it  is  fully  ex- 
plained by  a  further  chemical  examination  of  the  ash  itself.  The  so- 
luble matter  of  wood  ash  in  general  contains  but  a  small  quantity  of 
silica — while  that  part  of  the  straw  ash  which  is  taken  up  by  water 
contains  very  much.  Thus  a  wheat  ash  analyzed  by  Berthier  contained 
of— 


COMPOSITION    AND    USE    OF    DUTCH    ASHES. 


35» 


Soluble  salts 19  per  cent. 

Insoluble  matter 81        " 


100 
and  that  which  was  dissolved  by  water  consisted  of 


Silica 

Chlorine    . 
Potash  and  soda 
Sulphuric  acid  . 


35  per  cent. 
13        " 
50 

2        « 

100 
so  that  it  was  a  mixture  of  soluble  silicates  and  chlorides  with  a  little 
sulphate  of  potash  and  soda.  These  soluble  silicates  will  find  an  easy 
admission  into  the  roots  of  plants,  and  will  readily  supply  to  the  young 
stems  of  the  corn  plants  and  grasses  the  silica  which  is  indispensable^ to 
their  healthy  growth. 

/.  Turf  or  peat  ashes^  obtained  by  the  burning  of  peat  of  various 
qualities,  are  also  applied  with  advantage  lo  the  land  in  many  districts. 
They  consist  of  a  mixture  in  which  gypsum  is  usually  the  predominat- 
ing useful  ingredient — the  alkaline  salts  being  present  in  very  small 
proportion.  Of  ashes  of  this  kind  those  made  in  Holland,  and 
generally  distinguished  by  the  name  of  Dutch  ashes,  are  best  known, 
and  have  been  most  frecffently  analyzed.  The  following  table  exhi- 
bits the  composition  of  some  varieties  of  ashes  from  the  peat  of  Hol- 
land and  from  the  heath  of  Luneburg,  examined  by  Sprengel : — 
Dutch  Ashes  (grey). 


quality. 

Sihca 47-1 

Alumina 45 

Oxide  of  Iron 66 

Do.  of  Manganese  .     ...  1-0 

Lime 13-6 

Magnesia 49 

Potash 02 

Soda 10 

Sulphuric  Acid 7-2 

Phosphoric  Acid    ....  20 

Chlorine 12 

Carbonic  Acid 4*1 

Charred  Turf    .    .    .    .^ .  6-6 


Inferior 
quality. 
55-9 
35 
5-4 
43 
8-6 
1-6, 
0-2 
3-9 

6-4 

0-8 

30 
6.4 


Worst 
quality. 
70-4 
41 
41 
0-2 
6.1 
3-9 
01 
0-4 


34 

13 

0-5 
5-5 


Luneburg  Ashes  (reddish). 

Good 

Producing 

quality. 

little  effect. 

31-7 

43-3 

51 

•9-7 

17-7 

19-3 

05 

35 

31-9 

71 

10 

4-6 

01 



01 



Gypsum 

62 

0-2 

Phosph.  of  Lime 

1-2 

0-2 

Common  Salt 

01 

01 

4-4 

120 

— 

— 

1000      1000      1000     1000  1000* 

In  the  most  useful  varieties  of  these  ashes  it  appears,  from  the  above 
analyses,  that  lime  abounds — partly  in  combination  with  sulphuric  and 
phosphoric  acids,  forming  gypsum  and  phosphate  of  lime — and  partly 
with  carbonic  acid,  forming  carbonate.  These  compounds  of  lime, 
therefore,  may  be  regarded  as  the  active  ingredients  of  peat  ashes. 

*  Sprent^el  Lehre  vom  Dunger^  p.  363  e<  *eq. 


369  COMPOSITION    AND    USE    OF    COAL    ASHES. 

"iet  the  small  quantity  of  saline  matter  they  contain  is  not  to  be  con- 
sidered as  wholly  without  effect.  For  the  Dutch  ashes  are  often  ap- 
plied to  the  land  to  the  extent  of  two  tons  an  acre — a  quantity  which, 
eren  when  the  proportion  of  alkali  does  not  exceed  one  per  cent.,  will 
contain  45  lbs.  of  potash  or  soda,  equal  to  twice  that  weight  of  sulphates 
or  of  common  salt.  To  the  minute  quantity  of  saline  matters  present  in 
them,  therefore,  peat  ashes  may  owe  a  portion  of  their  beneficial  in- 
fluence, and  to  the  almost  total  absence  of  such  compounds  from  the 
less  valuable  sorts,  their  inferior  estimation   may  have  in  part  arisen. 

In  Holland,  when  applied  to  the  corn  crops,  they  are  either  ploughed 
in,  drilled  in  with  the  seed,  or  applied  as  a  top  dressing  to  the  young 
shoots  in  autumn  or  spring.  Lucerne,  clover,  and  meadow  grass  are 
dressed  with  it  in  spring  at  the  rale  of  15  to  18  cwt.  per  acre,  and  the 
latter  a  second  time  with  an  equal  quantity  after  the  first  cutting.  In 
Belgium  the  Dutch  ashes  are  applied  to  clover,  rape,  potatoes,  flax, 
and  peas — but  never  to  barley.  In  Luneburg  the  turf  ash  which 
abounds  in  oxide  of  iron  is  applied  at  the  rate  of  3  or  4  tons  per  acre, 
and  by  this  means  the  physical  character  of  the  clay  soils,  as  well  as 
their  chemical  constitution,  is  altered  nnd  improved. 

In  England  peat  is  in  many  places  burned  for  the  sake  of  the  ashes 
it  yields.  Among  the  most  celebrated  for  their  fertilizing  qualities  are 
the  reddish  turf  ashes  of  Newbury,  in  Berlnhire.  The  soil  from  be- 
neath which  the  turf  is  taken  abounds  in  lime,  and  the  ashes  are  said  to 
contain  from  one-fourth  to  one-third  of  their  weight  of  gypsum,  [Bri- 
tish Husbandry,  ii.,  p.  334.]  They  are  used  largely  both  in  Berkshire 
and  Hampshire,  and  are  chiefly  applied  to  green  crops,  and  especially 
to  clover.* 

g.  Coal  ashes  are  a  mixture  of  which  the  composition  is  very  varia- 
ble. They  consist,  however,  in  general,  of  lime  often  in  the  state  of 
gypsum,  of  silica,  and  of  alumina  mixed  with  a  quantity  of  bulky  and 
porous  cinders  or  half  burnt  coal.  The  ash  of  a  coal  from  St.  Etienne, 
in  France,  after  all  the  carbonaceous  matter  had  been  burned  away, 
was  found  by  Berthier  to  consist  of 

Alumina,  insoluble  in  acids       ....  62  per  cent. 

Alumina,  soluble 5         " 

Lime 6        " 

Magnesia 8         " 

Oxide  of  Manganese        .   '     .        .        .        .  3        " 

Oxide  and  Sulphuret  of  Iron    .        .        .        .  16        " 

100 

Such  a  mixture  as  this  would  no  doubt  benefit  many  soils  by  the 
alumina  as  well  as  by  the  lime  and  magnesia  it  contains;  but  in  the 
English  and  Scotch  coal  ashes  a  small  quantity  of  alkaline  matter, 
chiefly  soda,f  is  generally  present.  The  constitution  of  the  ash  of  our 
best  coals,  therefore,  may  be  considered  as  very  nearly  resembling  that 
of  peat  ash,  and  as  susceptible  of  similar  applications.     When  well 

*  50  bushels  per  acre  (at  3d.  a  bushel,  or  12s.  6d.  an  acre)  increase  the  clover  crop  folly 
one  fifth.— Morton  «  On  Soils,"  p.  170.  ' 

t  From  the  common  salt  with  which  our  coal  is  ao  often  impregnated. 


CANE  ASHES. CRUSHED  AND  DECAYED  TRAPS  AND  LAVAS.   361 

burned,  it  can  in  many  cases  be  applied  with  good  effects  as  a  top-dress- 
ing to  grass  lands  which  are  overgrown  with  moss ;  while  the  admix- 
ture of  cinders  in  the  ash  of  the  less  perfectly  burned  coal  produces  a 
favourable  physical  change  upon  strong  clay  soils. 

h.  Cane  Ashes. — I  may  allude  here  to  the  advantage  which  in  sugar- 
growing  countries  may  be  obtained  from  the  restoration  of  the  cane  ash 
to  the  fields  in  which  the  canes  have  grown.  After  the  canes  have  been 
crushed  in  the  mill  they  are  usually  employed  as  fuel  in  boiling  down 
the  syrup ;  and  the  ash,  which  is  not  unfrequently  more  or  less  melted, 
is,  I  believe,  almost  uniformly  neglected — at  all  events,  is  seldom  ap- 
plied again  to  the  land.  According  to  the  principles  I  have  so  often 
illustrated  in  the  present  Lectures,  such  procedure  must  sooner  or  later 
exhaust  the  soil  of  those  saline  substances  which  are  most  essential  to 
the  growth  of  the  cane  plant.  If  the  ash  were  applied  as  a  top-dressing 
to  the  young  canes,  or  put  into  the  cane  holes  near  the  roots — having 
been  previously  mixed  with  a  quantity  of  wood-ash,  and  crushed  il  it 
happen  to  have  been  melted — this  exhaustion  would  necessarily  take 
place  much  more  slowly. 

i.  Crushed  Granite. — We  have  already  seen  that  the  felspar  existing 
in  granite  contains  much  silicate  of  potash  and  alumina.  It  is,  in  fact, 
a  natural  mixture,  which  in  many  instances  may  be  beneficially  applied, 
especially  to  soils  which  abound  in  lime.  It  is  many  years  since  Fuchs 
proposed  to  manufacture  potash  from  felspar  and  mica  by  mixing  them 
with  quicklime,  calcining  in  a  furnace,  and  then  Wcishing  with  water. 
By  this  means  he  said  felspar  might  be  made  to  yield  one-fifth  of  its 
weight  of  potash.  (Journal  of  the  Royal  Institution,  I.,  p.  184.)  Mr. 
Prideaux  has  lately  proposed  to  mix  up  crushed  granite  and  quicklime, 
to  slake  them  together,  and  to  allow  the  mixture  to  stand  in  covered 
heaps  for  some  months,  when  it  may  be  applied  as  a  top-dressmg,  and 
will  readily  give  out  potash  to  the  soil.  Fragments  of  granite  are  easi- 
ly crushed  when  they  have  been  previously  heated  to  redness,  and  there 
can  be  little  doubt,  I  think,  that  such  a  mixture  as  that  recommended 
by  Mr.  Prideaux  would  unite  many  of  the  good  effects  of  wood  ashes 
and  of  lime. 

k.  Crushed  Trap. — I  need  not  again  remind  you  of  the  natural  fer- 
tility of  decayed  trap  soils  (Lee.  XII.,  §4,)  and  of  the  improvement  which 
in  many  districts  may  be  effected  by  applying  them  to  the  land.  When 
granite  decays,  the  potash  of  the  felspar  is  washed  out  by  the  rains,  and 
an  unproductive  soil  remains — when  trap  decays,  on  the  other  hand,  the 
lime  by  which  it  is  characterised  is  not  soon  dissolved  out,  so  that  the 
soil  which  is  produced  is  not  only  fertile  in  itself,  but  is  capable  of  being 
employed  as  a  fertilizing  mixture  for  other  soils.  Thus  when  it  is  much 
decayed  it  is  dug  out  from  pits  both  in  Cornwall  and  in  Scotland,  and 
is  applied  like  marl  to  the  land. 

l.  Crushed  Lavas. — Of  the  fertile  and  fertilizing naturerf  the  crushed 
or  decayed  lavas  I  ha^re  also  already  spoken  to  you  (Lee.  XII.,  §  4). 
In  St.  Michael's,  one  of  the  Azores,  the  natives  pound  the  volcanic  mat- 
ter and  spread  it  on  the  ground,  where  it  speedily  becomes  a  rich  mould 
capable  of  bearing  luxuriant  crops. .  At  the  foot  of  Mount  Etna,  when- 
ever a  crevice  appears  in  the  old  lavas,  a  branch  or  joint  of  an  Opuntia 


362  EXPERIMENTS    WITH    MIXED    MANURES. 

{Cactus  Opuntia, — European  Indian-Fig)  is  stuck  in,  when  the  roots  in- 
sinuate themselves  into  every  fissure,  expand,  and  finally  break  up  the 
lava  into  fi-agments.  These  plants  are  thus  not  only  the  means  of  pro- 
ducing a  soil,  but  they  yield  also  much  fruit,  which  is  sold  as  a  refresh- 
ing food  throughout  all  the  towns  of  Sicily.  (Decandolle,  quoted  in  the 
Quart.  Journ.  of  Agr.,  IV.  p.  737.) 

These  are  all  so  many  natural  mineral  mixtures  of  which  we  may 
either  directly  avail  ourselves,  or  which  we  may  imitate  by  art. 


Experiments  with  mixed  manures. 

Note. — As  a  valuable  appendix  to  the  preceding  observations  on 
mixed  manures,  I  am  permitted  to  insert  the  following  very  interesting 
results  obtained  during  the  present  season,  1842,  from  experiments  made 
on  the  estate  of  Mr.  Burnet,  of  Gadgirth,  near  Ayr.  The  crop  to  which 
the  several  manures  were  applied  waswheatof  the  ecZfpse  variety,  sown 
on  the  29th  of  October,  1841,  and  reaped  on  the  15th  of  August  last. 
The  soil  is  a  loam  with  subsoil  of  clay,  tile  drained  and  trenched  plough- 
ed. It  had  been  in  beans  the  previous  year,  and  gave  six  quarters  per 
acre,  which  were  sold  at  46s.  a  quarter.  No  manure  had  been  applied 
with  the  bean  crop,  and  except  a  good  dose  of  lime  before  sowing  the 
wheat,  nothing  but  the  saline  mixtures  mentioned  below  was  applied 
with  this  latter  crop. 


PBODUCB. 

100  lbs.  grain 

Applicatioa  per  imperial  acre. 

Weight  per 

produced  of 

Straw. 

Grain. 

bushel. 

fine  flour. 

,    cwt. 

buah.    lbs. 

lbs. 

lbs. 

Sulphate  of  Ammonia,  2  cwt. 
Wood-ashes,  4  cwt.  .     .     . 

:\  351 

39    54 

60 

66i 

Sulphate  of  Ammonia,  2  cwt 

,    1 

Sulphate  of  Soda,  2  cwt.     . 

.  >       441 

49      6 

60 

63J 

Wood-ashes,  4  cwt.  .     .     . 

Sulphate  of  Ammonia,  2  cwt 

.    1 

Common  Salt,  2  cwt.     .     . 

.  }      45 

49      0 

60 

651 

Wood-ashes,  4  cwt.       .     . 

.  ^ 

Sulphate  of  Ammonia,  2  cwt 

1 

Nitrate  of  Soda,.  1  cwt.      . 

>       44i 

48    20 

59 

541 

Wood-ashes,  4  cwt.     . 

\ 

No  Application 

.      29* 

31    38 

6U 

.  76j 

The  reader  will  observe  here  that  though  the  first  mixture  produced 
a  large  increase  both  of  straw  and  grain,  a  still  larger  additional  increase 
was  caused  by  mixing  with  the  substances  of  which  it  consisted  either  com- 
mon salt  or  sulphate  of  soda  or  nitrate  of  soda.  Each  of  these  three  sub- 
stances produced  nearly  the  same  effect.  The  soda,  therefore,  more 
than  the  acid  with  which  it  was  combined,  must  in  these  cases  have  act- 
ed beneficially.  The  comparatively  small  proportion  of  fine  flour  yield- 
ed by  the  nitrated  wheat,  and  the  comparatively  large  proportion  ob- 

•The  sulphate  of  ammonia  was  prepared  from  urine,  and,  therefore,  contained  other  ad- 
mixtures (page  349).  The  straw  was  strongest,  coarsest,  and  longest  in  ripening,  where 
this  sulphate  was  applied.  The  two  guanos  produced  little  luxuriance,  but  the  lots  to  which, 
they  were  applied  were  soonest  ripe. 


IMPORTANCE    OF    SUCH    EXPERIMENTS.  363 

tained  from  that  to  which  no  application  was  made,  are  also  highly  de- 
serving of  notice. 

Mr.  Burnet  has  transmitted  to  me  samples  of  the  flour  from  these 
several  growths  of  wheat,  with  the  view  of  determining  the  relative 
proportions  of  gluten  they  contain.  The  result  of  this  examination, 
which  cannot  fail  to  be  interesting,  will  be  given  in  a  succeeding  Lec- 
ture— before  which,  however,  I  hope  the  whole  of  Mr.  Burnet's  experi- 
ments will  be  laid  before  the  public. 

It  will  be  observed  that  Mr.  Burnet  has  exercised  a  sound  discretion 
in  making  and  trying  mixtures  not  hitherto  specifically  recommended. 
It  is  by  the  result  of  such  varied  experimental  trials,  made  by  intelli- 
gent practical  men,  on  different  soils  and  crops,  and  with  mixtures  of 
which  the  constitution  is  exactly  known,  that  we  shall  be  able  hereafter  to 
correct  our  theoretical  principles — as  well  as  to  simplify  and  render 
more  sure  our  general  practice. 


[Since  writing  the  above,  lam  informed  that  the  silicate  ofpotashj  re- 
ferred to  at  p.  349,  is  manufactured  by  Messrs.  Dymond,  of  London,  and 
may  be  obtained  from  the  London  dealers  at  56s.  a  cwt.  I  expect  also, 
that  a  silicate  of  soda  will  soon  be  brought  into  the  market  by  the  Messrs. 
Cooksons,  of  the  Jarrow  Alkali  Works,  at  a  much  lower  price.  The 
probable  efficacy  of  these  substances,  as  manures,  has,  no  doubt,  been 
extolled  too  highly  by  some — their  real  efficacy,  however,  is  well  de- 
serving of  investigation.  I  insert  in  the  Appendix  No.  VII,  therefore, 
some  suggestions  for  experiments  with  these  substances,  in  the  hope  that 
during  the  spring  of  1843,  some  experiments  on  the  subject  may  be 
made. 


LECTURE  XVII. 


Use  of  lime  as  a  manure. — Value  of  lime  in  improving  the  8oil. — Of  the  composition  of 
common  and  magnesian  lime-stones. — Burning  and  slaking  of  lime. — Changes  which 
slaked  lime  undergoes  by  exposure  to  the  air. — Various  natural  states  in  which  carbonate 
of  lime  is  applied  to  the  land. — Marl — shell  and  coral  sand,— limestone  sand  and  gravel, 
— crushed  lime-stone. — Chemical  composition  of  various  marls,  and  shell  and  lime-slone 
Bands. — Their  effects  on  the  soil. — Use  of  chalk. — Is  lime  necessary  to  the  soil? — Ex- 
hausting effect  of  lime Analogy  between  this  action  of  lime  and  that  of  wood-ashes. 

Quantity  of  lime  to  be  applied. — Effects  of  an  overdose. — Form  in  which  it  may  be  most 
prudently  used. — When  it  ought  to  be  applied  in  reference  to  the  season — to  the  rotation 
— and  to  the  application  of  manure.— Its  general  and  special  effects  on  different  soils  and 
cropa. — Circumstances  which  influence  its  action. — Length  of  time  during  w  hie  it  its  ef- 
fects are  perceptible. — Theory  of  the  action  of  lime. — Necessity  and  nature  of  the  ex- 
haustion which  it  sometimes  produces. — Sinking  of  lime  into  the  soil. — Why  the  a()pli- 
cation  of  lime  must  be  repeated. — Action  of  lime  on  living  animals  and  vegetables. 
Suggestions  of  theory. — Use  of  silicate  of  lime. 

Having  explained  to  you  the  action  of  the  most  important  saline 
and  mixed  mineral  substances  which  are  or  may  be  beneficially  ap- 
plied to  the  soil,  I  have  now  to  draw  your  attention  to  the  use  of  lime 
■—the  most  valuable  and  the  most  extensively  used  of  all  the  mineral 
substances  that  have  ever  been  made  available  in  practical  agricul- 
ture. It  has,  and  with  much  reason,  been  called  "  the  basis  of  all 
good  husbandry" — it  well  deserves,  therefore,  your  most  serious  atten- 
tion as  practical  men,  and  on  my  part  the  application  of  every  chem- 
ical light  by  which  its  usefulness  may  be  explained  and  your  practice 
guided.  This  consideration  also  will  justify  me  in  dwelling  upon  it 
with  some  detail,  and  in  illustrating  separately  the  various  points, 
both  of  theory  and  practice,  which  present  themselves  to  us,  when 
we  study  the  history  of  its  almost  universal  application  to  the  soil. 

§  1.  O/*  the  composition  of  common  and  magnesian  lime-stones. 

1°.  Common  limestones. — Lime  is  never  met  with  in  nature  except 
in  a  state  of  chemical  combination  (Lee.  I.,  §  5,)  with  some  other 
substance.  That  which  is  usually  employed  in  agriculture  is  met 
with  in  the  state  of  carbonate. 

Carbonate  of  lime,  or  common  lime-stone,  consists  of  lime  and  car- 
bonic acid,  and  when  perfectly  pure  and  dry,  in  the  following  propor- 
tions : — 

per  cent. 

Carbonic  acid 43-7  ^ 

Lime 56-3   (  or  one  ton  of  pure  dry  carbonate  of 

I       lime  contains  Hi  cwts,  of  lime. 

100    J 

Limestones,  however,  are  seldom  pure.  They  always  contain  a  sen- 
sible quantity  of  other  earthy  matter,  chiefly  silica,  alumina,  and  oxide 
of  iron,  with  a  trace  of  phosphate  of  lime,  sometimes  of  potash  and  soda, 
and  often  of  animal  and  other  organic  matter.  In  lime-stones  of  the 
best  quality  the  foreign  earthy  matter  or  impurity  does  not  exceed  5  per 
cent,  of  the  whole — while  it  is  often  very  much  less.     The  chalks  and 


COMMON    AND    MAGNESIAN    LIME-STONES.  365 

mountain  lime-stones  are  generally  of  this  kind.  In  those  of  inferior 
quality  it  may  amount  to  12  or  20  per  cent,  while  nmny  calcareous  beds 
are  met  with  in  which  the  proportion  of  lime  is  so  small  that  they  will 
not  burn  into  agricultural  or  ordinary  building  lime — refusing  to  slake 
or  to  fall  to  powder  when  moistened  with  water.  Of  this  kind  is  the 
Irish  calp  and  the  lime-stone  nodules  which  are  burned  for  the  man- 
ufacture of  hydraulic  limes  or  cements.*  It  is  easy  to  ascertain  the 
quantity  of  earthy  matter  contained  in  lime-stone,  by  simply  intro- 
ducing a  known  weight  of  it  into  cold  diluted  muriatic  acid,  and  ob- 
serving or  weighing  the  part  which,  after  12  hours,  refuses  to  dis- 
solve or  to  exhibit  any  efibrvescence.  It  is  to  the  presence  of  these 
insoluble  impurities  that  lime-stones  in  general  owe  their  color,  pure 
carbonate  of  lime  being  perfectly  white. 

2°.  Magnesian  lime-stone. — Though  often  nearly  white,  the  mag- 
nesian  lime-stones  of  our  island  are  generally  of  a  yellow  color.  They 
cannot  by  the  eye  be  distinguished  from  common  lime-stones  of  a  simi- 
lar color,  but  they  are  characterised  by  containing  a  greater  or  less 
proportion  of  carbonate  of  magnesia',  which  is  more  or  less  easily  de- 
tected by  analysis.  Pure  carbonate  of  magnesia  consists  of 
per  cent. 

Carbonic  acid.  .51-7  "^ 

Magnesia 48-3   !  or  one  ion  of  pure  dry  carbonate  of  magnfesia 

/       contains  9|  cwts.  of  magnesia. 

100      J 

It  contains,  therefore,  a  considerably  larger  proportion  of  carbonic 
acid  than  is  present  in  carbonate  of  lime. 

Magnesian  lime-stone  is  very  abundant,  is  indeed  the  prevailing 
rock  in  many  parts  of  England  (Lee.  XL,  sec.  4,)  but  the  proportion 
of  carbonate  of  magnesia  it  contains  is  very  various  in  different  lo- 
calities. Even  in  the  same  quarry  different  beds  contain  very  unlike 
proportions  of  magnesia,  and  are  therefore  more  or  less  fitted  for 
agricultural  purposes.  Thus  several  varieties  of  this  lime-stone,  ex- 
amined by  myself,  from  different  parts  of  the  county  of  Durham, 
contained  the  two  carbonates  in  the  following  proportions : 

Garmondswav 97-5      25      trace     trace  Hard  compact  grey. 

Stony-gate..'. 98  0      161     027      012   Crystalline  fine  grained  yellow 

Ful  well   95  0      2-1       0  3        2-6      \  Honey-combed  crystalline 

{        yellow. 

Seaham  (A) 96-5      2  3      0-2        10     Hard  fine-grained  compact. 

(B) 950       1-3      0-2        3  5      Hard  porous  brown. 

Hartlepool 54.5    4493    033    024     Oolitic  yellow. 

HumbledonHill(A)57-9    41-8        7        0  28     Perfect  encrinal  columns. 

"         "     (B)  60-41  38  78      ?        081      Consistingin  part  encrinal  col. 

Ferry  Hill 54-1     4472     1-58      46     Yellowish  compact. 

Some  of  these  varieties,  as  we  see,  contain  very  little  carbonate  of 

•  Thus  that  of  Aberlhaw  contains  about  86  of  carbonate  of  lime  and  11  of  clay,  &c. ; 
that  of  Yorkshire  62  of  carbonate  of  lime  and  34  of  clay  ;  of  Sheppy  66  of  carbonate  of 
lime  and  32  of  clay.  These  lime-stones  are  burned,  and  then  crushed  to  an  impalpable 
powder,  which  sets  almost  immediately  when  mixed  up  with  water. 


366  OF    THE    m  UNING    AND    SLAKING    OF    LIME. 

magnesia,  and  therefore,  nre  found  to  produce  excellent  lime  for  agri- 
cultual  purposes — while  in  others  this  substance  forms  nearly  one- 
half  of  the  whole  weight  of  the  rock.  Similar  differences  are  found 
to  prevail  in  almost  every  locality. 

This  admixture  of  magnesia  in  greater  or  less  quantity  is  not  con- 
fined to  the  lime-stones  of  the  magnesian  lime-stone  formation  pro- 
perly so  called.  It  is  found  in  sensible  quantity  in  certain  beds  of 
lime-stone  in  nearly  every  geological  formation,  and  there  are  few 
natural  lime-stones  of  any  kind  in  which  traces  of  it  may  not  be  dis- 
covered by  a  carefully  conducted  chemical  examination. 

The  simplest  method  of  detecting  magnesia  in  a  lime-stone  is  to  dis- 
solve it  in  diluted  muriatic  acid,  and  then  to  pour  clear  lime  water  into 
the  filtered  solution.  If  a  hght  white  powder  fall,  it  is  magnesia.  The 
relative  proportions  in  two  lime-stones  maybe  estimated  pretty  nearly 
by  dissolving  an  equal  weight  of  each,  pouring  the  filtered  solutions 
into  bottles  which  can  be  corked,  and  then  filling  up  both  with  lime 
water.  On  subsiding,  the  relative  bulks  of  the  precipitates  will  indi- 
cate the  respectivB  richness  of  the  two  varieties  in  magnesia. 

§  2.  Of  the  huTniing  and  slaking  of  lime. 

Burning. — When  carbonate  of  lime  or  carbonate  of  magnesia  is 
heated  to  a  high  temperature  in  the  open  air  the  carbonic  acid  they 
severally  contain  is  driven  oif,  and  the  lime  or  magnesia  remains  in 
the  caustic  state.  When  thus  heated  the  carbonate  of  magnesia 
parts  with  its  carbonic  acid  more  speedily  and  at  a  lower  temperature 
than  carbonate  of  lime. 

On  the  large  scale  this  burning  is  conducted  in  lime  kilns,  one  ton 
good  lime-stone  yielding  about  11  cwts.  of  burned,  shell,  quick,  or 
caustic  lime. 

Slaking. — When  this  shell  or  quick-lime,  as  it  is  taken  from  the  kiln, 
is  plunged  into  water  for  a  short  time  and  then  withdrawn,  or  when  a 
quantity  of  water  is  poured  upon  it,  heat  is  developed,  the  lime  swells, 
cracks,  gives  off  much  watery  vapor,  and  finally  falls  to  a  fine,  bulky, 
more  or  less  white  powder.  These  appearances  are  more  or  less  rapid 
and  striking  according  to  the  quality  of  the  lime,  and  the  time  that  has 
been  allowed  to  elapse  after  the  burning,  before  the  water  was  applied. 
All  lime  becomes  difficult  to  slake  when  it  has  been  for  some  time  ex- 
posed to  the  air.  When  the  slacking  is  rapid  as  in  the  rich  limes,  the 
heat  produced  is  sufficient  to  kindle  gunpowder  strewed  upon  it,  and 
the  increase  of  bulk  is  from  2  to  3i  times  that  of  the  original  lime 
shells.  If  the  water  be  thrown  on  so  rapidly  or  in  such  quantity  as 
to  chill  the  lime  or  any  part  of  it,  the  poAvder  will  be  gritty,  will  con- 
tain many  little  lumps  which  refuse  to  slake,  will  also  be  less  bulky 
and  less  minutely  divided,  and  therefore  will  be  less  fitted  either  for 
agricultural  or  for  building  purposes. 

When  quick-lime  is  left  in  the  open  air,  or  is  covered  over  with  sods 
in  a  shallow  pit;  it  gradually  absorbs  water  from  the  air  and  from  the 
soil,  and  falls,  though  much  more  slowly,  and  with  little  sensible  deve- 
lopment of  heat,  into  a  similar  fine  powder.  In  the  rich  limes  the  in- 
crease of  bulk  may  be  3  or  3i  times ;  in  the  poorer,  or  such  as  contain 
much  earthy  matter,  it  may  be  less  than  twice. 


FURTHER  CHANGES  UNDERGONE  BY  SLAKED  LIME.      367 

-Hydrate  of  lime. — Wlien  quick-lime  is  thus  slaked  it  combines  with 
the  water  which  is  added  to  it,  and  becomes  converted  into  a  milder  or 
less  caustic  compound,  \yhich  among  chemists  is  known  by  the  name  of 
hydrate  of  lime.     This'hydrate  consists  of 

Lime     .     .  76  per  cent.  I  or  one  ton  of  pure  burned  lime  becomes 
Water   .     .  24        "        \  nearly  25  cwt.  of  slaked  lime. 

100 

It  is  rare,  however,  that  lime  is  so  pure  or  so  skilfully  and  perfectly 
slaked  as  to  take  up  the  whole  of  this  proportion  of  water,  or  to  increase 
quite  so  much  as  one-fourth  part  in  weight. 

Hydrate  of  Magnesia. — When  calcined  or  caustic  magnesia  is 
slaked,  it  also  combines  with  water,  but  without  becoming  so  sensibly 
hot  as  quick-lime  does,  and  forms  a  hydrate,  which  consists  of 

Magnesia  .  69-7  per  cent.  ?  or  one  ton  of  pure  burned  magnesia  be- 

Water  .     .  30-0        »         \  comes  28|  cwt.  of  hydrate. 


100 

When  magnesian  lime  is  slaked,  the  fine  powder  which  is  obtained 
consists  of  a  mixifire  of  these  two  hydrates,  in  proportions  which  depend 
of  course  upon  the  composition  of  the  original  lime-stone. 

An  important  difference  between  these  two  hydrates  is,  that  the  hy- 
drate of  magnesia  will  harden  under  water  or  in  a  wet  soil  in  about  8 
days — forming  a  hydraulic  cement.  Hydrate  of  lime  will  not  so 
harden,  but  a  mixture  of  the  two  in  the  proportions  in  which  they  exist 
in  the  Hartlepool,  Humbledon,  and  Ferryhill  lime-stones  (page  365), 
will  harden  under  water,  and  form  a  solid  mass.  In  the  minute  state 
of  division  in  which  lime  is  applied  to  the  soil,  the  particles,  if  it  be  a 
magnesian  lime,  will,  in  wet  soils,  or  in  the  event  of  rainy  weather 
ensuing  immediately  after  its  application,  become  granular  and  gritty, 
and  cohere  occasionally  into  lumps,  on  which  the  air  will  have  little 
effect.  This  prop^ty  is  of  considerable  importance  in  connection  with 
the  further  chemioal  changes  which  slaked  limes  undergo  when  exposed 
to  the  air  or  buried  in  the  soil. 

§  3.   Changes  lohich  the  hydrates  of  lime  and  magnesia  undergo  by 
prolonged  exposure  to  the  air. 

When  the  hydrates  of  lime  or  magnesia  obtained  by  slaking  are  ex- 
posed to  the  open  air,  they  gradually  absorb  carbonic  acid  from  the  at- 
mosphere, and  tend  to  return  to  the  state  of  carbonate  in  which  they  ex- 
isted previous  to  burning.  By  mere  exposure  to  the  air,  however,  they 
do  not  attain  to  this  state  within  any  assignable  time.  In  some  walls 
600  years  old,  the  lime  has  been  found  to  have  absorbed  only  one  fourth 
of  the  carbonic  acid  necessary  to  convert  the  whole  into  carbonate ;  in 
others,  built  by  the  Romans  1800  years  ago,  the  proportion  absorbed 
has  not  exceeded  three  fourths  o^  ihe  quantity  contained  in  natural  lime- 
stones. In  damp  situations  the  absorption  of  carbonic  acid  proceeds 
most  slowly. 

1°.  Change  undergone  by  pure  lime  during  spontaneous  slaking. — 
In  consequence,  however,  of  the  strong  tendency  of  caustic  lime  to  ab- 
sorb carbonic  acid,  a  ejnsiderable  quantity  of  the  hydrate  of  lime  first 


368  OF    CALCINED    AND    SLAKED    MAGNESIA. 

formed,  during  spontaneous  slaking,  becomes  changed  into  carbonate 

during  the  slaking  of  the  rest.     But,  when  it  has  all  completely  fallen, 

the  rapidity  of  the  absorption  ceases,  and  the  fine  slaked  lime  consists  of 

Carbonate  of  lime 57*4 

Hydrate  ofli^e  I  i;™;^^:     ;     ;     ^l      42-6 

100 
or,  a  ton  of  lime,  left  in  the  open  air  till  it  has  completely  fallen  to 
powder,  contains  about  8i  cwt.  in  the  state  of  hydrate.  If  left  to  slake 
in  large  heaps,  the  lime  in  the  interior  of  those  heaps  will  not  absorb  so 
much  carbonic  acid  till  after  the  lapse  of  a  very  considerable  time. 
More  caustic  lime  (hydrate)  also  will  be  present  if  it  be  left  to  slake,  as 
is  often  done  for  agricultural  purposes,  in  shallow  pits  covered  with  sods, 
lo  defend  it  from  the  air  and  the  rains. 

After  the  lime  has  attained  the  state  above  described,  and  which  is  a 
chemical  compound*  of  carbonate  with  hydrate  of  lime,  the  further  ab- 
sorption of  carbonate  acid  from  the  air  proceeds  very  slowly,  and  is  only 
completely  elTected  after  a  very  long  period. 

2°.  When  slaked  in  the  ordinary  way  lime  falls  lo  powder,  without 
having  absorbed  any  notable  quantity' of  carbonic  acid.  Numerous 
small  lumps  also  remain,  which,  though  covered  with  a  coating  of  hy- 
drate, have  not  themselves  absorbed  any  water.  The  absorption  of 
carbonic  acid  by  this  slaked  lime  is  at  first  very  rapid, — so  that  where 
the  full  effect  of  caustic  lime  upon  the  soil  is  required,  it  ought  to  be 
ploughed  in  as  early  as  possible, — but  it  gradually  becomes  more  slow, 
a  variable  proportion  of  the  compound  of  carbonate  and  hydrate  above 
described  is  formed,  and  even  when  thinly  scattered  over  a  grass-field, 
an  entire  year  may  pass  over  without  effecting  the  complete  conversion 
of  the  whole  into  carbonate. 

3°.  Calcined  or  burned  magnesia,  whether  in  the  pure  stale  or  mixed 
with  quick-lime,  as  in  the  magnesian  limes,  absorbs  carbonic  acid  more 
slowly — and  by  mere  exposure  to  the  air  will  probably  never  return  to 
its  original  condition  of  carbonate. 

When  allowed  to  slake  spontaneously,  three-fourths  of  it  become 
ultimately  changed  into  carbonate,  and  form  a  compound  of  hydrate 
and  carbonate  which  is  identified  with  the  common  uncalcined  magne- 
sia of  the  shops.     This  compoundf  consists  of 

Carbonate  of  magnesia 69*37 

Hydrate  of  magnesia 16-03 

Water 14-60 


100 
and  it  undergoes  no  further  change  by  continued  exposure  to  the  air. 
But  if  slaked  by  the  direct  application  of  water,  magnesia,  like  lime, 

*  This  compound  consists  of  one  atom  of  carbonate  of  lime  (Ca  O  +  CO2)  combined  with 
one  of  hydrate  (Ca  O  +  HO,)  and  is  represented  shortly  by  Ca  C  -|-  Ca  H— in  which  Ca 
denotes  calcium  (Lee.  IX.,  §  4,)  Ca  O  or  (Ja  oxide  of  calcium  or  lime,  CO2  or  C  carbonic 
acid  (Lee.  IIL,  §  I,)  and  II  O  or  H  water  (Lee.  IL  §  6.) 

t  It  s  represented  by  the  formula  3  (Mg  C  +  H)  +  Mg  H. 


STATES    IN    WHICH    LIME    IS   APPLIED.  3b9 

forms  a  hydrate  only,  without  absorbing  any  sensible  quantity  of  car- 
bonic acid.  The  hydrate  thus  produced  is  met  with  in  the  form  of 
mineral  deposits  on  various  parts  of  the  earth's  surface,  and  this  mineral 
is  not  known  to  undergo  any  change  or  to  absorb  carbonic  acid  though 
exposed  for  a  great  length  of  time  to  the  air.  When  magnesian  limes 
are  slaked  by  water,  therefore,  the  magnesia  they  contain  may  remain 
in  whole  or  ui  part  in  the  caustic  state  (of  hydrate),  which  will  change 
but  slowly  even  when  exposed  to  the  air.  When  it  is  left  to  sponta- 
neous slaking,  one-fourlh  of  it  at  least  will  always  remain  in  the  caustic 
state,  however  long  it  may  be  exposed  to  the  air. 

Should  a  lime  be  naturally  of  such  a  kind,  or  be  so  mixed  with  the 
ingredients  of  the  soil  as  to  form  a  hydraulic  cement  or  an  ordinary 
mortar,  which  will  solidify  when  rains  come  upon  it,  or  when  the  natu- 
ral moisture  of  the  soil  reaches  it — the  absorption  of  carbonic  acid  will 
in  a  great  measure  cease  as  it  becomes  solid,  and  a  large  proportion  of 
the  lime  will  remain  caustic  for  an  indefinite  period. 

§  4.  Slates  of  chemical  combination  in  which  lime  may  be  applied  to 
the  land. 

There  are,  therefore,  four  distinct  slates  of  chemical  combination,  in 
which  pure  lime  may  be  artificially  applied  to  the  land. 

1^.  Quick-lime  or  lime-shells,  in  which  the  lime  as  it  comes  from  the 
kiln  is  uncombined  either  with  water  or  with  carbonic  acid. 

2°.  SlaJced  lime  or  hydrate  of  lime,  in  which  by  the  direct  application 
of  water  it  has  been  made  to  combine  with  about  one-fourth  of  its 
weight  of  water. 

In  both  these  states  the  lime  is  caustic,  and  may  be  properly  spoken 
of  as  caustic  lime. 

3°.  Spontaneously  slaked  liine,m  which  one-half  of  the  lime  is  com- 
bined with  water  and  the  other  half  with  carbonic  acid.  In  this  state 
it  is  only  half  caustic. 

4°.  Carbonate  of  lime — the  state  in  which  it  occurs  in  nature,  and  to 
which  burned  lime,  after  long  exposure  to  the  air,  more  or  less  perfectly 
arrives.  In  this  stale  lime  possesses  no  caustic  or  alkaline  (p.  48,  §  5< 
note)  properties,  but  is  properly  called  mild  lime. 

5°.  l^i-carbonale  of  lime  may  be  adverted  to  as  a  fifth  state  of  com- 
bination, in  which,  as  I  have  previously  explained  to  you  (pp.  45-6, 
§  1),  nature  usually  applies  lime  to  the  land.  In  this  state  it  is  combined 
with  a  double  proportion  of  carbonic  acid,  and  is  to  a  certain  extent 
readily  soluble  in  water.  Hence,  springs  are  often  impregnated  with 
it,  and  the  waters  that  gush  from  fissures  in  the  lime-stone  rocks  spread 
it  through  the  soil  in  their  neighbourhood,  and  sweeten  the  land. 

1  shall  hereafter  speak  of  these  several  states  under  the  names  of 
quick-Wme,  hydrate  of  lime,  spontaneously  slaked  lime,  carbonate  of 
lime,  and  Bi-carbonate  of  lime.  By  adhering  to  these  strictly  correct 
names,  we  shall  avoid  some  of  that  confusion  into  which  those  who 
have  hitherto  treated  of  the  use  of  lime  as  a  manure  have  unavoidably- 
fallen.  The  term  mild,  you  will  understand,  applies  only  to  that  which 
is  entirely  in  the  state  of  carbonate. 

Magnesia,  in  the  magnesian  limes,  may  in  like  manner  be  either  in 
the  state  o{  calcined  magnesia,  o^  hydrate  of  magnesia^  oi  spontaneously 


370  VARIOUS   NATURAL  FORMS    OF   CARBONATE    OF   LliME. 

slaked — meaning  by  this  the  compound  of  hydrate  with  carbonate — of 
carbonate^  or  of  'Bi- carbonate  of  magnesia,  the  latter  of  which  is  so- 
luble in  water  to  a  very  considerable  extent.  (It  dissolves  in  48  times 
its  weight  of  water — or  a  gallon  of  water  will  dissolve  5  ounces  of 
the  Bi-carbonate  containing  1^  ounces  of  magnesia.) 

§  5.  Of  the  various  natural  forms  in  which  carbonate  of  lime  is 
applied  to  the  land. 

In  the  unburned  or  natural  state,  lime  is  met  with  on  the  earth's 
surface  in  numerous  forms — in  many  of  which  it  can  be  applied 
largely,  easily,  and  with  economy  to  the  land. 

1°.  Marl. — Of  these  forms  that  of  marl  occurs  most  abundantly, 
and  is  most  extensively  used  in  almost  every  country  of  Europe.  By 
the  term  marl,  is  understood,  as  I  explained  to  you,  when  treating  of 
soils  (Lee.  XL,  §  3,)  an  earthy  mixture,  which  contains  carbonate  of 
lime,  and  effervesces  more  or  less  sensiljly  when  an  acid  (vinegar  or 
diluted  muriatic  acid — spirit  of  salt)  is  poured  upon  it.  Generally, 
also,  the  tenacious  marls,  when  introduced  into  water,  lose  their  co- 
'herence,  and  gradually  fall  to  powder.  This  test  is  often  employed 
to  distinguish  between  marly  and  other  clays,  yet  the  falling  asunder, 
though  it  afford  a  presumption,  is  not  an  infaUible  proof  that  the  sub- 
stance tried  is  really  a  marl. 

Marls  are  of  various  colors,  white,  grey,  yellow,  blue,  and  of  various 
'degrees  of  coherence,  some  occurring  in  the  form  of  a  more  or  less  fine, 
loose,  sandy  powder,  others  being  tenacious  and  clayey,  and  others, 
again,  hard  and  stony.  These  differences  arise  in  part  from  the  kind 
and  proportion  of  the  earthy  matters  they  contain,  and  in  part,  also,  from 
the  nature  of  the  locality,  moist  or  dry,  in  w^hich  they  are  found.  The 
hard  and  stony  varieties  are  usually  laid  upon  the  land,  and  exposed  to 
the  pulverising  influence  of  a  winter's  frost  before  they  are  either  spread 
over  the  pasture  or  ploughed  into  the  arable  land.  Some  rich  marls 
consist  in  part  or  in  whole  of  broken  and  comminuted  shells,  which 
clearly  indicate  the  source  of  the  calcareous  matter  they  contain. 

COMPOSITION   OF  MARLS    FROM 

Lureburg.  Osnabruck  Magdeburg.  Brunswick.  Wesermarsh.  Brunswick. 

powdery,  stony.  clayey.         loamy.      powdery.  stony. 

auartz-Sand&  Silica..    56  230  58-4          734          789  7M 

Alumina 04  100  8-4           1-9           31  40 

Oxides  of  Iron 42  1-9  67           32           38  65 

Do.  of  Magnesia trace  trace  03           03           03  1-1 

Carbonateof  Lime....  85-5  350  18-2         181           8-2  133 

Do.  of  Magnesia 1-25  09  38           1-5           3-0  26 

Sulphuret  of  Iron _  7.3  _            _            —  _ 

""tnldtuhtnir:}  «-»5  'race  1-6  08  0-9  02 

Common  Salt 0-03  trace  trace  trace  01         trace 

Gypsum 0-06         0-9  2-1  01  05        trace 

Phosphate  of  Lime      }  3.3  ^.^  ^.^  ^.^  ^.^  ^.3 

(bone  earth) j 

Nitrate  of  Lime 001  —  —  -  — 

carbon 

Organic  Matter 0-6  205  _  —  —  — 

100  100  100  100         100         100 


DNLIKE    EFFECTS    OF    DIFFERENT    MARLS.  371 

The  characteristic  property  of  true  marls  of  every  variety  is,  I  have 
said,  the  presence  of  a  considerable  per  centage  of  carbonate  of  lime  in 
the  state  of  a  fine  powder,  and,  in  general,  diffused  uniformly  through 
the  entire  mass.  To  this  calcareous  matter  the  chief  efficacy  of  these 
marls  is  no  doubt  to  be  ascribed,  yet  as  they  always  contain  other  chem- 
ical compounds  to  which  the  special  efficacy  of  certain  varieties  has 
sometimes  been  ascribed,  it  may  not  be  improper  to  direct  your  attention 
to  the  preceding  table,  in  which  the  constitution  of  several  marls,  from 
different  localities,  is  represented,  after  the  analyses  ot  Sprengel. 

Several  reflections  will  occur  to  you  on  looking  at  these  tables — such 
as. 

First — that  marls  differ  very  much  in  composition,  and  therefore 
must  differ  very  much  also  in  the  effects  which  they  are  capable  of  pro- 
ducing when  applied  in  the  same  quantity  to  the  same  kinds  of  land. 

Seco7id — that,  among  other  differences,  the  proportion  of  carbonate 
of  hme  is  very  unlike — in  so  Tie  varieties  amounting  to  85  lbs.  out  of 
every  hundred,  while  in  others  ^s  little  as  5  lbs.  are  present  in  the  same 
weight.  You  will  understand, .  ^erefore,  how  very  different  the  quan- 
tity applied  to  the  land  must  be,  it .  "ese  several  varieties  are  to  produce 
an  equal  liming  or  to  add  equal  quantities  of  lime  to  the  soil.  You 
will  see  that  each  of  three  persons  may  be  adopting  the  best  practice 
with  his  own  marl— though  the  one  add  only  12  to  20  tons  per  acre, 
while  the  second  adds  50  to  CO,  and  the  third  100  to  120  tons. 

Third — that  the  proportion  of  phosphate  of  lime  (bone-earth)  is  in 
some  marls  considerably  greater  than  in  other's.  Thus  with  every  ton 
of  the  first  of  the  above  marls  you  would  lay  on  the  soil  52  lbs.  of  bone 
earth — about  as  much  as  is  contained  in  a  cwt.  of  bone  dust — while 
with  the  second  you  would  only  add  11  lbs.  In  so  far  as  their  effects 
upon  the  land  depend,  or  are  influenced  by  the  presence  of  this  sub- 
stance, therefore,  they  must  also  be  very  different.     And, 

Fourth — that  the  mechanical  effects  of  these  marls  upon  the  soil  to 
which  they  are  added  must  be  very  unlike,  since  some  contain  70  or 
SO  lbs.  of  sand  in  every  hundred — while  others  contain  a  considerable 
quantity  of  clay.  The  opening  effects  of  the  one  marl,  and  the  stiff- 
ening effects  of  the  other,  when  they  are  laid  on  in  large  quantities, 
cannot  fail  to  produce  very  different  alterations  in  the  physical  cha- 
racters of  the  soil. 

2^.  Shell  Sand.— The  sands  that  skirt  the  shores  of  the  sea  are 
found  in  many  localities  to  be  composed,  in  large  proportion,  of  the 
fragments  of  broken  and  comminuted  shells.  These  form  a  calcare- 
ous sand,  mixed  occasionally  with  portions  of  animal  matter,  and, 
when  taken  fresh  from  the  sea-shore,  with  some  saline  matter  derived 
from  the  sea. 

Such  is  the  case  in  many  places  on  the  coast  of  Cornwall.  From 
these  spots  the  sand  is  transported  to  a  distance  of  many  miles  into 
the  interior  for  the  purpose  of  being  laid  upon  the  land.  It  has  been 
estimated  (De  la  Beche's  Geological  Report  on  Cornwall^  ^c,  p.  480) 
that  seven  millions  of  cubic  feet  are  at  present  employed  every  year 
in  that  county  for  this  purpose. 

On  the  western  coast  of  Scotland  also,  and  on  the  shores  of  the  island 
of  Arran  and  of  the  Western  Isles,  this  shell  sand  abounds,  and  is 
16* 


372         COMPOSITION  OF  SHELL  AND  CORAL  LANDS. 

applied  extensively,  and  with  remarkably  beneficial  effects,  both  to  the 
pasture  lands  and  to  the  peaty  soils  that  cover  so  large  an  area  in  this 
remote  part  of  Scotland.  It  is  chiefly  along  the  coasts  that  it  has  hith  • 
erto  been  extensively  employed,  and  it  is  transported  by  sea  to  a  dis- 
tance of  SO  or  100  miles.  "  In  the  island  of  Barray  alone,  there  are  four 
square  miles  of  shells  and  shell  sand  of  the  finest  quality  and  of  an 
indefinite  depth"  (Macdonald's  Agricultural  Survey  of  ike  Hebrides, 
p.  401.)  When  covered  with  a  dressing  of  this  shell  sand  the  peaty 
surface  becomes  covered  with  a  sward  of  delicate  grass — and  ihe 
border  of  green  herbage  that  skirts  the  shores  of  these  islands  in  so 
many  places  is  to  be  ascribed  either  to  the  artificial  applications  of 
such  dressing  or  to  the  natural  action  of  the  sea  winds  in  strewing 
the  fine  sand  over  them,  when  seasons  of  storm  occur. 

The  coast  of  Ireland  is  no  less  rich  in  such  sand  in  many  parts  both 
of  its  northern  and  southern  coasts.  A  century  and  a  half  ago,  it  is 
known  to  have  been  used  for  agriculture  x  purposes  in  the  north  of  Ire- 
land— and  nearly  as  long  ago  to  have  >een  brought  over  to  the  oppo- 
site (Galloway)  coast  of  Scotland  w'  n  a  view  of  being  applied  to  the 
land  (Macdonald.)  In  the  south,  according  to  Mrs.  Hall,  (Mrs.  Hall's 
Ireland,)  the  coral  sand  raised  in  Ban  try  Bay  alone  produces  £4000 
or  £5000  a-year  to  the  boatmen  who  procure  it  and  to  the  peasants 
who  convey  it  up  the  country. 

On  the  coast  of  France,  and  especially  in  Brittany,  opposite  to  Corn- 
wall, on  the  other  side  of  the  English  channel,  it  is  obip,ined  in  large 
quantity,  and  is  in  great  demand  (Payen  and  Boussingault,  Annates  de 
Chiw.  et  de  Phys.,  third  series,  in.,  p.  92.)  It  is  applied  to  the  clay  soils 
and  to  marshy  grass  lands  with  much  advantage,  and  is  carried  far 
inland  for  this  purpose.  It  is  there  called  trez,  and  is  laid  on  the  land  at 
the  rate  of  10  to  15  tons  per  acre.  On  the  southern  coasts  of  France, 
where  shell  sand  is  met  with,  it  is  known  by  the  name  of  tanque  or 
taiigue. 

The  shell  sand  of  Cornwall  contains  from  40  to  70  per  cent,  of  car- 
bonate of  lime,  with  an  equally  variable  small  admixture  of  animal 
matter  and  of  sea  salt.  The  rest  is  chiefly  siliceous  sand.  Other  va- 
rieties have  a  similar  composition.  Two  specimens  oHaiigue  from  the 
south  of  France,  analysed  by  Vitalis,  and  one  of  shell  sand  from  the 
island  of  Isla,  partially  examined  by  myself,  consisted  of 

Tangiie  from  the  Shell  Sand 

Sotifh  of  France.  from  Isla. 

Sand,  chiefly  siliceous 20-3  40  ^  71  7  f^  cs  7 

Alumina  and  Oxide  of  Iron 4-6      4-6  \^  '  ^' '  "^^ '^^' ' 

Carbonate  of  Lime 66-0  47.5  28     to  34 

Phosphate  of  Lime ?          ?  0-3 

Water,  and  loss". 9-1       7-9  — 

100     100  100 

3°.  Coral  sand  is  similar  in  its  nature  to  the  shell  sand  with  which 
it  is  often  intermixed  on  the  sea-shore.  It  is  collected  in  considerable 
quantities,  however,  by  the  aid  of  the  drag — being  torn  up  by  the  fish- 
ermen in  a  living  state — on  the  coasts  of  Ireland  (Bantry  Bay  and 
elsewhere,)  and  on  the  shores  of  Brittany,  especially  near  the  mouths  of 
the  rivers.   In  this  fresh  s»;'ate  it  is  preferred  by  the  farmer,  probably  be- 


USE   OF    LIME-STONE    SAND    AND   GRAVEL.  373 

cause  it  contains  both  more  saline  and  more  animal  matter.  This  ani- 
mal matter  enables  it  to  unite  in  some  measure  the  beneficial  effects 
which  follow  from  the  application  of  marl  and  of  a  small  dressing  of 
farm-yard  or  other  valuable  mixed  manure. 

Payen  and  Boussingault  ascribe  the  principal  efficacy  of  the  shell 
and  coral  sands  to  the  small  quantity  of  animal  matter  which  is  present 
in  them.  These  chemists  estimate  the  relative  manuring  powers  of 
different  substances  applied  to  the  land  by  the  quantities  of  nitrogen 
which  they  severally  contain,  and  thus,  compared  with  farm-yard 
manure,  attribute  to  the  shell  and  coral  sands  the  following  relative 
values: — 

Contain  of  Relative 

Nitrogen.  value. 

100  lbs.  of  Farm-yard  Manure     .     .     .     0-40    lbs.  100 

do.      of  Coral  Sand  (Merl)      .     .     .     0-512  lbs.  128 

do.      of  Shell  Sand  (Trez)      .     .     .     0-13    lbs.  32^* 

That  is  to  say,  that,  in  so  far  as  the  action  of  these  substances  is  de- 
pendent upon  the  nitrogen  they  contain,  fresh  coral  sand  is  nearly  one- 
third  more  valuable  than  farm-yard  manure,  while  fresh  shell  sand  is 
only  equal  in  virtue  to  one-third  of  its  weight  of  the  same  substance. 

Though,  as  I  have  already  had  frequent  occasion  to  observe  to  you, 
much  weight  is  not  to  be  attached  to  such  methods  of  estimating  the  re- 
lative values  of  manuring  substances  by  the  proportions  of  any  one  of 
the  ingredients  they  hajipen  to  contain — yet  the  fact,  that  so  much  ani- 
mal matter  is  occasionally  present  in  the  living  corals,  accounts  in  a 
satisfactory  manner  for  the  immediale  effects  of  this  form  of  calcareous 
application.  This  animal  matter  acts  directly  and  during  the  first  year; 
the  carbonate  of  lime  begins  to  show  its  beneficial  influence  most  dis- 
tinctly when  two  or  three  years  have  passed. 

4°.  Lime-stone  Sand  and  Gravel. — In  coimtries  which  abound  in 
lime-stones,  there  are  found  scattered  here  and  there,  in  the  hollows  and 
on  the  hill-sides,  banks  and  heaps  of  sand  and  gravel,  in  which  rounded 
particles  of  lime-stone  abound.  These  are  distinguished  by  the  names 
of  lime-stone  sand  and  gravel,  and  are  derived  from  the  decay  or  wear- 
ing down  of  the  lime-stone  and  other  rocks  by  the  action  of  water. 
Such  accumulations  are  frequent  in  Ireland.  They  are  indeed  exten- 
sively diffused  over  the  surface  of  that  island,  as  we  might  expect  in  a 
country  abounding  so  much  in  rocks  of  mountain  lime-stone.  In  the 
neighbourhood  of  peat  bogs  these  sands  and  gravels  are  a  real  blessing. 
They  are  a  ready,  most  useful,  and  largely  employed  means  of  im- 
provement, producing,  upon  arable  land,  the  ordinary  effects  of  liming, 
and,  when  spread  upon  boggy  soils,  alone  enabling  it  to  grow  sweet 
herbage  and  to  afford  a  nourishing  pasture.  The  proportion  of  carbon- 
ate of  lime  these  sands  and  gravels  contain  is  very  variable.  I  have 
examined  two  varieties  from  Kilfinaue,  in  the  county  of  Cork  (?).  The 
one,  a  yellow  sand,  contained  26  per  cent,  of  carbonate  of  lime — the  re- 
sidue, being  a  fine  red  sand,  chiefly  siliceous  ;  the  other,  a  fine  gravel 
of  a  grey  colour,  contained  40  per  cent,  of  carbonate  of  lime  in  the 
form  chiefly  of  rounded  fragments  of  blue  lime-stone,  the  residue  con- 
sisting of  fragments  of  sand-stone,  of  quartz,    and  of  granite. 

•  Annalee  de  Chim.  st  de  Phys.^  third  series,  iii.,  p.  103. 


374  CRUSHED    LIME-STONES. EFFECTS    OF    MARLS. 

The  application  of  such  mixtures  must  not  only  improve  the  physi- 
cal characters  of  the  soil,  but  the  presence  of  the  fragments  of  granite, 
containing  undecomposed  felspar  and  mica  (Lee.  XII.,  §  1),  must  con- 
tribute materially  to  aid  the  fertilizing  action  of  the  lime-stone  with 
which  they  are  mixed. 

5°.  Crushed  Lime-stone. — The  good  effects  of  calcareous  marls^and 
of  lime-stone  gravels  naturally  suggest  the  crushing  of  lime-stones^as  a 
means  of  obtaining  carbonate  of  lime  in  so  minute  a  state  of  division 
that  it  may  be  usefully  applied  to  the  soil.  Lord  Karnes  was,  I  be- 
lieve, the  first  who  in  this  country  endeavoured  to  bring  this  suggestion 
into  practical  operation.  He  is  said  to  have  caused  machinery  to 
be  erected  for  the  purpose  in  one  of  the  remotest  districts  of  Scotland, 
but  from  some  cause  the  plan  seems  never  to  have  obtained  a  proper 
trial. 

One  of  the  results  which,  as  we  have  already  seen,  follows  from  the 
burning  of  rich  lime  is  this,  that  it  naturally  falls  to  a  very  fine  powder 
as  it  slakes.  Where  coal  or  other  combustible  is  cheap,  therefore,  it 
may  possibly  be  reduced  to  a  fine  powder  by  burning,  at  a  less  cost 
than  it  could  be  crushed. 

Yet  there  are  two  cases  or  conditions  in  which  crushing  might  be  re- 
sorted to  with  equal  advantage  and  economy  : 

FirsU  where  coal  is  dear  or  remote,  while  lime-stones  and  water 
power  are  abundant.  There  are  many  inland  districts  in  each  of  the 
three  kingdoms  where  these  conditions  exist,  and  in  which,  therefore, 
the  erection  of  cheap  machinery  might  afford  the  means  of  greatly  fer- 
tilizing the  land  ;  and. 

Second,  there  are  in  many  localities  rocks  rich  in  calcareous  mat- 
ter, which  are  nevertheless  so  impure,  or  contain  so  much  other  earthy 
matter,  that  they  cannot  be  burned  into  lime.  Yet,  if  crushed,  these 
same  masses  of  rock  would  form  a  valuable  dressing  for  the  land. 
Many  lime-stones  of  this  impure  character,  which  are  really  useless  for 
building  purposes — which  do  not  fall  to  powder  when  burned,  and 
which  have,  therefore,  been  hitherto  neglected  as  useless — might,  by 
crushing,  be  made  extensively  available  for  agricultural  purposes.  The 
siliceous  lime-stones  (corn-stones)  of  the  old  red  sand-stone,  the  earthy 
beds  of  the  mountain  lime-stone,  and  many  of  the  calcareous  strata  of 
the  Silurian  system  might  thus  be  made  to  improve  more  extensively 
the  localities  in  which  they  are  severally  met  with.  The  richer  limes 
now  brought  from  a  great  distance,  and  at  much  expense — as  on  the 
Scottish  borders — might  be  in  a  great  measure  superseded  by  the  native 
produce  of  the  district. 

§  6.  Effects  of  marl  and  of  the  coral,  shelly  and  lime-stone  sands, 
upon  the  soil. 

The  effects  which  result  from  the  application  of  the  above  natural 
forms  of  carbonate  of  lime  are  of  two  kinds. 

1°.  Their  physical  effect  in  altering  the  natural  texture  of  the  soils  to 
which  they  are  added.  This  effect  will  necessarily  vary  with  the  na- 
ture of  the  earthy  matter  associated  with  the  lime.  Thus  the  clay 
marls  will  improve,  by  stiffening,  such  soils  as  are  light  and  sandy — 
the  shell  sands  and  lime-stone  gravels,  by  opening  and  rendering  more 


OBSERVED    EFFECTS   OF    MARLS.  375 

free  and  easier  worked  such  soils  as  are  stiff,  intractable,  and  more  or 
less  impervious — while  either  will  impart  solidity  and  substance  to 
such  as  are  of  a  peaty  nature  or  over-bound  with  other  forms  of  vege- 
table matter. 

2°.  Their  chemical  effect  in  actually  rendering  the  soil  productive  of 
larger  crops.  This  effect  is  altogether  independent  of  any  alteration  in 
the  physical  properties  of  the  soil,  and  is  nearly  the  same  in  Icind,  what- 
ever be  the  variety  of  marl,  &c.,  we  apply.  It  differs  in  degree,  chiefly 
according  to  the  proportion  of  calcareous  matter  which  each  variety 
contains.  This  action  of  the  pure  carbonate  of  lime  they  contain  is 
supposed  to  be  modified  in  some  cases  by  the  proportion  of  phosphate  of 
lime,  &c.  (p.  370,)  with  which  it  maybe  mixed — it  is  certainly  modified 


7 

als 


s  and  shell  sands. 

The  several  effects  of  marls  and  calcareous  sands  being  dependent 
upon  circumstances  so  different,  it  is  not  surprising  that  the  opinions  of 
practical  men  should,  in  former  times,  have  been  divided  in  regard  to 
the  action  of  this  or  that  marl  itpon  their  respective  soils.  In  no  two 
localities  was  the  substance  applied  to  the  land  exactly  alike,  and 
hence  unlike  results  must  necessarily  have  followed,  and  disappoint- 
ment been  occasionally  experienced  from  their  use.  And  yet  the  im- 
portance of  rightly  understanding  the  kind  and  degree  of  eflfect  which 
these  manuring  substances  ought  to  produce  may  be  estimated  from 
the  fact^  that  a  larger  surface  of  the  cropped  land  in  Europe  is  improved 
by  the  assistance  of  calcareous  marls  and  sands — than  by  the  aid  of 
burned  lime  and  farm-yard  manure  put  together. 

It  is  not  easy  in  any  case  to  estimate  with  precision  what  portion  of 
the  effect  caused  by  a  given  marl  is  due  to  its  chemical  and  what  to  its 
physical  action.  Even  the  pure  limes,  when  applied  in  large  doses, 
produce  a  change  in  the  texture  of  the  soil,  which  on  stiff'  lands  is  ben- 
eficial, and  on  light  or  sandy  fields  often  injurious.  In  all  cases,  there- 
fore, the  action  of  lime  applied  in  any  form  may  be  considered  as  part- 
ly physical  and  partly  chemical — the  extent  of  the  chemical  action  in 
general  increasing  with  the  proportion  of  lime  which  the  kind  of  cal- 
careous matter  employed  is  known  to  contain. 

The  observed  effects  of  marls  and  shell  sands,  in  so  far  as  they  are 
chemical,  are  very  analogous  to  those  produced  by  lime  as  it  is  gener- 
ally applied  in  the  quick  or  slaked  state  in  so  many  parts  of  our  islands. 

They  alter  the  nature  and  quality  of  the  grasses  when  applied  to 
pasture — they  cover  even  the  undrained  bog  with  a  short  rich  grass — 
they  extirpate  heath,  and  bent,  and  useless  moss — they  exterminate 
the  weeds  which  infest  the  unlimed  corn  fields — they  increase  the 
quantity  and  enable  the  land  to  grow  a  hetter  quality  of  corn — they  ma- 
nifest a  continued  action  for  many  years  after  they  have  been  applied — 
like  the  purer  limes  they  act  more  energetically  if  aided  by  the  occa- 
sional addition  of  other  manure — and  hke  them  they  finally  exhaust* 
a  soil  from  which'the  successive  crops  are  reaped,  without  the  requisite 
return  of  decaying  animal  or  vegetable  matter. 

*  Of  shell  marl  the  same  quantity  exliausis  sooner  than  clay  marl  (Kames).  This  is 
owing  chiefly  to  the  larger  proportion  of  hme  contained  in  the  former. 


376  OF    THE    USE    OF    CHALK    AS    A    MANURE. 

But  to  these  and  other  effects  I  shall  have  occasion  to  draw  your  at- 
tention more  particularly  in  a  subsequent  part  of  the  present  lecture. 

§  7.  Of  the  use  of  chalk  as  a  manure. 

Chalk  is  another  form  of  carbonate  of  lime  which  occurs  very  abun- 
dantly in  nature,  and  which,  from  its  softness,  has  in  many  parts  of 
England  been  extensively  applied  to  the  land  in  an  unburned  state. 

The  practice  of  chalking  prevails  more  or  less  extensively  in  all 
that  part  of  England  (Lec."XI.,  §  8,)  over  which  the  chalk  formation 
extends.  It  is  usually  dug  up  from  pits  towards  the  close  of  the  au- 
tumn or  beginning  of  winter,  when  full  of  water,  and  laid  upon  the 
land  in  heaps.  During  the  winter's  frost  the  lumps  of  chalk  fall  to 
pieces,  and  are  readily  spread  over  the  fields  in  spring.  The  quantity 
laid  on  varies  with  the  quality  of  the  soil  and  of  the  chalk  itself,  and 
with  the  more  or  less  perfect  crumbling  it  undergoes  during  the  season 
of  winter,  and  with  the  purpose  it  is  intended  to  serve.  It  gives  tena- 
city and  closeness  to  gravelly  soils,*  opens  and  imparts  freeness  to  stiff 
clays,  and  adds  firmness  to  such  as  are  of  a  sandy  nature. 

If  a  physical  improvement  of  this  kind  be  required,  it  is  laid  on  at 
the  rate  of  from  400  to  1000  bushels  an  acre.  But  some  chalks  con- 
tain much  more  clay  than  others,  and  are  employed,  therefore,  in  small- 
er proportions. 

For  the  improvement  of  coarse,  sour,  marshy  pasture,  it  is  applied  at 
the  rate  of  I'SO  to  250  bushels  an  acre,  and  speedily  brings  up  a  sweet 
and  delicate  herbage.  It  is  also  said  to  root  out  sorrel  from  lands  that 
are  infested  with  this  plant. 

These  effects  are  precisely  such  as  usually  follow  from  the  applica- 
tion of  marl,  and,  like  marl,  the  repetition  of  chalk  exhausts  the  land,  if 
manure  be  not  afterwards  added  to  it  in  sufficient  quantity. 

But  tlie  chalking  of  the  Southern  Downs  and  of  the  Wolds  of  Lin- 
colnshire and  Yorkshire  would  appear  to  differ  in  some  respects  from 
ordinary  marling.  On  the  thin  soils  immediately  resting  upon  the 
chalk,  experience  has  shown  that  repeated  dressings  of  chalk  recently 
dug  up,  may  be  applied  with  much  benefit.  To  a  stranger,  also,  it  ap- 
pears singular  that  an  admixture  of  that  chalk  which  lies  immediately 
beneath  the  soil  is  not  productive  of  the  same  advantage.  Even  the 
chalk  of  an  entire  district  is,  in  some  cases,  rejected  by  the  farmer, 
and  he  will  rather  bring  another  variety  from  a  considerable  distance, 
than  incur  the  less  expense  of  laying  on  his  land  that  which  is  met 
with  on  his  own  or  on  his  neighbors'  farms.  Thus  the  Suffolk  farmers 
prefer  the  chalk  of  Kent  to  lay  on  their  lands,  and  are  at  the  cost  of 
bringing  it  across  the  estuary  of  the  Thames,  though  chalk  rocks  lie  al- 
most everywhere  around  and  beneath  them. 

The  cause  of  the  diversities  which  thus  present  themselves  in  the 
practice  of  experienced  agriculturists,  partly  at  least,  is  to  be  sought  for 
in  the  qualities  of  the  different  varieties  of  chalk  employed.  Careful 
analyses  have  not  yet  shown  in  what  respects  these  chalks  differ  in  che- 
mical constitution,  and  until  this  is  ascertained  we  must  remain  in 

*  Mr.  Gawler,  North  Hampshire,  states  that  a  gravel  thus  stiflFened,  instead  of  12  to  16 
bushels  of  wheat,  yielded  afterwards  24  to  30  bu&lieis.— British  Husbandry ,  i.,  p.  280. 


EFFECTS    OF    CHALK   ON    THE    WOLDS.  377 

some  measure  in  the  dark,  both  as  to  the  way  in  which  a  dressing  of 
chalk  acts  in  improving  a  soil  already  rich  in  chalk,  and  why  chalk 
from  one  locality  should  act  so  much  more  beneficially  than  another. 

With  one  thing,  however,  we  are  familiar,  that  the  upper  beds  of 
chalk  abound  in  flint,  and  where  they  form  the  surface  support  a  thin 
and  scanty  herbage — while  the  under  chalks  are  more  tenacious  and 
apparently  more  rich  in  clay,  and  support  generally  a  soil  which  yields 
valuable  crops  of  corn.  An  admixture  of  the  lower,  therefore,  ought  to 
improve  the  soils  of  the  upper;  and  as  the  chalks  of  Kent  consist  of 
these  lower  beds,  we  can  understand  why  the  practical  farmer  in  Suf- 
folk should  prefer  them  to  the  upper  chalks  of  his  own  neighbourhood. 
Still  we  cannot,  as  yet,  give  the  scientific  reasons  why  the  one  chalk 
should  be  better  than  the  other.  A  rigorous  chemical  analysis  can 
alone  determine  with  certainty  why  the  one  should  produce  a  differ- 
ent effect  from  the  other. 

Chalks  may  differ  in  the  proportion  of  clay  or  of  organic  matter  with 
wliich  they  are  associated — in  the  quantity  of  silica  (the  substance  of 
flints)  or  of  silicates  they  contain, — in  the  amount  of  magnesia  or  of 
phosphate  of  lime  which  can  be  detected  in  them — or  of  saline  matter 
wliich  a  careful  examination  will  discover, — and  they  may  even  differ 
ph3^sically  in  the  fineness  of  the  ultimate  particles  of  which  the  sub- 
stance of  the  chalk  is  composed.*  All  such  differences  may  modify 
the  action  of  the  several  varieties  in  such  a  way  as,  when  accurately 
investigated,  to  enable  us  to  account  for  the  remarkable  preference 
manifested  by  practical  men  for  the  one  over  the  other.  Until  such 
an  investigation  has  been  carefully  made,  it  is  unfair  hastily  to  class 
among  local  prejudices  what  may  prove  to  be  the  results  of  long  prac- 
tical experience. 

On  the  chalk  Wolds  of  Lincolnshire  and  Yorkshire  the  practice  of 
chalking  even  the  thin  soils  is  now  comparatively  old  in  date.  The 
lowest  chalks  are  there  also  much  preferred, — they  are  laid  on  at  the 
rate  of  60  to  80  cubic  yards  per  acre,  and  they  cause  a  great  improve- 
ment, especially  upon  the  deep  lands,  as  they  are  called,  where  the 
soil  is  deepest.  Corn  does  not  yield  so  well,  nor  ripen  so  early,  on 
these  deep  soils,  as  where  a  thinner  covering  rests  upon  the  chalk.  It 
is  naturally  also  unfit  for  barley  or  turnips,  the  latter  plant  being  espe- 
cially infested  with  the  disease  called  fingers  and  toes  [British  Hus- 
bandry, iii.,  p.  124  ]  (Strickland).  But  a  heavy  chalking  removes  all 
the  above  defects  of  these  deep  soils,  and  for  a  long  period  of  lime. 
The  corn  ripens  sooner,  is  larger  in  quantity,  and  better  in  quality, 
and  the  turnips  grow  perfectly  free  from  disease. 

These,  however,  are  to  be  regarded  as  only  the  usual  effects  of  a  large 
addition  of  lime  to  a  soil  in  which  previously  little  existed.  It  is  a 
fact  which  will  naturally  strike  you  as  remarkable,  that  soils  which  rest 
upon  chalk,  as  well  as  upon  other  lime-stone  rocks,  even  at  the  depth 
of  a  few  inches  only,  are  often,  and  especially  when  in  a  state  of  nature, 
so  destitute  of  lime  that  not  a  particle  can  be  detected  in  them^.  That 
lime  in  any  form  should  benefit  such  soils  is  consistent  with  uniform 

•  Ehrenberg  has  discovered  that  chalk  is  in  a  great  measure  composed  of  the  skeletoM^ 
stiells,  or  other  exuvial  (spoils)  of  marine  microscopic  animals. 


378  LIME    ALWAYS    PRESENT    IN    FERTILE    SOILS. 

experience.  I  shall  presently  have  an  opportunity  of  directing  your 
attention  to  the  two  concurring  causes  by  the  joint  operation  of  which 
lime  is  sooner  or  later  wholly  removed  from  the  soil,  even  where,  as  in 
the  Wolds,  it  rests  immediately  upon  the  cJjalk. 

§  8.  /^  lime  indispensable  to  the  fertility  of  the  soil  1 

It  is  the  result  of  universal  experience  wherever  agriculture  has  been 
advanced  to  the  state  of  an  art,  that  the  presence  of  lime  is  useful  to 
the  soil. 

Not  only  is  this  fact  deduced  from  the  result  of  innumerable  applica- 
tions of  this  substance  (o  lands  of  every  quality,  but  it  is  established 
also  by  a  consideration  of  the  known  chemical  constitution  of  soils 
which  are  naturally  possessed  of  unlike  degrees  of  fertility. 

Thus  sandy  or  siliceous  soils  are  more  or  less  barren  if  lime  be  ab- 
sent— while  the  addition  of  this  substance  in  (he  form  of  marl  or  other- 
wise renders  them  susceptible  of  cultivation.  So  clay  soils,  in  which 
no  lime  can  be  detected,  are  often  at  once  changed  in  character  by  a 
sufficient  liming.  Felspar  soils  contain  no  lime,  and  they  are  barren— 
and  the  same  is  true  of  such  as  are  derived  immediately  from  the  de- 
gradation of  the  serpentine  rocks. 

Trap  soils,  on  the  other  hand — such  as  are  derived  from  decayed 
basalts  or  green-stones — are  poor  in  proportion  as  felspar  abounds  in 
them.  Where  augites  and  zeolites  are  present  in  large  proportion  in 
the  trap  from  which  they  are  formed,  the  soils  are  rich,  and  may  even 
be  used  as  marl.  The  only  difference  in  this  latter  case  is,  that  lime  is 
not  deficient  (Lee.  XIT.,  §  4), — and  to  this  difference  the  greater  fertility 
iviay  fairly  be  ascribed. 

But  let  it  be  conceded  that  lime  is  useful  to  or  benefits  the  soil  in 
whicli  it  exists,  you  may  still  ask — is  lime  indispensable  to  the  soil  ? — 
is  it  impossible  for  even  an  average  fertility  to  be  manifested  where 
lime  is  entirely  absent  ? 

There  are  two  different  considerations,  from  each  of  which  we  may 
deduce  a  more  or  less  satisfactory  answer  to  this  question. 

1°.  The  resHlt  of  all  the  analyses  hitherto  made  of  soils  naturally 
fertile  show  that  lime  is  universally  present.  The  per-centage  of  lime 
in  a  soil  may  be  very  small,  yet  it  can  always  be  detected  when  valua- 
ble and  healthy  crops  will  grow  upon  it.     Thus  the  fertile  soil  of  the 

Marsh  lands  in  Hoistein  contains  0-2  per  cent,  of  carbonate  of  lime. 

Salt  marsh  in  East  Friesland         0*6  "  *' 

Rich  pasture  near  Durham     .       1*31  "  " 

But  though  the  per  centage  of  lime  in  these  cases  appears  small,  the 
absolute  quantity  of  lime  present  in  the  land  is  still  large.  Thus  sup- 
pose the  first  of  these  soils,  which  contains  the  least,  to  be  only  six 
inches  in  depth,  and  each  cubic  foot  to  weigh  only  80  lbs. — it  would 
contain  about  3500  lbs.  of  carbonate  of  lime,  upwards  of  a  ton  and  a 
half,  in  every  acre.  And  this  lime  would  be  intimately  mixed  with  the 
whole  soil,  in  which  state  it  is  always  mosr effective  in  its  operation.  S' 
may  also  be  inferred  with  safety,  that  if  the  upper  six  inches  containei 
this  proportion  of  lime,  the  under  soil  would  probably  be  richer  still, 
since  lime  tends  not  so  much  to  diffuse  itself  through,  as  to  sink  down- 
wards into  the  soil. 


STATE    IN    WHICH    LIME    EXISTS    IN    THE    SOIL.  379 

2°.  The  results  of  all  the  chemical  examinations  hitherto  made  in 
regard  to  the  nature  of  the  inorganic  matter  contained  in  the  sap  and 
substance  of  plants  indicate, — if  not  the  absolute  necessity  of  lime  to  the 
growth  of  plants, — at  least  that  in  nature  all  cultivated  plants  do  ab- 
sorb it  by  their  roots  from  tlie  soil,  and  make  use  of  it  in  some  way  in 
aid  of  their  growth.  In  so  far  as  our  practice  is  concerned,  this  is  very 
much  the  same  as  if  we  could  prove  lime  to  be  absolutely  indispensable. 

The  ash  of  the  leaf  and  bulb  of  the  turnip  or  potatoe,  of  the  grain 
and  straw  of  our  corn-bearing  plants,  and  of  the  stems  and  seeds  of  our 
grasses,  all  contain  lime  whenever  and  wherever  they  are  grown.  And 
most  of  them  attain  high  health  and  luxuriance  only  where  lime  is 
easily  attained. 

Grant,  then,  that  lime  appears  to  be,  perhaps  virtually  is,  a  necessary 
food  of  plants,  without  which  their  natural  health  cannot  be  maintained, 
nor  functions  discharged, — still  the  quantity  which  must  be  present  in 
the  soil  to  supply  this  food  is  not  necessarily  large.  Even  in  favor- 
able circumstances  we  have  seen  (Lee.  X.,  §  3,)  that  the  average  crops 
during  an  entire  rotation  of  four  years  may  not  carry  off  more  than  250 
lbs.  of  lime  from  the  acre  of  land,  a  quantity  which  even  the  marsh 
soils  of  Holstein  would  be  able  to  supply  for  half  a  century,  could  the 
roots  readily  make  their  way  into  every  part  of  the  soil. 

Still  we  may  safely  hold,  I  think,  that  this  quantity  of  lime  at  least 
is  indispensable — if  cultivated  plants  are  to  flourish  and  ripen.  So 
much,  at  least,  must  in  practice  be  every  year  added  to  cultivated  land 
in  one  form  or  another,  where  the  crops  are  in  whole  or  in  part  carried 
off  the  land.  Where  it  is  not  added  either  artificially  or  by  some  natu- 
ral process,  infertility  must  gradually  ensue.  We  shall  presently  see 
that  lime  has  other  functions  to  perform  in  the  soil,  and  that  there  are 
natural  causes  in  constant  operation  in  our  climate  which  render  a 
larger  addition  than  this  desirable  at  least,  if  not  indispensable  to  con- 
tinued fertility. 

§  9.  State  of  comhination  in  which  lime  exists  in  the  soil. 

This  lime,  which  we  have  concluded  to  be  an  indispensable  constitu- 
ent of  fertile  soils,  may  be  present  in  several  distinct  states  of  combi- 
nation. 

1°.  In  that  of  chloride  of  calcium. — This  compound,  as  we  have  al- 
ready seen  (Lee.  IX.,  §  4,)  is  very  soluble  in  water,  and  is  not  unfre- 
quently  to  be  detected  in  the  sap,  especially  of  the  roots  of  plants.  Its 
solubility,  however,  exposes  it  to  be  readily  washed  out  of  the  soil  by 
the  rains,  and  perhaps  for  this  reason  it  is  not  one  of  those  forms  of  com- 
bination in  which  lime  is  recognised  as  a  uniform  or  necessary  consti- 
tuent of  the  soil.  Its  presence  may  be  detected  by  boiling  half  a  pound 
of  the  soil  in  distilled  water,  filtering  and  evaporating  the  solution  to 
dryness.  If  the  dry  mass  become  moist  on  exposure  to  the  air,  and  if, 
after  being  dissolved  in  water,  it  give  a  white  precipitate  with  oxalate 
of  ammonia,  and  after  being  rendered  sour  by  a  few  drops  of  nitric  acid, 
a  white  precipitate  again  with  nitrate  of  silver,  it  may  be  inferred  to 
con-tain  chloride  of  calcium. 

2°.  In  that  of  sulphate  of  lime  or  gypsum. — In  this  state  also  it  is  not 
a  constant,  and  in  a  few  cases  only  an  abundant,  constituent  of  the  soil. 


380  liLMATK  OF  LIMK  I.N   TlIK  SOIL,. 

Its  presence  may  be  detected  by  the  deposition  of  minute  crystals  on  the 
sides  of  the  vessel  during  the  evaporation  of  the  solution  obtained  by 
boiling  the  soil  in  distilled  water.  Or,  its  presence  may  be  inferred  if, 
after  observing  that  oxalate  of  ammonia  causes  a  precipitate  in  one 
small  portion  of  the  solution,  it  be  found  that  nitrate  of  baryta  also 
throws  down  a  white  precipitate  from  another  small  portion. 

3°.  In  the  state  o/ phosphate. — This  compound  is  probably  present, 
though  always  in  small  })roportion,  in  every  soil  which  is  capable  of 
raising  a  nutritious  vegetation.  It  may  be  readily  detected  by  treating 
500  grains  of  the  dry  soil  for  12  hours  with  dilute  muriatic  acid,  and  oc- 
casionally stirring.  If  to  the  filtered  solution  caustic  ammonia  be  add- 
ed, a  brownish  precipitate  will  usually  fall.  If  this  precipitate  be  se- 
parated, and  treated  with  acetic  acid  (vinegar),  it  will  all  dissolve  if  no 
phosphoric  acid  be  present.  If  this  experiment  be  carefully  performed, 
and  a  residue  remain  undissolved,  the  presence  of  phosphoric  acid  in 
the  solution,  and  of  phosphate  of  lime  in  the  soil,  may  be  safely  inferred. 

4°.  In  the  state  of  silicate,  lime  rarely  exists  in  the  soil  in  any  con- 
siderable quantity.  It  is  chiefly  in  such  as  are  derived  from  the  decay 
of  the  trap  rocks  or  of  some  varieties  of  granite  (sienite),  that  silicate 
of  lime  is  to  be  expected  to  occur. 

If,  after  being  treated  with  dilute  sulphuric  acid,  as  above  described, 
the  soil  be  digested  for  some  hours  at  a  gentle  heat  with  concentrated 
muriatic  acid — a  solution  will  be  obtained  from  which  ammonia  will 
again  throw  down  a  brown  precipitate.  If  oxalate  of  ammonia  now 
cause  a  white  precipitate  of  oxalate  of  lime,  and  if,  on  evaporating  to 
dryness,  the  solution  leave  a  portion  of  silica  insoluble  in  acids,  we  may 
infer  that  the  soil  most  probably  contains  some  lime  in  the  state  of  sili- 
cate. 

5°.  In  the  state  of  carbonate,  lime  is  generally  supposed  most  usually 
to  exist,  and  most  abundantly  in  all  soils.  If  on  pouring  dilute  muri- 
atic acid  upon  a  soil,  a  visible  effervescence  or  escape  of  minute  bubbles 
of  gas  manifest  itself,  or  if,  when  the  experiment  is  made  in  a  tube 
closed  at  one  end,  and  inverted  over  water  or  mercury,  bubbles  of  gas 
collect  in  the  upper  end  of  the  tube — the  soil  contains  some  carbonate. 
If  after  ammonia  has  been  added  to  the  solution,  oxalate  of  ammonia 
throws  down  a  white  precipitate  of  oxalate  of  lime — the  soil  contains 
carbonate  of  lime. 

6°.  In  the  state  ofhumate. — In  combination  with  humic  acid  (Lee. 
XIII.,  §  1,)  lime  exists  most  frequently  in  soils  which  abound  in  vege- 
table matter — in  peaty  soils,  for  example,  to  which  quick-lirne  or  marl 
of  any  kind  has  been  added  for  the  purpose  of  agricultural  improve- 
ment. The  presence  of  lime  in  the  state  of  humate  is  only  to  be  detect- 
ed by  carefully  determining  the  relative  weights  of  the  carbonic  acid 
given  off' during  the  action  of  dilute  muriatic  acid  upon  the  soil,  and  of 
the  lime  contained  in  the  solution  thus  obtained,  (see  Appendix.)  If  for 
every  100  grains  of  carbonic  acid  there  be  more  than  77-24  grains  of 
Xxme,  the  remainder  or  excess  has  existed  in  the  soil  in  combination  with 
humic  or  some  analogous  organic  acid.* 

*  To  such  analogous  acids  belong  the  crenic  and  apocrenic  acids  (Lee.  Xlll.,  §  1.)  The 
existence  of  these  acids  in  the  soil  is  by  no  means  problematical.  According  to  Professor 
Hermann,  of  Moscow,  they  exist  in  the  rich  black  sof.  'Tchornoi  Zem.)  of  Little  Russia, 
to  the  amount  of  4  per  cent. 


QUANTITY   OF  LIME  TO  BE    APPLIED  TO  THE  SOIL.  381 

Few  investigations  have  as  yet  been  made  in  regard  to  the  proportion 
of  lime  which  exists  in  the  soil  in  the  state  of  humate.  It  has  gene- 
rally been  taken  for  granted — either  that  a  soil  was  destitnte  of  lime  if 
it  exhibited  no  sensihle  effervescence  with  dilute  muriatic  acid.-^or 
when  further  research  was  made,  and  the  quantity  of  hme  taken  up  by 
this  acid  rigorously  determined,  that  the  whole  of  this  lime  must  have 
existed  in  the  soil  in  the  stale  of  carbonate.  That  this  is  not  necessarily 
the  case,  however,  appears  to  be  proved  by  some  recent  examinations 
of  certain  soils  in  Normandy,  which  contain  as  much  as  14  to  15  per 
cent,  of  lime,  and  yet  exhibit  no  effervescence,  and  contain  no  carbo- 
nate.    The  whole  of  the  lime  is  said  to  be  in  the  state  of  humate. 

M.  Dubuc,  who  has  published  the  analyses  of  these  soils,  attributes 
much  of  their  fertility  to  the  presence  of  the  humate  of  lime.  Thus  he 
says  that  the  soils  of 

Containing  per  cent. 
Of  Carbonate.     Of  Humate.  Yields  of  Wheat. 

Lieuvin,  Neubourg,  and  Sistot,      0  18  to  20  12  to  15  fold. 

Pavilli 0  5  8  to  10    " 

Bieville 24  0  8  to  10    " 

ClayofOuche 0  1  4  to    5    *' 

The  first  two  yielding  a  wheat  crop  every  second  year,  the  third  only  at 
longer  intervals. 

Whatever  degree  of  influence  on  the  fertility  of  the  soil  it  may  ap- 
pear proper  to  attribute  to  the  existence  of  lime  in  the  soil  in  the  state 
of  humate,  it  is  manifestly  of  some  importance  that  its  presence  in  this 
state  of  combination  should  be  more  frequently  and  more  carefully 
sought  after. 

The  only  one  of  the  above  compounds  which  is  usually  added  to  the 
land,  for  the  purpose  of  producing  the  ordinary  effects  of  lime,  is  the 
carbonate.  Gypsum  is  applied  only  in  small  quantity  for  certain  spe- 
cial purposes,  and  does  not  always  produce  a  sensible  effect.  It  is  in- 
capable, therefore,  of  performing  those  jjurposes  in  the  soil  which  are 
served  either  by  quick-lime  or  by  the  carbonate.  The  humate  of  lime 
is  probably  formed  in  our  lime  composts,  especially  when  much  vege- 
table matter  is  contained  in  them,  and  may  thus  be  not  unfrequentlv 
applied  directly  to  the  land. 

^  10.  Of  the  quantity  of  lime  which  ought  to  he  added  to  the  soil. 

The  quantity  of  lime  which  ought  to  be  added  to  the  soil  is  dependent 
upon  so  many  circumstances,  that  it  is  impossible  to  state  any  general 
rule  by  which,  in  all  cases,  the  practical  man  can  safely  regulate  his 
procedure. 

1°.  To  soils  which  contain  no  lime,  or  to  which  it  is  added  for  the 
first  time,  a  larger  dose  must  be  given. 

We  have  seen  that  a  certain  minim.um  portion  of  lime  is  indispensa- 
ble to  a  productive  soil.  If  we  suppose  this  smallest  quantity  to  be  no 
greater  than  in  the  surface  of  the  marsh  lands  of  Holstein  (p.  378) — 
then  with  a  soil  six  inches  in  depth,  which  contains  no  lime,  we  ought 
to  mix  a  ton  and  a  half,  say  40  bushels  of  slaked  lime,  and  by  succes- 
sive yearly  additions  to  supply  the  annual  waste. 

But  to  mix  this  feeble  dose  of  lime  intimately  with  the  soil  to  a  depth 
of  six  inches  would  obviously  require  an  expenditure  of  labor  which 


382      MORE  OUGHT  TO  BE  LAID  ON  CLAY,  WET,  AND  MARSHY  SOILS, 

the  practical  farmer  could  rarely  afford.  It  would  be  greater  economy, 
therefore,  in  most  cases  to  add  a  dose  several  times  larger,  and  this  not 
only  because  the  same  amount  of  labor  would  diffuse  it  more  general- 
ly through  the  whole  soil,  but  because  this  larger  liming  would  render 
less  necessary  the  immediate  addition  of  new  supplies  to  repair  the  un- 
avoidable waste. 

But  there  is  reason  to  believe  that  the  proportion  of  lime  which  the 
soil  ought  to  contain,  if  it  is  to  be  successfully  subjected  to  arable  cul- 
ture, ought  to  be  much  larger  than  is  above  assumed  as  the  smallest 
or  minimum  quantity.  If  we  suppose  one  per  cent,  to  be  necessary, 
then  eight  tons  of  lime-shells,  or  upwards  of  300  bushels  of  slaked  lime, 
must  be  mixed  with  a  soil  six  inches  in  depth,  to  impart  to  it  this  pro- 
portion— or  half  the  quantity,  if  it  be  kept  within  three  inches  of  the  sur- 
face. Even  a  very  large  dose  of  lime,  therefore,  does  not,  if  it  be  well 
mixed,  materially  alter  the  constitution  of  the  soil. 

2°.  But  experience  has  proved  that  the  quantity  of  lime  which  a 
skilful  farmer  will  add  to  his  land  will  vary  with  many  other  circum- 
stances besides  the  depth  of  his  soil,  and  the  proportion  of  lime  it  al- 
ready contains.     Thus — 

a.  On  clay  lands  more  lime  is  necessary  than  on  light  and  sandy 
soils.  This  may  be  partly  ascribed  to  the  physical  effect  of  the  lime 
in  opening  and  loosening  the  stiff"  clay — but  independent  of  this  action 
the  particles  of  lime  are  liable  to  be  coated  over  and  enveloped  by  the 
fine  clay,  and  thus  shut  out  from  the  access  of  the  air.  These  parti- 
cles, therefore,  must  be  more  numerous  in  such  a  soil,  if  as  many  of 
them  are  to  be  exposed  to  the  air  as  in  lighter  land,  through  which  the 
atmospheric  air  continually  permeates. 

b.  On  wet  and  marshy  soils,  a  larger  application  still  may  be  made 
whh  safety,  and  partly  for  the  same  reason. 

The  moisture  surrounding  the  lime  shuts  out  the  air,  without  the 
ready  access  of  which  lime  cannot  perform  its  important  functions.  The 
same  moisture  tends  to  carry  down  the  lime  and  lodge  it  more  speedily 
in  the  subsoil.  The  continued  evaporation  also  keeps  such  soils  too 
cold  (Lee.  II.,  §  7),  to  allow  the  chemical  changes,  which  lime  in  fa- 
vorable circumstances  produces,  to  proceed  with  the  requisite  degree 
of  rapidity.  The  soluble  compounds  which  are  formed  as  the  conse- 
quence of  these  changes  are,  in  wet  and  marshy  soils,  dissolved  by  the 
moisture,  and  so  diluted  as  to  enter  in  smaller  quantity  into  the  roots  of 
plants.  And  lastly,  in  certain  cases,  new  compounds  of  the  lime  with 
the  earthy  and  stony  matters  of  the  soil  are  formed,  which  may  either 
harden  into  visible  lumps  of  mortar  and  cement,  or  into  smaller  parti- 
cles of  indurated  matter,  in  which  the  lime  is  no  longer  in  such  a  state 
as  to  be  able  to  act  in  an  equal  degree  as  an  improver  of  the  soil. 

In  cold  and  wet  clays,  in  which  all  these  evil  conditions  occasionally 
meet,  it  is  not  surprising,  therefore,  that  large  doses  of  lime  should 
sometimes  have  been  added  without  producing  any  sensible  benefit 
whatever.  ("  An  instance  is  mentioned  in  the  Nottingham  Report  of 
720  bushels  having  been  laid  on  an  acre  of  clod  clay  land  without  any 
benefit  whatever." — British  Husbandry,  i.,  p.  296.) 

c.  Again,  when  the  soil  is  also  rich  in  vegetable  matter,  lime  may 
be  still  more  abundantly  applied.     Thus,  when  a  field  is  at  once  wet 


AND  SUCH  AS  ARE  RICH  IN  VEGETABLE  MATTER.  383 

or  marshy,  and  full  of  vegetable  matter,  as  our  peat  bogs  are,  lime  may- 
be laid  on  more  unsparingly  than  under  any  other  circumstances. 
For  in  this  case,  besides  the  action  of  the  access  of  water,  as  above  ex- 
plained, the  vegetable  matter  combines  with  and  masks  the  ordinary 
action  of  a  considerable  quantiiy  of  the  lime.  By  this  combination,  no 
part  of  the  ultimate  influence  of  the  whole  lime  upon  the  soil  is  neces- 
sarily lost ;  in  most  cases  the  immediate  effect  only  is  lessened,  which 
the  same  quantity  applied  to  odier  soils  would  have  been  seen  to  pro- 
duce. In  favorable  circumstances  its  action  is  retarded  and  prolonged, 
the  compounds  it  forms  with  vegetable  matter  decomposing  slowly,  and, 
therefore,  remaining  long  in  the  soil. 

To  the  exact  chemical  constitution  of  the  compounds  thus  formed, 
as  soon  as  lime  is  mixed  up  with  a  soil  rich  in  vegetable  matter,  and  to 
the  chemical  changes  which  these  compounds  gradually  undergo,  it  will 
be  necessary  to  direct  our  attention  when  we  come  to  study  the  theory 
of  the  action  of  lime,  as  an  improverof  the  soil. 

d.  Not  only  the  natural  depth  of  the  soil,  as  already  stated,  but  also 
the  depth  to  which  it  is  usually  ploughed,  and  to  which  it  is  customary 
to  bury  the  lime,  will  materially  affect  the  quantity  which  can  be  safely 
applied.  A  dose  of  lime  which  would  materally  injure  a  soil  into 
which  the  plough  rarely  descends  beyond  two  or  three  inches,  might  be 
too  small  an  application  where  six  or  eight  inches  are  usually  turned 
over  by  the  plough.  When  new  soil,  also,  is  to  be  brought  up,  which 
may  be  supposed  to  contain  no  lime,  or  in  which  noxious  substances  are 
present,  a  heavier  dose  of  lime  must  necessarily  be  laid  upon  the  land. 

3°.  Such  are  the  circumstances  in  which  large  applications  of  lime 
may  be  usefully  applied  to  the  land.  In  soils  of  an  opposite  character, 
not  only  will  smaller  quantities  of  lime  produce  an  equally  beneficial 
effect,  but  serious  injury  would  often  be  inflicted  by  spreading  it  too  lav- 
ishly upon  your  fields. 

The  more  dry  and  shallow^  the  soil,  the  more  light  and  sandy,  the 
less  abundant  in  vegetable  matter,  the  more  naturally  mild  its  locality, 
and  the  drier  and  warmer  the  climate  in  which  it  is  situated — the  less 
the  quantity  of  lime  which  the  prudent  farmer  will  venture  to  mix  with 
it.  It  is  to  the  neglect  of  these  natural  indications  that  the  exhaustion 
and  barrenness  that  have  occasionally  followed  the  application  of  lime 
are  to  be  ascribed.  It  is  only  in  rare  cases,  such  as  the  presence  of 
much  noxious  mineral  matter  in  the  soil,  that  these  indications  can  be 
safely  neglected. 

§  11.  Ought  lime  to  he  applied  in  large  doses  at  distant  intervals^  or  in 
smaller  quantities  more  frequently  repeated  1 

The  quantity  of  lime  which  ought  to  be  applied  to  the  land  must,  as 
we  have  seen,  vary  with  its  quality,  and  with  the  conditions  in  which  it 
is  placed.  Hence  the  practice  in  this  respect  necessarily  varies  in  every 
county  and  in  almost  every  district. 

But  a  difference  of  opinion  also  prevails  among  practical  men,  as  to 
whether  that  quantity  of  lime  which  land  of  a  given  kind  may  require 
ought  to  be  applied  in  large  doses  at  long  intervals,  or  in  smallquantities 
frequently  repeated.  The  indications  of  theory  in  reference  to  this  point 
are  clear  and  simple. 


384         OUGHT  LIME  TO  BE  APPLIED  IN  LARGE  OR  SMALL  DOSES. 

A  certain  proportion  of  lime  is  indispensable  in  our  climate  to  the 
production  of  the  greatest  possible  fertility.  Let  us  suppose  a  soil  to  be 
wholly  destitute  of  lime — the  first  step  of  the  improver  would  be  to  add 
to  this  indispensable  proportion.  This  would  necessarily  be  a  large 
quantity,  and,  therefore,  to  land  limed  for  the  first  time  theory  indicates 
the  inopriety  of  adding  a  large  dose. 

Every  year,  however,  a  certain  variable  proportion  of  the  lime  is  re- 
moved from  the  soil  by  natural  causes.  The  effect  of  this  removal  in  a 
few  years  becomes  sensibly  apparent  in  the  diminished  productiveness 
of  the  land.  After  the  lapse  of  five  or  six  years,  during  which  it  has 
been  gradually  mixing  with  the  soil,  the  beneficial  effects  of  the  lime  is 
generally  the  most  striking — after  this  they  gradually  lessen,  till  at  the 
end  of  a  longer  or  shorter  period,  the  land  reverts  to  its  original  condition. 
To  keejy  land  in  its  best  possible  state,  therefore,  the  natural  ivaMe  ought 
from  time  to  time  to  be  sujyplied  by  the  addition  of  smaller  doses  of  lime 
at  shorter  intervals. 

Such  is  obviously  the  most  natural  course  of  procedure,  and  he  who 
farms,  his  ovi^n  estate,  and  has  therefore  no  strong  inducement  to  do  oth- 
erwise, will,  on  the  first  breaking  up  of  new  land,  give  it  a  heavy 
liming,  and  whether  he  afterwards  retain  it  in  arable  culture  or  lay  it 
down  to  grass,  will  at  intervals  of  4  to  6  years  give  it  a  new  doseof  one- 
fourth  to  one-eighth  of  the  original  quantity.  But  local  circumstances 
and  customs  interfere  in  many  well-farmed  districts  with  this  most  na- 
tural treatment  of  the  soil.  In  the  county  of  Roxburgh,  for  example, 
on  entering  upon  his  farm,  which  holds  on  a  lease  of  19  or  21  years,  the 
tenant  begins  by  liming  that  portion  of  his  land  which  is  in  fallow,  or. 
in  preparation  for  turnips,  at  the  rate  of  240  to  300  bushels  of  quick-lime 
per  acre.  A  similar  liming  is  given  to  the  other  portions  as  they  come 
into  fallow,  so  that  at  the  end  of  his  first  rotation  (4  or  5  years)  the  whole 
of  his  land  has  been  limed  at  the  same  rate.  He  now  continues  crop- 
ping for  three  or  four  rotations  (14  to  16  years),  when  if  he  is  sure  of  re- 
maining on  his  farm  he  begins  to  lime  again  with  the  same  quantity  as 
before.  If  he  is  to  quit,  however,  he  takes  the  best  crops  he  can  get, 
but  incurs  no  further  outlay  in  the  addition  of  lime.  His  successor  fol- 
lows the  same  course — begins  by  expending  perhaps  dElOOO  in  lime, 
and  before  he  leaves  at  the  end  of  his  lease,  has,  by  continued  cropping, 
brought  back  his  land  nearly  to  the  same  state  in  which  he  found  it. 

In  the  district  of  Kyle  and  other  parts  of  Ayrshire,  again,  lime  is  laid 
on — often  when  preparing  for  the  wheat  crop,  either  by  ploughing  in  the 
second  furrow,  or  by  harrowing  in  with  the  seed — at  the  rate  of  40  bush- 
els of  shells  an  acre,  and  this  dose  is  of  course  repeated  every  4  or  6  years, 
according  to  the  length  of  the  rotation.  If  we  consider  the  probable  dif- 
ference in  the  soil  and  climate,  the  proportion  of  lime  added  in  the  two 
districts  does  not  materiallydiffer.  In  Ayrshire  from  8  to  10  bushels,  and 
in  Roxburgh  from  10  to  12  bushels,  are  added  for  each  year.*  In  both 
counties,  however,  many  farms  may  be  met  with  in  which  the  treatment 
of  the  land  in  this  respect  differs  from  that  which  is  generally  followed. 

*  According  to  General  Beatson  {New  System  of  Cultivation,  1820),  upwards  100 bushels 
an  acre,  at  a  cost  of  jE7.  16s.,  used  to  be  applied  to  the  clay  Jandsof  Sussex— on  the  fallow, 
before  wheat— every  foui  years.  This  was  25  bushels  per  acre  for  each  year.  In  such 
lands  as  these  the  saving  in  the  article  of  lime  alone,  which  would  follow  a  judicious  drain* 
age,  would  be  very  great. 


COMPARATIVE  ECONOMY    OF    THE    TWO  METHODS.  385 

In  Flanders  a  similar  difference  in  the  practice  prevails  in  different 
districts.  In  Some  the  land  is  limed  only  once  in  12  years,  in  others 
every  third,  fourth,  or  sixth  year,  according  to  the  length  of  the  rotation. 
In  the  former  case  from  40  to  50  bushels  are  applied  per  acre,  in  the  lat- 
ter from  10  to  12  bushels  every  third  year.  In  both  modes  of  proceduo 
the  quantity  of  lime  applied  by  the  year  is  nearly  the  same — between 
3i  and  4  bushels  per  acre.  These  quantities  are  very  much  less  than 
those  employed  in  our  island,  but  the  soils  are  also  greatly  lighter,  and 
the  climate,  as  well  as  the  general  treatment  of  the  land,  very  different. 

We  may  consider  it,  therefore,  as  a  principle  recognized  or  involved 
in  the  agricultural  practice  both  of  our  own  and  of  foreign  countries, 
that  nearly  the  same  annual  addition  of  lime  ought  to  be  made  to  the 
land,  whether  it  be  applied  at  long  intervals  or  at  the  recurrence  of  each 
rotation.  There  is,  therefore,  on  the  whole,  no  saving  in  the  cost  of  lime, 
whichever  method  you  adopt.  A  slight  consideration  of  the  subject, 
however,  may  satisfy  us  that  there  is  a  real  difference  in  the  compara- 
tive economy  or  profit  of  the  two  methods. 

Let  us  suppose  two  acres  of  the  same  clay  land  to  be  limed  respec- 
tively with  200  bushels  each,  and  that  the  one  is  cropped  for  twenty 
years  afterwards  without  further  liming,  while  the  other  at  the  end  of 
every  five  years  is  dressed  with  an  additional  dose  of  40  to  50  bushels. 
In  both  cases  the  land  would  have  attained  the  most  productive  con- 
dition in  five  or  six  years.  Let  us  suppose  that  in  this  condition  it  pro- 
duced annually  a  crop  of  (or  equivalent  in  nutritive  value  to)  30  bushels 
of  wheat,  and  that  on  neither  acre  did  a  sensible  diminution  appear  be- 
fore the  end  often  years.  Then  during  the  second  ten  the  crops  would 
gradually  lessen  in  the  one  acre,  while,  in  consequence  of  the  re- 
addition  of  the  lime  as  it  disappears,  the  amount  of  produce  would  re- 
main sensibly  the  same  in  the  other  acre.  Suppose  the  produce  of 
the  former  gradually  to  diminish  from  30  to  20  bushels  during  these  ten 
years, — or  that  while  the  one  has  continued  to  yield  30  bushels  during 
the  whole  perio'd,  the  other  has,  on  an  average,  yielded  only  25  bushels 
during  the  latter  ten  years.  If  now  the  second  large  dose  of  200  bushels 
be  added  to  thi.s  latter  acre,  the  cost  of  liming  both  will  have  become 
sensibly  the  same,  but  the  amount  of  produce  or  of  profit  from  the  two 
acres  during  the  second  ten  years  will  stand  thus — 

10  crops,  of  30  bushels  each,   amount  to     300  bushels. 
10  crops,  of  25  bushels  each,   amount  to     250  bushels. 

Difference  in  favour  of  frequent  liming,       50  bushels  per  acre, 
or  nearly  two  whole  crops  every  lease  of  twenty  years. 

Thus  it  appears 

1".  That,  according  to  the  practice  of  different  countries,  the  quantity 
of  lime  which  ought  to  be  added,  and  consequently  the  cost  of  adding  it, 
is  very  nearly  the  same,  whether  it  be  applied  in  larger  doses  at  longer 
intervals,  or  in  smaller  doses  more  frequently  repeated. 

2^.  That,  after  the  first  heavy  liming,  the  frequent  application  of  small 
doses  is  the  more  natural  method — a-nd 

3°.  That  it  is  also  the  most  economical  or  profitable  method. 

It  is  possible  that  other  considerations,  such  as  the  tenure  by  which 
your  land  is  held,  may  appear  sufl&cient  to  induce  you  to  depart  from 


386  MANURE    MUST    BE   ADDED    WHERE    LIME    ABOUNDS. 

this  metliod  ;  but  there  seems  every  reason  to  believe  that  it  vi^ill  best 
reward  those  who  feel  themselves  at  liberty  to  follow  tbff  indications  at 
once  of  sound  theory  and  of  enlightened  practice. 

One  thing,  however,  must  be  borne  in  mind  by  those  who,  in  adopt- 
ing the  best  system  of  liming,  do  not  wish  both  to  injure  their  land  and 
to  meet  with  ultimate  disappointment.  Organic  matter — in  the  form  of 
farm-yard  manure,  of  bone  or  rape  dust,  of  green  crops  ploughed  in,  or 
of  peat,  and  oth'er  composts — must  be  abundantly  and  systematically 
added,  if  at  the  end  of  20  or  40  years  the  land  in  which  the  full  supply 
of  lime  is  kept  up  is  to  retain  its  original  fertility.  High  farming  is  the 
most  profitable — for  the  soil  is  ever  grateful  for  skilful  treatment — but 
he  who  farms  high  in  the  sense  of  keeping  up  the  supply  of  lime,  must 
eAso  farm  high  in  the  sense  of  keeping  up  the  supply  of  organic  and 
other  manures  in  the  soil — otherwise  present  fertility  and  gain  will  be 
followed  by  future  barrenness  and  loss.  If  this  is  not  to  be  done,  it 
were  better  to  add  lime  at  long  intervals,  since  as  the  quantity  of  lime 
diminishes,  the  land  begins  to  enjoy  a  little  respite,  and  has  had  time  in 
some  measure  to  recover  itself — the  cropping  in  both  instances  being  the 
same — before  the  new  dose  is  laid  upon  its  surface.* 

§  12.  Form  and  state  of  combination  in  which  lime  ought  to  be 
applied  to  the  land. 

The  form  and  state  of  combination  in  which  lime  ought  to  be  applied 
to  the  land  depend  upon  the  nature  of  the  soil,  on  the  kind  of  cropping 
to  which  it  is  subjected,  and  on  the  special  purpose  which  the  lime  is 
intended  to  effect.  The  soil  may  be  heavy  or  light,  in  arable  culture, 
or  laid  down  to  grass,  and  each  of  these  conditions  indicates  a  different 
mode  of  procedure  in  the  application  of  lime.  So  the  lime  itself  may 
be  intended  either  to  act  more  immediately  or  to  be  more  permanent  in 
its  action — or  it  may  be  applied  for  the  purpose  of  destroying  unwhole- 
some herbage,  of  quickening  inert  vegetable  matter,  of  generally  sweet- 
ening the  soil,  or  simply  of  adding  to  the  land  a  substance  which  is  in- 
dispensable to  its  fertility.  The  skilful  agriculturist  will  modify  the 
form  and  mode  of  application  according  as  it  is  intended  to  serve  one  or 
other  of  these  purposes- 

From  the  considerations  already  presented  to  you  (§  3 )  in  regard  to 
the  changes  which  quick-lime  undergoes  in  the  air,  it  appears  to  be  ex- 
pedient, 

1°.  To  slake  lime  quickly,  and  to  apply  it  immediately  upon  clay, 
boggy,  marshy,  or  peaty  lands — upon  such  also  as  contain  much  inert 
or  generally  which  abound  in  other  forms  of  vegetable  matter. 

2°.  To  bents  and  heaths  which  it  is  desirable  to  extirpate,  it  should 
be  applied  in  the  same  caustic  state,  or  to  unwholesome  subsoils  which 
contain  much  iron  (sulphate  of  iron),  as  soon  as  they  are  turned  up  by 
the  plough.  In  both  these  cases  the  unslaked  lime-dust  from  the  kilns 
might  be  laid  on  with  advantage. 

*  "  In  the  neighbourhood  of  Taunton,  in  Somersetshire,  and  over  all  the  soil  of  the  new 
red  sandstone,  the  farmers  lime  their  land  every  time  it  comes4n  course  of  fallow  for  tur- 
nips, and  this  produces  excellent  crops,  even  without  dung." — Morton  on  Soils-,  third  edition, 
p.  181.  The  practical  reader  must  not  consider  this  custom  of  the  Somersetshire  farmers 
as  at  all  at  variance  with  what  is  stated  in  the  text :  he  must  conclude,  rather,— if  the  sen- 
tence here  quoted  is  meant  to  apply  that  they  lime  their  arable  land  so  repeatedly,  and  ye 
add  no  organic  manure— that  lh«y  will,  sooner  or  later,  cease  tp  boast  of  its  fertility 


COMPARATIVE    ECONOMY    OF    LIME    AND    MARL.  387 

3°.  Where  it  is  to  be  spread  over  grass  lands  without  destroying  the 
herbage,  it  is  in  most  cases  safer  to  allow  the  lime  to  slake  spontaneous- 
ly, and  in  the  open  air  rather  than  in  a  covered  pit.  It  is  thus  obtained 
in  an  exceedingly  fine  powder,  which  can  be  easily  spread,  and,  while 
it  is  sufficiently  mild  to  leave  the  tender  grasses  unharmed,  it  contains 
a  sufficient  quantity  of  caustic  lime  (p.  368)  to  produce  those  chemical 
changes  in  the  soil  on  which  the  efficacy  of  quick-lime  depends. 

4°.  Where  lime  is  applied  to  the  fallow,  is  ploughed  in,  well  har- 
rowed or  otherwise  mixed  with  the  soil,  it  is  generally  of  little  conse- 
quence in  which  of  the  above  states  it  is  laid  on.  The  chief  condition 
is,  that  it  be  in  the  state  of  a  fine  powder,  and  that  it  be  well  spread 
and  intimately  mixed  with  the  soil.  Before  these  operations  are  con- 
cluded the  lime  will  be  very  nearly  in  the  state  of  combination  in 
which  it  exists  in  spontaneously  slaked  lime — whatever  may  have 
been  the  state  of  causticity  in  which  it  has  been  applied. 

You  will  understand  that  the  above  remarks  apply  only  to  localities 
where  burned  lime  is  usually  or  alone  used  for  agricultural  purposes. 
There  may  be  localities  where  marl  also  exists,  or  shell  or  lime-stone 
sand,  in  greater  or  less  abundance,  and  in  such  places  it  may  be  a  ques- 
tion of  some  importance  to  determine  which  it  would  be  better  or  more 
economical  to  apply.  In  such  a  case  you  may  safely  proceed  upon 
the  principle  that  the  lime  in  the  marls,  &c.,  will  ultimately  produce 
precisely  the  same  efTects,  upon  your  land  as  the  lime  from  the  kiln, 
provided  you  lay  on  an  equal  quantity,  and  in  an  equally  minute  state 
of  division.  The  effect  will  only  be  a  little  more  slow,  and  the  full 
fertility  of  the  land  a  year  or  two  longer  in  being  brought  out.  You 
would  therefore  consider, 

1°.  How  niuch  of  the  marl  or  sand  must  I  add  to  be  equal  to  a  ton 
of  lime-shells?  This  will  depend  on  the  per-centage  of  lime  which 
the  marl  contains.  Suppose  it  to  contain  20  per  cent.,  or  one-fifth  of  its 
weight  of  lime,  (not  carbonate  of  lime,  but  of  lime  in  the  state  in  which 
it  comes  from  the  kiln,  100  lbs.  of  carbonate  containing  56  lbs.  quick 
lime,  p.  364,)  then  five  tons  of  the  marl  will  be  equal  to  one  ton  of  lime 
shells.  But  as  the  lime  in  the  marls  and  sands  is  never  in  so  minute 
a  stale  of  division  as  in  the  slaked  lime,  the  same  quantity  of  lime  in 
the  former  cannot  be  so  equally  diffused  through  the  soil  as  in  the  lat- 
ter state.  An  allowance  must  therefore  be  made  on  this  account,  and 
an  additional  quantity  equal  to  one-fourth  or  one-fifth  of  the  whole  add- 
ed, for  the  purpose  of  equalizing  the  effect. 

2°.  Which  of  the  two,  the  quick-lime  or  its  equivalent  of  marl,  can 
I  obtain  and  apply  at  the  less  cost  ?  This  will  not  be  difficult  to  calcu- 
late, the  proportion  of  Hme  contained  in  the  marl  being  once  ascertained. 

3°.  This  question  of  economy  being  decided,  it  is  necessary  to  con- 
sider the  kind  and  quantity  of  the  earthy  matter  with  which  the  lime 
in  the  marl  is  mixed.  If  it  be  a  lime-sand  or  sandy  marl,  it  may  be  un- 
fit to  apply  to  light  and  sandy  soils  ;  if  it  be  a  stiff  unctuous  clay  marl,  it 
may  only  render  stiffer  and  more  difficult  to  work  the  clay  lands  on 
which  you  may  propose  to  spread  it.  In  such  cases  as  these,  however 
economical  the  use  of  marls  or  lime-stone  sands  may  be,  the  intelligent 
farmer  will  prefer  the  addition  of  quick-lime  wherever  it  is  readily  ac- 
cessible. 

17 


S88  USE  ASD  ADVANTAGE  OF  THE  COMPOST  KORM. 

Sussex  is  one  of  those  districts  in  which  the  ancient  use  of  marl  has 
given  place  to  the  employment  of  burned  lime,  (Beatson,)— chiefly,  I 
believe,  from  the  nature  of  the  local  marl  being  less  adapted  to  the  stiff 
clay  lands  of  that  county. 

§  13.   Of  the  use  ana  advantage  of  the  compost  form. 

As  there  are  many  cases  in  which  lime  ought  to  be  applied  unmixed 
and  in  the  caustic  state,  so  there  are  others  in  which  it  is  best  and  most 
beneficially  laid  upon  the  land  in  a  mild  state  and  in  the  form  of  compost. 

1°.  When  lime  is  required  only  in  small  quantities,  it  can  be  more 
evenly  spread  when  previously  well  mixed  with  from  3  to  8  times  its 
bulk  of  soil. 

2°.  On  light,  sandy,  and  gravelly  soils,  when  of  a  dry  character,  un- 
mixed lime  will  bring  up  much  cow-wheat  {melampyrum)  and  red 
poppy.  If  they  are  moist  soils,  or  if  rainy  weather  ensue,  the  lime  is 
apt  to  run  into  mortar,  and  thus  to  form  either  an  impervious  subsoil, 
or  lumps  of  a  hard  conglomerate,  which  are  brought  up  by  the  plough, 
but  do  not  readily  yield  their  lime  to  the  soil.  These  had  consequences 
are  all  avoided  by  adding  the  lime  in  the  form  of  compost. 

3°.  Applied  to  grass  lands — unless  the  soil  be  stiff  clay— or  much 
coarse  grass  is  to  be  extirpated, — it  is  generally  better  and  safer  to  apply 
it  in  the  compost  form.  The  action  of  the  lime  on  the  tender  herbage 
is  by  this  means  moderated,  and  its  exhausting  effect  lessened  upon 
soils  which  contain  little  vegetable  matter. 

4°.  In  the  compost  form  the  same  quantity  of  lime  acts  more  imme- 
diately. While  lying  in  a  state  of  mixture,  those  chemical  changes 
which  lime  either  induces  or  promotes  have  already  to  a  certain  extent 
taken  place,  and  thus  the  sensible  effect  of  the  lime  becomes  apparent 
in  a  shorter  time  after  it  has  been  laid  upon  the  land. 

6°.  This  is  still  more  distinctly  the  case  when,  besides  earthy  mat- 
ter, decayed  vegetable  substances,  ditch  scourings,  and  other  refuse,  are 
mixed  with  the  lime.  The  experience  of  every  practical  man  has  long 
proved  how  very  much  more  enriching  such  composts  are,  and  more 
obvious  in  their  effects  upon  the  soil,  than  the  simple  application  of 
lime  alone. 

6°.  It  is  stated  as  the  result  of  extended  trial  in  Flanders  and  in  parts 
of  France,  that  a  much  smaller  quantity  of  lime  laid  on  in  this  form 
will  produce  an  equal  effect.  For  this,  one  cause  may  be,  that  the  rains 
are  prevented  from  acting  upon  the  mass  of  compost  as  they  would  do 
upon  the  open  soil — in  washing  out  either  the  lime  itself  or  the  saline 
substances  which  are  produced  during  its  contact  with  the  earthy  and 
vegetable  matter  with  which  it  is  mixed. 

7°.  The  older  the  compost  the  more  fertilizing  is  its  action.  This 
fact  is  of  the  same  kind  with  that  generally  admitted  in  respect  to  the 
action  of  marls  and  unmixed  lime — that  it  is  more  sensible  in  the  se- 
cond year,  or  in  the  second  rotation,  than  in  the  first. 

In  conclusion,  it  may  be  stated  that  this  form  of  application  is  especi- 
ally adapted  to  the  lightest  and  driest  soils,  and  to  such  as  are  poorest  in 
vegetable  matter.  In  this  form,  lime  has  imparted  an  unexpected  fertility 
even  to  the  white  and  barren  sands  of  the  Landes  (Puvis,)  and  upon 
the  dry  hills  of  Derbyshire  it  has  produced  an  almost  equal  benefit. 


PERIOD  rOR  THE  APPLICATION  OF  LIME.  389 

§  14.    When  ought  lime  to  be  ajyplied  ? 

This  question  may  refer  either  to  the  period  in  the  lease,  in  the  rota- 
tion, or  of  the  year  in  which  lime  may  most  beneficially  be  laid  upon 
the  land.  We  have  already  considered  this  point  in  so  far  as  it  refers 
to  the  lease,  while  discussing  the  propriety  of  applying  lime  in  large  or 
small  doses. 

In  regard  to  the  period  of  the  year  and  of  the  rotation,  there  are  three 
principles  by  which  the  procedure  of  the  practical  man  ought  chiefly  to 
be  directed. 

1°.  That  lime  takes  some  time  to  'produce  its  known  effects  upon  the 
soil. — It  ought,  therefore,  to  be  applied  as  long  as  possible  before  the 
crop  is  sown.  That  is,  in  the  early  autumn,  where  either  winter  or 
spring  corn  is  about  to  be  sown, — on  the  naked  fallow  where  the  land 
is  allowed  to  be  at  rest  for  a  year, — or  on  the  grass  fields  before  break- 
ing up,  where  the  pasture  is  to  be  immediately  succeeded  by  corn. 

2°.  That  quick-lime  expel&  ammonia  from  decomposed  and  fermenting 
manure. 

When  such  manure,  therefore,  is  applied  to  the  land,  as  it  is  in  all 
our  well-farmed  districts,  quick-lime  should  not  be  so  laid  upon  the 
land  as  to  come  into  immediate  contact  with  it.  If  both  must  be  ap- 
plied in  the  same  year,  they  should  be  laid  on  at  periods  as  distant  from 
each  other  as  may  be  convenient,  or  if  this  necessity  does  not  exist,  the 
lime  should  be  spread  either  a  year  before  or  a  year  after  the  period  in 
the  rotation  at  which  the  manure  is  usually  applied. 

It  is  for  this  reason,  as  well  as  for  the  other  already  stated,  (1°.)  that 
lime  is  applied  to  the  naked  fallow,  to  the  grass  before  breaking  up,  or 
along  with  the  winter  wheat  after  a  green  crop  which  has  been  aided 
by  fermented  manure.  When  ploughed  into  the  fallow,  or  spread  upon 
the  grass,  it  has  had  time  to  be  almost  completely  converted  into  the 
mild  si^te  (that  of  carbonate,)  before  the  manure  is  laid  on.  In  this 
mild  state  it  has  no  sensible  effect  in  expelling  the  ammonia  of  decom- 
posing manure.  Again,  when  it  is  applied  in  autumn  along  with,  or 
immediately  before  the  seed,  the  volatile  or  ammoniacal  part  of  the 
manure  has  already  been  expended  in  nourishing  the  green  crop,  so  that 
loss  can  rarely  accrue  from  the  admixture  of  the  two  at  this  period  ot 
the  rotation. 

The  excellent  elementary  work  of  Professor  Lowe,  (Elements  oi 
Practical  Agriculture,  third  edition,  p.  63,)  contains  the  following  re- 
mark : — "  It  is  not  opposed  to  theory  that  lime  should  be  applied  to  the 
soil  at  the  same  time  with  dung  and  other  animal  and  vegetable  sub- 
stances, as  is  frequent  in  the  practice  of  farmers."  This  is  strictly  cor- 
rect only  in  regard  to  marls,  lime-sand,  &;c.,  or  to  perfectly  mild  lime, 
any  of  which  may  be  mixed,  without  loss,  with  manure  in  any  state. 
Of  quick  or  caustic  lime  it  is  correct  only  when  the  animal  or  vegetable 
matter  has  not  yet  begun  to  ferment.  With  recent  animal  or  vegetable 
matter,  quick-lime  may  be  mixed  up  along  with  earth  into  a  compost, 
not  only  without  the  risk  of  much  loss,  but  with  the  prospect  of  mani- 
fest advantage. 

3°.  That  quick-lime  hastens  or  revives  the  decomposition  of  inert  or- 
ganic matter. — This  fact  also  indicates  the  propriety  of  allowing  the 


390  LIME  HASTE>-S  ORGANIC  DECOMPOSITION. 

lime  as  much  time  as  possible  to  operate  before  a  crop  is  taken  from 
land  in  which  organic  matter  already  abounds.  Or  where  fermenting 
manure  is  added,  it  advises  the  farmer  to  wail  till  spontaneous  decom- 
position becomes  languid,  when  the  addition  of  lime  will  bring  it  again 
into  action  and  thus  maintain  a  more  equable  fertility. 

In  a  work  upon  soils,  which  1  have  fretjuently  commended  to  your 
notice,  (Morton  ''On  Soils,''  third  edition,  p.  181,)  you  will  fijsd  the 
following  observations  : — "  Writers  on  agriculture  have  stated  that  lime 
hastens  the  decay  of  vegetable  matter,  whereas  the  fact  is,  that  it  retards 
the  process  of  the  decomposition  of  vegetable  matter.  If  straw  or  long 
dung  be  mixed  with  slaked  lime,  it  will  be  preserved  ;  while  if  mixed 
with  an  equal  portion  of  earth,  the  earth  will  hasten  its  decay."  The 
two  facts  stated  in  ttiis  last  sentence  are,  I  believe,  correct,  yet  it  is 
nevertheless  consistent  both  with  theory  and  universal  observation,  that 
lime  in  the  soil  promotes  the  decomposition  of  organic  matters,  both 
animal  and  vegetable.  This  will  appear  more  clearly  when  we  come 
to  study  the  precise  nature  of  the  action  of  lime  upon  organic  substan- 
ces in  general. 

The  above  remarks,  in  regard  to  the  best  time  for  applying  lime,  re- 
fer chiefly  to  quick-lime,  the  state  in  which,  in  England,  it  is  so  exten- 
sively used.  Marls  and  shell-sands  can  cause  no  loss  when  mixed 
with  the  manure,  and  therefore  may  with  safety  be  laid  on  at  any  pe- 
riod of  the  rotation.  The  same  remark  applies  with  greater  force  to  the 
lime  composts.  These  may  be  used  precisely  in  the  same  way  as,  and 
even  instead  of,  the  richer  manures — may  be  laid,  without  risk,  upon 
grass  lands  of  any  quality,  and  at  any  j)eriod — or  as  a  top  dressing  on 
the  young  com  in  spring,  when  the  grass  and  clover  seeds  are  sown  by 
which  the  corn  crop  is  to  be  succeeded.  And  as  the  compost  acts 
more  speedily  than  lime  in  any  other  form,  it  is  especially  adapted  for 
immediate  application  to  the  crop  it  is  intended  to  benefit.  To  wet 
lands  also,  it  is  well  suited,  and  to  such  as  are  subject  to  much  rain,  by 
which,  while  the  surface  is  naked,  the  soluble  matters  produced  in  the 
soil  are  likely  to  be  very  much  washed  away. 

§  15.  Of  the  effects  produced  by  lime. 

The  effects  of  pure  lime  upon  the  land,  and  upon  vegetation,  are  ul- 
timately the  same,  whether  it  be  laid  on  in  a  state  of  hydrate  or  of  car- 
bonate. If  different  varieties  produce  unlike  effects,  the  quantity  of 
lime  applied  being  the  same,  it  is  because  in  nature  lime  is  always 
m®re  or  less  mixed  with  other  substances  which  are  capable  of  modi- 
fying the  effects  which  pure  lime  would  alone  produce.  The  special 
effects  of  marls,  &c.,  when  they  differ  from  those  of  burned  lime,  are 
to  be  ascribed  to  the  presence  of  such  admixtures.  In  general,  how- 
ever, riie  chemical  action  of  the  marls  and  calcareous  sands  is  precisely 
the  same  in  kind  as  that  of  lime  in  the  burned  and  slaked  state,  and  sc 
far  the  effects  which  we  have  already  seen  to  be  produced  by  marls, 
(p.  374,)  represent  also  the  general  effects  of  lime  in  any  form. 

These  general  effects  may  be  considered  in  reference  to  the  land  on 
which  it  is  laid,  and  to  the  crops  which  are,  or  may  6c,  made  to  grow 
upon  it. 


E^TECTS  OF  LIME  UPON  TiiE  LAND  AND  CROPS.  391 

I. EFFECTS  OF  LIME  UPON  THE  LAND. 

Pure  lime,  like  the  marls,  produces  both  a  mechanical  and  a  chemi- 
cal effect  upon  the  soil.  The  former  is  constant  with  all  varieties  of 
tolerably  pure  lime,  and  is  easily  understood.  It  opens  and  renders  freer 
such  sods  as  are  stiff"  and  clayey,  while  it  increases  the  porosity  of  such 
as  are  already  light  and  sandy.  To  the  former  its  mechanical  action  is 
almost  always  favourable,  to  the  latter  not  unfrequently  the  reverse. 

From  its  chemical  action  ihe  benefits  which  follow  the  use  of  lime 
are  cliiefly  derived.     These  benefits  are  principally  the  following: — 

1°.  It  mcreases  the  fertility  of  all  soils  in  which  lime  does  not  already 
abound,  and  especially  adds  to  the  productiveness  of  such  as  are  moist 
or  contain  much  inert  vegetable  matter. 

2°.  It  enables  the  same  soils  to  produce  crops  of  a  superior  quality 
also.  Land  which,  unlimed,  will  produce  only  a  scanty  crop,  (3  or  4 
fold,)  of  rye,  by  the  addition  of  lime  alone,  will  yield  a  6  or  7  fold  re 
turn  of  wheat.  From  some  clays,  also,  apparently,  unfit  to  grow  corn 
it  brings  up  luxuriant  crops. 

3°.  It  increases  the  effect  of  a  given  application  of  manure;  calls 
into  action  that  which,  having  been  previously  added,  appears  to  lie 
dormant ;  and  though,  as  we  have  already  seeu,  (p.  386,)  manure  must 
be  plentifully  laid  ujjon  the  land,  after  it  has  been  well-limed,  yet  the 
same  degree  of  productiveness  can  still  be  maintained  at  a  less  cost  of 
manure  than  where  no  lime  has  been  applied. 

4°.  As  a  necessary  result  of  these  important  changes,  the  money 
value  and  annual  return  of  the  land  is  increased,  so  that  tracts  of  coun- 
try which  had  let  with  difficulty  for  5s.  an  acre,  have  in  many  locali- 
ties been  rendered  worth  30s.  or  40s.  by  the  application  of  lime  alone, 
(Sir  J.  Sinclair.) 

II. EFFECTS  OF  LIME  ON  THE  PRODUCTIONS  OF  THE  SOIL. 

1°.  Il  alters  the  natural  produce  of  the  land,  by  killing  some  kinds 
of  plants  and  favouring  the  growth  of  others,  the  seeds  of  which  had 
before  lain  dormant.  Thus  it  destroys  the  plants  which  are  natural  to 
siliceous  soils  and  to  moist  and  marshy  places.  From  the  corn-field  it 
extirpates  the  corn-marigold,  (chrysanthemum  segetum,  [Bonninghau- 
sen,])  while,  if  added  in  excess,  it  encourages  the  red  poppy,  the  yel- 
low cow-wheat,  {melartipyrum  pratense,)  and  the  yellow  rattle,  {rhinan- 
Ihus  crista  galli,)  and  when  it  has  sunk,  favours  the  growth  of  the  trou- 
blesome and  dee ()- rooted  coltsfoot. 

Similar  effects  are  ])roduced  upon  the  natural  grasses.  It  kills  heath, 
moss,  and  sour  and  benty*  (agrostis)  grasses,  and  brings  up  a  sweet 
and  lender  herbage,  mixed  with  white  and  red  clovers,  more  greedily 
eaten  and  more  nourishing  to  the  cattle.  Indeed,  all  fodder,  whether 
natural  or  artificial,  is  said  to  be  sounder  and  more  nourishing  when 
grown  upon  land  to  which  lime  has  been  abundantly  applied.  On 
benty  grass  the  richest  animal  manure  often  produces  little  improvement 
until  a  dressing  of  lime  has  been  laid  on. 

*  In  Lic](Jisdale,  on  tlie  Scottish  border,  is  a  large  tract  of  land  in  what  is  there  called 
Jhing  bent,  not  worth  more  than  3s.  an  acre.  If  surface-drained  and  limed  at  a  ccst  oi 
£2  to  j53  an  acre,  thi.s  becomes  worth  123.  an  acre  for  sheep  pasture.  An  intelligent  and 
experienced  border  farmer  assures  me  that  such  land  would  never  fvrget  40  lo  60  busheU 
of  lime  per  acre. 


392  LIME  IMPROVES  THE  QUALITY  OF  THE  CROP. 

It  is  partly  in  consequence  of  the  change  which  it  thus  produces  in 
the  nature  of  the  herbage,  that  the  application  of  quick-lime  to  old  grass- 
lands, some  time  before  breaking  up,  is  found  to  he  so  useful  a  practice. 
The  coarse  grasses  being  destroyed,  tough  grass  land  is  opened  and 
softened,  and  is  afterwards  more  easily  worked,  while,  when  turned 
over  by  the  ])lough,  the  sod  sooner  decays  and  enriches  the  soil.  It  is 
another  advantage  of  this  practice,  however,  that  the  lime  has  time*  to 
diffuse  itself  through  the  soil,  and  to  induce  some  of  those  chemical 
changes  by  which  the  succeeding  crops  of  corn  are  so  greatly  benefitted. 

2°.  It  improves  the  quality  of  almost  every  cultivated  crop.  Thus, 
upon  limed  land, 

a.  The  grain  of  the  corn  crops  has  a  thinner  skin,  is  heavier,  and 
yields  more  flour,  while  this  flour  is  said  also  to  be  richer  in  gluten. 
On  the  other  hand,  these  crops,  after  lime,  run  less  to  straw,  and  are 
more  seldom  laid,  [n  wet  seasons,  (in  Ayrshire,)  wheat  preserves  its 
healthy  appearance,  while  on  unlimed  land,  of  equal  quality,  it  is  yel- 
low and  sickly.  A'more  marked  improvement  is  said  also  to  Tbe  pro- 
duced both  in  the  quantity  and  in  the  quality  of  the  spring-sown  than  of 
the  winter-sown  crops,  (Puvis.) 

h.  Potatoes  grown  upon  all  soils  are  more  agreeable  to  the  taste  and 
more  mealy  after  li-me  has  been  applied,  and  this  is  especially  the  case 
on  heavy  and  wet  lands,  which  lie  still  undrained. 

c.  Turnips  are  often  improved  both  in  quantity  and  in  quality  when 
it  is  laid  on  in  preparing  the  ground  for  the  seed.  It  is  most  efficient, 
and  causes  the  greatest  saving  of  farm-yard  manure  where  it  is  applied 
in  the  compost  form,  and  where  the  land  is  already  rich  in  organic  mat- 
ter of  various  kinds. 

(I.  Peas  are  grown  more  pleasant  to  the  taste,  and  are  said  to  be 
more  easily  boiled  soft.     Both  beans  and  peas  also  yield  more  grain. 

e.  Rape,  after  a  half-Wmmg  and  manuring,  gives  extraordinary  crops, 
and  the  same  is  the  case  with  the  colsa,  the  seed  of  which  is  largely 
raised  in  France  for  the  oil  which  it  yields. 

/.  On  flax  alone  it  is  said  to  be  injurious,  diminishing  the  strength  of 
the  fibre  of  the  stem.  Hence,  in  Belgium,  flax  is  not  grown  on  limed 
land  till  seven  years  after  the  lime  has  been  applied. 

3°.  It  hastens  the  maturity  of  the  crop. — It  is  true  of  nearly  all  our 
cultivated  crops,  but  especially  of  those  of  corn,  that  their  full  growth 
is  attained  more  speedily  when  the  land  is  limed,  and  that  they  are 
ready  for  the  harvest  from  10  to  14  days  earlier.  This  is  the  (;aseeven 
with  buck-wheat,  which  becomes  sooner  ripe,  though  it  yields  no  larger 
a  return,  when  lime  is  applied  to  the  land  on  which  it  is  grown. 

4°.  The  liming  of  the  land  is  the  harbinger  of  health  as  well  as  of 

abundance.     It  salubrifies  no  less  than  it  enriches  the  well  cultivated 

district.     I  have  already  drawn  your  attention  (p.  310)   to  this  as  one 

of  the  incidental  results  which  follow  the  skilful  introduction  of  the 

drain  over  large  tracts  of  country.     Where  the  use  of  lime  and  of  th(^ 

drain  go  together,   it  is  difficult  to  say  how  much  of  the  increased 

heahhiness  of  the  district  is  due  to  the  one  improvement,  and  how  much 

*  A  comparatively  long  period  is  sometimes  permitted  to  elapse  before  the  grass  land  is 
broken  up  after  liming.  Thus  at  Nelhcrby,  "  hnie  or  compost  is  always  applied  to  the 
thifd  year's  ))asture,  which  is  renovated  by  it,  and  in  two  or  three  years  breaks  up  admi- 
rably for  oats." 


LIME  SHOULD  BE  KEPT  NEAR  THE  SURrACE.  393 

lo  the  other.  The  lime  arrests  the  noxious  effluvia  which  tend  to  rise 
more  or  less  from  every  soil  at  certain  seasons  of  the  year,  and  decom- 
poses them  or  causes  their  elements  to  assume  new  forms  of  chemical 
combination,  in  which  they  no  longer  exert  the  same  injurious  influ- 
ence upon  animal  life.  How  beautiful  a  consequence  of  skilful  agri- 
cuhure,  that  the  health  of  the  community  should  be  promoted  by  the 
same  methods  which  most  largely  increase  the  produce  of  the  land  ! 
Can  you  doubt  that  the  All-benevolent  places  this  consequence  so 
plainly  before  you,  as  a  stimulus  to  further  and  more  general  improve- 
ment— to  the  application  of  other  know^ledge  still  to  the  amelioration  of 
the  soil  ? 

§  16.   Circumstances  by  which  the  effects  of  lime  are  modified. 

These  effects  of  lime  are  modified  by  various  circumstances.  We 
have  already  seen  that  the  quantity  which  must  be  applied  to  produce 
a  given  effect,  and  the  form  in  wliich  it  will  prove  most  advantageous, 
are,  in  a  great  measure,  dependent  upon  the  dryness  of  the  soil,  upon 
the  quantity  of  vegetable  matter  it  contains,  and  on  its  stiff" or  open  1;ex- 
lure.  There  are  several  other  circumstances,  however,  to  which  it  is 
pro|)er  still  to  advert.     Thus, 

1°.  Its  effects  are  greatest  when  well  mixed  with  the  soil,  and  kept 
near  the  surface  ivithin  easy  reach  of  the  atmosphere.  The  reason  of 
this  will  hereafter  appear. 

2°.  On  arable  soils  of  the  same  kind  and  quality,  the  effects  are 
greatest  upon  such  as  are  newly  ploughed  out,  or  upon  subsoils  just 
brought  to  day.  In  the  case  of  subsoils,  this  is  owing  partly  lo  their 
contaitiing  naturally  very  little  lime,  and  partly  to  the  presence  of  nox- 
ious ingredients,  which  lime  has  the  power  of  neutralizing.  In  the  case 
of  surface  soils  newly  ploughed  out,  the  greater  effect,  in  addition  to  these 
two  causes,  is  due  also  to  the  large  amount  of  vegetable  and  other  or- 
ganic matter  which  has  gradually  accumulated  within  them.  It  is  tne 
presence  of  this  organic  matter  which  has  led  to  the  establishment  of 
the  excellent  practical  rule — "  that  lime  ought  always  to  precede  putres- 
cent manures  when  old  leys  are  broken  up  for  cultivation.^^ 

3^.  Its  effects  are  greater  on  certain  geological  formations  than  on 
others.  Thus  it  produces  much  effect  on  drifted  (diluvial)  sands  and 
clays — on  the  soils  of  the  plastic  and  wealden  clays  (Lee.  XL,  §  8) — 
on  those  of  the  new  and  old  red  sand-stones,  of  the  granites,  and  of 
many  slate-rocks — and,  generally,  on  the  soils  formed  from  all  rocks 
which  contain  little  lime,  or  from  which  the  lime  may  have  been  washed 
out  during  their  gradual  degradation. 

On  the  other  hand,  it  is  often  applied  in  vain  to  the  soils  of  the  oolites 
(Lee.  XL,  §  8),  and  other  calcareous  formations,  because  of  the  abund- 
ance of  lime  already  present  in  them.  The  advantage  derived  from 
chalking  thin  clay  soils  resting  immediately  upon  the  chalk  rock  (Lee. 
XL,  §  8,  and  page  376),  is  explained  by  the  almost  entire  absence  oi 
lime  from  these  soils.  The  clay  covering  of  the  chalk  wolds  has  pro 
bably  been  formed,  not  from  the  ruins  of  the  chalk  rock  itself,  but 
from  the  tkposit  of  muddy  waters,  which  rested  upon  it  for  some  time 
before  those  localities  became  dry  land. 

4°.  Lime  produces  a  greater  proportionzl  improvement  upon  poor  soils 


394  LAND  MAY  BE  SATURATKD  WITH  LIMK. 

than  on  such  as  are  richer  (Dr.  Anderson.)  This  is  also  easily  under- 
stood, It  is  of  poor  soils  in  iheir  natural  slate  of  which  Dr.  Andersoa 
speaks.*  In  this  state  they  contain  a  greater  or  less  quantity  of  organic 
matter,  but  are  nearly  destitute  of  lime,  and  hence  are  in  the  most  favour- 
able condition  for  being  benefitted  by  a  copious  liming.  Experience 
has  proved  that  by  ibis  one  operation  such  land  may  be  raised  in  money 
value  eight  times,  or  from  5s.  to  40s.  per  acre  ;  but  no  practical  man 
would  expect  that  arable  land  already  worth  £.2  per  acre,  could,  by 
liming  or  any  other  single  operation,  become  worth  MlQ  per  acre  of  an- 
nual rent.  The  greater  proportional  improvement  produced  upon  poor 
lands  by  lime  is  only  an  illustration,  therefore,  of  the  general  truth — 
that  on  poor  soils  the  efforts  of  the  skilful  improver  are  always  crowned 
with  the  earliest  and  most  apparent  success. 

5°.  In  certain  cases,  the  addition  of  lime,  even  to  land  in  good  culti- 
vation, and  according  to  the  ordinary  and  approved  practice  of  the  district, 
produces  no  effect  whatever.  This  is  sometimes  observed  where  the 
custom  prevails,  as  in  some  parts  of  Ayrsliire  and  elsewhere,  to  apply 
lime  along  with  every  wheat  crop  (p.  384,)  and  on  such  farms  especially 
where  the  land  is  of  a  lighter  quality.  Where  from  40  to  GO  bushels 
of  lime  are  added  at  the  end  of  each  rotation  of  4  or  5  years,  the  land 
may  soon  become  so  saturated  with  lime  that  a  fresh  addition  will  pro- 
duce no  sensible  effect.  Thus  Mr.  Campbell,  of  Craigie,  informs  me 
of  a  trial  made  by  an  intelHgent  farmer  in  his  neighbourhood,  where  al- 
ternate ridges  only  were  limed  without  any  sensibledifference  being  ob- 
served. No  result  could  show  more  clearly  than  this — that  for  one  ro- 
tation at  least  the  expense  of  lime  might  be  saved,  while  at  the  same  time 
the  land  would  run  the  less  risk  of  exhaustion.  Another  fact  mentioned 
by  Mr.  Campbell  proves  the  soundness  of  this  conclusion.  The  lime 
never  fails  to  produce  obvious  benefit  where  the  land  is  allowed  to  be  4 
or  5  years  in  grass — where  it  is  applied,  that  is,  only  once  in  8  or  9 
years.  The  fair  inference  is,  therefore,  that  in  this  district  as  well  as 
m  others  where  similar  effects  are  observed,  too  much  lime  is  habitually 
added  to  the  land,  whereby  not  only  is  a  needless  expense  incurred,  but 
a  speedier  exhaustion  of  the  soil  is  insured.  Good  husbandry,  therefore, 
indicates  either  the  application  of  a  smallerdose  at  the  recurrence  of  the 
wheat  crop — or  the  occasional  omission  of  lime  altogether  for  an  entire 
rotation.  The  practical  farmer  cannot  have  a  better  mode  of  ascer- 
taining when  his  land  is  thus  fully  supplied  with  lime — than  by  mak- 
ing the  trial  upon  alternate  ridges,  and  marking  the  effect. 

Q^.  On  poor  arable  lands,  which  are  not  naturally  so,  but  which  are 
worn  out  or  exhausted  by  repeated  liming  and  cropping,  lime  produces 
no  good  whateverf  (Anderson,  Brown,  Morton.)  Such  soils,  if  they  do 
not  already  abound  in  lime,  are,  at  least,  equally  destitute  of  numerous 
other  kinds  of  food,  organic  and  inorganic,  by  which  healthy  plants  are 
nourished, — and  they  are  only  to  be  restored  to  a  fertile  condition  by  a 

*  "  I  never  met,"  he  says,  "  with  a  poor  soil  in  its  natural  state,  which  was  not  benefitied 
in  a  very  great  degree  by  calcareous  matter  when  administered  in  proper  quantities.  But 
I  have  met  with  several  rich  soils,  which  are  fully  impregnated  with  dung,  on  which  lime 
applied  in  any  quantity  produced  not  the  smallest  sensible  effect." 

t  "  It  is  scarcely  practicable  to  restore  fertility  to  land,  even  of  the  best  natural  quality, 
which  has  been  thus  abused  ;  and  thia  moorish  soils,  after  being  exhausted  by  lime,  are 
Bot  to  be  restored."  (IJrown.) 


LIME  DOES  >-0T  BENEFIT  EXHAUSTED  LANDS.  395 

judicious  admixture  of  all  This  truth  is  confirmed  by  the  practical 
observation,  that  on  soils  so  exhausted  farm  yard  manure  along  with 
the  lime  does  not  produce  the  same  good  results  as  in  other  cases.  All 
that  the  soil  requires  is  not  supplied  in  sufficient  abundance  by  these 
two  substances  laid  on  alone. 

7°.  On  lands  of  this  kind,  and  on  all  in  which  vegetable  matter  is 
wanting,  lime  may  even  do  harm  to  the  immediate  crop.  It  is  apt  to 
singe  or  burn  the  corn  sown  upon  them  (Brown) — an  effect  which  is 
probably  chemical,  but  which  may  in  part  be  owing  to  its  rendering 
more  open  and  friable  soils  already,  by  long  arable  culture,  too  open. 
(Morton.) 

8°.  A  consideration  of  the  circumstances  above  adverted  to  explains 
why,  in  some  districts,  and  even  in  some  whole  provinces,  the  use  of 
lime  .in  any  form  should  be  condemned  and  even  entirely  given  up. 
The  soil  has  been  impoverished  through  its  unskilful  application — or, 
by  large  admixtures  of  lime  or  marl  for  a  series  of  years,  the  soil  has 
been  so  changed  as  to  yield  no  adequate  return  for  new  additions.  Thus 
for  a  generation  or  two  the  practices  of  liming  and  marling  are  abandoned, 
to  be  slowly  and  reluctantly  resumed  again,  when  natural  causes  have 
removed  the  lime  from  the  soil,  and  produced  an  accumulation  of  those 
other  substances  which,  when  associated  with  it,  contribute  to  the  pro- 
ductiveness of  the  land. 

§  17.  Effects  of  an  overdose  of  lime. 

There  are  several  effects  which  are  familiar  to  the  practical  man  as 
more  or  less  observable  when  lime  in  any  form  is  laid  too  lavislily  upon 
the  land.     Thus 

1°.  It  is  rendered  so  loose  by  an  overdose  as  to  be  capable  of  hold- 
ing no  water  (Karnes).  Upon  stiff*  clays  a  very  large  quantity  indeed 
will  be  required  to  produce  this  effect. 

2°.  By  an  overdose  of  quick-lime  the  land  is  hardened  to  such  a  degree 
as  to  be  impervious  to  water  or  to  the  roots  of  plants.  Several  parts  of 
the  (/arse  of  Gowrie  are  thus  rendered  so  hard  as  to  be  unfit  for  vegeta- 
tion— (Lord  Karnes'  Gentleman  Farmer,  edit.  1802).  This  effect  will 
be  observed  only  in  soils  which  are  naturally  wet  and  undrained,  or 
where  much  rain  has  fallen  and  lingered  on  the  land  after  the  lime 
has  been  applied  (p.  388). 

3°.  But  the  most  injurious  effect  of  an  over-liming,  whether  it  be 
laid  on  at  one  or  at  successive  periods,  is  the  exhaustion  by  which  it  is 
succeeded.  "  An  overdose  of  shell-marl,"  says  Lord  Kames,  "laid  per- 
haps an  inch  thick,  produces  for  a  time  large  crops,  but  at  last  renders 
the  soil  capable  of  bearing  neither  corn  nor  grass,  of  which  there  are 
many  examples  in  Scotland."  The  same  is  true  of  lime  in  any  form. 
The  increased  fertility  continues  as  long  as  there  remains  an  adequate 
supply  of  organic  (animal  and  vegetable)  matter  in  the  soil,  but  as  that 
disappears  the  crops  every  year  diminish  both  in  quantity  and  in  quality. 

An  interesting  illustration  of  this  exhausting  power  of  lime  is  afforded 

by  the  observed  effects  of  long-continued  marling  upon  certain  poor  soils 

in  the  province  of  Isere,  in  France.     The  marl  there  emplo3'ed  is  a 

•audy  marl,  containing  from  30  to  60  per  cent,  of  carbonate  of  lime — • 

17* 


396  LENGTH  OF  TIME  DURING  WHICH  LI3IE  ACTS. 

very  much  like  the  lime-sand  of  Ireland  or  the  shell-sand  of  the  West- 
ern Islands  already  described  (p.  371).  A  layer  of  this  marl  one-third 
of  an  inch  thick,  applied  at  intervals  to  a  soil  producing  in  its  natural 
state  only  a  threefold  return  of  rye  every  other  year,  causes  it  to  yield 
for  the  first  10  or  12  years  an  eight-fold  return  of  wheat.  But  after  40 
years'  marling,  the  farmers  now  complain  that  the  land  will  give  only  a 
four-fold  return  of  wheat.  But  the  cause  of  this  reduction  is  to  be 
found  in  the  constant  cropping  with  corn,  in  the  growing  of  no  green 
crops,  and  in  the  addition  of  no  manure.  Yet  even  with  this  treat- 
ment the  land  is  still  more  productive  than  before  the  marling  was  com- 
menced. It  produces  four  returns  instead  of  three,  and  it  grows  wheat 
where  before  only  rye  would  thrive  and  ripen. 

From  the  possession  of  this  exhausting  property  has  arisen  the  al- 
most universally  diffused  proverb,  that  lime  enriches  the  fathers  hut 
impoverishes  the  sotis.  The  fault,  however,  is  not  in  the  lime,  but  in 
the  improvident  fathers,  who  in  this  case,  as  in  so  many  others,  exhaust 
and  inconsiderately  squander  the  inheritance  of  their  sons.  If  care 
be  taken  to  keep  up  the  supply  of  organic  matter  in  the  soil — by  copi- 
ous additions  of  manure  or  otherwise  (p.  380) — lime  may  be  added 
freely  and  a  system  of  high  farming  kept  up,  by  which  both  the  pres- 
ent holder  of  the  land  and  his  successors  will  be  equally  benefitted. 

The  opinion  expressed  by  some  of  the  highest  authorities  among 
practical  men,  that  too  much  lime  cannot  be  added,  provided  the  soil 
abound  sufficiently  in  vegetable  matter,  may  perhaps  be  rather  over- 
stated ;  but  it  undoubtedly  embodies  the  result  of  long-continued  gen- 
eral observation — that  the  exhausting  effect  of  lime  may  be  postponed 
indefinitely  by  a  liberal  management  of  the  land.* 

§  18.  Length  of  time  during  which  lime  acts. 

It  is  the  fate  of  nearly  all  the  superficial  improvements  of  the  soil, 
that  they  are  only  temporary  in  their  duration.  The  action  of  lime 
ceases  after  a  time,  and  the  land  returns  to  its  original  condition.  The 
length  of  time  which  must  elapse  before  this  takes  place  will  depend, 
among  other  circumstances,  upon  the  quantity  of  lime  added  to,  or  ori- 
ginally contained  in,  the  soil — upon  the  kind  of  cropping  to  which  it  is 
subjected — on  the  nature  of  the  soil  itself— on  the  slope  and  exposure 
and  natural  moisture  of  the  land,  and  on  the  climate  in  which  it  is 
situated. 

We  have  seen  that  on  the  arable  lands  of  the  south  of  Scotland  20 
years  is  the  longest  period  during  which  the  doses  there  applied  act 
beneficially  upon  the  crops — while  in  other  parts  of  the  country  re- 
newed applications  are  considered  necessary  at  much  shorter  intervals. 
Mr.  Dawson,  of  Frogden,  who  introduced  the  practice  of  liming  into  the 
Border  counties  of  Scotland,  observed  that,  when  harrowed  in  with  the 
grass  seeds,  its  effect  in  improving  the  subsequent  pasture  was  sensible 
for  30  years  after.     A  heavy  marling  or  chalking*  in  the  southern  and 

'  In  Germany  the  necessary  union  of  manure  and  marl  is  in  (he  mouth  of  every  peasant— 

— Ohne  mist 

1st  das  Geld  fur  mergeln  verquist. 

T  Applied  at  a  cost  of  30s.  lo  50s.  per  acre,  accc  fing  to  the  localit;  —Mr.  Pusey, 
Agricultural  Journal,  iii.,  p.  186. 


LIME  NATURALLY  SINKS  INTO  THE  SOIL.  397 

Midland  counties  of  England  is  said  also  to  last  for  30  years,  and  the 
same  period  is  assigned  to  the  sensible  effect  of  the  ordinary  doses  of 
lime-sand  in  Ireland,  and  of  shell-sands  and  marls  in  several  parts  of 
France. 

The  effect  of  the  lime  lessens  gradually,  and  though  at  the  end  of  an 
assignable  number  of  years  it  becomes  almost  insensible,  yet  it  does  not 
altogether  cease  till  a  much  ater  period.  This  period  is  in  some  cases 
so  protracted  that  intelligenj:  practical  men  are  in  many  districts  to  be 
met  with  who  believe — that  certain  grass  lands  would  never  forget  a 
good  dose  of  lime  (p.  391,  note). 

§  19.  Of  the  sinking  of  lime  into  the  soil. 

One  of  the  causes  of  this  gradual  diminution  of  the  action  of  lime  is  to 
be  found  in  the  singular  property  it  possesses  of  slowly  sinking  into  the 
land,  until  it  almost  entirely  disappears  from  the  surface  soil.  It  has 
been  long  familiar  to  practical  men,  that  when  grass  lands,  which  have 
been  limed  on  the  sward,  are  after  a  time  broken  up,  a  white  layer  or 
band  of  lime  is  seen  at  a  greater  or  less  depth  beneath  the  surface,  but 
lodging,  generally,  where  it  has  attained  its  greatest  depth  between  the 
upper,  loose  and  fertile,  and  the  lower,  more  or  less  impervious  and  un- 
productive soil.  In  arable  lands  the  action  of  the  plough  counteracts 
this  tendency  in  some  measure,  bringing  up  the  lime  again  from  be- 
neath, and  keeping  it  mixed  with  the  surface  mould.  Yet,  through 
ploughed  land  it  sinks  at  length,  especially  where  the  ploughing  is 
shallow,  and  even  the  industry  of  the  gardener  can  scarcely  prevent  it 
from  descending  beyond  the  reach  of  his  spade. 

The  chief  cause  of  this  sinking  is  to  be  found  in  the  extreme  minute- 
ness of  the  particles  into  which  slaked  lime  naturally  falls.  If  a  por- 
tion of  slaked  lime  be  mixed  with  water  it  forms  a  milky  mixture,  in 
which  some  lime  is  dissolved,  but  much  more  is  held  in  suspension  in 
an  extremely  divided  state.  When  this  milk  is  allowed  to  stand  undis- 
turbed, the  fine  particles  subside  very  slowly,  and  are  easily  again  dis- 
turbed, but  if  thrown  upon  a  filter  they  are  arrested  immediately,  and 
the  lime-water  passes  through  clear.  Suppose  these  fine  particles  to 
be  mixed  with  the  soil,  and  the  rain  to  fall  upon  them,  it  will  carry 
them  downwards  through  the  pores  of  the  soil  till  the  close  subsoil  acts 
the  part  of  a  filter,  and  arrests  them.  This  tendency  to  be  washed 
flown  is  common  not  only  to  lime,  but  to  all  minutely  divided  earthy 
rnaUer  of  a  sufficiently  iricoherent  nature.  Hence  the  formation  of  that 
more  or  less  impervious  layer  of  finely  divided  matter  which  so  often 
form.=?  the  subsoil  beneath  free  and  open  surface  soils.  And  that  hme 
ciliould  appear  alone  or  chiefly  to  sink  on  any  cultivated  field,  may  arise 
from  this  circumstance — that  the  continued  action  of  the  rains  had  long 
before  carried  downwards  the  finer  incoherent  particles  of  other  kinds 
which  existed  naturally  in  the  soil,  and  therefore  could  find  little  else 
but  the  lime  on  which  this  action  could  be  exercised. 

This  explanation  is  satisfactory  enough  in  the  case  of  light  and  open 
soils,  which  are  full  of  pores,  but  it  appears  less  so  in  regard  to  stift 
clays  and  to  loamy  soila  which  are  not  only  close  and  apparently  void 
of  pores,  but  seem  then.selves  to  consist  of  particles  in  a  sufficiently 
niinute  state  of  divisi-^n  to  admit  of  their  being  carried  down  by  the 


398  EFFECTS    OF    SINKING,    AND    REMEDIES    FOR    IT. 

rains  .1  an  equal  degree  with  lime  itself.  This  difficulty  induced  Lord 
Dundcnald  to  suspect  the  agency  of  some  chemical  principle  in  produ- 
cing the  above  effect.*  As  the  lime,  however,  is  unchanged  after  it  has 
descended,  is  still  in  a  powdery  state,  and  exhibits  no  appearance  of 
having  been  dissolved;  it  is  difficult  to  imagine  any  chemical  action  by 
which  such  a  sinking  could  have  been  brought  about. 

It  is  possible  that  in  grass  lands  the  earth-worms,  which  contribute  so 
much  to  the  gradual  production  of  a  fine,  mould,  may,  b)  bringing  up 
the  other  earthy  matters  only,  contribute  to  the  apparent  sinking  of  the 
lime,  as  well  as  of  certain  other  top-dressings.f 

The  effects  of  this  sinking  are  to  remove  the  lime  from  the  surface 
soil,  and  to  form  a  layer  of  calcareous  matter  which  in  wet  or  imper- 
vious bottoms  will  harden  and  form  a  more  or  less  solid  bed  or  pan, 
through  which  the  rains  and  roots  refuse  to  penetrate,  and  which  the 
subsoil  plough  in  some  districts  can  tear  up  with  difficulty.  On  our 
stiffer  soils  it  encourages  the  growth  of  the  troublesome  coltsfoot,  and  in 
the  open  ditches  of  the  wholesome  water-cress. 

The  practical  remedies  for  this  sinking  are  of  two  kinds  : 

1°.  The  ploughing  of  a  deeper  furrow,  and  hence  one  of  the  benefits 
which  in  many  localities  follow  the  use  of  the  trench  plough  (p.  322). 

2°.  The  sowing  of  deep-rooted  and  lime-loving  crops,  such  as  lucerne 
and  sainfoin,  which  in  such  soils  not  only  thrive,  but  bring  up  in  their 
stems,  and  restore  to  the  surface,  a  portion  of  the  lime  which  had  pre- 
viously descended,  and  thus  make  it  available  to  the  after-crops. 

§  20.  Why  liming  must  be  repeated. 

Lime  which  sinks,  as  above  described,  does  not  wholly  escape  from 
the  soil,  but  may  by  judicious  management  be  again  brought  to  the 
surface.  Such  a  sinking^  therefore,  does  not  necessarily  call  for  the  ad- 
dition of  a  fresh  dose  of  lime^  nor  does  it  explain  the  reason  why  in  prac- 
tice the  application  of  lime  to  the  land  must  at  certain  intervals  be  every 
where  repeated. 

We  have  already  seen  that  the  influence  of  the  lime  we  have  laid 
upon  our  fields  after  a  time  gradually  diminishes — the  grass  becomes 
sensibly  less  rich  year  by  year,  the  crops  of  corn  less  abundant,  the  kind 
of  grain  it  will  ripen  less  valuable.  Does  the  lime,  you  might  ask,  ac- 
tually disappear  from  the  soil,  or  does  it  merely  cease  to  act  ?  This 
question  has  been  most  distinctly  answered  by  an  experiment  of  Lam- 
padius.  He  mingled  lime  with  the  soil  of  a  piece  of  ground  till  it  was 
in  the  proportion  of  149  per  cent,  of  the  whole,  and  he  determined  sub- 
sequently, by  analysis,  the  quantity  of  lime  it  contained  in  each  of  the 
three  succeeding  years. 

The  first  year  it  contained     .     1-19  per  cent,  carbonate  of  lime. 
The  second  year      ....     0-89        «  " 

The  third  year 0-52        "  « 

The  fourth  year 0-24        "  "  | 

*  «'In  clayey  and  loamy  soils,  which  are  (7)  equally  ditfusible  with  lime,  and  nearly  of  the 
same  specific  gravity,  the  tendency  which  lime  has  to  sink  cannot  be  accounted  for  simply 
on  mechanical  principles  " — Lord  Diindonald's  Agricultural  Chemistry,  p.  46. 

t  See  in  a  subsequent  lecture  the  remarks  on  laying  down  to  grcm  ;  also  the  Author'a 
Elements  of  Agricultural  Chemistry,  p.  212, 

}  Schiibler,  Agr'.eu  tural  Chemie,  ii.,  p.  141. 


WHY    LIMING    MUST    BE    REPEATED.  399 

There  can  be  no  question,  therefore,  that  the  lime  gradually  disappears 

or  is  removed  from  the  soil. 

^   The  agencies  by  which  this  removal  is  effected  are  of  several  kinds. 

1°.  In  some  cases  it  sinks,  as  we  have  already  seen,  and  escapes  into 
the  subsoil  beyond  the  reach  of  the  plough  or  of  the  roots  of  our  culti- 
vated crops. 

2°.  A  considerable  quantity  of  lime  is  annually  removed  from  the 
soil  by  the  crops  which  are  reaped  fr#m  it.  We  have  already  seen 
(Lee.  X.,  §  4,)  that  in  a  four  years'  rotation  of  alternate  green  and  corn 
crops  the  quantity  of  lime  contained  in  the  average  produce  of  good 
land  amounts  to  248  lbs.  This  is  equal  to  60  lbs.  of  quick-lime  or 
107  lbs.  of  carbonate  of  lime  every  year.  The  whole  of  this,  however, 
is  not  usually  lost  to  the  land.  Part  at  least  is  restored  to  it  in  the  ma- 
nure into  which  a  large  proportion  of  the  produce  is  usually  converted. 
Yet  a  considerable  quantity  is  always  lost — escaping  chiefly  in  the 
liquid  manure  and  in  the  drainings  of  the  dung-heaps— and  this  loss 
must  be  repaired  by  the  renewed  addition  of  lime  to  the  land. 

3°.  Bat  the  rains'^ and  natural  springs  of  water  percolating  through 
the  soil  remove,  in  general,  a  still  greater  proportion.  While  in  the 
quick  or  caustic  state,  lime  is  soluble  in  pure  water.  Seven  hundred 
and  fifty  pounds  of  water  will  dissolve  about  one  pound  of  lime.  The 
rains  that  fall,  therefore,  cannot  fail,  as  they  sink  through  the  soil,  to 
dissolve  and  carry  away  a  portion  of  the  hme  so  long  as  it  remains  in 
the  caustic  state. 

Again,  quick-lime,  when  mixed  with  the  soil,  speedily  attracts  car- 
bonic acid,  and  becomes,  after  a  time,  converted  into  carbonate,  which 
is  nearly  insoluble  in  pure  water.  But  this  carbonate,  as  we  have 
already  seen  (Lee.  III.,  §  1),  is  soluble  in  water  impregnated  with  car- 
bonic acid — and  as  the  drops  of  rain  in  falling  absorb  this  acid  from  the 
air,  they  become  capable,  when  they  reach  the  soil,  of  dissolving  an 
appreciable  quantity  of  the  finely  divided  carbonate  which  they  meet 
with  upon  our  cultivated  lands.  Hence  the  water  that  flows  from 
the  drains  upon  such  lands  is  always  impregnated  with  lime,  and 
sometimes  to  so  great  a  degree  as  to  form  calcareous  deposits  in  the  in- 
terior of  the  drains  themselves,  where  the  fall  is  so  gentle  as  to  allow  the 
water  to  linger  a  sufficient  length  of  time  in  the  soil. 

It  is  impossible  to  estimate  the  quantity  of  lime  which  this  dissolving 
action  of  the  rains  must  gradually  remove.  It  will  vary  with  the 
amount  of  rain  which  falls  in  each  locality,  and  with  the  slope  or  inchna- 
tion  of  the  land ;  but  the  cause  is  at  once  universal  and  constantly  oper- 
ating, and  would  alone,  therefore,  render  necessary,  after  the  lapse  of 
years,  the  application  of  new  doses  of  lime  both  to  our  pastures  and  to 
our  n.rable  fields. 

4°.  During  the  decay  of  vegetable  matter,  and  the  decomposition  of 
mineral  compounds,  which  take  place  in  the  soil  where  lime  is  present, 
new  combinations  are  formed  in  variable  quantities  which  are  more  so- 
luble than  the  carbonate,  and  which  therefore  hasten  and  facilitate  this 
washing  out  of  the  lime  by  the  action  of  the  rains.  Thus  chloride  of 
calcium,  nitrate  of  lime,  and  gypsum,  are  all  produced— of  which  the 
two  former  are  eminently  soluble  in  water — while  organic  acids  also  re- 
sult from  the  decay  of  the  organic  matter,  with  some  of  which  the  lime 
tbrms  readily  soluble  compounds  (salts)  easily  removed  by  water. 


400      ACTION  OF  LIME  UPON  THE  SOIL,  AND  AS  THE  FOOD  OF  PLAN  a  k.. 

The  ultimate  resolution  of  all  vegetable  matter  in  the  soil  into  carbo- 
nic acid  and  water  (Lee.  VIII.,  §  3,)  likewise  aids  the  removal  of  the 
lime.  For  if  the  soil  be  everywhere  impregnated  with  carbonic  acid, 
the  rain  and  spring  waters  that  flow  through  it  will  also  become  charg- 
ed with  this  gas,  and  thus  be  enabled  to  dissolve  a  larger  portion  of  the 
carbonate  of  lime  than  they  could  otherwise  do.  Thus  theory  indi- 
cates, what  I  believe  experience  confirms,  that  a  given  quantity  of  lime 
will  disappear  the  sooner  from»a  field,  the  more  abundant  the  animal 
and  vegetable  matter  it  contains. 

§21.  Theory  of  the  action  of  lime. 

Lime  acts  in  two  ways  upon  the  soil.  It  produces  a  mechanical  al- 
teration which  is  simple  and  easily  understood,  and  is  the  cause  of  a 
series  o^ chemical  changes,  which  are  really  obscure,  and  are  as  yet 
susceptible  of  only  partial  explanation. 

In  the  finely  divided  state  of  quick-lime,  of  slaked  lime,  or  of  soft 
and  crumbling  chalk,  it  stiffens  very  loose  soils,  and  opens  the  stifTer 
clays, — while  in  the  form  of  hmestone  gravel  or  of  shell-sand,  it  may 
be  employed  either  for  opening  a  clay  soil  or  for  giving  body  and  firm- 
ness to  boggy  land.  These  effects,  and  their  explanation,  are  so  obvi- 
ous to  you,  that  it  is  unnecessary  to  dwell  upon  them. 

The  purposes  served  by  lime  as  a  chemical  constituent  of  the  soil  are 
at  least  of  four  distinct  kinds. 

1°.  It  supplies  a  kind  of  inorganic  food  which  appears  to  be  necessa- 
ry to  the  healthy  growth  of  all  our  cultivated  plants. 

2°.  It  neutralizes  acid  substances  which  are  naturally  formed  in  the 
soil,  and  decomposes  or  renders  harmless  other  noxious  compounds 
which  are  not  unfrequently  within  reach  of  the  roots  of  plants. 

3°.  It  changes  the  inert  vegetable  matter  in  the  soil,  so  as  gradual- 
ly to  render  it  useful  to  vegetation. 

4°.  It  causes,  facilitates,  or  enables  other  useful  compounds,  both 
organic  and  inorganic,  to  be  produced  in  the  soil, — or  so  promotes 
the  decomposition  of  existing  compounds  as  to  prepare  them  more 
speedily  for  entering  into  the  circulation  of  plants. 

These  several  modes  of  action  it  will  be  necessary  to  illustrate  in 
eome  detail. 

§  22.   Of  lime  as  the  food  of  plants. 

In  considering  the  chemical  nature  of  the  ash  of  plants  (Lee.  X., 
§  3  and  4),  we  have  seen  that  lime  in  all  cases  forms  a  considerable 
proportion  of  its  whole  weight.  Hence  the  reason  why  lime  is  re- 
garded as  a  necessary  food  of  plants,  and  hence  also  one  cause  of  its 
beneficial  influence  in  general  agricultural  practice. 

The  quantity  of  pure  lime  contained  in  the  crops  produced  upon  one 
acre  during  a  four  years'  rotation  amounts,  on  an  average,  to  242  lbs. 
which  are  equal  to  about  430  lbs.  (say  4  cwt.  )  of  carbonate  of  lime,  m 
the  state  of  marl,  shell-sand,  or  hme-stone  gravel.  (See  Lee.  X.,  §  3.) 
It  is  obvious,  therefore,  that  one  of  the  most  intelligible  purposes  served 
by  lime,  as  a  chemical  constituent  of  the  soil,  is  to  supply  this  compara- 
tively large  quantity  of  lime,  which  in  some  form  or  other  must  enter 
into  the  roots  of  plants. 


Wheat,  25  bushels, 
Barley,  38  bushels, 
Oats,  50  bushels,  . 
Turnips,  25  tons,  . 
Potatoes,  9  tons,  . 
Red  clover,  2  tons. 
Rye  grass,  2  tons, 


ACTS  CHIEFLY  UPON  TOE  ORGANIC  MATTER  OF  THE  SOIL.    401 

But  the  different  crops  which  we  grow  contain  lime  in  unlike  propor- 
tions. Thus  the  average  produce  of  an  acre  of  land  under  the  follow- 
ing crops  contains  of  hme — 

'  I  rain  or  roots.        Straw  or  tops.  Total. 

1-5  7-2  8-7  lbs. 

2-1  12-9  15-0  lbs. 

2-5  5-7  8-2  lbs. 

45-8  93-0  138-8  lbs. 

6-6  259-4  266-0  lbs. 

—  126-0  126-0  lbs. 

—  33-0  33-0  lbs. 
'These  quantities  are  not  constant,  and  wheat  especially  contains 

much  more  lime  than  is  above  stated,  when  it  is  grown  upon  land  to 
which  lime  has  been  copiously  applied.  But  the  very  different  quanti- 
ties contained  in  the  several  crops,  as  above  exhibited,  shew  that  one 
reason  why  lime  favours  the  growth  of  some  crops  more  than  others  is, 
that  some  actually  take  up  a  larger  quantity  of  lime  as  food.  These 
crops,  therefore,  require  the  presence  of  lime  in  greater  proportion  in  the 
soil,  in  order  that  they  may  be  able  to  obtain  it  so  readily  that  no  delay 
may  occur  in  the  performance  of  those  functions  or  in  the  growth  of  those 
parts  to  which  lime  is  indispensable. 

§  23.  The  chemical  action  of  lime  is  exerted  chiefly  upon  the  organic 
matter  of  the  soil. 

There  are  four  circumstances  of  great  practical  importance  in  regard 
to  the  action  of  lime,  which  cannot  be  too  carefully  considered  in  refe- 
rence also  to  the  theory  of  its  operation.     These  are — 

1°.  That  lime  has  little  or  no  effect  upon  soils  in  which  organic  mat- 
ter is  deficient. 

2^.  That  its  apparent  effect  is  inconsiderable  during  the  first  year 
afler  its  application,  compared  with  that  which  it  produces  in  the  second 
and  third  years. 

3°.  That  its  effect  is  most  sensible  when  it  is  kept  near  the  surface  of 
the  soil,  and  gradually  becomes  less  as  it  sinks  towards  the  subsoil. 
And, 

4°.  That  under  the  influence  of  lime  the  organic  matter  of  the  soil 
disappears  more  rapidly  than  it  otherwise  would  do,  and  that  after  it 
has  thus  disappeared  fresh  additions  of  lime  produce  no  further  good 
effect. 

It  is  obvious  from  these  facts,  that  in  general  the  main  beneficial  pur- 
pose served  by  lime  is  to  be  sought  for  in  the  nature  of  its  chemical  ac- 
tion upon  the  organic  matter  of  the  soil — an  action  which  takes  place 
slowly,  which  is  hastened  by  the  access  of  air,  and  which  causes  the 
organic  matter  itself  ultimately  to  disappear. 

§  24.  Of  the  forms  in  which  organic  matter  usually  exists  in  the  soil, 
and  circum.stances  under  which  its  decomposition  may  take  place. 

I. — The  organic  matter  which  lime  thus  causes  to  disappear  is  pre- 
sented to  it  in  one  or  other  of  five  different  forms : 

1°.  In  that  of  recent  often  grom  moist,  and  ufcdecomposed  roots, 
leaves,  and  stems. of  plants. 


402  UPON    THE    DECOMPOSITION    OF    ORGANIC    MATTER. 

2^.  In  that  of  dry,  and  still  undecomposed,  vegetable  mat  ter,  such 
as  straw. 

3°.  In  a  more  or  less  decayed  or  decaying  state,  generally  black  or 
brown  in  colour — and  often  in  some  degree  soluble  in  water. 

4°.  In  what  is  called  the  inert  state,  when  spontaneous  decay  ceases 
to  be  sensibly  observed.     And 

5°.  In  the  state  of  chemical  combination  with  the  earthy  substances 
— with  the  alumina  for  example,  and  with  the  lime  or  magnesia — al- 
ready existing  in  the  soil. 

Upon  these  several  varieties  of  organic  matter  lime  acts  with  differ- 
ent degrees  of  rapidity. 

II. — The  final  result  of  the  decomposition  of  these  several  forms  of 
organic  matter,  when  they  contain  no  nitrogen,  is  their  conversion  into 
carbonic  acid  and  water  only  (Lee.  VIII.,  §3).  They  pass,  however, 
through  several  intermediate  stages  before  they  reach  this  point — the 
number  and  rapidity  of  which,  'and  the  kind  of  changes  they  undergo 
at  each  stage,  depend  upon  the  circumstances  under  which  the  decom- 
position is  effected.     Thus  the  substance  may  decompose — 

1°.  Alo7ie,  in  which  case  the  changes  that  occur  proceed  slowly,  and 
arise  solely  from  a  new  arrangement  of  its  own  particles.  This  kind  of 
decomposition  rarely  occurs  to  any  extent  in  the  soil. 

2°.  In  the  presence  of  water  only. — This  also  seldom  takes  place  in 
the  soil.  Trees  long  buried  in  moist  clays  impervious  to  air  exhibit  the 
kind  of  slow  alteration  which  results  from  the  presence  of  water  alone. 
In  the  bottoms  of  lakes,  ditches,  and  boggy  places  also,  from  which  in- 
flammable gases  arise,  water  is  the  principal  cause  ofthe  more  rapid 
decomposition. 

3°.  In  the  presence  of  air  only. — In  nature  organic  matter  is  never 
placed  in  this  condition,  the  air  of  our  atmosphere  being  always  largely 
mixed  with  moisture.  In  dry  air  decomposition  is  exceedingly  slow, 
and  the  changes  which  dry  organic  substances  undergo  in  it  are  often 
scarcely  perceptible. 

4°.  In  the  presence  of  both  water  a7id  air. — This  is  the  almost  uni- 
versal condition  of  the  organic  matter  in  our  fields  and  farm-yards. 
The  joint  action  of  air  and  water,  and  the  tendency  ofthe  elements  of 
the  organic  matter  to  enter  into  new  combinations,  cause  new  chem- 
ical changes  to  succeed  each  other  with  much  rapidity.  It  will  of 
course  be  understood  that  moderate  Avarmth  is  necessary  to  the  pro- 
duction of  these  effects.* 

5°.  In  the  presence  of  lime,  or  of  some  other  alkaline  substance  (pot- 
ash, soda,  or  magnesia). — Organic  matter  is  often  found  in  the  soil  in 
such  a  state  that  the  conjoined  action  of  both  air  and  water  are  unable 
to  hasten  on  its  decomposition.     A  new  chemical  agency  must  then  be 

'  A  familiar  illustration  of  tlie  conjoined  efficacy  of  air  and  water  in  producing  oxidation  is 
exhibited  in  their  action  upon  iron.  If  a  piece  of  polished  iron  be  kept  in  perfectly  dry  air 
it  will  not  rust.  Or  if  it  be  completely  covered  over  with  pure  water  in  a  well  stoppered 
bottle,  from  which  air  is  excluded,  it  will  remain  bright  and  untarnished.  Dut  if  a  polished 
rod  of  iron  be  put  into  an  open  vessel  half  full  of  water,  so  that  one  part  of  its  lengih  only 
is  under  water— then  the  rod  will  begin  very  soon  to  rust  at  the  surface  of  tlie  water,  and  a 
brown  ochrey  ring  of  oxide  will  form  around  it,  exactly  where  the  air  and  water  meet. 
From  this  point  the  rust  will  gradually  spread  upwards  and  downwards.  So  it  is  with  tha 
organic  matter  of  the  soil.  Wherever  the  air  and  water  meet,  their  decomposing  action 
upon  it,  in  ordinary  temperatures,  soon  becomes  perceptible. 


INFLUENCE   OF   ALKALINE    SUBSTANCES.  403 

introduced,  by  which  the  elements  ofthe  organic  mattermay  again  be 
set  in  motion.  Lime  is  the  agent  which  for  this  purpose  is  most  large- 
ly employed  in  practical  agriculture. 

§  25.  General  action  of  alkaline  substances  upon  organic  matter. 

It  is  this  action  of  alkaline  matters  upon  the  organic  substances  of  the 
soil  in  the  presence  of  air  and  water  that  we  are  principally  to  investigate. 

When  organic  matter  undergoes  decay  in  the  presence  of  air  and 
water  only,  it  first  rots,  as  it  is  called,  and  blackens,  giving  off  water 
or  its  elements  chiefly,  and  forming  humus — a  mixture  of  humic,  ulmic, 
and  some  other  acids,  (Lee.  XIII.,  §  1.)  with  decaying  vegetable  fibre. 
It  tlien  commences,  at  the  expense  of  the  oxygen  of  the  air  and  of 
water,  to  form  other  more  soluble  acids  (malic,  acetic,  lactic,  crenic, 
mudesic,  &c.;)  among  which  is  a  portion  of  carbonic — and,  by  the  aid 
of  the  hydrogen  of  the  water  which  it  decomposes,  one  or  more  of 
the  many  compounds  of  carbon  and  hydrogen,  which  often  rise  up, 
as  the  marsh-gas  does,  and  escape  into  the  air,  (Lee.  VIII.,  §  3.) 

Thus  there  is  a  tendency  towards  the  accumulation  of  acid  substances 
of  vegetable  origin  in  the  soil,  and  this  is  more  especially  the  case  when 
t'le  soil  is  moist,  and  where  much  vegetable  matter  abounds.  The  effect 
of  this  saper-abundance  of  acid  matter  is,  on  the  one  hand,  to  arrest  the 
further  natural  decay  of  the  organic  matter,  and,  on  the  other,  to  render 
the  soil  unfavorable  to  the  healthy  growth  of  young  or  tender  plants. 

The  general  effect  of  the  presence  of  alkaline  substances  in  the  soil 
is  to  counteract  these  two  evils.  They  combine  with  and  thus  remove 
the  sourness  of  the  acid  bodies  as  they  are  formed.  In  consequence  of 
tliis  the  soil  becomes  sweeter  or  more  propitious  to  vegetation,  while  the 
natural  tendency  of  the  vegetable  matter  to  decay  is  no  longer  arrested. 

It  is  thus  clear  that  an  immediate  good  effect  upon  the  land  must  fol- 
low either  from  the  artificial  application  or  from  the  natural  presence  of 
alicaline  matter  in  the  soil — while  at  the  same  time  it  will  cause  the 
vegetable  matter  to  disappear  more  rapidly  than  would  otherwise  be 
the  case.  But  the  effect  of  such  substances  does  not  end  here.  They 
actually  dispose  or  provoke — pre-dispose0\\Gm\s,i&  call  it — the  vegeta- 
ble matter  to  continue  forming  acid  substances,  in  order  that  they  may 
combme  with  them,  and  thus  cause  the  organic  matters  to  disappear 
more  rapidly  than  they  otherwise  would  do — in  other  words,  they 
hasten  forward  the  exhaustion  of  the  vegetable  matter  of  the  soil. 

Such  is  the  general  action  of  all  alkaline  substances.  This  action 
they  exhibit  even  in  close  vessels.  Thus  a  solution  of  grape  sugar, 
mixed  with  potash,  and  left  in  a  warm  place,  slowly  forms  melassic 
acid — while  in  cold  lime-water  the  same  sugar  is  gradually  converted 
into  another  acid  called  the  glucic.  But  in  the  air  other  acids  arc 
formed  in  the  same  mixtures,  and  the  changes  proceed  more  rapidly. 
Such  is  the  case  also  in  the  soil,  where  the  elements  of  the  air  and 
of  water  are  generally  at  hand  to  favor  the  decomposition. 

But  the  nature  of  the  alkaline  matter  which  is  present  determines 
also  the  rapidity  with  which  such  changes  are  produced.  The  most 
powerful  alkaline  substances — potash  and  soda — produce  all  the  above 
effects  most  quickly ;  lime  and  magnesia  are  next  in  order ;  and  the 
alumina  of  the  clay  soils,  though  much  inferior  to  all  of  these,  is  far 
from  being  without  an  important  influence. 


404  ACTION    OF    CAUSTIC    LIME    UPON    ORGANIC    MATTER 

Hence  one  of  the  benefits  which  result  from  the  use  of  wood-ashes 
containing  carbonate  of  potash,  when  employed  in  small  quantities, 
and  along  with  vegetable  and  animal  manures,  as  they  are  in  this  coun- 
try ;  but  hence  also  the  evil  effects  which  are  found  to  follow  from  the 
application  of  them  in  too  large  doses.  Thus  in  countries  wher&  wood 
abounds,  and  where  it  is  usual,  as  in  Sweden  and  Northern  Russia, 
to  burn  the  forests  and  to  lay  on  their  ashes  as  manure,  the  tillage 
can  be  continued  for  a  few  years  only.  After  one  or  two  crops  the 
lairtl  is  exhausted,  and  must  ag  'm  be  left  to  its  natural  produce. 

§  26.  Special  efects  of  cavstu    lime  upon  the  several  varieties  of 
organic  matter  in  the  soil. 

The  eftects  of  lime  upon  organic  matter  are  precisely  the  same 
in  kind  as  those  of  the  alkaUes  in  general.  They  are  only  less  in  de- 
gree, or  take  place  more  slowly,  than  when  soda  or  potash  is  em- 
ployed. Hence,  the  greater  adaptation  of  lime  to  the  purposes  of 
practical  agriculture. 

1°.  Action  of  caustic  lime  alone  upon  vegetable  matter. — If  the  fresh 
leaves  and  twigs  of  plants,  or  blades  and  roots  of  grass,  be  introduced 
into  a  bottle,  surrounded  with  slaked  lime,  and  corked,  they  will  slowly 
undergo  a  certain  change  of  color,  but  they  may  be  preserved,  it  is 
said,  for  years,  without  exhibiting  any  striking  change  of  texture  (Mr. 
Garden.)  If  dry  straw  be  so  mixed  with  slaked  lime,  .  -  will  exhibit 
still  less  alteration.  In  either  case  also  the  changes  will  be  even  less 
perceptible,  if  instead  of  hydrate  of  lime,  the  carbonate  (or  7nild  lime.) 
in  any  of  its  forms,  be  mixed  with  these  varieties  of  vegetable  matter. 
On  some  other  varieties  of  vegetable  matter, — such,  for  example,  as  are 
undergoing  rapid  decay,  or  have  ai ready  reached  an  advanced  stage  of 
decomposition, — an  admixture  of  slaked  hme  produces  certain  percepti- 
ble changes  immediately,  and  mild  lime  more  slowly,  but  these  changes 
being  completed,  the  tendency  of  lime  alone  is  to  arrest  rather  than  to 
promote  further  rapid  alterations.  Hence,  the  following  opinions  of 
experienced  practical  observers  must  be  admitted  to  be  theoretically 
correct — in  so  far  as  they  TeSt$  to  the  action  of  lime  alone. 

"  If  straw  of  long  dung  be  mixed  with  slaked  lime,  it  will  be  pre- 
served." (Morton,  On  Soils,  3d  edition,  p.  181.) 

"  Lime  mixed  in  a  mass  of  earth  containing  the  live  roots  and  seeds 
of  plants,  will  7iot  destroy  them."  (Morton.) 

"  Sir  H.  Davy's  theory,  that  lime  dissolves  vegetable  matter,  is 
given  up ;  in  fict,  it  hardens  vegetable  matter.  (Mr.  Pusey,  Royal 
Agricultural  Journal,  iii.,  p.  212. 

These  opinions,  I  have  said,  are  probab.y  correct  in  so  far  as  re- 
gards the  unaided  action  of  lime.  They  even  express,  with  an  ap- 
proach to  accuracy,  what  will  take  place  in  the  interior  of  compost 
neaps  of  a  certain  kind,  or  in  some  dry  soils  ;  but  that  they  cannot 
apply  to  the  ordinary  action  of  lime  upon  the  soil  is  proved  by  the 
other  result  of  universal  observation,  that  lime,  so  far  from  preserv- 
ing the  organic  matter  of  the  land  to  which  it  is  applied,  in  reality 
wastes  it — causes,  that  is,  or  disposes  it  to  disappear. 

2=*.  Action  ofca.ustic  lime  on  organic  matter  in  the  presence  of  air 
and.  'Water. — In  the  presence  of  air  and  water,  when  assisted  by  a 


IN    THE    PRESENCE    OF   AIR    AND    WATER.  405 

favoring  temperature,  vegetable  matter,  as  we  have  already  seen, 
undergoes  spontaneous  decomposition.  In  the  same  circumstances 
Hme  promotes  and  sensibly  hastens  this  decomposition, — altering  the 
ibrms  or  stages  through  which  the  organic  matter  must  pass — but 
bringing  about  more  speedily  the  final  conversion  into  carbonic  acid 
and  water.  During  its  natural  decay  in  a  moist  and  open  soil,  organic 
matter  gives  off'  a  portion  of  carbonic  acid  gas,  which  escapes,  and 
forms  certain  other  acids  which  remain  in  the  dark  mould  of  the  soil 
itself  When  quick  or  slaked  hme  is  added  to  the  land,  its  first  effect 
is  to  combine  with  these  acids — to  form  carbonate,  humate,  &c.,  of 
lime — till  the  whole  of  the  acid  matter  existing  at  the  time  is  taken 
up.  That  portion  of  the  lime  which  remains  uncombined,  either  slowly 
absorbs  carbonic  acid  from  the  air  or  unites  with  the  carbonate  already 
formed,  to  produce  the  known  compound  of  hydrate  with  carbonate 
of  lime, — (that  compound,  namely,  which  is  produced  when  quick-hme 
slakes  spontaneously  in  the  air — see  p.  368.) — waiting  in  this  state  in 
the  soil  till  some  fresh  portions  of  acid  matter  are  formed  with  which 
it  may  combine.  But  it  does  not  inactively  wait ;  it  persuades  and 
influences  the  organic  matter  to  combine  withjthe  oxygen  of  the  air 
and  water  with  which  it  is  surrounded,  for  the  production  of  such  acid 
substances — till  finally  the  whole  of  the  lime  becomes  combine^  either 
with  carbonic  or  with  some  other  acid  of  organic  origin. 

Nor  at  this  stage  are  the  action  and  influence  of  lime  observed  to 
cease.  On  the  contrary,  this  result  will,  in  most  soils,  be  arrived  at  in 
the  course  of  one  or  two  years,  while  the  beneficial  action  of  the  lime 
itself  may  be  perceptible  for  20  or  30  years.  Hence  there  is  much  ap- 
parent ground  for  the  opinion  of  Lord  Kames,  '•  that  lime  is  as  effica- 
cious in  its  (so  called)  effete  as  in  its  caustic  state."  Even  the  more 
strongly  expressed  opinion  of  the  same  acute  observer,  "  that  lime  pro- 
duces little  effect  upon  vegetables  till  it  becomes  effete" — derives  much 
support  from  experience — since  lime  is  known  to  have  comparatively 
little  effect  iipon  the  productiveness  of  the  land  till  one  or  two  years 
after  its  application ;  and  this  period,  as  I  have  said,  is  in  most  locali- 
ties sufficient  to  deprive  even  slaked  lime  of  all  its  caustic  properties. 

Of  the  saline  compounds,  (sahne  compounds  or  salts  are  always 
formed  when  hme,  magnesia,  potash,  soda,  &c.,  combine  with  acids,) 
which  caustic  lime  thus  forms,  either  immediately  or  ultimately,  some, 
like  the  carbonate  and  humate,  being  very  sparingly  soluble  in  water, 
remain  more  or  less  permanently  in  the  soil ;  others,  like  the  acetate 
of  lime,  being  readily  soluble,  are  either  washed  out  by  the  rains  or 
are  sucked  up  by  the  roots  of  the  growing  plants.  In  the  former  case 
fhey  cause  the  removal  of  both  organic  matter  and  of  lime  from  the 
land  ;  in  the  latter  they  supply  the  plant  with  a  portion  of  organic  food, 
and  at  the  same  time  with  lime — without  which,  as  we  have  frequent- 
ly before  remarked,  plants  cannot  be  maintained  in  their  most  healthy 
condition. 

§  27.  Action  of  mild  {or  carbonate  of)  lime  upon  the  vegetable  matter 
of  the  soil. 

The  main  utility  of  lime,  therefore,  depends  upon  its  prolonged 
a/)!er-action  upon  the  vegetable  matter  of  the  soil.  What  is  this  ac- 
"  '  ■       1    -         •       ^p  benefits  to  which  /,  gives  rise? 


W'^ 


406      ACTION  OF  CARBONATE  OF  LIME  UPON  VEGETABLE   MATTER. 

In  answering  this  question,  it  is  of  importance  to  observe  that  all 
the  effects  produced  by  alkahne  matter  in  general — whether  by  lime 
or  by  potash — in  the  caustic  state,  are  produced  in  kind  also  by  the 
same  substances  in  the  state  of  carbonate.  The  carbonic  acid  with 
which  they  are  united  is  retained  by  a  comparatively  feeble  affinity 
and  is  displaced  with  greater  or  less  ease  by  almost  every  other  acid 
compound  which  is  produced  in  the  soil.  With  this  displacement  is 
connected  an  interesting  series  of  beautiful  reactions,  which  it  is  of 
consequence  to  understand. 

You  will  recollect  that  the  great  end  which  nature,  so  to  speak,  has 
in  view,  in  all  the  changes  to  which  she  subjects  organic  matter  in  the 
soil,  is  to  convert  it— with  the  exception  of  its  nitrogen — into  carbonic 
acid  and  water.  For  this  purpose  it  combines  at  one  time,  with  the 
oxygen  of  the  air,  while  at  another  it  decomposes  water  and  unites  with 
the  oxygen  or  the  hydrogen  which  are  liberated,  or  with  both,  to  form 
new  chemical  combinations.  Each  of  these  new  combinations  is  either 
immediately  preliminary  to  or  is  attended  by  the  conversion  of  a  por- 
tion to  the  elements  of  the  organic  matter  into  one  or  other  of  those 
simpler  forms  of  matter  on  which  plants  live.  Now  during  these  pre- 
liminary or  preparatory  steps,  acid  substances,  as  I  have  already  ex- 
plained, are  among  others  constantly  produced.  With  these  acids,  the 
carbonate  of  lime,  when  present  in  the  soil,  is  ever  ready  to  combine. 
But  in  so  combining,  it  gives  off  the  carbonic  acid  with  which  it  is  al- 
ready united,  and  thus  a  continual,  slow  evolution  of  carbonic  acid  is 
kept  up  as  long  as  any  undecomposed  carbonate  remains  in  the  soil. 

I  do  not  attempt  to  specify  by  name  the  various  acid  substances 
which  are  thus  formed  during  the  oxidation  of  the  organic  matter,  and 
which  successively  unite  with  the  hme,  because  the  entire  series  of 
interesting  and  highly  important  changes,  which  organic  substances 
undergo  in  the  soil,  has  as  yet  been  too  little  investigated,  to  permit 
us  to  do  more  than  speak  in  general  terms  of  the  nature  of  the  che- 
mical compounds  which  are  most  abundantly  produced.  Of  two  facts, 
however,  in  regard  to  them,  we  are  certain — that  they  are  simpler  in 
their  constitution  than  the  original  organic  matter  itself^  from  which 
they  are  derived — and  that  they  have  a  tendency  to  assume  still 
simpler  forms,  if  they  continue  to  be  exposed  to  the  same  united  action 
of  air,  water,  and  alkaline  substances. 

Hence  the  compounds  which  lime  has  formed  with  the  acid  sub- 
stances of  the  soil,  themselves  hasten  forward  to  new  decompositions, 
— unite  with  more  oxygen,  liberate  sloAvly  portion  after  portion  of 
their  carbon  in  the  form  of  carbonic  acid,  and  of  their  hydrogen  in  the 
form  of  water,  till  at  length  the  lime  itself  is  left  again  in  the  state 
of  carbonate,  or  in  union  with  carbonic  acid  only.  This  residual  car- 
bonate begins  again  the  same  round  of  changes  through  which  it  had 
pre v/:ously  passed.  It  gives  up  its  carbonic  acid  at  the  bidding  of 
some  more  powerful  organic  acid  produced  in  its  neighborhood,  while 
this  acid,  by  exposure  to  the  due  influences,  undergoes  new  altera- 
tions till  it  also  is  finally  resolved  into  carbonic  acid  and  water. 

Two  circumstances  are  deserving  to  be  borne  in  mind  in  reference 
to  these  successive  decompositions— ^r^^,  that  in  the  course  of  them 
more  soluble  compounds  of  lime  are  now  and  then  formed,  some  of 


SUMMARY    OF   THE  CHANGES    PRODUCED   BY    LIME.  407 

which  are  washed  out  by  the  rains,  and  escape  from  the  soil,  while 
others  minister  to  the  growth  of  plants  ; — and  second,  that  very  much 
carbonic  acid  is  produced  as  their  final  result — of  which  also  part  is 
taken  up  by  the  roots  of  plants,  and  part  escapes  into  the  air.  Thus 
at  every  successive  stage  a  portion  of  organic  matter  is  lost  to  the 
soil.  If  this  quantity  be  greater  than  that  which  is  yearly  gained  in 
the  form  of  roots  or  decayed  leaves  and  stems  of  plants,  or  of  manure 
artificially  added,  the  soil  will  be  gradually  exhausted — if  less,  it  will 
every  year  become  more  rich  in  vegetable  matter. 

It  is  also  to  be  borne  in  mind,  that  although,  for  the  purpose  of  il- 
lustration, I  have  supposea  the  carbonate  of  lime  first  formed  in  the 
soil  to  be  subsequently  combined  with  other  acids,  which  gradually 
decompose  and  leave  it  again  in  the  state  of  carbonate, — yet  it  will 
rarely  happen  that  the  whole  of  the  carbonate  of  lime  in  the  soil 
will  be  in  any  of  these  new  states  of  combination.  In  general,  a  part 
of  it  only  is  thus  at  any  one  time  employed  in  working  up  the  acid 
substances  produced.  But  it  is  necessary  that  it  should  be  univer- 
sally diffused  through  the  soil  in  order  that  it  may  be  everywhere  at 
hand  to  perform  the  important  part  of  its  functions  above  explained. 
It  is  only  where  little  lime  is  present,  or  where  decaying  vegetable 
matter  is  in  exceeding  abundance,  that  the  whole  of  the  carbonate 
can  at  one  and  the  same  time  disappear  (p.  380.) 


The  changes,  therefore,  which  lime  and  organic  matter,  supposed 
to  be  free  from  nitrogen,  respectively  undergo,  and  their  mutual  ac- 
tion in  the  soil,  may  be  summed  up  as  follows : — 

1°.  The  organic  matter,  under  the  influence  of  air  and  moisture, 
spontaneously  decomposes,  and  besides  carbonic  acid  which  escapes, 
forms  also  other  acid  substances  which  linger  in  the  soil. 

2°.  With  these  acids  the  quick-lime  combines,  and,  either  by  its 
union  with  them  or  with  carbonic  acid  from  the  air,  soon  (compara- 
ratively)  loses  its  caustic  state. 

3 -•.  The  production  of  acid  substances  by  the  oxidation  of  the  organ- 
ic matter — goes  on  more  rapidly  under  the  disposing  influence  of  the 
lime,  whether  caustic  or  carbonated.  These  acids  combine  with  the 
lime,  liberating  from  it,  when  in  the  state  of  carbonate,  a  slow  but 
constant  current  of  carbonic  acid,  upon  which  plants  at  least  partly 
live. 

4°.  The  organic  acid  matter  which  thus  unites  with  the  lime  con- 
tinues itself  to  be  acted  upon  by  the  air  and  water,  aided  by  heat  and 
light — itself  passes  through  a  succession  of  stages  of  decomposition, 
at  each  of  which  it  gives  off  water  or  carbonic  acid,  retaining  still 
its  hold  of  the  lime,  till  at  last  being  wholly  decomposed  it  leaves  the 
lime  again  in  the  state  of  carbonate,  ready  to  begin  anew  the  same 
round  of  change. 

Durmg  this  series  of  progressive  decompositions,  certain  more  so- 
luble compounds  of  lime  are  formed,  by  which  plants  are  in  part  at 
least  supplied  with  this  earth,  and  which  with  the  aid  of  the  rains 
carry  off  both  lime  and  organic  matter  from  the  soil. 

And,  again,  the  more  rapid  the  production  of  the  acid  substances 


i  '8      COMPARATIVE    UTILITY    OF   BURNIJD   AND   UNBDRNED    LIME. 

which  result  I'rom  the  union  of  the  organic  matter  with  oxygen,  the 
more  abundant  in  general  also  the  production  of  those  gaseous  and 
t^olatile  compounds  which  they  form  by  uniting  with  hydrogen,  so 
that,  in  promoting  the  formation  of  the  one  class  of  bodies,  lime  also 
favors  the  evolution  of  the  other  in  greater  abundance,  and  thus  in 
a  double  measure  contributes  to  the  exhaustion  of  the  soil. 

The  disposmg  action  of  lime  to  this  twin  form  of  decomposition,  few 
varieties  of  organic  matter  can  resist, — and  hence  arises  the  well 
known  efficacy  of  lime  in  resolving  and  rendering  useful  the  appa- 
rently inert  vegetable  substances  that  not  unfrequently  exist  in  the 
soil. 

§  28.  Of  the  comparative  utility  of  burned  and  unburned  lime. 

Is  there  no  advantage,  then,  you  may  ask,  in  using  caustic  or  burned 
rather  than  carbonated  or  unburned  lime?  If  the  ultimate  effects  of 
both  upon  the  land  be  the  same,  why  be  at  the  expense  of  burning  ? 
Among  other  benefits  may  be  enumerated  the  following : — 

1°.  By  burning  and  slaking^  the  lime  is  reduced  to  the  state  of  an  iin- 
palpable^owder,  finer  than  could  be  obtained  by  any  available  method 
of  crushing.  It  can  in  consequence  be  diffused  more  uniformly  through 
he  soil,  and  hence  a  smaller  quantity  will  produce  an  equal  effect. 
This  minute  state  of  division  also  promotes  in  a  wonderful  degree  the 
chemical  action  of  the  lime.  In  all  cases  chemical  action  takes  place 
between  exceedingly  minute  particles  of  matter,  and  among  sohd  sub- 
stances the  more  rapidly,  the  finer  the  powder  to  which  they  can  be  re- 
duced. Thus  a  mass  of  iron  or  lead  slowly  rusts  or  tarnishes  in  the  air, 
but  if  the  mass  of  either  metal  be  reduced  to  the  state  of  an  impalpable 
powder — which  can  be  done  by  certain  chemical  means — it  will  take 
fire  when  simply  exposed  to  the  air  at  the  ordinary  temperature,  and 
will  burn  till  it  is  entirely  converted  into  oxide.  .  By  mere  mechanical 
division  the  apparent  action  of  the  oxygen  of  the  air  upon  metals  is  aug- 
mented and  hastened  in  this  extraordinary  degree — and  a  similar  re- 
sult follows  when  lime  in  an  impalpable  state  is  brought  into  contact 
with  the  vegetable  matter  upon  which  it  is  intended  to  act. 

2^.  The  effect  of  burned  lime  is  more  powerful  and  more  immediate 
than  that  of  unburned  Hme  in  the  form  of  chalk,  marl,  or  shell  sand. 
Hence  it  sooner  neutralizes  the  acids  which  exist  in  the  soil,  and 
sooner  causes  the  decomposition  of  vegetable  matter  of  every  kind  to 
commence,  upon  which  its  efficacy,  in  a  greater  degree,  depends. 
Hence,  when  it  can  easily  be  procured,  it  is  better  fitted  for  sour  grass 
or  arable  lands,  for  such  as  contain  an  excess  of  vegetable  matter,  and 
especially  for  such  as  abounds  in  that  dead  or  inert  form  of  organic  mat- 
ter which  requires  a  stronger  stimulus — the  presence  of  more  power- 
ful chemical  affinities,  that  is — to  bring  it  into  active  decomposition. 
In  such  cases,  the  lime  has  already  done  much  good  before  it  has  been 
brought  into  the  mild  state — and  remaining  afterwards  in  this  state  in 
the  soil,  it  still  serves,  in  a  great  measure,  the  same  slower  after-pur- 
poses as  the  original  addition  of  carbonate  would  have  done. 

3°.  Besides,  if  any  portion  of  it,  after  the  lapse  of  two  or  three 
years,  still  linger  in  the  caustic  state,  (p.  368,)  it  will  continue  to  pro- 
voke more  rapid  changes  among  the  organic  substances  in  the  soi^ 
than  mild  lime  alone  could  have  done. 


CRGANIC    MATTER    OF   THE    SOIL    CONTAINS    NITROGEN.  409 

4°.  Further,  quick-lime  is  soluble  in  water,  and  hence  every  shower 
that  falls  and  sinks  into  the  soil  carries  with  it  a  portion  of  lime,  so 
long  as  any  of  it  remains  in  the  caustic  state.  It  thus  reaches  acid 
matters  that  lie  beneath  the  surface,  and  alters  and  ameliorates  even 
tlie  subsoil  itself 

5°.  It  is  not  a  small  additional  recommendation  of  quick-lime,  that 
by  burning  it  loses  about  44  per  cent,  of  its  weight,  thus  enabling 
nearly  twice  the  quantity  to  be  conveyed  from  place  to  place  at  the 
same  cost  of  transport.  This  not  only  causes  a  direct  saving  of 
money, — as  when  the  burned  chalk  of  Antrim  is  carried  by  sea  to 
the  Ayrshire  coasts — but  an  additional  saving  of  labor  also  upon  the 
farm, — where  the  number  of  hands  and  horses  is  often  barely  suffici- 
ent for  the  necessary  work. 

§  29.  Action  of  lime  on  organic  substances  which  contain  nitrogen. 

I  have  hitherto,  for  the  sake  of  simplicity,  directed  your  attention 
solely  to  the  action,  whether  immediate  or  remote,  which  is  exercised 
by  lime  upon  organic  matter  supposed  to  contain  no  nitrogen.  Its  action 
upon  compounds  in  which  nitrogen  exists  is  no  less  beautiful  and  simple, 
perhaps  even  more  intelligible  and  more  obviously  useful  to  vegetation. 

There  are  several  well  known  facts  which  it  is  here  of  importance 
for  us  to  consider — 

1°.  That  the  black  vegetable  matter  of  the  soil  always  contains  ni- 
trogen. Even  that  which  is  most  inert  retains  a  sensible  proportion  of 
it.  It  exists  in  dry  peat  to  the  amount  of  about  2  per  cent,  of  its  weight, 
and  still  clings  to  the  other  elements  of  the  organic  matter,  even  after  it 
has  undergone  those  prolonged  changes  by  which  it  is  finally  converted 
into  coal.  Since  nitrogen,  therefore,  is  so  important  an  element  in  all 
^^egetable  food,  and  so  necessary  in  some  form  or  other  to  the  healthy 
gr?wth  and  maturity  of  plants,  it  must  be  of  consequence  to  awaken 
this  element  of  decaying  vegetable  matter,  when  it  is  lying  dormant, 
and  tt  cause  it  to  assume  a  form  in  which  it  can  enter  into  and  be- 
come useful  to  our  cultivated  plants. 

2^.  Thu,t  if  vegetable  matter  of  any  kind  be  heated  with  slaked  lime, 
the  whole  of  the  nitrogen  it  may  contain,  in  whatever  state  of  combina- 
tion it  may  previously  exist,  will  be  given  off  in  the  form  of  ammonia. 
The  same  takes  place  still  more  easily  if  a  quantity  of  hydrate  of  potash 
or  of  hydrate  of  soda  be  mixed  with  the  hydrate  of  lime.  Though  it 
has  not  as  yet  been  proved  by  direct  experiment — yet  I  consider  it  to  be 
exceedingly  probable,  that  what  takes  place  quickly  in  our  laboratories^ 
at  a  comparatively  high  temperature,  may  take  place  more  slowly  also 
in  the  soil,  and  at  the  ordinary  temperature  of  the  atmosphere. 

3°.  That  when  animal  and  vegetable  substances  ai^  mixed  with 
earth,  lime,  and  other  alkaline  matters,  in  the  so-called  nitre  beds,  (Lee. 
VIII.,  §  5,)  ammonia  and  nitric  acid  are  both  produced,  the  quantity  of 
nitrogen  contained  in  the  weight  of  these  compounds  extracted  being 
much  greater  than  was  originally  present  in  the  animal  and  vegetable 
matter  employed  (Dumas.)  Under  the  influence  of  alkaline  substances, 
therefore,  even  when  not  in  a  caustic  state,  the  decay  of  animal  and  ve- 
getable matter  in  the  presence  of  air  and  moisture  causes  some  of  the 
nitrogen  of  the  atmosphere  to  become  fixed  in  the  soil  in  the  form  of 


410      ANALOGOUS    DECOMPOSITION    OF    ALL    ORGANIC  SUBSTANCES. 

ammonia  or  of  nitric  acid.  What  takes  place  on  the  confined  area  of  a 
nitre  bed,  may  take  place  to  some  extent  also  in  the  wider  area  of  a 
well-limed  and  well-manured  field. 

In  the  action  of  alkalies  in  the  nitre  bed,  disposing  to  the  produc- 
tion of  nitric  acid,  we  observe  the  same  kind  of  agency,  which  we 
have  already  attributed  to  lime,  in  regard  to  the  more  abundant  ele- 
ments which  exist  in  the  vegetable  matter  of  the  soil.  It  gently  per- 
suades ah  the  elements — nitrogen  and  carbon  alike — to  unite  with 
the  oxygen  of  air  and  water,  and  thus  ultimately  to  form  acid  com- 
pounds with  which  it  may  itself  combine. 

The  action  of  hme  upon  such  organic  matters  containing  nitrogen  as 
usually  exist  in  the  soil,  may,  therefore,  be  briefly  stated  as  follows : — 

1^.  These  substances,  like  all  other  organic  matter,  undergo  in  moist 
air — and,  therefore,  in  the  soil — a  spontaneous  decomposition,  the  ge- 
neral result  of  which  is  the  production  of  ammonia,  and  of  an  acid 
substance  with  which  the  ammonia  may  combine.  This  change  is 
precisely  analogous  to  that  which  takes  place  in  such  substances  as 
starch  and  woody  fibre,  which  contains  no  nitrogen.  In  each  case, 
one  portion  of  the  elements  unites  with  oxygen  to  produce  an  acid, 
the  other  with  hydrogen  to  form  a  compound  possessed  of  alkaline  or 
indifferent  properties.     Thus, — 

With  oxygen,— vegetable  matter  produces  carbonic,  ulmic,  and  other 
acids. 
"  animal  matter  produces  carbonic,  nitric,  ulmic,  and 

other  acids. 
With  hydrogen, — vegetable  matter  produces  marsh  gas  or    other 
carburetted  hydrogens, 
"  animal  matter  produces  ammonia. 

If  the  ammonia  happen  to  be  produced  in  larger  relative  quantity 
than  the  acids  with  which  it  is  to  combine,  or  if  the  carbonic  be  the 
only  acid  with  which  it  unites,  a  portion  of  it  may  escape  into  the  air. 
This  rarely  happens,  however,  in  the  soil,  the  absorbent  properties  of 
the  earthy  matters  of  which  it  consists  being  in  most  cases  sufficient 
to  retain  the  ammonia,  till  it  can  be  made  available  to  the  purposes 
of  vegetable  life. 

When  caustic  (hydrate  of)  lime  is  added  to  a  soil  in  which  ammonia 
exists  in  this  state  of  combination  with  acid  matter,  it  seizes  upon  the 
acid  and  sets  the  ammonia  free.  This  it  does  with  comparative  slow- 
ness, however — for  it  does  not  at  once  come  in  contact  with  it  all — 
and  by  degrees,  so  as  to  store  it  up  in  the  pores  of  the  soil  till  the  roots 
of  plants  can  reach  it,  or  till  it  can  itself  undergo  a  further  change 
by  which  its  nitrogen  may  be  rendered  more  fixed  (p.  411.) 

Carbonate  of  lime,  on  the  other  hand,  still  more  slowly  persuades 
the  ammonia  to  leave  the  acid  substances  (ulmic,  nitric?  &c.,)  with 
which  it  is  combined,  and  yielding  to  it  in  return  its  own  carbonic 
acid,  enables  it  in  the  state  of  soluble  carbonate  of  ammonia  to  be- 
come more  immediately  useful  to  vegetation. 

2°.  But  in  undergoing  this  spontaneous  decay,  even  substances  con- 
taining nitrogen  reach  at  length  a  point  at  which  decomposition  appears 
to  stop — an  inert  condition  in  which,  though  nitrogen  be  present  as  in 
peat,  they  cease  sensibly  to  give  it  off  in  such  a  form  or  quantity  as  to 


AMMONIA   AND    NITRIC    ACID    FORMED.  411 

be'capable  of  ministering  to  vegetable  growth.  Here  caustic  lime  steps 
in  more  quickly,  and  mild  lime  by  slower  degrees,  to  promote  the  fur- 
ther decay.  It  induces  the  carbonaceous  matter  to  take  oxygen  from 
the  air  and  from  water  and  to  form  acids,  and  the  nitrogen  to  unite  with 
the  hydrogen  of  the  water  for  the  production  of  ammonia — thus  help- 
ing forward  the  organic  matter  in  its  natural  course  of  decay,  and 
enabling  it  to  fulfil  its  destined  purposes  in  reference  to  vegetable  life. 

3°.  But  the  ammonia  which  is  thus  disengaged  in  the  soil  by  decay- 
ing organic  matter,  though  not  immediately  worked  up,  so  to  speak,  by 
living  plants,  is  not  permitted  to  escape  in  any  large  quantity  into  the 
air.  The  soil,  as  I  have  already  stated,  is  usually  absorbent  enough  to 
retain  it  in  its  pores  for  an  indefinite  period  of  time.  And  as  in  nature 
and  upon  the  earth's  surface  the  elements  of  matter  are  rarely  permitted 
to  remain  in  a  state  of  repose,  the  ammonia,  though  retained  apparently 
inactive  in  the  soil,  is  yet  slowly  uniting  with  a  portion  of  the  surround- 
ing oxygen  and  forming  nitric  acid  (Lee.  VIII.,  §  5,  note.)  When  no 
other  base  is  present,  this  nitric  acid,  as  it  is  produced,  unites  with  some 
of  the  ammonia  itself  which  still  remains,  forming  nitrate  of  ammonia 
—but  if  potash  or  lime  be  present  within  its  reach,  it  unites  with  them 
in  preference,  and  forms  the  nitrate  of  potash  or  of  lime. 

But  lime,  if  present,  is  not  an  inactive  spectator,  so  to  speak,  of 
this  slov/  oxidation  of  ammonia.  On  the  contrary,  it  promotes  this- 
final  change,  and  by  being  ready  to  unite  with  the  nitric  acid  as  it 
forms,  increases  and  accelerates  its  production,  at  the  expense  of  the 
ammonia  which  it  had  previously  been  instrumental  in  evolving. 

4P.  One  other  important  action  of  lime,  by  which  the  same  com- 
pounds of  nitrogen  are  produced  in  the  soil,  may  in  this  place  be  most 
properly  noticed.  It  is  a  chemical  law  of  apparently  extensive  applica- 
tion, that  when  one  elementary  substance  is  undergoing  a  direct  chemi- 
cal union  with  a  second  in  the  presence  of  a  third,  a  tendency  is  impart- 
ed to  tlie  third  to  unite  also  with  one  of  with  both  of  the  other  two,  al- 
though in  the  same  circumstances  it  w^ould  not  unite  with  either,  if  pre- 
sent alone.  Thus,  when  the  carbonaceous  matter  of  the  soil  is  under- 
going oxidation  in  the  air — that  is,  combining  with  the  oxygen  of  the 
atmosphere — it  imparts  a  tendency  to  the  nitrogen  also  to  unite  with 
oxygen,  which  when  mixed  with  that  gas  alone,  (the  atmosphere  con- 
sisting, as  you  will  recollect,  of  nitrogen  and  oxygen — Lee.  II.,  §  4,) — 
it  has  no  known  disposition  to  do.  The  result  of  this  is  the  production  of 
a  small,  and  always  a  variable,  proportion  of  nitric  acid  during  the  de- 
composition in  the  soil,  of  organic  matter  even,  which  itself  contains  no 
nitrogen. 

Again,  it  is  an  equally  remarkable  chemical  law,  that  elementary 
bodies  which  refuse  to  combine,  however  long  we  may  keep  them  to- 
gether in  a  state  of  mixture,  will  yet  unite  readily  when  presented  to 
each  other  in  what  is  called  by  chemists  the  nascent  state — that  is,  at 
the  moment  when  one  or  other  of  them  is  produced  or  is  separated 
from  a  previous  state  of  combination. 

Thus  when  the  organic  matter  of  the  soil  decomposes  water  in  the 

presence  of  atmospheric  air,  its  carbon  unites  with  the  greater  part 

of  the  oxygen  and  hydrogen  which  are  set  at  liberty,  and  at  the  same 

time  with  more  or  less  of  the  oxygen  of  the  atmosphere — but  at  the 

18 


412         HOW   THESE    CHEMICAL   CHANGES    BENEFIT   VEGETATION. 

same  instant  the  nitrogen  of  the  atmosphere,  which  is  everywhere 
present,  seizes  a  portion  of  the  hydrogen  and  forms  ammonia.  Thus 
a  variable,  and  in  any  one  Hmited  spot  a  minute,  but  over  the  entire 
surface  of  the  globe,  a  large  quantity  of  ammonia  is  produced  during 
the  oxidation  even  of  the  purely  carbonaceous  portion  of  the  organic 
matter  of  the  soil. 

Now  in  proportion  as  the  presence  of  lime  promotes  this  decay  of 
vegetable  and  other  organic  matter  in  the  soil — in  the  same  propor- 
tion does  it  promote  the  production  of  ammonia  and  nitric  acifl,  at  the 
expense  of  the  free  nitrogen  of  the  atmosphere,  and  this  may  be  re- 
garded as  one  of  the  valuable  and  constant  purposes  served  by  the 
presence  of  calcareous  matter  in  the  soil. 

§  30.  How  these  chemical  changes  directly  benefit  vegetation. 

You  will  scarcely,  I  think,  inquire  how  all  these  interesting  chemical 
changes  which  attend  upon  the  presence  of  lime  in  the  soil  are  di- 
rectly useful  to  vegetation,  and  yet  it  may  be  useful  shortly  to  answer 
the  question. 

1°.  Lime  combines  with  the  acid  substances  already  existing  in  the 
soil,  and  thus  promotes  the  decomposition  of  vegetable  matter  which 
those  acid  substances  arrest.  The  further  decompositions  which  en- 
sue are  attended  at  every  step  by  the  production  either  of  gaseous 
compounds — such  as  carbonic  acid  and  light  carburetted  hydrogen — 
which  are  more  or  less  abundantly  absorbed  by  the  roots  and  leaves 
of  plants,  and  thus  help  to  feed  them — or  of  acid  and  other  compounds, 
soluble  in  water,  which,  entering  by  the  roots,  bear  into  the  circula- 
tion of  the  plant  not  only  organic  food,  but  that  supply  of  hme  also 
which  healthy  plants  require. 

2°.  The  changes  it  induces  upon  substances  in  which  nitrogen  is 
present  are  still  more  obviously  useful  to  vegetation.  It  eliminates  am  • 
monia  from  the  compounds  in  which  it  exists  already  formed,  and  pro- 
motes its  slow  conversion  into  nitric  acid,  by  which  the  nitrogen  is 
rendered  more  fixed  in  the  soil.  It  disposes  the  nitrogen  of  more  or 
less  inert  organic  matter  to  assume  the  form  of  ammonia  and  nitric 
acid,  in  which  state  experience  has  long  shown  that  this  element  is 
directly  favorable  to  the  growth  of  plants, 

3°.  It  influences  in  an  unknown  degree,  the  nitrogen  of  the  atmos- 
phere to  become  fixed  in  larger  proportion  in  the  soil,  in  the  form  of  nitric 
acid  and  ammonia,  than  would  ott^rwise  be  the  case,  and  this  it  does 
both  by  the  greater  amount  of  decay  or  oxidation  which  it  brings 
about  in  a  given  time,  and  by  the  kind  of  compounds  which,  under  its 
influence,  the  organic  matter  is  persuaded  to  form.  The  amount  of 
nitrogenoua  food  placed  within  reach  of  plants  by  this  agency  of  lime 
will  vary  with  the  climate,  with  the  nature  of  the  soil,  with  its  con- 
dition as  to  drainage,  and  with  the  more  or  less  liberal  and  skilful 
manner  in  which  it  is  farmed. 

§  31.  Why  lime  must  he  kept  near  the  surface. 

Nor  will  you  fail  to  see  the  important  reasons  why  lime  ought  to 
be  kept  near  the  surface  of  the  soil — since 
P.  The  action  of  hme  upon  organic  matter  is  almost  nothing  m 


ACTION    OF    LIBIE    UPON    SALINE    SUBSTANCES.  41.3 

the  absence  of  air  and  moisture.  If  the  lime  sink,  therefore,  beyond 
the  constant  reach  of  fresh  air,  its  efficacy  is  in  a  great  degree  lost. 

2°.  But  the  agency  of  the  hght  and  heat  of  the  sun,  though  I  have 
not  hitherto  insisted  upon  their  action — are  scarcely  less  necessary  to 
the  full  experience  of  the  benefits  which  lime  is  capable  of  conferring. 
The  light  of  the  sun  accelerates  nearly  all  the  chemical  decompositions 
that  take  place  in  the  soil — while  some  it  appears  especially  to  promote. 
The  warmth  of  the  sun's  rays  may  penetrate  to  some  depth,  but  their 
light  can  only  act  upon  the  immediate  surface  of  the  soil.  Hence  t!ie 
skilful  agriculturist  will  endeavor,  if  possible,  to  keep  some  of  his  lime 
at  least  upon  the  very  surface  of  his  arable  land.  Perhaps  this  in- 
fluence of  light  might  even  be  adduced  as  an  argument  infavor  of  the 
frequent  application  of  lime  in  small  doses,  as  a  means  of  keeping  a 
portion  of  it  always  within  reach  of  the  sun's  rays ;  and  this  more  es- 
pecially on  grass  lands,  to  which  no  mechanical  means  can  be  applied 
for  the  purpose  of  bringing  again  to  the  surface  the  lime  that  has  sunk. 

There  are,  at  the  same  time,  as  you  will  recollect,  good  reason  also 
why  a  portion  of  the  hme  should  be  diffused  through  the  body  of  the 
soil,  both  for  the  purpose  of  combining  with  organic  acids,  already 
existing  there,  and  with  the  view  of  acting  upon  certain  inorganic  or 
mineral  substances,  which  are  either  decidedly  injurious,  or  by  the  ac- 
tion of  lime  may  be  rendered  more  wholesome  to  vegetation. 

In  order  that  this  diffusion  may  be  effected,  and  especially  that  lime 
may  not  be  unnecessarily  wasted  where  pains  are  taken  by  mechanical 
means  to  keep  it  near  the  surface,  an  efficient  system  of  under-drainage 
should  be  carefully  kept  up.  Where  the  rains  that  fall  are  allowed 
to  flow  off  the  surface  of  the  land,  they  wash  more  lime  away  the  more 
carefully  it  is  kept  among  the  upper  soil — but  where  a  free  outlet  is  af- 
forded to  the  waters  beneath,  they  carry  the  lime  with  them  as  they 
sink  towards  the  subsoil,  and  have  been  robbed  again  of  the  greater 
part  of  it  before  they  escape  into  the  drains.  Thus  on  drained  land 
the  rains  that  fall  aid  Hme  in  producing  its  beneficial  effects,  while  in 
undrained  land  they  in  a  greater  or  less  degree  counteract  it. 

§  32.  Action  of  lime  upon  the  inorganic  or  mineral  matter  of  the  soil. 

Though  the  main  general  agency  of  lime  is  exerted,  as  we  have 
seen,  upon  the  organic  matter  it  meets  with,  yet  it  often  also  produces 
direct  chemical  changes  upon  the  mineral  compounds  existing  in  the 
soil,  which  are  of  great  importance  to  vegetation.     Thus 

1°.  Lime,  either  in  the  mild  or  in  the  caustic  state,  possesses  the 
property  of  decomposing  the  sulphate  of  iron,  whic>  especially  abounds 
in  peaty  soils,  and  in  many  localities  so  saturates  the  subsoil  as  to 
make  it  destructive  to  the  roots  of  plants.  Sprengel  mentions  a  case 
where  the  first  year's  clover  always  grew  well,  while  in  the  second 
year  it  always  died  away.  This;,  upon  examination,  was  found  to  be 
owing  to  the  ferruginous  nature  of  the  subsoil,  which  caused  the  death 
of  the  plant  as  soon  as  the  roots  began  to  penetrate  it. 

When  salts  of  iron  exist  in  the  soil,  a  dressing  with  Hme  will  bring 
the  land  into  a  wholesome  state  without  other  aid.  The  lime  will 
combine  with  the  acid,  and  form  gypsum,  if  it  is  the  sulphate  of  iron 
that  is  present,  while  i\iQ  first  oxide  of  iron  which  is  set  free  will,  by 


414      LIMB    DECOMPOSES.  SULPHATES   AND    SILICATK?     SETS    FREE 

exposure  to  the  air,  be  converted  into  the  second  or  red  oxide,  in 
which  state  this  metal  is  no  longer  hurtful  to  vegetation. 

When  these  salts  are  to  be  decomposed  and  removed  from  the  sub- 
soil, lime  must  be  aided  by  the  subsoil  plough  and  the  drain.  Unless 
an  outlet  beneath  be  provided  for  the  surface  water,  by  which  the 
rains  may  be  enabled  to  wash  away  slowly  the  noxious  substances 
from  the  subsoil,  even  the  addition  of  a  copious  dose  of  lime  will  only 
produce  a  temporary  improvement. 

2°.  Lime  decomposes  also  the  sulphates  of  magnesia  and  of  alumi- 
na, both  of  which  are  occasionally  found  in  the  soil,  and,  being  very  so- 
luble salts,  are  liable  to  be  taken  up  by  the  roots  in  such  quantity  as  to 
be  hurtful  to  the  growing  plants.  When  soils  which  contain  any  of 
the  three  salts  I  have  mentioned  have  once  been  limed  or  marled^  it 
is  in  vain  to  add  gypsum  in  the  hope  of  favoring  the  clover  crop,  since 
the  lime,  in  decomposing  the  sulphates,  has  already  formed  an  abun- 
dant supply  of  this  compound  for  all  the  purposes  of  .vegetation. 

3°.  Among  the  earthy  constituents  of  the  soil,  we  have  already  seen 
that  there  often  exist  fragments  of  felspar  and  of  other  minerals  derived 
from  the  granitic  and  trap  rocks,  which  contain  potash  or  soda  in  the 
state  o^  silicates.  These  silicates  we  know  to  be  slowly  decomposer 
by  the  agency  of  the  carbonic  acid  of  the  air,  (Lee.  X.,  §  1,)  ana 
their  alkali  set  free  in  a  soluble  state.  This  decomposition  is  said  to 
be  prompted  by  the  presence  of  lime  (p.  361.) 

Again,  the  stalks  of  the  grasses  and  the  straw  of  the  corn-bearing 
plants  contain  much  silica  in  combination  with  potash  and  soda.  In 
farm-yard  manure,  therefore,  much  of  these  silicates  is  present,  and 
when  mixed  with  the  soil,  there  appears  little  reason  to  doubt  that 
they  are  of  much  benefit  to  the  growing  crops.  On  these  silicates, 
in  the  presence  of  carbonic  acid  and  moisture,  the  lime  acts  as  iidoes 
upon  the  mineral  silicates.  It  aids  in  the  liberation  of  the  potash  and 
soda,  and  thus  promotes  the  performance  of  those  important  functions 
which  these  alkalies  are  destined  to  exercise  in  reference  to  vegetable 
growth  (p.  328.) 

While  the  alkali  is  set  free  the  lime  itself  combines  with  the  silica, 
and  hence  one  source  of  the  silicate  of  lime  which,  as  I  have  already 
mentioned  to  you,  (p.  380,)  usually  exists  in  sensible  quantity  in  our 
cultivated  soils.  It  has  been  stated  by  Sprengel  (Lehre  vom  Diinger, 
p.  310,)  as  one  reason  why  the  addition  of  lime  must  be  repeated  so 
frequently  upon  some  soils  in  which  silica  abounds,  that  an  insoluble 
silicate  of  lime  is  found,  which  is  of  no  use  to  vegetation.  But  the 
silicates  of  lime  are  slowly  decomposed  by  the  agency  of  the  carbonic 
acid  of  the  air  and  of  decaying  vegetation,  and  to  this  cause  in  a  pre- 
vious lecture  (Lee.  XII.,  §  4,)  I  have  ascribed  much  of  the  fertile 
character  of  the  trap  and  syenitic  soils,  and  of  their  beneficial  action 
when  laid  on  as  a  manure. 

4°.  Potash  and  soda  exist  to  some  extent  in  clay  soils  in  combina- 
tion with  their  alumina.  The  presence  of  lime  has  a  similar  influence 
in  setting  the  alkalies  free  from  this  state  of  combination  also. 

5°.  Alumina  has  the  property  of  combining  readily  with  many  vege- 
table acids,  and  in  the  clay  soils  exercises  a  constant  influence,  similar 
jn  kind  to  that  of  lime  and  other  alkaline  substances,  in  persuading  the 


ALKALINE  SUBSTANCES,  AND  DECOMPOSES  COMMON  SALT.       4l0 

organic  matter  to  those  forms  of  decay  in  which  acid  compounds  are 
more  abundantly  produced.  Hence,  clay  soils  almost  always  contain  a 
portion  of  alumina  in  combination  with  organic  matter.  This  organic 
matter  is  readily  given  up  to  lime,  and  by  the  more  energetic  action  of 
this  substance  is  sooner  made  available  to  the  wants  of  new  races  of 
plants. 

6°.  I  shall  bring  under  your  notice  only  one  other,  but  a  highly  im- 
portant, decomposing  action,  which  lime  exercises  in  soils  that  abound 
in  vegetable  matter.  In  the  presence  of  decaying  organic  substances 
the  carbonate  of  lime  is  capable  of  slowly  decomposing  common  salt, 
producing  carbonate  of  soda  and  chloride  of  calcium.  It  exercises  also 
a  similar  decomposing  effect,  even  upon  the  sulphate  of  soda,  and,  ac- 
cording to  Berthollet,  (Dumas  7Vaite  de  Chemie,  ii.,  p.  334.)  incrus- 
tations of  carbonate  of  soda  (of  Trona  or  Natron,  w^hich  is  a  sesqui 
carbonate  of  soda,)  are  observed  on  the  surface  of  the  soil,  wherever 
carbonate  of  lime  and  common  salt  are  in  contact  with  each  other. 
If  we  consider  that  along  all  our  coasts  common  salt  may  be  said 
to  abound  in  the  soil,  being  yearly  sprinkled  over  it  by  the  salt  sea 
winds — that  generally,  along  the  same  coasts,  the  application  of 
sulphates  produces  little  sensible  effect  upon  the  crops,  and  that,  there- 
fore, in  all  probability  they  abound  in  the  soil,  derived,  it  may  be,  from 
the  same  sea  spray — we  may  safely  conclude,  I  think,  that  the  decom- 
position now  explained  must  take  place  extensively  in  all  those  parts  of 
our  island  which  are  so  situated,  if  lime  in  any  of  its  forms  either  exists 
naturally  or  has  been  artificially  added  to  the  land.  The  same  must  be 
the  case  also  in  those  districts  where  salt  springs  occur,  and  generally 
over  the  new  red  sand-stone  formation,  in  which  sea  salt  more  especially 
occurs. 

And  if  we  further  consider  the  important  purposes  which  the  carbo- 
nate of  soda  thus  produced  may  serve  in  reference  to  vegetation — that 
it  may  dissolve  vegetable  matter  and  carry  it  into  the  roots— ^that  it  may 
form  soluble  silicates,  and  thus  supply  the  necessary  siliceous  matter  to 
the  stems  of  the  grasses  and  other  plants — and  that  rising,  as  it  naturally 
does,  to  the  surfhce  of  the  soil,  it  there,  in  the  presence  of  vegetable  mat- 
ter, provokes  to  the  formation  of  nitrates,  so  wholesome  to  vegetable 
life — we  may  regard  the  decomposing  action  of  lime  by  which  this  car- 
bonate is  produced  as  among  the  most  valuable  of  its  properties  to  the 
practical  farmer,  wherever  circumstances  are  favorable  for  its  exercise. 

§  33.  Action  of  lime  on  animal  and  vegetable  life. 

It  is  only  necessary  to  allude,  in  conclusion,  to  one  or  two  other 
useful  purposes  which  lime  is  said  to  serve  in  reference  to  animal  and 
vegetable  life.     Thus 

P.  It  is  said  to  prove  fatal,  especially  in  the  caustic  state,  to  worms, 
to  slugs,*  and  to  many  insects  injurious  to  the  farmer,  and  to  destroy 
their  eggs  and  larvae.  In  Scotland  it  has  been  found  in  some  instances 
to  check  the  ravages  of  the  fly.  On  the  other  hand,  in  the  state  of  car- 
bonate, it  is  propitious  to  the  growth  of  the  land  snail  and  similar  crea- 

*  Whon  the  wheat  crop  is  attacked  by  slugs  above  ground,  nofhinjj  will  do  so  much  poos' 
as  slaked  lime,  sown  over  the  crop  before  suniise. — Hillyard,  Royal  Agricultural  Journa 
iii  ,  p.  302. 


416  LIME    KILLS    INSECTS    AND    SEEDS. 

tures  which  bear  shells.  In  highly  limed  land  the  former  may  be  seen 
crowded  at  the  roots  of  the  hedges,  from  which  they  make  frequent  in- 
cursions upon  the  young  crops,  and  are,  I  believe,  especially  hurtful 
to  the  turnips. 

2°.  It  is  found  to  prevent  smut  in  wheat.  For  this  purpose  the 
seed  is  steeped  in  lime,  and  afterwards  dried  with  slaked  lime,  or  lime 
water  is  poured  up;^  the  heap  of  corn,  which  is  turned  over,  and  left 
for  24  hours  (Hillyard.) 

3^.  It  is  also  said  to  prevent  the  rot  and  foot-rot  in  sheep  fed  upon 
pjistures  on  which,  before  hming.  the  stock  was  liable  to  be  affected 
by  these  diseases  (Prideaux.) 

4°.  In  regard  to  its  action  upon  living  plants,  it  is  certain  that  it  ex- 
tirpates certain  of  the  coarser  grasses  from  sour  pastures  and  brings  up 
a  tenderer  herbage ;  but  practical  men  appear  to  differ  in  regard  to  its  ef- 
fects upon  the  roots  and  seeds  of  the  more  troublesome  weeds.  Accord- 
ing to  some,  the  addition  of  lime  to  a  compost,  or  to  the  soil,  will  kill 
the  roots  of  weeds  and  render  unproductive  such  noxious  seeds  as  may 
happen  to  be  present.  According  to  others  (p.  405,)  this  is  a  mistake. 
I  believe  the  truth  to  be,  that  lime  will  lead  to  their  destruction  and 
decay,  if  the  circumstances  are  favorable  or  if  proper  pains  be  taken 
to  effect  it.  But  air  and  moisture  are  necessary  to  insure  this,  as  they 
are  to  effect  the  rapid  decay  of  dead  organic  matter.  If  the  ingre- 
dients of  the  compost  be  duly  proportioned,  or  if  the  dose  of  lime 
added  to  the  land  be  sufficiently  large,  and  if  in  each  case  the  mix- 
ture be  frequently  turned,  the  final  destruction  of  roots  and  seeds  may 
in  general  be  safely  calculated  upon. 

§  34.   Use  of  silicate  of  lime. 

There  is  one  compound  of  lime  which,  though  occurring  occasionally 
m  all  soils,  has  not  hitherto  been  applied  to  the  improvement  of  the  land 
even  in  localities  where  it  most  abounds.  This  compound  is  the  silicate 
of  lime.  I  have  already  directed  your  attention  to  the  presence  of  this 
compound  in  the  trap  rocks,  and  to  the  fertile  character  which  it  imparts 
to  the  soils  which  are  formed  by  the  natural  degradation  of  these  rocks. 

In  those  districts  where  the  smelting  of  iron  is  carried  on,  the  first 
slag  that  is  obtained  consists  in  great  part  of  silicate  of  lime.  This 
slag  accumulates  in  large  quantities,  and  is  employed  in  some  dis- 
tricts for  mending  the  roads.  It  is  not  unworthy  the  attention  of  the 
practical  farmer — as  an  improver  of  his  fields — especially  where  caus- 
tic lime  is  distant  and  expensive,  or  where  boggy  and  peaty  soils  are 
met  with  in  which  vegetable  matter  abounds.  On  such  land  it  may 
be  laid  in  large  quantity.  It  will  decompose  slowly,  and  while  it  im- 
parts to  the  soil  solidity  and  firmness,  will  supply  both  lime  and  silica 
to  the  growing  crops,  for  a  long  period  of  time. 

I  have  thuB  drawn  your  affention  to  the  most  important  topics  connected  with  the  use  of 
lime,  so  efRcacinijs  an  iiisfrnmenf  in  the  han(isorthe  skilful  arid  impiovinsr  farmer  forame- 
lioralin2  the  condition  and  increasing  the  productiveness  of  his  land.  If  I  have  appeared 
to  dwell  long  upon  this  subject,  it  is  because  of  (he  value  which  I  know  to  be  attached  by 
pr.ictical  men  to  a  correct  exposition  of  the  virtu<>s  of  lime  and  of  tlie  theory  by  which  its 
effects  are  to  be  e.^plained.  I  believe  thai  in  the  theoretical  part  I  have  been  able  to  point 
om  to  you  the  leading  chemical  principles  upon  which  its  influence  depends— if  any  thing 
is  still  dark,  it  is  becnn^e  our  knowledge  is  not  yet  complete.  A  few  years  more,  and  we 
may  hope  to  have  the  mists  which  hanjr  over  this,  as  over  many  other  branches  of  agricul- 
tural chemistry,  in  a  great  measure  cleared  away. 


LECTURE  XVII. 


Of  organic  manures.— Vegetable  and  animal  manures— Green  manuring ;  ploughing  in  of 
spurry,  the  white  lupin,  the  vetcii,  buck-wheat,  rape,  rye,  borage.— -Natural  green  manu- 
ring.— Improvement  of  the  soil  by  laying  down  to  grass  and  by  planting. — Use  of  sea- 
weed.— Dry  vegetable  manures  :  dry  straw,  chaff,  rape-dust,  malt-dust,  sawdust,  cotton 
seeds,  dry  leaves.— Decayed  vegetable  matter:  use  of  peat,  tanners'  bark,  and  composts 
of  vegetable  matter.— Charcoal  powder,  soot.— Relative  value,  theoretical,  and  practical, 
of  different  vegetable  manures. 

By  organic  manures  are  understood  all  those  substances  either  of 
vegetable  or  of  animal  origin,  which,  are  applied  to  the  land  for  the 
purpose  of  increasing  its  fertility.  It  will  be  convenient  to  consider 
these  two  classes  of  organic  substances  separately. 

The' parts  of  vegetables  may  be  applied  to  the  soil  in  three  dif- 
ferent forms — in  the  green,  in  the  dry,  and  in  the  more  or  less  natu- 
rally decayed,  fermented,  or  artificially  decomposed  state. 

§  1.  O/*  green  manuring^  or  the  application  of  vegetable  matter  in 
the  green  state. 

By  green  manuring  is  meant  the  ploughing  in  of  green  crops  in 
their  living  state — or  of  green  vegetables  left  or  spread  upon  the 
land  for  the  purpose. 

1°.  We  have  seen  in  the  preceding  lecture  how  important  air  and 
water  are  to  the  decomposition  of  organic  matter.  Now  green  ve- 
getable substances  contain  within  themselves  much  water,  undergo 
decomposition  more  readily,  therefore,  than  such  as  have  been  dried, 
and  are  more  immediately  serviceable  when  mixed  with  the  soil. 

2°.  In  the  sap  of  plants  also  there  generally  exist  certain  compounds 
containing  nitrogen,  which  not  only  decompose  very  readily  themselves, 
but  have  the  property  of  persuading  or  inducing  the  elements  of  the 
other  organic  matters,  with  which  they  are  in  contact,  to  assume  new 
forms  or  to  enter  into  new  chemical  combinations.  Hence,  the  sap  of 
plants  almost  invariably  undergoes  more  or  less  rapid  decomposition 
even  when  preserved  from  the  contact  of  both  air  and  water.  When 
this  decomposition  has  once  commenced  in  the  sap  it  is  gradually  propa- 
gated to  the  woody  fibre  and  to  the  other  substances  of  which  the  mass 
of  the  stems  and  roots  of  plants  is  composed.  Hence,  recent  vege- 
table  matter  will  undergo  a  comparatively  rapid  decomposition,  ever 
when  buried  to  some  depth  beneath  the  soil — and  the  elements  of  which 
it  consists  will  form  new  compounds  more  or  less  useful  to  living  plants, 
in  circumstances  where  dry  and  where  many  forms  even  of  partially 
decomposed  vegetable  matter  would  undergo  no  change  whatever. 

3^.  Further — when  green  vegetable  matter  is  allowed  to  decay  ir 
the  open  air,  it  is  gradually  resolved  more  or  less  completely  into  car 
bonic  acid,  which  escapes  into  the  air  and  is  so  far  lost.  But  when 
buried  beneath  the  surface,  this  formation  of  carbonic  acid  proceeds 
less  rapidly,  and  other  compounds — preparatory  to  the  final  resolution 
into  carbonic  acid  and  water — are  produced  in  greater  quantity  and 


418      GREEN  VEGETABLES  READILY  DECAY,  AND  ENRICH  THE  SOIL. 

linger  in  the  soil.  Thus  by  burying  vegetable  substances  in  his  lemd 
in  their  green  state,  the  practical  man  actually  saves  a  portion  of  the 
organic  food  of  plants,  which  would  otherwise  so  far  run  to  waste. 

4°.  FinaLy :  Green  vegetable  substances,  by  exposure  to  the  air, 
gradually  give  up  a  portion  of  the  saline  matter  they  contain  to  the 
showers  of  rain  that  fall.  This  more  or  less  escapes  and  is  lost.  But  if 
buried  beneath  the  soil  this  saline  matter  is  restored  to  the  land,  and 
where  the  green  matter  thus  buried  is  in  the  state  of  a  growing  crop, 
both  the  organic  and  inorganic  substances  it  contains  are  more  equally 
diffused  through  the  soil  than  they  could  be  by  any  other  known  process. 

On  one  or  other  of  these  principles  depend  nearly  all  the  special  ad- 
vantages which  are  known  to  follow  from  green  manuring  and  from  the 
employment  of  green  vegetable  matter  in  the  preparation  of  composts. 

§  2.  Important  practical  results  obtained  by  green  manuring. 

But  this  explanation  of  the  principles  on  which  thecfficacy  of  ^een 
manuring  depends,  does  not  fully  illustrate  the  important  practical  re- 
sults by  which,  in  many  localities,  it  is  uniformly  followed. 

Let  us  glance  at  these  results. 

P.  The  ploughing  in  of  green  vegetables  on  the  spot  where  they 
have  grown  may  be  followed  as  a  method  of  manuring  and  enriching 
all  land,  where  other  manures  are  less  abundant.  Growing  plants 
bring  up  from  beneath,  as  far  as  their  roots  extend,  those  substances 
which  are  useful  to  vegetation — and  retain  them  in  their  leaves  and 
stems.  By  ploughing  in  the  whole  plant  we  restore  to  the  surface 
what  had  previously  sunk  to  a  greater  or  less  depth,  and  thus  make 
it  more  fertile  than  before  the  green  crop  was  sown. 

2°.  This  manuring  is  performed  with  the  least  loss  by  the  use  of 
vegetables  in  the  green  state.  By  allowing  them  to  decay  in  the  open 
air,  there  is,  as  above  stated,  a  loss  both  of  organic  and  of  inorganic 
matter — if  they  be  converted  into  fermented  (farm-yard)  manure,  there 
is  also  a  large  loss,  as  we  shall  hereafter  see ;  and  the  same  is  the 
case,  if  they  are  employed  in  feeding  stock,  with  a  view  to  their  con- 
version into  manure.  In  no  other  form  can  the  same  crop  convey  to 
the  soil  an  equal  amount  of  enriching  matter  as  in  that  of  green 
Leaves  and  stems.  Where  the  first  object,  therefore,  in  the  farmer's 
practice,  is  so  to  use  his  crops  as  to  enrich  his  land — he  will  soonest 
effect  it  by  ploughing  them  in  in  the  green  state. 

3°.  Another  important  result  is,  that  the  beneficial  action  is  almost 
immediate.  Green  vegetables  decompose  rapidly,  and  thus  the  first 
crop  which  follows  a  green  manuring  is  benefitted  and  increased  by 
it.  But  partly  for  this  reason  also  the  green  manuring — of  corn  crop- 
ped land — if  aided  by  no  other  manure,  must  generally  be  repeated 
every  second  year. 

4°.  It  is  said  that  grain  crops  which  succeed  a  green  manuring  are 
never  laid — and  that  the  produce  in  grain  is  greater  in  proportion  to 
the  straw,  than  when  manured  with  fermented  dung. 

5°.  But  it  is  deserving  of  separate  consideration,  that  green  manu- 
ring is  especially  adapted  for  improving  and  enriching  soils  which  are 
poor  in  vegetable  matter.  The  principles  on  which  living  plants  draw 
a  part — sometimes  a  lari  >  part — of  their  sustenance  from  the  air, 


GREEN  MANURE  MOST  USEFUL  TO  POOR  AND  SANDY  SOIL.         419 

have  already  been  discussed,  and  I  may  presume  that  you  sufficiently 
understand  the  principles  and  admit  the  fact.  Living  i)lants,  then, 
contain  in  their  substance  not  only  all  they  have  drawn  up  from  the 
soil,  but  also  a  great  part  of  what  they  have  drawn  from  the  air. 
Plough  in  these  living  plants,  and  you  necessarily  add  to  the  soil 
more  than  was  taken  from  it — in  other  words,  you  make  it  richer  in 
organic  matter.  Repeat  the  process  with  a  second  crop  and  it  be- 
comes richer  still — and  it  would  be  difficult  to  define  the  limit  beyond 
which  the  process  could  no  further  be  carried. 

Is  there  any  soil  then,  in  the  ordinary  cUmates  of  Europe,  which  is  be- 
yond the  reach  of  this  improving  process  ?  Those  only  are  so  on  which 
plants  refuse  to  grow  at  all,  or  on  which  they  grow  so  languidly  as  to 
extract  from  the  air  no  more  than  is  restored  to  it  again  by  the  natu- 
ral decay  of  the  organic  matter  which  the  soils  already  contain. 

But  for  those  plants  which  grow  naturally  upon  the  soil,  agricultural 
skill  may  substitute  others,  which  will  increase  more  rapidly,  and  pro- 
duce a  larger  quantity  of  green  leaves  and  stems  for  the  purpose  of  being 
buried  in  the  soil.  Hence,  the  selection  of  particular  crops  for  the  pur- 
pose of  giving  manuring — those  being  obviously  the  fittest  which  in  the 
given  soil  and  climate  grow  most  rapidly,  or  which  produce  the  largest 
quantity  of  vegetable  matter  in  the  shortest  time  and  at  the  smallest  cost. 

§3.  Of  the  plants  which  in  different  soils  and  climates  are  employed 
for  green  manuring. 

On  this  prmciple  is  founded  the  selection  o^ different  plants  in  different 
soils  and  climates  for  the  purpose  of  green  manuring.  That  which 
in  Italy  will  yield  the  largest  produce  of  leaves  and  stems,  at  the  least 
cost,  and  in  the  shortest  time,  may  not  do  so  in  the  North  of^  England  or 
of  Germany — and  that  which  will  enrich  a  poor  clay  or  an  exhausted 
loam  may  refuse  even  to  groW;  in  a  healthy  manner,  upon  a  drifting  sand. 

1°.  Spiirry  (Spergula  Arvensis.) — It  is  to  poor  dry  sandy  soils  that 
green  manuring  has  been  found  most  signally  beneficial,  and  for  such 
soils  no  plant  has  been  more  lauded  than  spurry.  It  may  either  be 
sown  in  autumn  on  the  corn  stubble  or  after  early  potatoes,  and 
ploughed  in  in  spring  preparatory  to  the  annual  crop,  or  it  may  be 
used  to  replace  the  naked  fallow,  which  is  often  hurtful  to  lands  of  so 
light  a  character.  In  the  latter  case,  the  first  sowing  may  take  place 
in  March,  the  second  in  May,  and  the  third  in  July—  each  crop  being 
ploughed  in  to  the  depth  of  three  or  four  inches,  and  the  new  seed 
then  sown  and  harrowed.  When  the  third  crop  is  ploughed  in,  the 
land  is  ready  for  a  crop  of  winter  corn. 

Von  Voght  (Vortheile  der  griinen  Bediingung)  states  that  by  such 
treatment  the  worst  shifting  sands  may  be  made  to  yield  remunerative 
crops  of  rye — that  the  most  worthless  sands  are  more  improved  by  it 
than  those  of  abetter  natural  quality — that  the  green  manuring  every 
other  year  not  only  nourishes  sufficiently  the  alternate  crops  of  rye, 
but  gradually  enriches  the  soil — and  that  it  increases  the  effect  of  any 
other  manure  that  may  subsequently  be  put  on.  He  adds,  also,  that 
spurry  produces  often  as  much  improvement  if  eaten  off  by  cattle  as 
if  ploughed  in,  and  that  when  fed  upon  this  plant,  either  green  or  in 
the  statti  )f  hay,  cows  not  only  give  more  milk,  but  of  a  richer  quality. 
18* 


420  USE    OF   THE    VETCH,    BUCKWHEAT,    ETC. 

2°.  White  Lupins. — In  Italy,  and  in  the  south  of  France,  the  white 
lupin  is  extensively  cultivated  as  a  green  manure.  In  Germany,  also, 
it  has  been  found  to  be  one  of  those  plants  by  which  unfruitful  sandy 
soils  may  be  most  speedily  brought  into  a  productive  state.  The  supe- 
riority of  this  plant  for  the  purpose  of  enriching  the  soil  depends  upon 
its  deep  roots,  which  descend  more  than  two  feet  beneath  the  surface 
— upon  its  being  little  injured  by  drought,  and  Uttle  liable  to  be  at- 
tacked by  insects — on  its  rapid  growth — and  upon  its  large  produce 
in  leaves  and  stems.  Even  in  the  North  of  Germany  it  is  said  to 
yield,  in  three  and  a  half  to  four  months,  10  to  12  tons  of  green  herb- 
age. It  grows  in  all  soils  except  such  as  are  marly  and  calcareous, 
is  especially  partial  to  such  as  have  a  ferruginous  subsoil,  and  besides 
enriching,  also  opev^  stiff  clays  by  its  strong  stems  and  roots. 

3^.  T^Ae  Vetck  is  inferior  in  many  of  its  qualities  to  the  white  lu- 
pin— yet  in  Southern  Germany  it  is  often  sown  on  the  stubble,  and 
ploughed  in  after  it  has  been  touched  with  the  frost,  and  has  begun 
to  decay.  In  England  also  the  winter  tare  ploughed  in  early  in  spring 
has  been  found  highly  advantageous  (British  Husbandry,  I.,  p.  407.)  It 
is  a  more  precarious,  however,  and  a  more  expensive  crop  than  either 
of  the  former,  and  requires  a  better  soil  for  its  successful  growth. 

4°.  Buck-  Wheat  is  also  too  uncertain  a  crop,  and  the  high  price  of 
its  seed  renders  it  inferior  in  value  to  spurry  on  sandy  soils.  It  is  su- 
perior to  this  latter  plant,  however,  on  poor  heaths.  In  Southern 
Germany  it  is  sown  on  the  stubble,  and  ploughed  in  when  it  is  18  or 
20  inches  high. 

5°.  Rape  can  only  be  sown  upon  a  soil  which  is  already  in  some 
measure  rich,  but  it  has  the  advantage  of  continuing  to  grow  very  late 
in  the  autumn,  and  of  beginning  again  very  early  in  spring.  It  sends 
down  deep  roots  also,  and  loosens  clayey  soils  by  its  thick  stems.  In 
the  light  soils  of  Alsace  it  is  sown  after  early  peas  and  potatoes,  and 
manures  the  land  for  the  succeeding  crop  of  wheat  or  rye. 

5°.  Bye  is  pronounced  by  Von  Voght  to  be  the  best  of  all  green 
manures  for  sandy  soils,  but  it  is  also  the  most  expensive.  It  is  a 
very  sure  crop  and  begins  to  grow  very  early  in  the  spring,  but  it  is 
not  deep  rooted.  It  has  been  used  with  advantage  in  Northern  Italy 
and  in  Germany. 

6°.  Tinmips  have  been  sown  in  Sussex  with  good  effect  as  a  stub- 
ble crop  for  ploughing  in  in  spring,  and  in  Norfolk  and  elsewhere  the 
portions  of  the  turnip  bulbs  which  are  left  when  they  are  eaten  off 
by  sheep  contribute,  when  ploughed  in,  to  enrich  the  land  for  the 
barley  that  is  to  follow.  Turnip  tops  are  in  many  places  ploughed 
in  with  much  benefit  to  the  land.*  Potatoe  tops  also  might  be  dug 
or  ploughed  in  with  equal  advantage. 

7^.  Borate  has  been  strongly  recommended  in  Germany,  and  es- 
pecially by  Lampadius.  It  is  stated  by  this  experimenter  that  borage 
draws  from  the  air  ten  times  as  much  of  the  elements  of  its  organic 
matter  as  it  does  from  the  soil,  and  that  therefore  it  is  admirably  fitted 
for  enriching  the  land  on  which  it  grows. 

8°.  Red  Clover  is  often  ploughed  in  as  a  manure.     On  the  Rhine  it 

•  "  I  find  no  better  way  of  manuring  for  wheat  after  turnips,  than  ploughing  in  the  tops 
while  etill  green,  as  soon  as  the  turnips  arc  taken  off  the  land."— iWr.  Campbell,  of  Craigie. 


GREEN  MANURING  SUITABLE  FOR   AFTEH-CROPS  OF  CORN.         421 

IS  sown  for  this  purpose,  being  ploughed  in  before  it  begins  to  flower. 
In  French  Flanders  two  crops  ol'  clover  are  cut^  and  the  third  ploughed 
in,  and  in  some  parts  of  the  United  States  of  North  America  the  clover 
which  alternates  with  the  wheat  crop  is  ploughed  in  as  the  only  ma- 
nure (Barclay's  "-Agricultural  Tour  in  the  United  States.")  White 
Clover  is  not  so  valuable  for  this  purpose,  for  neither  is  it  so  deep 
rooted  nor  does  it  yield  so  large  a  crop  of  stems  and  leaves. 

9^.  Old  Grass. — Perhaps  the  most  common  form  of  green  manur- 
ing practised  in  this  country  is  that  of  ploughing  up  grass  lands  of 
various  ages.  The  green  matter  of  the  sods  serves  to  manure  the 
after-crop,  and  renders  the  soil  capable  of  yielding  a  richer  return  at 
a  smaller  expense  of  manure  artificially  added. 

In  regard  to  all  these  forms  of  green  manuring  it  is  to  be  observed 
that  they  enrich  the  soil  generally,  and  are  therefore  well  fitted  to 
prepare  it  for  after-crops  of  corn ;  they  will  not  fit  it,  however,  for  a 
special  crop,  such  as  turnips,  which  requires  to  be  unnaturally  forced 
or  pushed  forward  at  a  particular  period  of  its  growth. 

§  4.  Will  green  manuring  alone  prevent  land  from  becoming  exhausted? 

If  by  green  manuring  is  meant  the  growing  of  vegetable  matter  upon 
one  field,  and  ploughing  it  in  green  into  another,  as  is  sometimes  done, 
it  may  be  safely  said  that,  when  judiciously  practised,  land  may  by 
this  single  process  be  secured  for  an  indefinite  period  against  ex- 
haustion. But  if  we  plough  in  only  what  the  land  itself  produces, 
and  carry  off  occasional  crops  of  corn,  the  time  will  ultimately  come 
when  any  soil  thus  treated  will  cease  to  yield  remunerating  crops.  A 
brief  consideration  of  the  subject  will  satisfy  you  of  this. 

Suppose  a  loose  sand  to  be  improved  by  repeatedly  sowing  and 
ploughing  in  crops  of  spurry  or  white  lupins,  the  green  leaves  and  stems 
fix  the  floating  elements  of  the  atmosphere,  and  enrich  the  soil  with  or- 
ganic matter,  w^hile  the  roots,  more  or  less  deep,  bring  up  saline  matters 
to  the  surface,  and  thus  supply  to  the  plant  what  is  no  less  necessary  to 
its  healthy  growth.  But  the  rains  yearly  wash  away  from  the  surface, 
and  the  corn  crops  remove,  a  portion  of  this  saline  matter.  This  portion 
the  crops  grown  for  the  purpose  of  green  manuring  yearly  renew  by 
fresh  supplies  from  beneath.  But  no  subsoil  contains  an  inexhaustible 
store  of  those  saline  substances  which  plants  require.  Hence,  though  by 
skilful  green  manuring  waste  land  may  be  brought  to  a  remunerative 
state  of  fertility,  it  will  finally  relapse  again  into  a  state  of  nature,  if  no 
other  methods  are  subsequently  adopted  for  maintaining  its  productive- 
ness. The  process  maybe  a  slow  one,  and  practical  men  may  be  un- 
willing to  believe  in  the  possibility  of  a  result  which  does  not  exhibit  it- 
self within  the  currency  of  a  single  lease,  or  during  a  single  life-time — 
yet  few  things  are  more  certain  than  that  in  general  the  soil  must  sooner 
or  later  receive  supplies  of  saline  manure  in  one  form  or  another,  or 
else  must  ultimately  become  unproductive.  It  may  be  considered  as 
a  proof  of  this  fact  that,  in  all  densely  peopled  countries  in  which 
agriculture  has  been  skilfully  prosecuted,  the  manufacturing  of  such 
manures  has  become  an  important  branch  of  business,  giving  em- 
ployment to  many  hands,  and  aflbrding  an  investment  to  milch  capital. 

The  folk  wing  table,  in  addit.:ni  toother  particulars,  exhibits  the 


422 


THE    PRACTICE    OF    GREEN    MANURING. 


relative  proportions  of  dry  organic  and  saline  matter,  capable  of  be- 
ing added  to  the  surface  soil  by  a  few  of  those  plants  which  are  em- 
ployed for  the  purposes  of  remanuring : — 


Kind  of  Plant. 


Averaae  1000  lbs.  contain 
produce 
per  imp. 
acre. 


Spurry 

White  Lupin 


Vetch 

Buck-wheat. 
Rape 


6,500 
25,000 

11,000 
8,000 
16,000 


n  the  green  state  Depth  of  |    ;„  ^ 
Organic  Saline       Roots. 
Matter.   Matter. 


lbs. 
199 

188 

233 
170 
214 


lbs. 
21 
12 

17 
10 
16 


m  a 
year. 


inches. 

12  to  152  or  3 
24  to  26  I  or  li 

15  to  20       2 

12  to  15       2 
1      llorU 


Soil  for  which  they  are 
fitted. 


Dry,  loose,  sandy. 
Any  except    marly  or 

calcareous. 
Strong  soil. 

Dry,  sandy,  or  moorish. 
Rich  soil. 


§  5.   Of  the  practice  of  green  manuring. 

In  the  practical  adoption  of  green  manuring  it  is  of  importance  to 
bear  in  mind — 

1°.  That  a  sufficient  quantity  of  seed  must  be  sown  to  keep  the 
ground  well  covered,  one  of  the  attendant  advantages  of  stubble 
crops  being  that  they  keep  the  land  clean  and  prevent  it  from  becom- 
ing a  prey  to  weeds. 

2°.  That  the  plants  ought  to  be  mown  or  harrowed,  and  at  once 
ploughed  in  before  they  come  into  full  flower.  The  flower-leaves 
give  off  nitrogen  into  the  air,  and  as  this  element  is  supposed  especi- 
ally to  promote  the  growth  of  plants,  it  is  desirable  to  retain  as  much 
of  it  in  the  plant  and  soil  as  possible.  Another  reason  is  that,  if  al- 
lowed to  ripen,  some  of  the  seed  may  be  shed  and  afterwards  infest 
the  land  with  weeds. 

3°.  That  they  should  be  ploughed  in  to  the  depth  of  3  or  4  inches 
only,  that  they  may  be  covered  sufficiently  to  prevent  waste,  and  yet  be 
within  reach  of  the  air,  and  of  the  early  roots  of  the  succeeding  crop. 

§  6.  O/*  natural  manuring  with  recent  vegetable  matter. 
Besides  the  method  of  ploughing  in,  which  maybe  distinguished  as 
artificial  green  manuring, — there  is  another  mode  in  which  recent  ve- 
getable matter  is  employed  in  nature  for  the  purpose  of  enriching  the 
soil.  The  natural  grasses  grow  and  die  upon  a  meadow  or  pasture  field, 
and  though  that  which  is  above  the  surface  may  be  mowed  for  hay,  or 
cropped  by  cattle,  yet  the  roots  remain  and  gradually  add  to  the  quantity 
of  vegetable  matter  beneath.  The  same  is  the  case  to  a  gr(;ater  or  less 
extent  with  all  the  artificial  corn,  grass,  and  leguminous  crops  we  grow. 
They  all  leave  their  roots  in  the  soil,  and  if  ihe  quantity  of  organic  mat- 
ter which  these  roots  contain  be  greater  than  that  'A^hich  the  crop  we  car- 
ry off  has  derived  from  the  soil,  then,  instead  of  exhausting,  the  growth 
of  this  crop  will  actually  enrich  the  soil  in  so  far  as  the  presence  of  or- 
ganic matter  is  concerned.  No  crops,  perhaps,  the  whole  produce  of 
which  is  carried  off  the  field,  leave  a  sufficient  mass  of  roots  behind  them 
to  effect  this  end,  but  many  plants,  when  in  whole  or  in  part  eaten  upon 
tliie  field,  leave  enough  in  the  soil  materially  to  improve  the  condition  of 
the  land — while  in  all  cases  those  are  considered  as  the  least  exhaust- 


WEIGHT    OF    ROOTS    LEFT    IN    THE    SOIL.  423 

• 

ing,  to  v/hich  are  naturally  attached  Ifce  largest  weight  of  roots.  Hence, 
the  main  reason  why  poor  lands  are  so  much  benefitted  by  being  laid 
down  to  grass,  and  why  an  intermediate  crop  of  clover  is  often  as  benefi- 
cial to  the  after-crop  of  corn  as  if  the  land  had  lain  in  naked  fallow.  (If 
the  third  crop  be  ploughed  in,  the  land  is  actually  enriched.-^S'cAu-er^^;.) 
An  interesting  series  of  experiments  on  the  relative  weights  of  the 
roots  and  of  the  green  leaves  and  stems  of  various  grasses,  made  by 
Hlubek,  (Erniihrung  der  Pflanzen,  p.  466,)  throws  considerable  light 
upon  their  relative  efficacy  in  enriching  the  soil  by  the  vegetable  mat- 
ter they  diffuse  through  it  in  the  form  of  roots.  The  grasses  were 
grown  in  beds  of  equal  size  (180  square  feet)  in  the  agricultural  gar- 
den at  Laybach,  and  mowt:  on  the  fourth  year  after  sowing,  just  as 
they  were  coming  into  flower.  The  roots  were  then  carefully  taken 
up,  washed,  and  dried.     The  results  were  as  follows : 

Weight  of 
>  Produce  in     Produce  in  Roots,  dry  Roots 

.  Kind  of  Grass.  . • .      , " >     to  100  lbs. 

Grass.      Ilay.        Fresh.     Dry.        of  Hay. 

1.  FestucaElatior— TVzZZi^esc^ig-^ross..   124  lbs.  36  lbs.  56  lbs.  22  lbs.   61  lbs. 

2.  Festuca  Ovina — Sheep's  Fescue-grass.    90        30        —         80       266 

3.  Fhleum  Pratense— Tm^^ay-^mss...     90        25        56  17         60 

4.  Dactylis  Glomerata — Rough  Cock's-    , 

foot... 202        67        —         22i       33 

5.  Lolium    Perenne — Peremdal     Rye- 

grass       50        17        —         50       300 

6.  Alopecurus  Pratensis— Mmrf/?M?  Fox- 

toAl 106        35        —         24         70 

7.  Triticum   Repens — Creeping   Couch 

or  Quicken-grass 120        60        — ,        70        116 

8.  Poa  Annua — Annual  Meadow  grass.    —        —        —          —        111 

9.  Bromus    Mollis   and   Racemosus — 

Soft  and  smooth  Drovie-grass —        —        —  —        105 

10.  Anthoxanthum    Odoratum — Sweet- 
scented  Vernal- grass —        —        —          —  93 

A  mixture  of  white  clover,  of  ribwort,  of  hoary  plantain,  and  of 
couch-grass,  in  an  old  pasture  field,  gave  400  lbs.  of  dry  roots  to  100 
lbs.  of  hay — and  in  a  clover  field,  at  the  end  of  the  second  year,  the 
fresh  roots  were  equal  to  one-third  of  the  whole  weight  of  green  clo- 
ver obtained  at  three  cuttings — one  in  the  first,  and  two  in  the  second 
year — while  in  the  dry  state  there  were  56  lbs.  of  dry  roots  to  every 
100  lbs.  of  clover  hay  which  had  been  carried  off. 

The  fourth  column  of  the  above  table  shows  how  large  a  quantity  of 
vegetable  matter  some  of  the  grasses  impart  to  the  soil,  and  yet  how  un- 
like the  different  grasses  are  in  this  respect.  The  sheep's-fescue  and 
the  perennial  rye-grass — besides  the  dead  roots,  which  detach  them- 
selves from  time  to  time — leave,  at  the  end  of  the  fourth  year,  a  weight 
of  living  roots  in  the  soil  which  is  equal  to  three  times  the  produce  of 
that  year  in  hay.  If  we  take  the  mean  of  all  the  above  grasses  as  an 
average  of  what  we  may  fairly  expect  in  a  grass  field — then  the  amount 
of  living  roots  left  in  the  soil  when  afour-year-old  grass fieldis  plough- 
ed up,  will  be  equal  to  one-sixth  more  than  the  weight  of  that  yearns  crop. 

In  an  old  pasture  or  meadow  fie.d  again,  when  ploughed  up^  the 
living  roots  left  are  epual  to  four  times  the  weight  of  that  yearns  hay 


42^  MANURING    BY   THE    ROOTS    OF   CLOVER,    AND    BY 

crop.  If  a  ton  and  a  half  of  he^  have  been  reaped — then  about  six 
tons  of  dry  vegetable  matter  remain  in  the  soil  in  the  form  of  roots. 

In  the  case  of  clover,  at  the  end  of  the  second  year  the  quantity  of 
dry  vegetable  matter  left  in  the  form  of  roots  is  equal  to  upwards  ot 
one-half  the  weight  of  the  whole  hay  which  the  clover  has  yielded. 
Suppose  there  be  three  cuttings,  yielding  4  tons  of  hay,  then  2  tons 
of  dry  vegetable  matter  are  added  to  the  soil  in  the  form  of  roots, 
when  the  clover  stubble  is  ploughed  up. 

But  the  quantity  of  roots,  like  that  of  green  produce,  is  dependent 
upon  a  variety  of  circumstances.  It  will  sometimes,  therefore,  be 
greater  and  sometimes  less  than  is  above  stated.  It  may  be  received 
as  a  rule — not  without  exceptions  perhaps,  yet  still  eis  a  general  rule 
— that  whatever  causes  an  increased  produce  above  ground,  will 
cause  a  corresponding  increase  in  the  growth  of  roots.  Thus  nitrate 
of  soda,  which  gives  us  a  larger  yield  of  hay,  makes  the  roots  also 
stronger  and  deeper,  and  the  sward  tougher  and  more  difficult  to 
plough  {Appendix^  No.  III.)  Hence  it  is  that  the  farmer  is  anxious 
that  his  clover  crop  should  succeed,  not  merely  for  the  increased 
amount  of  green  food  or  of  hay  it  will  give  him,  but  because  it  wiU 
secure  him  also  a  better  after-crop  of  corn. 

This  burying  of  recent  vegetable  matter  in  the  soil,  in  the  form  of 
living  and  dead  roots  of  plants,  is  one  of  those  important  amehorating 
operations  of  nature  which  is  always  to  some  extent  going  on,  where- 
ever  vegetation  proceeds.  It  is  one  by  which  the  practical  man  is 
often  benefitted  unawares,  and  of  which — too  often  without  under- 
standing the  source  from  whence  the  advantage  comes — he  syste- 
matically a  vails,  himself  in  some  of  the  most  skilful  steps  he  takes 
vvith  a  view  to  the  improvement  of  his  land. 

§  7.  Improvement  of  the  soil  by  laying  down  to  grass. 

One  of  the  most  common  of  these  methods  of  improvement  is  that 
of  laying  down  to  grass.  This  may  be  done  for  two,  three  or  four 
years  only,  or  for  an  indefinite  period  of  time.  In  the  latter  case,  the 
land  is  said  to  be  laid  down  permanently,  or  to  permanent  pasture. 

1°.  Temporary  pasture  or  meadow. — If  the  land  be  sown  with 
grass  and  clover-seeds,  only  as  an  alternate  crop  between  two  sow- 
ings of  corn,  the  effect  is  fully  explained  by  what  has  been  already 
stated  (§6.)  The  roots  which  are  left  in  the  soil  enrich  the  surface 
with  both  organic  and  inorganic  matter,  and  thus  fit  it  for  bearing  a 
better  after-crop  of  corn. 

If,  again,  it  be  left  to  grass  for  three  or  five  years,  the  same  effect  is 
produced  more  fully,  and  therefore  this  longer  rest  iVom  corn  is  better 
fitted  for  soils  which  are  poor  in  vegetable  matter.  The  quantity  of 
organic  matter  which  has  accumulated  becomes  greater  every  year,  in 
consequence  of  the  annual  death  of  stems  and  roots,  and  of  the  soil  being 
more  closely  covered,  but  this  increase  is  probably  never  in  any  one 
after-year  equal  to  that  which  takes  place  durhig  the  first.  The  quan- 
tity of  roots  which  is  produced  during  the  first  year  of  the  young  plants' 
growth  must,  we  may  reasonably  suppose,  be  greater  than  can  ever 
afterwards  be  necessary  in  an  equal  space  of  time.  Hence,  one  good 
year  of  grass  or  clover  will  enrich  ihe  soil  more  in  proportion  to  the 


LAYING  DOWN  TO  GRASS. — PERMANENT  PASTURE.  425 

time  expended^  than  a  rest  of  two  or  three  years  in  grass,  if  annually 
'mowed. 

Or  if,  instead  of  being  mown,  the  produce  in  each  case  be  eaten  off 
by  stock,  the  result  will  be  the  same.  That  which  lies  longest  will  be 
the  richest  when  broken  up,  but  not  in  an  equal  proportion  to  the  time 
it  has  lain.  The  produce  of  green  parts,  as  well  as  of  roots,  in  the  ar- 
tificial grasses,  is  generally  greatest  during  the  first  year  after  they  are 
sown,  and  therefore  the  manuring  derived  from  the  droppings  of  the 
stock,  as  well  as  from  the  roots,  will  be  greatest  in  proportion  during  the 
first  year.  That  farming,  therefore,  is  most  economical — where  the 
land  will  admit  of  it — ^  which  permits  the  clover  or  grass  seeds  to  occupy 
the  land  for  one  year  only. 

But  if,  after  the  first  year's  hay  is  removed,  the  land  be  pastured  for 
two  or  three  years  more,  it  is  possible  that  each  succeeding  year  may 
enrich  the  surface  soil  as  much  as  the  roots  and  stubble  of  the  first 
year's  hay  had  done ;  so  that  if  it  lay  three  years  it  might  obtain 
three  times  the  amount  of  improvement.  This  is  owing  to  the  cir- 
cumstance that  the  whole  produce  of  the  field  remains  upon  it,  ex- 
cept what  is  carried  off  by  the  stock  when  removed — but  very  much, 
it  is  obvious,  ^vill  depend  upon  the  nature  of  the  soil,  and  upon  the 
selection  of  the  seeds  being  such  as  to  secure  a  tolerable  produce  of 
green  food  during  the  second  and  third  years. 

2°.  Permanent  pasture  or  meadow. — But  when  land  is  laid  down 
to  permanent  grass  it  undergoes  a  series  of  further  changes,  which 
have  frequently  arrested  attention,  and  which,  though  not  difficult  to 
be  understood,  have  often  appeared  mysterious  and  perplexing  to 
practical  men.     Let  us  consider  these  changes. 

a.  When  grass  seeds  are  sown  for  the  purpose  of  forming  a  per- 
manent sward,  a  rich  crop  of  grass  is  obtained  during  the  first,  and 
perhaps  also  the  second  year,  but  the  produce  after  three  or  four 
years  lessens,  and  the  value  of  the  pasture  diminishes.  The  plants 
generally  die  and  leave  blank  spaces,  and  these  again  are  slowly 
filled  up  by  the  sprouting  of  seeds  of  other  species,  which  have  either 
lain  long  buried  in  the  soil  or  have  been  brought  thither  by  the  winds. 

This  first  change,  which  is  almost  universally  observed  in  fields  of 
artificial  grass,  arises  in  part  from  the  change  which  the  soil  itself  has 
undergone  during  the  few  years  that  have  elapsed  since  the  grass 
seeds  vv^ere  sown,  and  in  part  from  the  species  of  grass  selected  not 
being  such  as  the  soil,  at  any  time,  could  permanently  sustain. 

h.  When  this  deterioration,  arising  from  the  dying  out  of  the  sown 
grasses,  has  reached  its  utmost  point,  the  sward  begins  gradually  to 
improve,  natural  grasses  suited  to  the  soil  spring  up  in  the  blank  places, 
and  from  year  to  year  the  produce  becomes  greater  and  greater,  and 
the  land  yields  a  more  valuable  pasture.  Practical  men  often  say 
that  to  this  improvement  there  are  no  bounds,  and  that  the  older  the 
pasture  the  more  valuable  it  becomes. 

But  this  is  true  only  w.ihin  certain  limits.  It  may  prove  true  for 
the  entire  currency  of  a  lease,  or  even  for  the  lifetime  of  a  single  ob- 
server^ but  it  is  not  generally  true.  Even  if  pastured  by  stock  only  and 
never  mown,  the  improvement  wiW  at  length  reach  its  limit  or  highest 
point,  and  from  this  time  the  value  of  the  sward  will  begin  to  diminish. 


426       THE  SOIL  AND  GRASSES  CONTINUALLY  CHANGE. 

c.  This,  agairi;  is  owing  to  a  new  change  which  has  come  over  the 
soil.  It  has  become,  in  some  degree,  exhausted  of  those  substances 
which  are  necessary  to  the  growth  of  the  more  valuable  grasses — 
less  nutritive  species,  therefore,  and  such  as  are  less  willingly  eaten 
by  cattle,  take  their  place. 

Such  is  the  almost  universal  process  of  change  which  old  grass  fields 
undergo,  whether  they  be  regularly  mown  or  constantly  pastured  only 
— provided  they  are  left  entirely  to  themselves.  If  mown  they  begin 
to  Ikil  the  sooner,  but  even  when  pastured  they  can  be  kept  in  a  state 
of  full  productiveness  only  by  repeated  top-dressings,  especially  of  sa- 
line manure — that  is,  by  adding  to  the  soil  those  substances  which  are 
necessary  to  the  growth  of  the  valuable  grasses,  and  of  which  it  suf- 
fers a  yearly  and  unavoidable  loss.  Hence,  the  rich  grass  lands  of 
our  fathers  are  found  now  in  too  many  cases  to  yield  a  herbage  of 
little  value.  Hence,  also,  in  nearly  all  countries,  one  of  the  first  steps 
of  an  improving  agriculture  is  to  plough  out  the  old  and  failing  pas- 
tures, and  either  to  convert  them  permanently  into  arable  fields,  or  after 
a  few  years'  cropping  and  manuring,  again  to  lay  them  down  to  grass. 

But  when  thus  ploughed  out.  the  surface  soil  upon  old  grass  land  is 
found  to  have  undergone  a  remarkable  alteration.  Wh^n  sown  with 
grass  seeds,  it  may  have  been  a  stiff,  more  or  less  grey,  blue,  or  yellow 
clay — when  ploughed  out  it  is  a  rich,  brown,  generally  light  and  fria- 
ble vegetable  mould.  Or  when  laid  down  it  may  have  been  a  pale- 
colored,  red,  or  yellow  sand  or  loam.  In  this  case  the  surface  soil 
is  still,  when  turned  up,  of  a  rich  brown  colour — it  is  lighter  only  and 
more  sandy  than  in  the  former  case,  and  rests  upon  a  subsoil  of  sand 
or  loam  instead  of  one  of  clay.  It  is  from  the  production  of  this  change 
that  the  improvement  caused  by  laying  down  to  grass  principally  re- 
sults.    In  what  does  this  change  consist  ?  and  how  is  it  effected  ? 

If  the  surface  soil  upon  stiff  clay  lands,  which  have  lain  long  in  grass, 
be  chemically  examined,  it  will  be  found  to  be  not  only  much  richer 
in  organic  matter,  but  often  also  poorer  in  alumina  than  the  soil  which 
formed  the  surface  when  the  grass  seeds  were  first  sown  upon  it. 
The  brown  mould  which  forms  on  lighter  lands  will  exhibit  similar 
differences  when  compared  with  the  soil  on  which  it  rests ;  but  the 
proportion  of  alumina  in  the  latter  being  originally  .small,  the  diffe- 
rence in  respect  to  this  constituent  will  not  be  so  perceptible. 

The  effect  of  this  change  on  the  surface  soil  is  in  all  cases  to  make 
it  more  rich  in  those  substances  which  cultivated  plants  require,  and 
therefore  more  fertile  in  corn.  But  strong  clay  lands  derive  the  fur- 
ther important  benefit  of  being  rendered  more  loose  and  friable,  and 
thus  more  easily  and  more  economically  cultivated. 

The  mode  in  which  this  change  is  brought  about  is  as  folloAVs  : — 

1°.  The  roots,  in  penetrating,  open  and  loosen  the  subjacent  stiff  clay. 
Diffusing  themselves  every  where,  they  gradually  raise,  by  increasing 
the  bulk  of,  the  surface  soil.  The  latter  is  thus  converted  into  a  mix- 
ture of  clay  and  decayed  roots,  which  is  of  a  dark  colour,  and  is  necessa- 
rily more  loose  and  friable  than  the  original  or  subjacent  unmixed  clay. 

2°.  But  this  admixture  of  roots  effects  the  chemical  composition  as 
well  as  the  state  of  aggregation  of  the  soil.  The  roots  and  stems  of 
the  grasses  contain  much  inorganic — earthy  ^ind  saline — matter  (Lee. 


AGENCY    OF    THE    RAINS    AND    WINDS.  427 

IX.,  §  1),  which  is  gathered  from  beneath,  wherever  the  roots  pene- 
trate, and  is  by  them  sent  upwards  to  the  surface.  A  ton  of  hay  con- 
t;ains  about  170  lbs.  of  this  inorganic  matter  (Lee.  X.,  §  3).  Suppose 
the  roots  to  contain  as  much,  and  that  the  total  annual  produce  of 
grass  and  roots  together  amounts  to  four  tons,  then  about  680  lbs.  of 
saline  and  earthy  matters  are  every  year  worked  up  by  the  living 
plants,  and  in  a  'great  measure  permanently  mixed  with  the  surface 
soil.  Some  of  this,  no  doubt,  is  carried  off  by  the  cattle  that  feed, 
and  by  the  rains  that  fall,  upon  the  land — some  remains  in  the  deeper 
roots,  and  some  is  again,  year  after  year,  employed  in  feeding  the 
new  growth  of  grass — still  a  sufficient  quantity  is  every  season 
brought  up  from  beneath,  gradually  to  enrich  the  surface  with  valua- 
ble inorganic  matter  at  the  expense  of  the  soil  below. 

3^.  Nor  are  mechanical  agencies  wanting  to  increase  this  natural 
difference  between  the  surface  and  the  under  soils.  The  loosening 
and  opening  of  the  clay  lands  by  the  roots  of  the  grasses  allow  the 
rains  more  easy  access.  The  rains  gradually  wash  out  the  fine  par- 
ticles of  clay  that  are  mixed  with  the  roots,  and  carry  them  down- 
wards, as  they  sink  towards  the  subsoil.  Hence  the  brown  mould,  as 
it  forms,  is  slowly  robbed  of  a  portion  of  its  alumina,  and  is  rendered 
more  open,*Hvhile  the  under  soil  becomes  even  stilTer  than  before. 
This  sinking  of  the  alumina  is  in  a  great  measure  arrested  when  the 
soil  becomes  covered  with  so  thick  a  sward  of  grass  as  to  break  the 
force  of  the  rain-drops  or  of  the  streams  of  water  by  which  the  land 
is  periodically  visited.  Hence  the  soil  of  some  rich  pastures  contains 
as  much  as  10  or  12,  of  others  as  Httle  as  2  or  3  per  cent,  of  alumina. 

4°.  The  winds  also  here  lend  their  aid.  From  the  naked  arable 
lands,  when  the  weather  is  dry,  every  blast  of  wind  carries  off  a  portion 
of  the  dust.  This  it  suffers  to  fall  again  as  it  sweeps  along  the  surface 
of  the  grass  fields — the  thick  sward  arresting  the  particles  and  sifting 
the  air  as  it  passes  through  them.  Everywhere,  even  to  remote  dis- 
tricts, and  to  great  elevations,  the  winds  bear  a  constant  small  burden 
of  earthy  matter;*  but  there  are  few  practical  agriculturists  who,  du- 
ring our  high  winds,  have  not  occasionally  seen  the  soil  carried  off  in 
large  quantities  from  their  naked  fields.  Upon  the  neighbouring  grass 
lands  this  soil  falls  as  a  natural  top-dressing,  by  which  the  texture  of 
the  surface  is  gradually  changed  and  its  chemical  constitution  altered. 

5^.  Another  important  agency  also  must  not  be  overlooked.  In  grass 
lands  insects,  and  especially  earth-worms,  abound.  These  almost 
nightly  ascend  to  the  surfice,  and  throw  out  portions  of  finely-divided 
earthy  matter.  On  a  close  shaven  lawn  the  quantity  thus  spread  over 
the  surface  in  a  single  night  often  appears  surprising.  In  the  lapse  of 
years  the  accumulation  of  the  soil  from  this  cause  must,  on  old  pasture 
fields,  be  very  great.  It  has  often  attracted  the  attention  of  practical 
men,t  and  so  striking  has  it  appeared  to  some,  that  they  have  been  in- 

*  It.  lia=!  been  observed  that  on  spots  purposely  sheltered  from  the  wind  and  rain  on  every 
Bide,  th'?  quantity  of  dust  that  is  collected,  when  pressed dotrn,  is  in  3  years  equal  to  one  line, 
or  in  36  years  to  one  inch  in  thickness. — Sprengel,  Z^hre  vom  Diinger,  p.  443. 

t  The  permanence  cf  a  fine  carpetmg  of  rich  sweet  grass  upon  a  portion  of  his  farm  is 
ascribed  (by  Mr.  Purdie)  to  "  the  spevvings  of  worms,  apparently  immensely  numerous, 
which  incessantly  act  as  a  rich  top  dressing."— Pr/ze  Essays  of  the  Highland  Society,  I. 


428  WHY    ARTIFICIAL    PASTURES    DETERIORATE. 

clined  to  attribute  to  the  slow  but  constant  labour  of  these  insects^  tho 
entire  formation  of  the  fertile  surface  soils  over  large  tracts  of  country. 
(^•Geological  Transactions.") 

I  have  directed  your  attention  to  these  causes  chiefly  in  explana- 
tion of  the  changes  which  by  long  lying  in  grass  the  surface  of  our 
stitf  clay  lands  is  found  to  undergo.  But  they  apply  equally  to  other 
soils  also — the  only  difference  being  that,  in  the  case  of  such  as  are 
already  light  and  open,  the  change  of  texture  is  not  so  great,  and 
therefore  does  not  so  generally  arrest  the  attention. 

Upon  this  subject  I  may  trouble  you  further  with  two  practical  re- 
marks : 

1°.  That  the  richest  old  grass  lands — those  which  have  remained 
longest  in  a  fertile  condition — are  generally  upon  our  strongest  clay 
soils  (the  Oxford  and  Lias  clays,  Lee.  XL,  §  8).  This  is  owing  to 
the  fact  that  such  soils  naturally  contain,  and  by  their  comparative 
impermeability  re-tain,  a  larger  store  of  those  inorganic  substances  on 
which  the  valuable  grasses  live.  When  the  surface  soil  becomes  de- 
ficient in  any  of  these,  the  roots  descend  further  into  the  subsoil  and 
bring  up  a  fresh  supply.  But  these  grass  lands  are  not  on  this  account 
exempt  from  the  law  above  explained,  in  obedience  to  which  all  pas- 
tured lands,  when  left  to  nature,  must  ultimately  become  exhausted. 
They  must  eventually  become  poorer  ;  but  in  their  case  the  deterio- 
ration will  be  slower  and  more  distant,  and  by  judicious  top-dressings 
may  be  still  longer  protracted. 

2°.  The  natural  changes  which  the  surface  soil  undergoes,  and  es- 
pecially upon  clay  lands  when  laid  down  to  grass,  explain  why  it  is  so 
difficult  to  procure,  by  means  of  artifical  grasses,  a  sward  equal  to  that 
wliich  grows  naturally  upon  old  pasture  lands.  As  the  soil  changes 
upon  our  artificial  pastures,  it  becomes  better  fitted  to  nourish  other  spe- 
cies of  grass  than  those  which  we  have  sown.  These  naturally  spring 
up,  therefore,  and  cover  the  soil.  But  these  intruders  are  themselves 
not  destined  to  be  permanent  possessors  of  the  land.  The  soil  under- 
goes a  further  change,  and  new  species  again  appear  upon  it.  We  can- 
not tell  how  often  diiferent  kinds  of  grass  thus  succeed  each  other  upon 
the  soil,  but  we  know  that  the  final  rich  sward  which  covers  a  grass  field 
when  it  has  reached  its  most  valuable  condition,  is  the  result  of  a  long 
series  of  natural  changes  which  time  only  can  bring  about. 

The  soil  of  an  old  pasture  field,  which  has  been  ploughed  up,  is  made 
to  undergo  an  important  change  both  in  texture  and  in  chemical  con- 
stitution, before  it  is  again  laid  down  to  grass.  The  same  grasses, 
therefore,  which  previously  covered  it  will  no  longer  flourish,  even 
when  they  are  sown.  Hence  the  unwillingness  felt  by  practical  men 
to  plough  up  their  old  pastures — but  hence,  also,  the  benefit  which 
results  from  the  breaking  up  of  such  as  are  old,  worn  out,  or  covered 
with  unwholesome  grasses.  When  again  converted  into  pasture  land, 
new  races  appear,  and  a  more  nourishing  sward  is  produced.* 


*  For  an  exccUent  article  on  the  superior  fes<Ung  qualities  of  recent  artificial  erasseg 
over  many  oM  pasture  lands,  by  Mr.  BosweJl,  of  Kingcaussiftj  see  the  Quarterly  Jojirnai 
if  Agriculture,  "N.,  p.  783. 


IMPROVEMENT  OF  THE  SOIL  BY  PLANTING  OF  TREES.  429 

§  8.  Improvement  of  the  soil  by  the  planting  of  trees. 

It  has  long  been  observed  by  practical  men,  that  when  poor,  thin, 
unproductive  soils  have  been  for  some  time  covered  with  wood,  Lheir 
quality  materially  improves.  In  the  intervals  of  the  open  forest,  they 
will  i)roduce  a  valuable  herbage — ?r  when  cleared  of  trees  they  may 
for  some  time  be  made  to  yield  profitable  crops  of  corn. 

This  fact  has  been  observed  in  almostevery  country  of  Europe,  but 
the  most  precise  observations  upon  the  subject  with  which  I  am  ac- 
quainted are  those  which  hav^e  been  made  in  the  extensive  plantations 
of  the  late  Duke  of  Athol.  These  plantations  consist  chiefly  of  white 
larch  (^Larix  Eiiropcea.)  and  grow  upon  a  poor  hilly  soil,  resting  on 
gneiss,  mica-slate,  and  clay-slate  (Lee.  XI.,  §  8.)  In  six  or  seven 
years  the  lower  branches  spread  out,  become  interlaced,  and  com- 
pletely overshadow  the  ground.  Nothing,  therefore,  grows  upon  it 
till  the  trees  ar6  24  years  old.  when  the  spines  of  the  lower  branches 
begirming  to  fall,  the  first  considerable  thinning  takes  place.  Air  and 
light  being  thus  re-admitted,  grasses  (chiefly  holcus  mollis  and  lana- 
tus)  spring  up,  and  a  fine  sward  is  gradually  produced.  The'ground, 
which  previously  was  worth  only  9d.  or  Is,  per  acre  as  a  sheep  pas- 
ture, at  the  end  of  30  years  becomes  worth  from  7s.  to  10s.  per  acre. 

The  soil  on  this  part  of  the  Duke's  estate  is  especially  propitious  to 
the  larch — and.  therefore,  this  tree  both  thrives  best  and  in  the  great- 
est degree  improves  the  soil.  -  Thus  in  oak  copses,  cut  every  24  years, 
the  soil  becomes  worth  only  5s.  or  6s.  per  acre,  and  this  during  the  last 
six  years  only.  UnTler  an  ash  plantation,  the  improvement  amounts 
to  2s.  or  3s.  per  acre ;  under  Scotch  fir,  it  does  not  exceed  6d.  an  acre 
— while  under  spruce  and  beech  the  land  is  worth  less  than  before. 
(Mr.  Stephens,  in  the  Transactions  of  the  Higliland  Society,  xi.,  p. 
189  ;  also  Loudon's  Encylopccdia  of  Agriculture,  p.  1346.) 

The  main  cause  of  this  improvement,  as  of  that  which  is  produced 
by  laying  down  to  grass,  is  to  be  found  in  the  natural  manuring  with 
recent  vegetable  matter,  to  which  the  soil  year  by  year  is  so  long 
subjected.  Trees  differ  from  grasses  only  in  this,  that  while  the  lat- 
ter enrich  the  soil  both  by  their  roots  and  by  their  leaves,  the  former 
manure  its  surface  only  by  the  leaves  which  they  shed. 

The  leaves  of  trees,  like  those  of  grasses,  contain  much  inorganic  mat- 
ter, and  this  when  annually  spread  upon  the  ground  slowly  adds  to  the 
depth  as  well  as  to  the  richness  of  the  soil.  Thus  the  leaves  of  the  fol- 
lowing trees,  when  dried  in  the  air,  contain  respectively  of  inorganic 
matter  ((Sprengel,  Chemiefur  Landwirthe,  ii.,  passim)  : — 

April.  August.  November. 

Oak —  5  per  cent.  4^  per  cent. 

Ash —  6i        «  — 

Beech •..—  7          "  6i        « 

Birch ..—  5          cc  _        « 

Elm    —  111        «  —        " 

Willow —  8.i        "  —        « 

White  Larch 6  J.  per  cent.  —        "  —        '* 

Scotch  Fir —  U        "  —        " 

In  looking  at  the  differences  among  these  numbers — especially  in 


430  RELATIVE  EFFECTS  OF  DIFFERENT  KINDS  OF  TREES. 

the  case  of  the  elm  and  of  the  Scotch  fir — one  would  naturally  sup- 
pose that  the  diversity  of  their  effects  in  improving  the  land  is  in  some 
measure  to  be  ascribed  to  the  quantity  and  kind  of  the  inorganic  mat- 
ter which  the  leaves  of  these  several  trees  contain.  And  to  this 
cause,  no  doubt,  some  effect  is  to  be  ascribed  in  localities  where  all 
the  trees  thrive  equally. 

But  upon  the  quantity  of  leaves  produced,  as  much  in  general  will 
depend,  as  upon  the  relative  proportions  of  organic  and  inorganic 
matter  vdiich  these  leaves  may  respectively  contain.  And  as  the 
quantity  of  leaves  is  always  greatest  where  the  tree  flourishes  best  or 
finds  a  most  propitious  soil — the  improvement  of  the  soil  itself,  by 
any  particular  tree,  will  be  always  in  a  great  measure  determined  by 
its  fitness  to  pronnote  the  growth  of  that  kind  of  tree* 

On  the  soil  planted  by  the  Duke  of  Athol,  the  larch  shot  up  luxu- 
riantly, while  the  Scotch  fir  lingered  and  languished  in  its  growth. 
Thus  the  quantity  of  leaves  produced  and  annually  shed  by  the 
former  was  vastly  greater  than  by  the  latter  tree.  Had  the  Scotch 
fir  thriven  better  than  the  larch,  the  reverse  might  have  been  the 
case,  and  the  value  of  the  soil  might  have  been  increased  in  a  great- 
er proportion  by  plantations  of  the  former  tree. 

Other  special  circumstances  also  will  account  for  the  relative  de- 
grees of  improvement  produced  by  the  larch  and  by  some  of  the 
other  trees — for  example,  the  oak.  In  the  oak  copse  the  soil  in  16 
years  become  worth  6s.  or  8s.  an  acre.  If,  therefore,  instead  of  being 
cut  down  for  their  bark  at  the  end  of  24  years,  \\^  trees  had  been  al- 
lowed to  grow  up  into  an  oak  forest,  the  permanent  improvement  of 
the  pasture,  even  on  this  soil,  would  probably  have  been  at  least  as 
great  as  under  the  larch.  The  above  experiments,  therefore,  are  in 
reality  not  so  decisive  in  regard  to  the  relative  improviJig-  power  of 
the  several  species  of  trees  as  they  at  first  sight  appear.  The  most 
rational  natural  rule  by  which  our  practice  should  be  guided  seems 
to  be  contained  in  these  three  propositions — 

1°.  That  the  soil  will  be  most  improved  by  those  trees  which  thrive 
best  upon  it. 

2°.  Among  those  which  thrive  equally,  by  such  as  yield  the 
argest  produce  of  leaves,  and — 

3°.  Among  such  as  yield  an  equal  weight  of  leaves,  by  those  whose 
leaves  contain  the  largest  proportion  of  inorganic  matter — which 
bring  up  from  beneath,  that  is,  and  spread  over  the  surface  in  largest 
quantity,  the  materials  of  a.fertile  soil. 

The  mode  in  which  the  lower  branches  of  the  larch  spread  out  and 
overshadow  the  surface  is  not  without  its  influence  upon  the  ultimate 
improvement  which  the  soil  exhibits.  All  vegetation  being  prevented, 
the  land,  besides  receiving  a  yearly  manurg  of  vegetable  mould,  is 
made  to  lie  for  upwards  of  20  years  in  uninterrupted  naked  fallow. 
It  is  sheltered  also  from  the  beating  of  the  min  drops,  which  descena 
slowly  and  gently  upon  it,  bearing  principles  of  fertility  instead  of 
washing  out  the  valuable  saline  substances  it  may  contain. 

Beneath  the  overshadowing  branches  of  a  forest,  the  soil  is  also  pro- 
tected from  the  wind,  and  to  this  protection  Sprengel  attributes  much 
of  that  rapid  improvement  so  generally  experienced  where  lands  are 


MANURING    WITH    SEA-WEED.  431 

covered  with  wood.  The  winds  bear  along  particles  of  earthy  mat- 
ter (see  note.  p.  427,)  which  they  deposit  again  in  the  still  forest.^ ;  and 
thus  gradually  form  a  soil  even  on  the  most  naked  places.  This  slow 
general  cause  of  accumulation  may  not  be  without  its  effect,  and 
should  not  be  forgotten,  but  it  evidently  affords  no  explanation  why, 
in  the  same  range  of  country,  the  soil  which  is  covered  by  forests  o^^ 
one  kind  should  improve  more  rapidly  than  those  which  are  shelterer. 
by  trees  of  another  species. 

§  9.   Of  the  use  of  sea-weed  as  a  manure.     . 

Among  green  manures  of  great  value  and  extensive  application 
there  remains  to  be  noticed  the  sea-weed  or  sea-ware  of  our  coasts. 
The  marine  plants  of  which  it  consists  differ  from  the  green  vege- 
tables grown  upon  land, — 

1°.  By  the  greater  rapidity  with  which  they  undergo  decay.  When 
laid  as  top-dressings  upon  the  land  they  melt  down,  as  it  were,  and  in 
a  short  time  almost  entirely  disappear.  Mixed  with  soil  into  a  com- 
post or  with  quick-lime,  they  speedily  crumble  down  into  a  black  earth, 
ill  which  little  or  no  trace  of  the  plant  can  be  perceived. 

2°.  By  the  greater  proportion  of  saline  or  other  inorganic  matter 
which  these  plants,  in  their  dry  state,  contain.  It  is  these  substances 
which  are  obtained  in  the  form  of  kelp  when  dry  sea-weeds  are  burn- 
ed in  the  air. 

We  have  seen  (Lee.  X.,  §  3,)  that  the  quantity  of  ash  left  by  1000 
lbs.  of  our  more  usually  cultivated  grasses,  in  the  dry  state,  varies 
from  5  to  nearly  10  per  cent,  but  the  fucus  vesiculosus^  which  is 
reckoned  the  most  valuable  for  the  manufacture  of  kelp,  gives  up- 
wards of  160  lbs.  of  ash  from  100  lbs.  of  the  dry  plant.  This  ash, 
Jiccording  to  Fagerstrom,  consists  of — 

Gypsum 63*4  lbs. 

Carbonate  of  Lime 34-1  " 

Iodide  of  Sodium 2-7  " 

Other  Salts  of  Soda 29-9  " 

Sihca,  Oxide  of  Iron,  and  earthy  Phosphates.31-1  " 

161-2* 
This  ash  contains  less  potash,  but  more  soda  and  gypsum,  than 
those  of  the  grasses,  (Lee.  X.,  §  3,)  and  hence,  as  you  will  readily 

'  Berxelius  Arsberdttelse,  1S24,  p.  225. — If  we  compare  the  composition  of  Ihia  asli  with 
that  of  the  several  varieties  of  Ae/p,  given  in  page  366,  it  will  be  seen  to  differ  from  them 
very  considerably.  But  kelp  is  always  manufactured  from  a  mixture  of  different  plants 
in  varying  proportions,  and  hence  om  cause  of  the  diversity  of  composition  among  diffar- 
ent  samples  of  this  substance. 

Sprengel  states  (Lehre  vom  Dunger,  p.  277,)  that  the  fucus  vesiculosiis  contains  only  16 
per  cent,  of  water.  I  do  not  l^now  whethar  this  is  the  result  of  experiments  of  his  own, 
but  I  have  not  introduced  it  into  the  text,  because  it  appears  to  me  inconsistent  with  the 
remarkable  manner  in  which  sea-weed  shrivels  up  when  dried,  and  with  its  little  perma- 
nence as  a  manure.  *'  If  an  acre  of  land  is  completely  covered  with  it,  after  a  few  days 
of  dry  weather,  the  whole  would  not  weigh  500  lbs.  The  fibrous  parts  reduced  fo  mere 
threads  alone  remain — so  that  it  is  like  manuring  land  with  cobwebs"  (Dr.  Walker.)  This 
would  seem  to  imply  the  presence  of  a  larger  quantity  of  water  in  fresh  seaweed  than  in 
preen  gras.s,  and  consequently  a  less  efficacy  as  a  manure  wlien  applied  in  equal  weights. 
According  to  Boussingault,  the  fucus  digitatus  contains  40  per  cent,  of  water,  and  the 
fucus  sacc/iarinus  76  per  cent,  when  newly  taken  from  the  sea,  and  40  per  cent,  after  being 
dried  in  the  air. 


432  MODE    IN    WHICH    SEA-WEED    IS    APPLIED. 

understand,  may  be  expected  to  exercise  a  somewhat  different  influ- 
ence upon  vegetation. 

It  is  of  importance,  however,  to  bear  in  mind  that  the  sahne  and 
other  inorganic  matters  which  are  contained  in  the  sea-weed  we  lay 
upon  our  fields,  form  a  positive  addition  to  the  land.  If  we  plough  in  a 
green  crop  where  it  grew,  we  restore  to  the  soil  the  same  saline  matter 
only  w^hich  the  plants  have  already  taken  from  it  during  their  growfh, 
while  the  addition  of  sea-weed  imparts  to  it  an  entirely  new  supply.  It 
brings  back  from  the  sea  a  portion  of  that  w^hich  the  rivers  are  con- 
stantly carrying  into  it,  and  is  thus  valuable  in  restoring,  in  some  mea-^ 
sure,  what  rains  and  crops  are  constantly  removing  from  the  land. 

Sea-weed  is  collected  along  most  of  our  rocky  coasts — and  is 
seldom  neglected  by  the  farmers  on  the  borders  of  the  sea.  In  the  Isle 
of  Thanet.  it  is  sometimes  cast  ashore  by  one  tide  and  carried  off  by 
the  next ; — so  that  after  a  storm  the  teams  of  the  farmers  may  be  seen 
at  work  even  during  the  night  in  collecting  the  weed,  and  carrying  it 
beyond  the  reach  of  the  sea  (British  Husbandry,  II.,  p.  418.)  In  that 
locality,  it  is  said  to  have  doubled  or  tripled  the  produce  of  the  land. 
On  the  Lothian  coasts,  a  right  of  way  to  the  sea  for  the  collection  of 
sea-ware  increases  the  value  of  the  land  from  25s.  to  30s.  an  acre 
(Kerr's  Berwickshire,  p.  377.)  In  the  Western  Isles  it  is  extensively 
collected  and  employed  as  a  manure— ("  sea-weeds  constitute  one- 
half  of  Hebridean  manures,  and  nine-tenths  of  those  of  the  remoter 
Islands,"  Macdonald's  Agricidture  of  the  Hebrides,  p.  401.) — and 
on  the  north-east  coast  of  Ireland,  the  farming  fishermen  go  out  in 
their  boats  and  hook  it  up  from  considerable  depths  in  the  sea  (Mrs. 
Hall's  Ireland.) 

It  is  applied  either  immediately  as  a  top-dressing,  especially  to  grass 
lands — or  it  is  previously  made  into  a  compost  with  earth,  with  lime, 
or  with  shell-sand.  Thus  mixed  with  lime,  it  has  been  used  with  ad- 
vantage as  a  top-dressing  for  the  young  wheat  crop,  (British  Hus- 
bandry, II.,  p.  419 ;)  and  with  shell-sand,  it  is  the  general  manure  for 
the  potatoe  crop  among  the  Western  Islanders  (Transactions  of  the 
Highland  Society,  1842-3,  p.  766.)  It  may  also  be  mixed  with  farm- 
yard manure  or  even  with  peat  moss,  both  of  which  it  brings  into  a 
more  rapid  fermentation.  In  some  of  the  Western  Isles,  and  in  Jer- 
sey, it  is  burned  to  a  light,  more  or  less  coaly  powder,  and  in  this 
form  is  applied  successfully  as  a  top-dressing  to  various  crops.  There 
is  no  reason  to  doubt  that  the  most  economical  method  is  to  make  it 
into  a  compost  with  absorbent  earth  and  lime,  or  to  plough  it  in  at 
once  in  the  fresh  state. 

.  In  the  Western  Islands  one  cart  load  of  farm-yard  manure  is  con- 
sidered equal  in  immediate  effect — upon  the  first  crop,  that  is — to  2i 
of  fresh  sea-weed,  or  to  H  after  it  has  stood  two  months  in  a  heap. 
The  sea-weedj  however,  rarely  exhibits  any  considerable  action  upon 
the  second  crop. 

Sea-weed  is  said  to  be  less* suited  to  clay  soils,  while  barren  sand 
has  been  brought  into  the  state  of  a  fine  loam  by  the  constant  appli- 
cation of  sea-weed  alone,  for  a  long  series  of  years  (Macdonald's 
Hebrides,  p.  407.) 

Conflicting  opinions  are  given  by  different  practical  men  m  regard 


USE    OF    STHAW    AS    A    MANURE.  433 

to  the  crops  to  which  it  is  best  suited.  But  the  explanation  of  most 
of  these  and  similar  discordances  is  to  be  found  in  the  answers  to  the 
three  following  questions — what  substances  does  the  crop  specially 
require  ? — how  many  of  these  abound  in  the  soil  ? — can  the  manure  we 
are  about  to  use  supply  all  or  any  of  the  remainder  ?  If  it  can,  it  maybe 
expected  to  do  good.  Thus  simply  and  closely  are  the  kind  of  crop,  the 
kind  of  soil,  and  the  kind  of  manure,  in  most  cases,  connected  together. 

§  10.  Of  manuring  with,  dry  vegetable  substances. 

The  main  general  difference  between  vegetable  matter  o/"  ^^e  sa77te 
kind^  and  cut  at  the  same  age,  when  applied  as  a  manure  in  the  green 
and  in  the  dry  state,  consists  in  this — that  in  the  former  it  decomposes 
more  rapidly,  and,  therefore,  acts  more  speedily.  The  total  effect  upon 
vegetation  will  probably  in  either  case  be  very  nearly  the  same. 

But  if  the  dry  vegetable  matter  have  been  cut  at  a  more  advanced 
age  of  the  plant  or  have  been  exposed  to  the  vicissitudes  of  the  weather 
while  drying,  it  will  no  longer  exhibit  an  equal  efficacy.  A  ton  of  dry 
straw,  when  unripe,  will  manure  more  richly  than  a  ton  of  the  same 
straw  in  its  ripe  state — not  only  because  the  sap  of  the  green  plant 
contains  the  materials  from  which  the  substance  of  the  grain  is  after- 
wards formed — but,  because,  as  the  plant  ripens,  the  stem  restores  to  the 
soil  a  portion  of  the  saline,  especially  of  the  alkaline,  matter  it  previous- 
ly contained  (Lee.  X.,  §  5.)  Afler  it  is  cut,  also,  every  shower  of  rain 
that  falls  upon  the  sheaves  of  corn  or  upon  the  new  hay,  washes  out 
some  of  the  saline  substances  which  are  lodged  in  its  pores,  and  thus 
diminishes  its  value  as  a  fertilizer  of  the  land.  These  facts  place  in 
a  still  stronger  light  the  advantages  which  necessarily  follow  from 
the  use  of  vegetable  matter  in  the  recent  state,  for  manuring  the  soil. 

1°.  Dry  straw. — It  is  in  the  form  of  straw  that  dry  vegetable  mat- 
ter is  most  abundantly  employed  as  a  manure.  It  is  only,  however, 
when  already  in  the  ground  in  the  state  of.  stubble,  that  it  is  usually 
ploughed  in  without  some  previous  preparation.  When  buried  in  the 
soil  in  the  dry  state,  it  decomposes  slowly,  and  produces  a  less  sensi- 
ble effect  upon  the  succeeding  crop ;  it  is  usuallj''  fermented,  there- 
fore, more  or  less  completely,  by  an  admixture  of  animal  manure  in 
the  farm-yard  before  it  is  laid  upon  the  land.  During  this  fermenta- 
tion a  certain  unavoidable  loss  of  organic,  and  generally  a  large  loss  oi 
saline  matter,  also  takes  place  (see  in  the  succeeding  lecture  the  sec- 
tion upon  mixed  animal  and  vegetable  manures.)  It  is,  therefore,  the- 
oretically true  of  dry,  as  it  is  of  green,  vegetable  matter,  that  it  will  add 
most  to  the  soil,  if  it  be  ploughed  in  without  any  previous  preparation. 

Yet  this  is  not  the  only  consideration  by  which  the  practical  man 
must  be  guided.  Instead  of  a  slow  and  prolonged  action  upon  his 
crops,  he  may  require  an  immediate  and  more  powerful  action  for  a 
shorter  time,  and  to  obtain  this  he  may  be  justified  in  fermenting  his 
straw  with  the  certainty  even  of  an  unavoidable  loss.  Thus  the  dis- 
puted use  of  short  and  long  du7ig  becomes  altogether  a  question  of 
expediency  or  of  practical  economy.  But  to  this  point  I  shall  again 
recur  when  treating  of  farm-yard  manure  in  the  succeeding  lecture. 

2°.  Chaff  partakes  of  the  nature  of  straw,  but  it  decomposes  more 
■lowly  when  buried  in  the  soil  in  the  dry  state.    It  is  also  difficult  to 


434  ACTION  OF  RAPE-DUST  ON  WHEAT  AND  BEANS. 

bring  into  a  state  of  fermentation,  even  when  mixed  with  the  liquid 
manure  of  the  farm-yard. 

3°.  Rape-dust. — When  rape  seed  is  exhausted  of  its  oil,  it  comes 
from  the  press  in  the  form  of  hard  (rape)  cakes,  which,  when  crushed 
to  powder,  form  the  rape-dust  of  late  years  so  extensively  employed  as 
a  manure.  It  is  occasionally  mixed  with  farm-yard  dung,  and  applied 
to  the  turnip  crop,  but  its  principal  employment  has  hitherto  been,  I 
believe,  as  a  top-dressing  for  the  wheat  crop,  either  harrowed  in  with 
the  seed  in  October,  or  applied  to  the  young  corn  in  spring. 

Rape-dust  requires  moisture  to  bring  out  its  full  fertilizing  virtues  ;- 
hence  it  is  chiefly  adapted  to  clay  soils  or  to  such  as  rest  upon  a  stiff 
subsoil.  It  is  seldom  applied,  therefore,  to  the  barley  crop,  and  even 
upon  wheat  it  will  fail  to  produce  any  decidedly  good  effect  in  a  very 
dry  season.  Several  interesting  circumstances  have  been  experi- 
mentally ascertained  in  regard  to  the  action  of  rape-dust,  to  which  it 
is  proper  to  advert : — 

a.  That  in  very  dry  seasons  it  may  produce  little  benefit  upon  tur- 
nips, potatoes,  and  other  crops,  while  in  the  same  circumstances  the 
effect  of  guano  may  be  strikingly  beneficial.  Thus  in  one  experi- 
ment, made  in  1842,  upon  unmanured  land  sown  with  turnips — 

16  cwt.  of  rape-dust  gave  3|  tons  of  bulbs  per  acre. 

2  cwt.  of  guano  gave       5  do. 
Unmanured  gave                3i              do. 

And  in  another,  in  the  same  season,  upon  unmanured  land — 
1  ton  of  rape-dust  gave  14^  tons  of  bulbs  per  acre. 

3  cwt.  of  guano  gave    23i  do. 
Unmanured  gave             12 J*                do. 

.  Again,  upon  potatoes,  planted  without  other  manure,  in  three  ex- 
periments the  produce  per  acre,  in  tons,  was  as  follows : — 

Unmanured.  1  ton  Rape-dust.  3  cwt.  Guano.  4  cwt.  Guano. 

White  Don  Potatoes —  12i  18^  — 

Red  Don  Potatoes ...!...  6|  10  —  14i 

Connaught  Cups 5|  13  —  13| 

In  none  of  the  above  experiments  did  the  action  of  the  large  quan- 
tity of  rape-dust  equal  that  of  the  comparatively  small  quantity  of 
guano — though,  from  being  buried  in  the  soil,  the  difference  was  less 
striking  in  the  case  of  the  potatoe  crops. 

b.  Rape-dust  may  actually  cause  the  crop  to  be  less  than  the  land 
alone  would  naturally  produce — if  in  a  dry  season  it  be  laid  on  in 
any  considerable  quantity. 

Thus  in  1842,  in  an  experiment  upon  Oats,  made  at  Lennox  Love — 
16  cwt.  of  rape-dust  gave  45  bushels. 
2  cwt.  of  guano  gave       68     do. 
Unmanured  soil  gave         49     do. 
In  this  property  of  injuring  the  crop,  when  rain  does  not  happen  to 
fall,  rape-dust  resembles  very  much  those  saline  substances  which,  as 
we  have  seen,  may  often  be  applied  with  much  advantage  to  the  land. 

c.  Yet  it  would  appear  to  exercise  less  of  this  evil  influence  upon 
wheat  and  beans,  and    n  similar  circumstances.     Thus  in  the  same 

•  See  AppendLx,  No.  VIU. 


THE    aUANTITY   MUST   NOT    BE   TOO    GREAT.  435 

season,  1842,  and  in  the  same  locality,  Lennox  Love,  a  crop  of  wheat, 
with — 

16  cwt.  of  rape-dust  gave  51  bushels  per  acre. 
2  cwt.  of  guano  gave       48  do. 

Unmanured  gave  47  §  do. 

And  a  crop  of  beans,  with — 

16  cwt.  of  rape-dust  gave  38    bushels. 
2  cwt.  of  guano  gave        35i      do. 
Unmanured  gave  30        do. 

In  both'bf  these  cases,  notwithstanding  the  drought,  the  rape-dust 
Improved  the  crop,  and  though  not  sufficiently  so  to  pay  the  cost  of  the 
application,  yet  to  a  greater  extent  than  the  same  quantity  of  guano. 
It  is  deserving  of  investigation,  therefore,  whether  rape-dust  be  more 
especially  adapted  to  wheat  and  beans.  Even  in  favorable  seasons 
it  may  possibly  prove  more  economical  than  guano  as  a  manure  for 
these  two  crops  (see  Appendix,  No.  VIII.) 

d.  But  even  in  favorable  seasons,  and  to  the  wheat  crop,  there  is 
reason  to  believe  that  rape-dust  cannot  be  economically  applied  in  more 
than  a  certain,  perhaps  variable,  quantity  per  acre.  Thus  four  equal 
plots  of  ground  (nearly  half  an  acre  each,)  sown  with  wheat,  were  top- 
dressed  with  rape-dust  in  different  proportions  with  the  following  results: 

With    7  cwt.  the  produce  was  26  bushels  of  market  corn. 

With  10  cwt.  the  produce  was  28  do. 

With  15  cwt.  the  produce  was  2%  do. 

With  26  cwt.  the  produce  was  27|  do. 

Unmanured  the  produce  was    22 i*  do. 

In  this  experiment  not  only  was  the  crop  diminished  when  more 
than  15  cwt.  was  added,  but  the  increased  produce  was  not  sufficient 
to  defray  the  additional  cost  of  the  application,  when  more  than  7 
cwt.  of  rape-dust  was  put  on. 

e.  It  may  be  noticed  as  another  curious  fact,  that  the  action  of 
rape-dust  is  dependent  upon  the  presence  or  absence  of  certain  other 
substances  in  the  soil.  Common  salt  and  sulphate  of  soda,  when 
mixed  with  it  under  certain  circumstances,  lessen  the  effect  which  it 
would  produce  alone,  and  the  same  will  probably  happen  when  it  is 
applied,  without  admixture,  to  soils  in  which  these  saline  compounds 
happen  to  be  already  present.  Some  remarks  upon  this  interesting 
point  will  be  found  in  the  Appendix,  No.  VIII. 

4°.  Lintseed,  poppy-seed,  cotton-seed,  and  cocoa-nut  cakes. — The 
cake  which  is  lefl  when  other  oils  are  extracted  from  the  seeds  or  fruits 
in  which  they  exist  is,  also,  in  almost  every  case,  useful  as  a  manure. 
Thus  the  seeds  of  the  cotton  plant  yield  an  oil  and  leave  a  cake  which  is 
now  used  as  a  manure  in  the  United  States,  though  Httle  known  as  yet,  I 
believe,  in  England.  The  cocoa-nut  cake  is  employed  in  Southern  In- 
dia partly  in  feeding  cattle  and  partly  as  a  manure  for  the  cocoa-nut  tree 
itself  Some  trials  have  recently  been  made  with  it  among  ourselves, 
but  I  am  ignorant  of  the  precise  results.  In  this  country  lintseed  cake 
is  made  in  large  quantity,  but  as  it  is  relished  by  cattle,  is  fattening,  and 
enriches  the  droppings  of  the  stock  fed  upon  it,  it  is  seldom  applied  di- 

*  British  Husbandry,  I.,  p  412. 
19 


436        USE  OF  MALT-DUST,  DRY  LEAVES,  AND  PEAT,  AS  MANURES. 

rectly  to  the  land.  In  France  and  some  parts  of  Belgium,  where  the 
poppy  is  largely  cultivated  for  the  oil  yielded  by  its  seeds,  the  cake 
v^rhich  these  seeds  leave  is  highly  esteemed  as  a  manure. 

5°.  Malt-dust. — When  barley  is  made  to  sprout  by  the  malster,  and 
is  afterwards  dried,  the  small  shoots  and  rootlets  drop  off',  and  form 
the  substance  known  by  the  name  of  malt-dust.  One  hundred  bushels 
of  barley  yield  4  or  5  bushels  of  this  dust.  It  is  sold  at  the  rate  of 
from  5s.  to  8s.  a  quarter,  and  has  been  applied  with  success  as  a  top- 
dressing  to  the  barley  and  wheat  crops.  It  may  also  be  drilled  in 
with  turnips  or  dusted  over  the  young  grass  in  spring. 

6°.  Saw-dust  is  usually  rejected  by  the  agriculturist,  in  consequence 
of  the  difficulty  which  is  generally  experienced  in  bringing  it  into  a  state 
of  fermentation.  It  decomposes  slowly  when  ploughed  into  the  soil  in 
its  dry  state,  but  it  nevertheless  gradually  benefits  the  land,  and  should 
not,  therefore,  be  permitted  in  any  case  to  run  to  waste.  It  forms  an 
excellent  absorbent  also  for  liquid  manures  of  any  kind,  which  it  pre- 
serves from  sinking  too  rapidly  when  they  are  to  be  applied  to  porous, 
sandy,  or  chalky  soils,  while  these  liquids  again  hasten  the  decomposi- 
tion of  the  saw-dust  and  augment  its  immediate  effect  upon  the  land.  In 
localities  favorable  for  the  collection  of  sea- weed,  it  may  also  be  more 
rapidly  fermented  by  an  admixture  with  this  substance.  Saw-dust 
forms  an  ingredient  in  some  of  the  mixed  manures  which  have  re- 
cently come  into  use  (see  Appendix,  No.  VIII.,  Exp.  B.) 

7°.  Dry  leaves  may  either  be  dug  into  the  land  at  once,  or  maybe 
laid  up  in  heaps,  when  they  will  gradually  decay,  and  form,  in  most 
cases,  an  enriching  manure.  They  gradually  improve  the  soil  (as 
we  have  already  seen,  p.  429,)  on  which  they  annually  fall,  but  the 
same  quantity  of  leaves  will  do  mora  good  if  collected  and  immedi- 
ately dug  in,  or  if  made  into  a  compost  heap,  than  if  left  to  undergo 
a  slow  natural  decay  on  the  surface  of  the  land. 

§  12.   Of  the  icse  of  decayed  vegetable  matter  as  a  manure. 

The  most  abundant  forms  of  partially  decayed  vegetable  matter 
which  come  within  the  reach  of  the  practical  farmer,  are  peat  and 
tanner's  bark. 

1°.  Peat. — To  soils  which  are  deficient  in  vegetable  matter,  it  is 
clear  that  a  judicious  admixture  of  peat  must  prove  advantageous,  be- 
cause it  will  supply  some  at  least  of  those  substances  which  are  neces- 
sary to  the  production  of  a  higher  degree  of  fertility.  But  peat  decays 
very  slowly  in  the  air,  and  hence  its  apparent  effect  when  mixed  with 
the  soil  is  very  small.  It  may  gradually  ameliorate  its  quality,  espe- 
cially if  the  soil  be  calcareous,  but  it  will  not  immediately  prepare  the 
land  for  the  growth  of  any  particular  crop.  But  if  the  obstacles  to 
its  further  decomposition  be  removed — that  is,  if  by  artificial  means 
its  decay  be  promoted — then  its  immediate  and  apparent  effect  upon 
the  soil  is  increased,  and  it  becomes  an  acknowledged  fertilizing  ma- 
nure. Different  methods  have  been  successfully  practised  for  bring- 
ing it  into  this  more  rapid  state  of  decay  or  fermentation. 

a.  The  half-dried  peat  may  be  mixed  with  from  one-fourth  to  one- 
half  of  its  weight  of  fermenting  farm-yard  manure — the  whole  heap 


FERMENTATION    OF   PEAT    AND    TANNER's    BARK.  437 

being  carefully  covered  o^«r  with  a  layer  of  peat  to  prevent  the  es- 
cape of  fertilizing  vapors.  By  this  method — first  introduced  to  pub- 
lic notice  by  the  late  Lord  Meadowbank — the  entire  mixture  is  gra- 
dually brought  into  an  equable  state  of  heat  and  fermentation,  and 
as  a  manure  for  the  turnip  crop,  is  said  to  be  as  efficacious  as  an 
equal  weight  of  unmixed  farm-yard  manure. 

5.  Or  the  liquid  manure  of  the  farm-yard  may  be  employed  for  the 
same  purpose,  either  in  whole  or  in  part.  If  the  heap  of  mixed  peat 
and  dung  be  watered  occasionally  with  the  liquid  manure,  the  fer- 
mentation will  be  more  speedily  effected,  and  at  a  less  expense  of 
common  farm-yard  dung.  Or  the  half-dried  peat  may  be  used  un- 
mixed, as  an  absorbent  for  the  liquid  of  the  farm-yard,  by  which, 
without  other  aid,  it  wnll  be  brought  into  a  state  of  fermentation  with 
comparative  rapidity. 

c.  Or  instead  of  the  liquid  manure,  the  ammoniacal  liquor  of  the 
gas-Avorks  may  be  employed,  with  less  prominent  benefit  certainly, 
but  still  with  great  advantage. 

d.  Or  the  peat  may  be  mixed  with  from  one-sixth  to  one-fourth  of  its 
bulk  of  fresh  sea- weed,  the  rapid  decay  of  which  will  gradually  reduce 
the  entire  heap  into  a  fertilizing  mass  (British  Husbandry,  II.,  p.  417.) 

e.  Or  rape-dust  in  the  proportion  of  1  ton  to  30  cubic  yards  may 
be  mixed  with  the  half-dried  peat  from  two  to  six  weeks  before  the 
time  of  sowing  the  turnip  crop.  The  fermentation  of  the  rape-dust 
takes  place  so  quickly,  that  this  short  time  is  usually  sufficient  to  con- 
vert the  whole  into  a  uniform  and  rapidly  decaying  mass. 

In  short,  it  is  only  necessary  to  mix  half-dried  peat  with  any  sub- 
stance which  undergoes  rapid  spontaneous  decomposition — when  it 
will  more  or  less  speedily  become  infected  with  the  sanie  tendency  to 
decay,  and  will  thus  be  rendered  capable  of  ministering  to  the  growth 
of  cultivated  plants. 

2°.  Tanner^s  bark  is  still  more  difficult  to  reduce  or  to  bring  into  a 
rapid  state  of  decomposition.  Any  of  the  methods  above  recommended 
for  peat,  however,  will  to  a  certain  extent  succeed  also  with  the  spent 
bark  of  the  tan  pits.  But  in  the  case  of  substancet  so  solid  and  refrac- 
tory as  the  lumps  of  bark  are,  the  admixture  of  a  quantity  of  lime  and 
earth,  so  as  to  form  a  compost  keap,  is  perhaps  the  most  advisable 
m.ode  of  procedure.  The  way  in  which  lime  promotes  the  decay  of 
woody  fibre  in  such  heaps  has  already  been  "explained  (see  p.  382.) 

§  13.   Use  of  charred  vegetable  matters  as  a  manure. 

Soot  and  charcoal  are  the  principal  substances  of  this  class  which 
have  been  more  or  less  extensively  eraployed  for  the  purpose  of  in- 
creasing the  productiveness  of  the  land. 

1°.  Soot  is  a  complicated  and  variable  mixture  of  substances  pro- 
duced during  the  combustion  of  coal.  Its  composition,  and  consequent- 
ly its  effects  as  a  manure,  vary  with  the  quality  of  the  coal,  with  the 
way  in  which  the  coal  is  burned,  and  with  the  height  of  the  chimney 
in  which  it  is  collected. 

Soot  has.  not  been  analyzes  since  the  year  1826,  when  a  variety  ex 
ammed  by  Braconnot  was  fou».i  by  him  to  consist  in  a  thousand  parts  ol 


438  COMPOSITION  OF  SOOT — ITS  EFFECTS  UPON  RYE-GRAS3. 

Ulmic  acid  ?  (a  substance  resembling  that  portion  of  the 
vegetable  matter  of  the  soil  which  is  soluble  in  caustic 

potash— (see  Lee.  XIII.,  §  1) 302-0 

A  reddish  brown  soluble  substance,  containing  nitrogen,  and 

yielding  ammonia  when  heated 200-0 

A  sboline 5-0 

Carbonate  of  lime,  with  a  trace  of  magnesia  (probably  de- 
rived in  part  from  the  sides  of  the  chimney) 146-6 

Acetate  of  lime 56-5 

Sulphate  of  lime  (gypsum) 50-0 

Acetate  of  magnesia , 5-3 

Phosphate  of  lime,  with  a  trace  of  iron 15-0 

Chloride  of  potassium 3-6 

Acetate  of  potash 41-6 

Acetate  of  ammonia 2-0 

Silica  (sand). 9-5 

Charcoal  powder 38*5 

Water 125-0 


1000* 


The  earthy  substances  which  the  soot  contains  are  chiefly  derived 
from  the  walls  of  the  chimney,  and  from  the  ash  of  the  coal,  part  of 
which  is  carried  up  the  chimney  by  the  draught.  These,  therefore, 
must  be  variable,  being  largest  in  quantity  where  the  draught  is  strong- 
est and  where  the  earthy  matter  or  ash  in  the  coal  is  the  greatest.  The 
quantity  of  gypsum  present  depends  upon  the  sulphur  contained  in  the 
coal,— that  which  is  freest  from  sulphur  will  give  a  soot  containing  the 
least  gypsum.  The  ammonia  and  the  soluble  substances  containing  ni- 
trogen will  vary  with  the  quantity  of  nitrogen  contained  in  the  coal  and 
with  certain  other  causes — so  that  the  composition  of  different  samples 
of  soot  may  be  very  unlike,  and  their  influence  upon  vegetation  there- 
fore very  unequal.  The  consequence  of  this  must  be,  that  the  results 
obtained  in  one  spot  or  upon  one  crop,  are  not  to  be  depended  upon,  as 
indicative  of  the  precise  effect  which  another  specimen  of  soot  will 
produce  in  another  locality,  and  upon  another  crop  even  of  the  same 
kind.  And  thus  it  happens  that  the'use  of  soot  is  more  general,  and 
is  attended  with  more  beneficial  effects,  in  some  districts  than  in  others. 

a.  In  general  it  may  be  assumed  that  where  ammonia  or  its  salts 
will  benefit  the  crop,  soot  also  will  be  of  use,  and  hence  its  successful 
application  to  grass  lands.  From  its  containing  gypsum  it  should  also 
especially  benefit  the  clover  crops.  Yet  Dr.  Anderson  says,  "  I  have 
used  soot  as  a  top-dressing  for  clover  and  rye- grass  in  all  proportions, 
from  one  hundred  bushels  per  acre  to  six  hundred,  and  I  cannot  say 
that  ever  I  could  perceive  the  clover  in  the  least  degree  more  luxuri- 
ant than  in  the  places  where  no  soot  had  been  applied.  But  upon 
rye-grass  its  effects  are  amazing,  and  increase  in  proportion  to  the 
quantity  so,  far  as  my  trials  have  gone."  (Dr.  Anderson's  Essays, 
edit.  1800,  ii.,  p.  304.)  And  his  general  conclusion  is,  that  soot  does 
not  affect  the  growth  of  clover  in  any  way.  while  it  wonder/idly  promotes 

*  Annales  de  Chcmie  et  de  Physigtie,  xxxi.,  p.  37. 


ACTION  OF  SOOT  UPON  WHEAT  AND  OATS.  439 

that  of  rye-grass.     Will  any  of  you,  by  experiment,  ascertain  if  such 
be  really  the  case  with  the  soot  of  your  own  neighborhood? 

b.  The  presence  of  ammonia  in  soot  causes  it,  when  laid  in  heaps, 
to  destroy  all  the  plants  upon  the  spot ;  and  Dr.  Anderson  adds  the  in- 
teresting observation,  "  that  the  first  plant  which  appears  after^vards 
is  constantly  the  common  couch-grass  (triticum  repens).  (Dr.  Ander- 
son's Essays,  edit.  1800,  ii.,  p.  305.) 

c.  This  ammonia  also  causes  soot  to  injure  and  diminish  the  crop  in 
very  dry  seasons.  Thus  the  produce  of  a  crop  of  beans,  after  oats,  in 
1842,  upon  an 

Unmanured  part  of  the  field  was 29|  bushels. 

Dressed  with  4  bushels  of  soot 28  bushels.* 

It  also  diminished,  in  a  small  degree,  the  potatoe  crop  in  the  same 
vear  in  the  experiments  of  Lord  Blantyre,  atErskine  (Appendix,  No. 

ix.)- 

With  manure  alone,  the  produce  was 11  tons  17  cwt. 

With  30  bushels  of  soot  sprinkled  over  the  dung.  11  tons    4  cwt. 

Like  rape-dust  (p.  434)  and  saline  substances,  therefore,  soot  seems 
to  require  moist  weather,  or  a  naturally  moist  soil,  to  bring  out  all  its 
virtues. 

d.  Yet  even  in  the  dry  season  of  1842,  its  effect  upon  wheat  and  oats 
in  the  same  locahty  (Erskine)  was  very  beneficial.  Thus  the  com- 
parative produce  of  these  crops,  when  undressed  and  when  top-dress- 
ed with  10  bushels  of  soot  per  acre,  was  as  follows : — 

Unmanured Wheat  44 Oats  49. 

Top-dressed  with  soot Wheat  54 Oats  55. 

But  the  dressed  wheat  was  inferior  in  quality  to  the  undressed — the 
former  weighing  only  58,  the  latter  62  lbs.  a  bushel.  In  the  oats  there 
was  no  difference.  Are  we  to  infer  from  these  results  that,  even  in 
dry  seasons,  soot  may  be  safely  applied  to  crops  of  corn,  while  to  pulse 
and  roots  it  is  sure  to  do  no  good  ?  Further  precise  observations,  no 
doubt,  are  still  necessary — and  the  more  especially  as  the  experiments 
upon  oats  and  wheat,  made  in  the  still  drier  locality  of  Lennox  Love 
(Appendix,  No,  VIII.).  gave  a  decrease  in  the  produce  of  grain — while 
in  Mr.  Fleming's  experiments  upon  turnips  (Appendix,  No.  VIII.),  50 
bushels  of  soot,  applied  alone,  gave  an  increase  of  4  tons  in  the  crop. 

e.  An  experiment  of  Lord  Blantyre's  (Appendix,  No.  IX.),  enables 
us  to  judge  of  the  efficacy  of  soot  in  a  dry  season,  compared  with  that 
of  nitrate  of  soda  and  of  guano  upon  the  produce  of  hay.  Thus  the 
crop  of  hay,  per  imperial  acre,  from  the 

Cost, 
tons.     cwts.  £    s.   d. 

Undressed  portion,  weighed 1  8     • 

Dressed  with  40  bushels  of  soot 1  15  0  11     8 

160  lbs.  nitrate  of  soda 1  19  1  15    9 

160  lbs.  guano 2  2  1  15    9 

In  this  experiment  the  soot  proved  a  more  profitable  application  than 
either  of  the  other  manures. 
/.  In  regard  to  this  substance,  I  shall  only  advert  to  one  other  obser- 

•  See  >..5pendix,  No.  VIII. 


440  USE    CF    CHARCOAL-DUSTj    AND    OF   COAL-TAR. 

vation — but  it  is  an  important  one — made  by  Mr.  Morton,  when  des- 
cribing the  management  of  a  well  conducted  farm  in  Gloucestershire, 
(that  of  Mr.  Dimmery,  described  in  the  Journal  of  the  Royal  Agri- 
cultural Society^  I.,  p.  400.)  "  The  quantity  of  soot  used  upon  this 
farm  amounts  to  3000  bushels  a-year,  one-half  of  which  is  applied  to  the 
potatoe,  the  other  half  to  the  wheat  crop."  All  the  straw  grown  upon 
this  farm  is  sold  for  thatch,  and  for  the  last  30  years  the  only  manure 
that  has  been  purchased  to  replace  this  straw  is  the  soot,  which  is 
brought  from  Gloucester,  Bristol,*  and  Cheltenham.  Soot  no  doubt 
contains  many  things  useful  to  vegetation,  yet  where  all  the  produce  is 
carried  off,  and  soot  only  added  in  its  stead — even  the  rich  soils  of  tlie 
vale  of  Gloucester  cannot  be  expected  to  retain  a  perpetual  fertility. 
The  slow  changes  which  theory  indicates  may  altogether  escape  the 
observation  of  the  practical  man,  who  makes  no  record  of  the  history 
of  his  land,  and  yet  may  be  ever  slowly  proceeding. 

2^.  Charcoal. — Wood-charcoal,  from  its  porous  nature,  and  its  tend- 
ency to  absorb  animal  odors  and  other  unpleasant  effluvia  (Lee.  I.,  §  2), 
has  beeu  found,  when  reduced  to  fine  powder,  to  be  an  excellent  admix- 
ture for  night  soil,  for  hquid  manure,  and  for  other  substances  which 
undergo  putrescent  decay.  It  is  therefore  employed  to  a  considerable 
extent  by  the  manufacturers  of  artificial  manures.  It  is  also  applied 
with  advantage  in  some  cases  as  a  top-dressing  to  various  cropsf — its 
eflicacy  being  probably  due  in  part  to  its  power  of  absorbing  from  the 
air,  or  of  retaining  in  the  soil,  those  gaseous  substances  which  plants  re- 
quire, and  in  part  to  the  slow  decay  which  it  is  itself  capable  of  under- 
going. In  moist  charcoal  powder  seeds  are  said  to  germinate  with 
great  ease  and  certainty. 

3°.  Coal-tor. — Another  product  of  coal,  the  tar  of  the  gas-works,  has 
recently  been  recommended  as  an  admixture  for  peat  and  similiar  com- 
posts, and  it  is  one  of  the  substances  with  which  Mr.  Daniel  impreg- 
nates his  saw-dust  in  the  manufacture  of  his  patent  manure.  It  is  im- 
possible to  say  how  much  of  the  good  effect  derived  from  the  use  of 
such  mixtures  as  that  described  in  the  Appendix,  No.  VIII.,  is  due  to 
the  coal-tar  they  contain, — and  as  no  experiments  have  hitherto  been 
made  from  which  the  true  action  of  coal-tar  can  be  inferred,  it  may 
still  be  considered  as  a  matter  of  doubt  whether  it  can  at  all  add  direct- 
ly to  the  fertility  of  the  soil. 

^  14.  Of  the  theoretical  value  of  different  vegetable  substances 
as  manures. 

Vegetable  manures  are  known  to  differ  in  fertihzing  virtue.  Thus, 
1  ton  of  rape-dust  is  said  to  be  equal  to  16  of  sea-weed  or  to  20  of  farm- 
yard manure.*  On  what  principles  do  these  unlike  fertilizing  virtues 
depend  ? 

1°.  According  to  Boussingault  and  other  French  authorities,  the  re- 
lative efficacy  of  all  manures  depends  upon  the  proportions  of  nitrogen 

*  At  Bristol  the  price  of  soot  Is  9(i.  a  bushel,  at  Gloucester  only  6d.,  yet  the  former  is  pre- 
ferred even  at  the  higher  price.  It  is  of  better  quality,  owing,  it  is  said,  to  the  greater  length 
of  the  chimnies — it  may  be  also  to  ihe  quality  of  the  coal  and  to  the  way  it  is  burned. 

t  See  Mr.  Fleming's  experiment  ipon  Swedes  (Appendix  No.  VIII.),  in  which  50  bunh- 
e'8  of  charcoal  powder  increased  the  crop  by  three  cms  an  acre; 


THEORETICAL   VALUE    OF  VEGETABLE    MANURES.  441 

^n&y  severally  contain,  { Annates  de  Ckemieet  de  Phys.^  3d  series,  III., 
D.  76. )     And  taking  farm-yard  manure — consisting  of  the  mixed  drop- 
ings  and  litter  of  cattle — as  a  standard,  they  arrange  vegetable  sub- 
dances,  as  manures,  in  the  following  order  of  value : — 

Equal  effects  are  produced  by 

Farm-yard  manure '. 1000  lbs. 

Potatoe  and  turnip  (?)  tops 750  " 

Carrot  tops 470  « 

Natural  grass 760  " 

Clover  roots 250  " 

Fresh  sea-weed 450  to  750  " 

Sea-weed  dried  in  the  air 300  " 


Pea  straw 220  " 

Wheat  straw 750  to  1700  « 

Oat  straw •  . .    1400  " 

Barley  straw 1750  " 

Rye  straw 1000  to  2400  <' 

Buck-wheat  straw 850  " 

Wheatchaff 470  " 


Fir  saw-duyt 1700  to  2500  « 

Oak     do 750  « 

Soot,  from  coal 300  " 

Lint  and  rape-dust 80  " 

The  numbers  in  this  table  agree  with  the  results  of  experiment  in 
so  far  as  they  indicate  that  green  substances  generally,  when  ploughed 
in  as  manures,  should  enrich  the  soil  more  tnan  an  equal  weight  of 
farm-yard  manure — that  the  roots  of  clover  should  be  more  enriching 
still — and  that  sea-weed  is  likewise  a  very  valuable  manure.  They 
agree  also  with  practical  observation  in  placing  pea,  and  probably 
bean  straw,  far  above  the  straws  of  wheat,  oats,  &c.,  in  fertilizing 
power,  and  in  representing  soot  and  rape-dust  as  more  powerful  than 
any  of  the  other  substances  in  the  table.  '  So  far,  therefore,  a  certain 
general  reliance  may  be  placed  upon  the  fertilizing  value  of  a  sub- 
stance as  represented  by  the  proportion  of  nitrogen  it  contains. 

But  if  we  bear  in  mind  that  plants,  as  we  have  frequently  had  occa- 
sion to  mention,  require  inorganic  as  well  as  organic /oo(Z,  it  is  quite 
clear  that  the  mere  presence  of  nitrogen  in  a  substance  is  not  sufficient 
to  render  it  highly  nutritive  to  growing  plants.  Otherwise  the  salts 
of  ammonia  would  be  the  richest  manures  of  all,  and  would  best  nourish 
and  bring  to  perfection  every  crop  and  in  all  circumstances — which  ex- 
perience has  proved  to  be  by  no  means  the  case.     Hence 

2°.  The  value  of  vegetable  substances  as  manures  must  depend  in 
some  degree  wpon  the  quantity  and  kind  of  inorganic  matter  they 
contain.  In  reference  to  the  quantity  of  inorganic  matter  which  they 
respectively  impart  to  the  soil,  their  relative  values  are  represented 
by  the  following  numbers : — 


442  INFLUENCE    OF   THE   CARBCNACEOUS    MATTER. 

One  ton  contains  of  inorganic 
mafier  about 

Potato  tops,      green 26  lbs. 

Turnip  tops,         do 48    " 

Carrot  tops,  do 45    " 

Rye-grass,  do 30    " 

Vetch,  -do 38    " 

Green  sea-weed,  do 22    " 

Hay 90  to  180  " 

Pea  straw 100  " 

Bean  straw 60  to    80  « 

Wheat  straw 70  to  360  " 

Oatstraw 100  to  180  " 

Barley  straw 100  to  120  " 

Rye  straw 50  to    70  « 

Fir  saw-dust 6    " 

Oak  saw-dust 5     ' 

•  Soot ^ 500 

Rape-dust 120 

This  table  places  the  several  vegetable  substances  in  an  order  of 
efficacy  considerably  different  from  the  former,  in  which  they  are 
arranged  according  to  the  quantity  of  nitrogen  they  respectively  con- 
tain. We  know  that  wood-ashes  (p.  353),  kelp,  and  the  ashes  of  straw 
(p.  356),  do  promote  the  fertility  of  the  land,  and  therefore  the  abso- 
lute as  well  as  the  relative  efficacy  of  the  above  vegetable  substances 
must  depend  in  some  degree  upon  the  quantity  of  inorganic  matter 
they  contain.  But  we  should  be  wrong  were  we  to  ascribe  the  total 
effect  of  any  of  them  to  the  inorganic  matter  alone. 

3°.  Even  the  carbonaceous  matter  of  plants  contributes  its  aid  in 
increasing  the  produce  of  the  soil,  by  supplying,  either  directly  or  in- 
directly, a  portion  of  the  necessary  food  of  plants.  This  has  already 
been  shown  in  various  parts  of  the  preceding  lectures. 

It  is  the  property  of  substances  which  contain  a  larger  proportion 
of  nitrogen,  to  undergo  rapid  decay  in  the  presence  of  air  and  moisture, 
and  thus  to  produce  a  more  immediate  and  sensible  action  upon  grow- 
ing plants.  But  the  carbon  changes  more  slowly,  and  the  inorganic 
matter  also  separates  slowly  from  decaying  vegetables  in  the  soil — 
and  hence  the  apparent  effects  of  these  constituents  are  less  striking. 
Thtis  the  immediate  and  visible  effect  of  different  vegetable  substances, 
in  the  same  state,  is  measured  by  the  relative  quantities  of  nitrogen 
they  contain — their  'permanent  effects  by  the  relative  quantities  of  in- 
organic and  of  carbonaceous  matters.  In  the  case  of  rape-dust,  for  ex- 
ample, the  immediate  effect  is  determined  chiefly  by  its  nitrogen — the 
permanent  effects,  by  the  ash  it  leaves  when  burned,  or  when  caused 
to  undergo  complete  decay  in  the  air. 


LECTURE  XVlll. 


Animal  manures.— Flesh,  blood,  and  skin.— Wool,  woollen  rags,  hair,  horn,  and  bones.— On 
what  does  the  fertilizing  action  of  bones  depend  7— Animal  charcoal  and  the  refuse  of  the 
sugar  refineries.— Fish  and  fish-refuse,  whale  blubber  and  oil. — Relative  fertilizing  value 
of  the  substances  previously  described. — Pigeon  dung. — Dung  of  sea-fowl :  guano. — 
Liquid  manures  :  the  urine  of  various  animals. — Mixed  animal  and  vegetable  manures. — 
Night  soil,  the  droppings  of  the  horse,  the  cow,  the  pig. — Effects  of  digestion  upon  vege- 
table food. — Why  equal  weights  of  vegetable  matter,  and  the  droppings  of  animals  fed 

me.— W( 


upon  it,  possess  different  fertilizing  powers.- Farm-yard  dung.— Weight  of  dung  pro- 
duced from  a  given  weight  of  grass,  straw,  and  other  produce.— Loss  undergone  by 
farm-yard  manure  during  fermentation.— Improvement  of  the  soil  by  irrigation. 


Animal  substances  have  always  been  considered  as  more  fertilizing 
to  the  land  than  such  as  are  of  vegetable  origin.  Their  action  is  in 
general  more  immediate  and  apparent,  and  it  takes  place  within  such  a 
Innited  period  of  time  that  the  farmer  can  calculate  upon  its  being  ex- 
ercised in  benefitting  the  crop  to  which  it  is  applied.  The  reason  of  this 
more  immediate  action  will  presently  appear. 

§  1.  Of  Jiesh,  blood,  and  skin. 

1°.  Flesh. — The  flesh  of  animals  is  not  only  a  rich  manure  m  itself, 
but  the  rapidity  with  which  it  undergoes  decay  in  our  climate  enables 
it  speedily  to  bring  other  organic  substances  with  which  it  may  be  mixed 
into  a  state  of  active  fermentation.  It  is  only  the  flesh  of  such  dead 
animals,  however,  as  are  unfit  for  food,  that  can  be  economically  ap- 
plied to  the  land  as  a  manure. 

The  flesh  of  animals  consists  of  a  lea7i  part,  called  the  muscular  fibre, 
or  by  chemists  fibrin,  and  i\  fatty  part,  intermixed  with  the  lean  in 
greater  or.less  proportion,  according  to  the  condition  of  the  animal. 
Of  these  two  it  is  the  lean  part  which  acts  most  immediately  and  most 
energetically  in  the  promotion  of  vegetation.  Lean  beef,  in  the  recent 
state,  contains  77  per  cent,  of  its  weight  of  water,  so  that  100  lbs.  consists 
of  77  lbs.  of  water  and  23  lbs.  of  dry  animal  matter. 

2°.  Blood. — The  blood  of  animals  is  more  extensively  employed  as 
a  manure.  It  is  carried  ofl'in  large  quantities  from  the  slaughter-houses 
of  the  butchers,  and  makes  rich  and  fertilizing  composts.  In  some 
parts  of  Europe  it  is  dried,  and  in  the  state  of  dry  powder  is  applied  with 
much  effect  as  atop-dressing  to  many  crops. 

Liquid  blood  consists  of  fibrin — the  substance  of  lean  meat,  of  albu- 
men— the  same  as  the  white  of  eggf^ — of  a  red  coloring  matter,  and  of 
certain  saline  substances  dissolved  in  a  considerable  quantity  of  water. 
When  blood  cools  it  gradually  congeals,  and  separates  into  two  parts, 
a  gelatinous  red  portion,  called  the  clot,  and  a  liquid,  nearly  colorless, 
part  called  the  serum.  The  clot  contains  most  of  the  fibrin  and  color- 
ing matter,  and  a  portion  of  the  albumen ;  the  serum,  the  greater  part 
of  the  albumen  and  of  the  soluble  saline  substances  which  are  present 
m  the  blood. 

The  relative  composition  of  fresh  muscular  fibre  and  of  liquid  blood 
is  thus  represented  in  100  parts : — 
19* 


444  coMPOsncN  of  blood,  and  of  skin. 

Wafer.  Dry  animal  malfer 

Muscular  fibre 77  23 

Blood .79  21* 

It  appears  singular  that  the  solid  muscle  of  animals  should  contain 
so  nearly  the  same  quantity  of  water  as  their  liquid  blood  does. 

But  it  is  no  less  striking  that  the  dry  animal  matter  which  remains, 
when  lean  muscular  fibre  and  when  blood  are  fully  dried,  has  nearly  the 
same  apparent  composition.  Thus,  according  to  the  analyses  of  Play- 
fair  and  Boeckman,  dry  flesh  and  dry  blood  consist  respectively  of— 

Dry  be*^         Dry  ox  blood. 

Carbon 51-83  51-96 

Hydrogen 7-57  7-25 

Nitrogen 15-01  15-07 

Oxygen 21-37  21-30 

Ashes 4-23  4-42 


100  loot 

The  org-amc  part,  therefore,  of  blood  and  of  flesh  is  nearly  identical 
in  ultimate  composition,  and  the  final  result  of  equal  weights  of  each, 
when  applied  as  manures,  should  be  nearly  the  same.  The  ashes,  how- 
ever, or  inorganic  part,  though  present  in  each  nearly  in  the  same  pro- 
portion (4-23  and  4-42  per  cent),  are  somewhat  different  in  composition, 
and  therefore  the  action  of  blood  and  flesh  will  be  a  little  unlike  in  so 
far  as  it  depends  upon  the  saline  substances  they  are  respectively  capa- 
ble of  conveying  to  the  roots  of  plants. 

3°.  Skin. — The  skins  of  nearly  all  animals  find  their  way  ultimately 
into  the  soil  as  manure,  in  a  more  or  less  changed  state. 

The  refuse  parings  from  the  tan-yards,  and  from  the  curriers'  shops, 
though  usually  employed  for  the  manufacture  of  glue,  are  sometimes 
used  as  a  manure,  and  with  great  advantage.  They  may  either  be 
ploughed  in  sufficiently  deep  to  prevent  the  escape  of  volatile  matter 
when  they  begin  to  decay,  or  they  may  be  made  into  a  compost  by 
which  their  entire  virtues  will  be  more  effectually  retained. 

Skin  differs  considerably  in  its  constitution  from  flesh  and  blood.  It 
contains,  in  the  recent  state,  about  58  per  cent,  of  water,  and  leaves, 
when  burned,  only  1  per  cent,  of  ash.  The  combustible  or  organic  part 
consists  of — 

Carbon 50-99 

Hydrogen 7-07 

Nitrogen 18-72 

Oxygen 23-22 

100 
It  contains,  therefore,  3*  per  cent,  more  nitrogen  than  flesh  or  blood. 
So  far  as  the  fertilizing  action  of  these  substances  depends  upon  the 
proportion  of  this  constituent — glue,  the  parings  of  skins,  and  all  gelati- 
nous substances,  will  consequently  exhibit  a  greater  efficacy  than  flesh 
or  blood. 

*  Thomson's  Animal  Chemistry,  pp.  285  and  367. 

T  Liebig's  Organic  Chemistry  applied  to  Physiology,  p.  314. 


USE  AND  COiMPOSITION  OF  WOOL.  HAIR,  AND  HORN.  445 

§  2.   Wool,  woollen  rags,  hair,  horn,  and  hones. 

1°.  Wool,  in  the  form  of  the  waste  of  the  spinning-mills,  and  espe- 
cially in  that  of  woollen  rags,  acts  very  efficaciously  as  a  manure. 
The  rags  are  used  with  good  effect  upon  light  chalks  and  gravels,  in 
which  they  retain  the  water.  They  are  sometimes  ploughed  in  for 
wheat  along  with  the  clover  stubble,  in  the  winter  with  the  corn  stub- 
ble, when  the  land  is  intended  for  turnips,  and  are  sometimes  applied 
as  a  top  dressing  to  clover  and  grass  lands  (British  Husbandry,  I.,  p. 
425.)  They  are  used  most  extensively,  however,  in  the  hop-grounds, 
being  dug  in  round  the  roots,  to  which  they  continue  for  a  long  time  to 
supply  much  nourishment.  The  estimation  in  which  they  are  held  may 
be  judged  of  by  the  price  they  bring,  which  is  from  £5  to  £10  a  ton. 

2°.  Hair  also  is  fitted  to  produce  effects  similar  to  those  which  fol- 
low the  use  of  wool.  It  can  seldom,  however,  be  obtained  by  the 
farmer  at  so  economical  a  rate  as  to  enable  him  to  trust  to  it  as  an 
available  resource  when  other  manures  become  scarce. 

3=".  Horn,  in  the  form  of  horn  shavings,  parings,  and  turnings,  is  just- 
ly considered  as  a  very  powerful  manure.  Even  in  the  state  of  shav- 
ings, however,  it  undergoes  decay  still  more  slowly  than  woollen  rags ; 
and,  therefore,  like  them,  will  always  be  most  safely  and  economically 
employed  when  previously  rotted,  by  being  made  into  a  compost. 

Wool,  hair,  and  horn,  differ  from  flesh,  blood,  and  skin,  by  contain- 
ing very  much  less  water  in  their  natural  state,  and  by  undergoing, 
in  consequence,  a  much  slower  decay,  and  exhibiting  a  much  less 
immediate  action  upon  any  crop  to  which  they  may  be  applied.  The 
intelligent  farmer,  therefore,  will  bear  this  important  distinction  in 
mind,  in  any  opinion  he  may  form  as  to  the  relative  efficacy  of  these 
several  substances  as  general  fertilizers  of  the  land. 

In  chemical  composition,  these  three  substances  are  nearly  identi- 
cal, and  they  do  not  differ  widely  from  the  lean  of  beef  or  from  dried 
blood.     When  burned  they  leave  only  a  small  quantity  of  ash  • — 

Wool  leaves. ....... 2-0    per  cent,  of  ash. 

Hair 0-72  "  " 

Horn 0-7  «  « 

And  the  part  which  burns  away — the  organic  part — consists  of— 

Wool.  Hair,  Horn. 

Carbon 50-65  51-53  51-99 

Hydrogen 7-03  6-69  6-72 

Nitrogen 17-71  17-94  17-28 

Oxygen  and  Sulphur 24-61  23-84  24-01 

100  100  100 

The  organic  part  of  these  three  substances,  therefore,  is  nearly 
identical  in  composition,  and  hence,  when  equally  decomposed,  they 
ought  to  produce  the  same  effects  upon  the  young  crops.  They  con- 
tain a  little  more  nitrogen  than  dried  flesh  and  blood,  and  a  little  less 
than  dried  slcin,  and  therefore  in  so  far  as  their  fertilizing  action  de- 
pends upon  this  element,  they  ought  to  occupy  an  intermediate  place 
between  these  several  substances. 


446  THE  INORGANIC  MATTER  CONTAINED  IN  BONES. 

§  3.  Of  the  composition  of  hones. 
Few  substances  have  of  late  years  done  so  much  to  increase  the 
agricultural  produce  of  various  parts  of  England  as  the  use  of  crushed 
bones  for  manuring  the  land. 

1°.  Recent  bones  contain  a  variable  quantity  of  water  and  fat. 
The  proportion  of  fat  depends  upon  the  position  of  the  bone  in  the 
body,  and  upon  the  condition  of  the  animal.  The  proportion  of  water 
depends  partly  upon  the  solidity  of  the  bone  and  partly  upon  its  age. 
According  to  Denis,  the  radius  of  a  female, 

Aged  3  years,  contained 33-3  per  cent,  water,  with  a  httle  fat 

Aged  20  years,       "     13-0  "  " 

Aged  78  years,       "     15-4  "  " 

The  quantity  of  water  thus  present  in  bones  performs  an  important 
part  in  determining  the  action  which  bone-dust  is  known  to  exercise 
upon  the  land.  The  oil  is  sometimes  extracted  by  boiling  the  bones. 
During  this  boiling  they  absorb  more  water,  and  thus,  when  laid  upon 
the  land,  undergo  a  more  rapid  decomposition,  and  exercise,  in  conse- 
quence, a  more  immediate  and  apparent,  and  therefore,  as  some  may 
think,  a  more  powerful  and  fertilizing  action. 

2°.  But  bones  differ  from  the  other  animal  substances  already  de- 
Bcribed  chiefly  by  containing  a  much  larger  proportion  of  inorganic 
matter,  or  by  leaving,  when  burned,  a  greater  percentage  of  ash. 
The  quantity  of  inorganic  matter,  however,  contained  in  bones  is  not 
constant.  It  is  less  in  the  young  than  in  the  full-grown  animal — less 
m  the  spongy  than  in  the  compact  or  more  solid  bones — and  less  in 
those  of  some  animals  than  in  those  of  others.  Thus,  when  freed 
from  fat  and  perfectly  dried — 

Of  inorganic  matter. 

The  lower  jaw-bone  of  an  adult left  68-0  per  cent. 

a  child  of  3  years.  —  62-8        " 

A  compact  human  bone —  58-7        " 

A  spongy  human  bone ; —  50-2        " 

The  tibia  of  a  sheep —  48-03      « 

The  vertebrse  of  a  haddock —  60-51       " 

It  is  obvious  that  the  relative  efficacy  of  equal  weights  of  bones 
must  be  affected  by  such  differences  in  the  relative  productions  of 
organic  and  inorganic  matter  which  they  severally  contain. 

3°.  This  inorganic  matter  or  ash  consists  in  great  part  of  phosphate 
of  lime  (Lee.  IX.,  §  4,)  but  it  contains  also  a  considerable  though 
variable  proportion  of  carbonate  of  lime,  with  smaller  quantities 
of  several  other  ingredients.  The  proportion  of  carbonate  of  lime 
appears  to  be  smallest  in  carnivorous  animals. 

Thus,  for  every  100  parts  of  phosphate  of  lime  there  exists  in — 

Human  bones  about 20-7  carbonate  of  ime. 

Bones  of  the  sheep 24-1  " 

Do.  ox 13-5  « 

Do.  fowl 11-7  « 

Do.  haddock 6-2  « 

Do.  frog 5-8  «* 

Do.  lion 2-6  " 


COMPOSITION    OF    BURNED  BONES.  417 

These  proportions  are  not  to  be  considered  as  constant,  because  it 
varies  not  only  in  the  different  bones  of  the  same  animal  but  also  in 
bones  from  the  same  part  of  the  body  of  different  animals  of  the  same 
species.  (Thomson^s  Animal  Chernistry, -p.  242.)  But  the  existence  of 
such  differences  must  render  unhke  the  fertilizing  action  of  the 
bones  of  different  animals — if,  as  many  think,  this  action  depends  in 
any  great  degree  upon  the  quantity  of  phosphate  of  lime  which  they 
respectively  contain, 

4°.  Besides  the  phosphate  and  carbonate  of  lime,  I  have  stated  that 
bones  contain  certain  other  inorganic  substances,  which  are  found  in 
small  quantity  in  the  ash.  What  these  substances  are  will  appear 
in  the  following  table,  which  represents  the  constitution  of  the  bones 
of  some  animals,  as  analysed  by  Dr.  Thompson  : 

Ileum  Ileum  Vertebra, 

of  a  sheep.      of  an  ox.    of  a  haddock. 

Organic  or  combustible  matter 43-3.  48-5  39-5 

Phosphate  of  hme 50-6  45-2  56-1 

Carbonate  of  lime . .  .• 4-5  6-1  3-6 

Magnesia 0-9  0-2  0-8 

Soda 0-3  0-2  0-8 

Potash 0-2  0-1  — 


99-8  100-3  100-8 
The  soda  exists  in  bones  probably  in  the  state  of  common  salt,  and 
the  magnesia  in  that  of  phosphate.  An  appreciable  quantity  of  fluor- 
ide of  calcium,  with  traces  of  iron  and  magnesia,  are  also  generally 
found  in  bones,  in  addition  to  the  substances  indicated  in  the  pre- 
ceding analyses. 

5°.  When  bones  are  heated  to  redness  in  the  open  air  the  organic 
part  burns  away,  and  leaves  the  white  earthy  matter  in  the  form,  and 
nearly  of  the  bulk,  of  the  original  bone.  But  if  a  dry  bone  be  cover- 
ed with  dilute  muriatic  acid,  the  earthy  or  inorganic  part  is  slowly  dis- 
solved out,  and  the  organic  part — the  cartilage  or  gelatine — will  alone 
remain,  retaining  also  the  form  and  size  of  the  organic  bone.  In  this 
state  it  is  flexible  and  somewhat  soft,  and  by  prolonged  boiling  may 
be  dissolved  in  water,  and  manufactured  into  glue. 

This  organic  or  combustible  part  of  bones  is  identical  in  chemi- 
cal composition  with  skin  and  glue,  and  is  nearly  the  same  as  wool, 
hair,  and  horn,  of  which  the  analysis  has  already  been  given.  In 
so  far,  therefore,  as  their  efficacy  depends  upon  the  organic  consti- 
tuent, dry  bones  must  be  greatly  inferior  to  an  equal  weight  of  any 
of  the  other  animal  substances  above  described,  because  of  the  much 
greater  proportion  of  earthy  matter  they  contain. 

§  4.  On  what  does  the  fertilizing  action  of  bones  depend  ? 

Bones  contain,  as  we  have  seen,  a  large  proportion  both  of  organic 
and  of  inorganic  matter  ; — on  which  of  these  two  constituents  does 
their  fertilizing  action  most  depend  ?  Some  regard  the  phosphate  of 
lime  or  bone  earth,  as  the  only  source  of  the  benefits  so  extensively 
derived  from  them — and  it  is  by  supposing  the  soil  to  be  already  suf- 
ficiently impregnated  with  th  s  phosphate.,  that  Sprengel  accounts  for 


448  :;ffect  of  boiling  upon  bones. 

the  little  success  which  has  attended  the  use  of  bones  in  Mecklenburg 
and  North  Germany.  Others,  again,  attribute  the  whole  of  their  in- 
fluence to  the  organic  part — the  gelatine — which  bones  contain. 
Neither  of  these  views  is  strictly  correct.  Plants,  as  we  have  seen, 
require  a  certain  quantity  of  phosphoric  acid,  limej  and  magnesia, 
which  are  present  in  the  inorganic  part  of  bones,  and  so  far,  therefore, 
are  capable  of  deriving  inorganic  food  from  bone-dust.  But  the  or- 
ganic part  of  bones  will  decompose,  and  therefore  will  act  nearly  in 
the  same  way  as  skin,  wool,  hair,  and  horn  do — which  substances  it 
resembles  in  ultimate  composition.*  It  cannot  be  doubted,  therefore, 
that  a  considerable  part  of  the  effect  of  bones  upon  all  crops  must  be 
due  to  the  gelatine  which  they  contain. 

The  principal  facts,  now  known  in  regard  to  the  action  of  bones, 
may  be  thus  stated  : — 

1°.  The  organic  matter  of  bones  acts  like  that  of  skin,  woollen  rags, 
horn  shavings,  &c.,  but-as  bone-dust  contains  only  about  one-third  of 
the  organic  matter  which  is  present  in  an  equal  weight  of  either  of  the 
above  substances,  its  total  effect,  in  so  far  as  it  depends  upon  the  or- 
ganic matter,  will  be  less  in  an  equal  proportion. 

2°.  But  as  the  organic  matter  of  bones  contains  more  water  than 
horn  or  wool,  (p.  446,)  it  will  decay  more  rapidly  than  these  substan- 
ces when  mixed  with  the  soil,  and  will  therefore  be  more  immediate  in 
its  action.  Hence  the  reason  why  woollen  rags  and  horn  shavings  must 
be  ploughed  in  in  the  preceding  winter,  if  they  are  to  benefit  the  subse- 
quent wheat  or  turnip  crops,  while  bone-dust  can  be  beneficially  ap- 
plied at  the  sowing  of  the  seed. 

3*^.  When  bones  are  boiled  the  oil  will  be  separated,  and  a  p^Ttion  of 
the  gelatine  will  at  the  same  time  be  dissolved  out.j  The  bones, 
therefore,  will  be  in  reality  rendered  less  rich  as  a  manure.  But  us 
they  at  the  same  time  take  up  a  considerable  quantity  of  water,  boiled 
bones  will  decompose  more  rapidly  when  mixed  with  the  soil,  and 
thus  will  appear  to  act  as  beneficially  as  unboiled  bones.  Hence  the 
reason  why  in  Cheshire,  where  boiled  bones  are  used  to  a  considerable 
extent,  many  practical  men  are  of  opinion  that  their  action  upon  the 
crops  is  not  inferior  to  that  of  bones  from  which  the  oil  has  not  been 
extracted  by  boihng.  The  immediate  effect  may  indeed  be  equal,  or 
even  greater,  than  that  of  unboiled  bones,  but  the  total  effect  must 
be  less  in  proportion  to  the  quantity  of  organic  matter  which  has 
been  removed  by  boiling.     Cases,  however,  may  occur  in  which  the 

'  The  main  difference  is  in  the  quantity  of  sulphur  contained  in  hair.  An  analysis  of 
human  hair,  by  Van  Laer  {Annalen  dcr  Pharmacie,  xiv..  p.  168,)  which  has  reached  me 
since  the  preceding  sheet  went  to  press,  shows  the  proportion  of  sulphur  more  accurately 
than  that  which  is  given  at  page  445.  lie  found  human  hair  of  various  colors  to  leave  froih 
one-third  to  nearly  two  per  cent,  of  ash  when  burned,  and  to  consist  besides  of  Carbon^ 
50-65— Hydrogen,  6  36— Nitrogen,  17-l4-Oxygcn,  20-85— Sulphur,  500— Total,  100— and 
nearly  half  a  per  cent,  of  Phosphorus. 

t  The  prolonged  boiling  of  bones,  so  as  to  dissolve  a  portion  of  the  gelatine,  is  practised 
to  a  considerable  extent  as  a  mode  of  manufacturing  size  or  glue.  In  the  large  dyeing  es- 
tablishments in  Manchester,  the  bones  are  boiled  in  open  pans  for  24  hours,  the  fat  skim- 
med off  and  sold  to  the  candle-makers,  and  the  size  afterwards  boiled  down  in  another 
vessel  till  it  is  of  sufficient  strength  for  stiffening  the  thick  goods  for  which  it  is  intended. 
The  size  liquor,  when  exhausted,  or  no  longer  of  sufficient  strength  for  stiffening,  is  applied 
with  much  benefit  as  a  manure  to  the  adjacent  pasture  and  artificial  grass  lands,  and  the 
bones  are  readily  bought  up  by  the  Lancashire  and  Cheshire  farmers.  The  boiled  bones 
must  evidently  lose  all  the  fertilizing*virtue  which  the  size  liquor  acquires. 


COMPOSITION    OF    LONG-BURIED    BONES.  449 

skilful  man  will  prefer  to  use  boiled  bones  because  they  are  fitted  to 
produce  more  immediate  effect  wiiere — as  in  the  pushing  forward  of 
the  young  turnip  plant — such  an  effect  is  particularly  required. 

4°.  When  bones  are  buried  in  a  more  or  less  entire  state,  as  they  oc- 
casionally are  about  the  roots  of  vines  and  fruit  trees,  they  gradually 
decay,  and  sensibly  promote  the  growth  of  the  trees  to  which  they  are 
applied.  Yet  after  the  lapse  of  years  these  same  bones  may  be  dug  up 
nearly  unaltered  either  in  form  or  in  size.  The  bones  of  a  bear  and  of  a 
stag,  after  being  long  buried,  were  found  by  Marchand  to  consist  of— 

Bones  of  the  bear  buried 

deep.  shallow.      Femur  of  a  stag. 

Animal  matter 16-2  4-2  7-3 

Phosphate  of  lime 56-0  62-1  54-1 

Carbonate  of  lime 13-1  13-3  19-3 

Sulphate  of  lime 7-1  12-3  12-2 

Phosphate  of  magnesia 0-3  0-5  2-1 

Fluoride  of  calcium 2-0  2-1  24 

Oxide  of  iron  and  manganese.  2-0  2-1  2-9 

Soda M  1-3  — 

Silica 2-2  2-1  — 


100  100  100 

The  most  striking  change  undergone  by  these  bones  was  the  large 
loss  of  organic  or  animal  matter  they  had  suffered.  The  relative 
proportions  of  the  phosphate  and  carbonate  of  lime  had  been  com- 
paratively little  altered.  The  main  effect,  therefore,  produced  by 
bones  when  buried  at  the  roots  of  trees,  and  their  first  effect  in  all 
cases,  must  be  owing  to  the  animal  matter  they  contain — the  ele- 
ments of  this  animal  matter,  as  it  decomposes,  being  absorbed  by  the 
roots  with  which  the  bones  are  in  contact. 

Such  facts  as  this  prove,  I  think,  the  incorrectness  of  the  one-sided 
opinion  too  hastily  advanced  by  Sprengel,  and  after  him  reiterated 
by  Liebig  and  his  followers — that  the  principal  efficacy  of  bones  is, 
in  all  cases,  to  be  ascribed  to  their  earthy  ingredients,  and  especially 
to  the  phosphate  of  lime. 

This  opinion  of  Sprengel  rests  mainly  on  two  facts  put  forward  by 
himself  (Lehre  vom  Diinger,  p.  153.)  Bones,  he  says,  have  failed  to 
produce  in  North- Western  Germany  the  good  effects  for  which  they 
are  so  noted  in  England,  yet  in  the  same  districts,  farm-yard  and  other 
animal  manures  exhibit  their  usual  fertilizing  action.  It  cannot,  there- 
fore, he  concludes,  be  the  animal  matter  of  bones  to  which  their  benefi- 
cial influence  is  to  be  ascribed.  But  to  this  conclusion  we  may  fairly 
demur,  when  we  know  how  often  on  heavy  and  undrained  lands  bone- 
dust  fails  even  among  ourselves.  Let  bones  be  tried  for  the  turnip 
crop — a  crop  still  almost  unknown  in  Northern  Germany — and  upon 
well  drained  soils  similar  to  those  of  our  best  turnip  lands,  and  I  ven- 
ture to  predict,  in  opposition  to  SprengePs  experience,  that  bones  will 
no  longer  fail  even  in  Mecklenburg. 

Again,  having  drawn  his  conclusion  in  regard  to  the  inutility  of  the 
animal  matter,  Sprengel  states  that  the  marl  which  is  applied  to  the 
land  in  Holstein  and  the  neighboring  provinces,  contains  phosphato 


450  CAUSE    OP    THE    PROLONGED    EFFECT    OF    BONES. 

of  lime  (p.  371,)  and  hence  the  reason  why  the  earthy  matter  of  the 
bones  apphed  does  not  improve  the  land.  In  so  far  as  the  efficacy  of 
bones  really  depends  upon  their  earthy  constituents,  the  use  of  a  marl 
containing  phosphate  of  lime*  will,  no  doubt,  greatly  supersede  them ; 
: — but  in  so  far  as  it  depends  upon  the  animal  matter  they  contain, 
bones  will  exhibit  their  natural  fertilizing  action,  however  rich  the 
soil  may  already  be  in  those  compounds  of  which  their  earthy  or  in- 
combustible part  consists. 

5°.  Yet  there  is  reason  to  believe — nay,  it  may  be  assumed  as  cer- 
tain— that  the  phosphate  and  carbonate  of  lime  which  bones  contain  so 
largely,  are  not  without  effect  in  promoting  vegetation.  All  our  culti- 
vated plants  require  and  contain  both  phosphoric  acid  and  lime,  (see 
Lee.  X.,  §  3,)  and  from  the  vegetables  on  which  they  feed,  all  animals 
derive  the  entire  substance  of  their  bones.  This  same  phosphoric 
acid  and  lime,  therefore,  must  exist  in  the  soil  on  which  the  plants 
grow,  or  they  will  neither  thrive  themselves  nor  be  able  properly  lo 
nourish  the  animals  they  are  destined  to  feed.  If  a  soil,  then,  be  de- 
ficient in  phosphate  of  lime  or  its  constituents,  it  is  clear  that  the  ad- 
dition of  bones  will  benefit  the  afler-crops  not  only  by  the  animal,  but 
by  the  earthy  matter  also  which  they  contain.  And  that  such  is  the 
case,  in  many  instances,  there  is  good  reason  for  believing.  But  that 
this  can  by  no  means  account  for  the  whole  effect  of  bones,  even  sup- 
posing the  soil  to  which  they  are  applied  to  be,  in  every  instance,  defi- 
cient in  phosphates,  is  clear  from  the  fact  (see  Lee.  X.,  §  4,)  that  260 
lbs. — less  than  6  bushels — of  bone-dust  per  acre  are  sufficient  to  sup- 
ply all  the  phosphates  contained  in  the  crops  which  are  reaped  during 
an  entire  fourshift  rotation  of  turnips,  barley,  clover,  and  wheat.  Yet 
the  quantity  of  bones  actually  applied  to  the  land  is  from  three  to  five 
times  the  above  weight,  repeated  every  time  the  turnip  crop  comes 
round. 

6°.  Still,  granting  that  the  chief  effect  of  bones  upon  the  immedi- 
ately succeeding  crops  is  due  to  their  organic  part,  upon  what  does 
their  prolonged  good  effect  depend  ?  Some  lands  remember  a  single 
dressing  of  bones  for  16  or  20  years,  and  some  after  the  appHcation 
of  2  or  2\  tons  of  bones  have  yielded  10  to  15  successive  crops  of 
oats,  and  have  been  sensibly  benefitted  for  as  many  as  sixty  years 
after  the  bones  were  applied.  (See  Appendix,  No.  I.,  and  British 
Husbandry,  I.,  p.  398.) 

This  prolonged  effect  is  also  due  m  part  to  both  constituents.  When 
not  crushed  to  powder,  the  organic  matter  of  bones  is  always  slow  in 
disappearing,  and  slower  the  deeper  they  are  buried.  In  some  soils, 
also,  the  process  is  more  slow  than  in  others.  The  long-buried  bones  of 
the  bear  and  of  the  stag,  of  which  the  analysis  is  given  above  (p.  449.) 
had  lain  in  the  soil  for  an  unknown  period,  and  yet  they  still  contained 
a  sensible  proportion  of  animal  matter.  So  it  is  with  the  bones  used  for 
manure,  when  they  are  not  crushed  too  fine.  They  long  retain  a  por- 
tion of  their  organic  matter,  which  they  give  out  more  slowly,  and 

*  Most  lime-stones  and  shell  sands  contain  an  appreciable  quantity  of  this  phosphate,  and 
will,  therefore,  to  the  same  extent,  supersede  the  use  of  the  earthy  matter  of  hones.  Much 
of  the  marl  of  Holsfein  consists  of  the  detritus  of  chalk  rocks,  anciently  broken  up  and 
carried  off— by  the  waters  of  the  sea  with  which  that  part  of  Europe  was  covered  at  no 
very  remote  geological  epoch. 


FERTILITY    OF   ANCIENT    BATTLE-FIELDS.  4> 

HI  smaller  quantity,  every  year  that  passes,  yet  still  in  such  abun- 
dance as  to  contribute  sensibly  to  the  nourishment,  and  in  some  de- 
gree to  promote  the  growth  of  the  crops  which  the  land  is  made  to. 
bear.*  So  it  would  be  with  the  horns  and  hoofs  of  cattle,  if  laid  on  in 
equal  quantity,  for  they  also  decay  with  exceeding  slowness. 

Still  the  inorganic  part  is  not  without  its  use.  If  the  soil  be  defici- 
ent in  phosphates  or  in  lime,  the  earthy  matter  of  the  bones  will  sup- 
ply these  substances.  1  only  wish  to  guard  you  against  the  conclu- 
sion, that  because  bones  often  act  for  so  long  a  period,  that  therefore 
the  organic  matter  can  have  no  share  in  the  influence  they  exercise 
after  a  limited  period  of  years. 

He  who  candidly  weighs  the  considerations  above  presented  will,  I 
think,  conclude  that  the  whole  effect  of  bones  cannot  in  any  case  be 
ascribed  exclusively  either  to  the  one  or  to  the  other  of  their  principal 
constituents.  He  will  believe,  indeed,  that  in  the  turnip  husbandry  the 
organic  part  performs  the  most  prominent  and  most  immediately  useful 
office,  but  that  the  earthy  part,  nevertheless,  affords  a  ready  supply  ot 
certain  organic  kinds  of  food,  which  in  many  soils  the  plants  would 
not  otherwise  easily  obtain.  He  will  assign  to  each  constituent  its 
separate  and  important  function,  being  constrained,  at  the  same  time, 
o  confess  that  while  in  very  many  cases  the  earthy  part  of  hones  ap- 
plied alone  would  fail  to  benefit  the  land,  there  are  few  cullivated 
fields  in  which  the  organic  part  applied  alone  would  not  materially 
promote  the  growth  of  most  of  our  artificial  crops. 

§  5.  Of  the  application  of  hone-dust  to  pasture  lands. 

If  the  soil  be  deficient  in  phosphate  of  lime,  bone-earth  alone,  or  the 
mineral  phosphate  (Lee.  IX.,  §  4,)  may  be  advantageously  applied  to 
increase  its  fertility.  In  a  four-years'  rotation  of  turnips,  barley,  clover, 
and  wheat,  if  bones  be  used  for  the  turnip  crop,  the  land  will  every  ro- 
tation become  richer  in  bone-earth,  (see  preceding  page,)  and  there- 
fore the  application  of  earthy  phosphates  cannot — after  a  few  rota- 
tions— be  expected  materially  to  affect  its  productiveness.  But  pas- 
ture lands  are  treated  differently,  and  it  is  not  unlikely  that  in  some 
instances  the  earth  of  bones,  even  applied  alone,  may  to  such  lands 
be  productive  of  considerable  benefit. 

The  application  of  bone-dust  to  permanent  pasture  has  of  late 
years  been  practised  with  great  success  in  Cheshire.  Laid  on  at  the 
rate  of  30  to  35  cwt.,  or  at  a  cost  of  £10  per  acre,  it  has  increased 
the  value  of  old  pastures  from  10s.  or  15s.  to  30s.  or  40s.  per  acre : 
and  after  a  lapse  of  20  years,  though  sensibly  becoming  less  valu  - 
able,  land  has  remained  still  worth  two  or  three  times  the  rent  it  paid 
before  the  bones  were  .aid  on. 

It  is  this  lengthened  good  effect  of  bone-dust  that  affords  the  strongest 
ground  for  believing  that  the  earthy  phosphate  has  a  large  share  in  the 

*  This  opinion  derives  a  singularly  interestinst  confirmation  from  the  fact  that  a  portion 
of  the  soil  of  an  arable  district  in  Sweden,  "which  from  time  immemorial  hail  grown  ex- 
cellent  wheat  without  manure,"  was  found  by  Berzelius  to  contain  minute  fragments  of 
4.one  capable  ?:[u»n  boiling  with  water  of  yielding  a  weak  solution  of  jtelatine.  It  wag 
concluded,  therefore,  that  the  spot  had  been  an  ancient  battlefield,  and  that  its  prolonged 
crtility  was  due  to  the  bonea  of  old  time  buried  in  it,  and  still  to  some  extent  undecom* 
>03cd  (Marchand  ) 


452  PHOS/PATE    OF    LIME    YEARLY    CARRIED    OFF. 

effect.  I  have  already  shown  that  this  prolonged  action  is  not  conclu- 
eivc  upon  the  point — since  the  organic  matter  lingers  long,  ev^n  in  buri- 
ed bones — but  a  consideration  of  the  necessary  effect  of  long  continu- 
ed pasturage  upon  soils  to  which  nothing  is  artificially  added,  lends  a 
singular  support  to  the  view  that  the  bone-earth  may  act  an  important 
and  beneficial  part  upon  old  meadow  and  other  grass  lands.  Take 
the  instance  of  a  dairy  farm  in  the  neighborhood  of  a  large  town, — 

1°.  The  milk  is  all  carried  off  the  farm,  either  directly  or  in  the  shape 
of  butter;  cheese,  &c.,  and  every  40  gallons  of  milk  contain  1  lb.  of 
bone-earth,  besides  other  phosphates.  Estimate  the  average  yield  of  a 
good  cow  at  JOOO  quarts,  or  750  gallons  a-year,  its  milk  will  contain  19 
lbs.  of  earthy  phosphate — as  much  as  is  present  in  30  lbs.  of  bone-dust. 

2^.  Again,  the  urine  of  a  milk  cow,  taken  at  700  gallons  a-year, 
contains  about  11  lbs.  of  the  same  phosphate.  (A  cow,  not  in  milk, 
gives  on  an  average  about  1300  gallons  of  urme — see  page  460.) 
Suppose  only  a  third  of  this  to  run  to  waste,  and  the  farm  will  lost  for 
every  cow  in  this  way  about  4  lbs. — equal  to  about  6  lbs.  of  bone-dust. 

3°.  But  for  every  cow  an  annual  calf  is  reared  and  sold  off.  Let  this 
calf  contain  but  20  lbs.  of  bone — then,  for  every  cow  it  maintains^  a  dairy 
farm  will  lose  of  earthy  phosphates  upon  the  whole  as  much  as,  is 
contained  in  56  lbs.  of  bo?ie-dust.  Suppose  a  farm  to  be  pastured 
for  centuries,  as  those  of  Cheshire  have  been,  and  the  produce  to  be 
carried  off  in  the  form  of  milk,  butter,  and  veal — we  may  reasonably 
suppose  that  it  will  at  length  begin  to  feel  the  want  of  those  phos- 
phates which  year  by  year  have  been  drawn  from  its  surface.  It  is 
reasonable  also  to  suppose  that  the  addition  of  these  deficient  phos- 
phates would  impart  new  vigor  to  the  soil,  would  cause  new  grasses 
to  sprout,  and  a  more  milk-yielding  herbage  to  spring  up. 

Such  is  the  reasoning  upon  which  I  some  years  ago  attempted  to 
found  an  explanation  of  the  singularly  striking  effects  produced  by  bone- 
dust  on  the  grass  lands  of  Cheshire,  while  it  failed  materially  to  im- 
prove those  of  other  districts  on  which  it  had  been  tried.  I  still  consider 
it  as  by  no  means  without  its  weight,  though  I  cannot  concur  with  the 
extreme  views  which  some  have  since  adopted — that  either  in  the  case 
of  Cheshire,  or  in  any  other  case  with  which  I  am  acquainted,  the  benefi- 
cial action  of  bone-dust  is  to  be  ascribed  solely  to  its  earthy  constituents. 

§  Q.  Of  animal  charcoal  the  refuse  of  the  sugar  refineries^  and 
animalized  carbon. 

1°.  Animal  charcoal,  (bone  black.) — When  bones  are  charred  or 
distilled  at  a  red  heat  in  close  vessels,  they  leave  behind  a  coaly  re- 
siduum to  which  the  name  of  animi'  :iharcoal  is  usually  given.  By 
this  calcination  the  animal  matter  is  almost  entirely  decomposed. 
The  charcoal  still  retains,  however,  a  little  nitrogen,  and  though  it  is 
seldom  employed  as  a  manure,  yet  it  is  not  wholly  without  effect  m 
promoting  the  growth  of  our  cultivated  crops.  Thus  in  1842,  when 
applied  to  Swedish  turnips,  Mr.  Fleming  obtained  from  the  unma- 
mired  soil  12  tons  5  cwt.  per  acre  ;  but  when  manured  with  .10  cwt. 
of  animal  charcoal,  21  tons  2  cwt.  (see  Appendix,  No.  VIII.) 

2*^.  Refuse  charcoal  of  the  sugar  refiners. — The  animal  charcoal 
;J»OYe  described  is  c  3  afly  employed  for  the  purpose  of  removing  the 


REFUSE    CHARCOA..     :F   THE    SDGAR-REFINERS.  453 

color  from  solutions  of  raw  sugar.  Blood  is  also  used  for  clarifying 
the  sajiie  solutions,  and  quick-lime  for  neutralizing  the  acid  matter 
they  contain — thus  rendering  the  syrups  more  capable  of  easy  crys- 
tallization. Hence  the  animal  charcoal,  the  blood,  the  lime,  and  the 
coloring  and  other  matters  separated  from  the  sugar,  become  mixed 
together,  and  form  the  refuse  of  the  sugar  refiners.  This  refuse  often 
contains  from  one-fifth  to  one-fourth  of  its  weight  of  blood,  and  hence 
is  in  general — and  especially  in  France,  where  it  is  extensively  em- 
ployed as  a  manure — considered  from  four  to  six  times  more  power- 
ful than  the  pure  animal  charcoal  alone.  In  the  western  parts  of 
France  this  mixture  has  for  some  years  been  in  great  repute  among 
agriculturists,  and  in  addition  to  that  which  is  produced  at  home,  has 
been  largely  imported  from  other  countries.  Into  the  ports  upon  the 
river  Loire  alone  there  were  entered,  in  1S39,  upwards  of  ten  thousand 
tons.  ('Boussingault,  An.  de  Cliim.  et  de  Phys.,  3d  series,  iii.,  p.  96.) 
It  sells  at  about  five  pounds  a  ton. 

The  value  of  this  substance  depends  very  much  upon  the  propor- 
tion of  blood  which  it  contains,  and  as  this  is  in  some  measure  vari- 
able, its  fertilizing  qualities  must  be  variable  also.  In  England  blood 
is  used  much  more  sparingly  in  the  refining  of  sugar  than  it  used  to 
be,  and  hence  the  refuse  of  our  refineries  is  probably  less  valuable 
as  a  manure  now  than  it  was  in  former  years.*  This  is  probably  one 
reason  why  Mr.  Fleming  obtained  from  the  use  of  it  a  somewhat 
smaller  crop  of  turnips  than  from  an  equal  quantity  of  the  unused 
animal  charcoal.  Upon  Swedish  turnips  10  cwt.  of  unused  animal 
charcoal  gave  him  21  tons  2  cwt. ;  while  10  cwt.  of  the  refuse  gave 
10  tons  7  cwt.  (Appendix,  No.  VIII.) 

Still  this  result  is  sufficiently  favorable  to  recommend  the  refuse  or 
exhausted  animal  charcoal  to  the  practical  agriculturist  where  more 
economical  manures  cannot  readily  be  obtained. 

3^.  Anim,altzed  carbon. — The  estimation  in  which  the  refuse  char- 
coal of  the  sugar  works  was  held,  has  led  to  the  manufacture  of  very 
useful  imitations  of  it  under  the  name  of  animalized  carbon.  A  cal- 
careous soil,  rich  in  vd§etable  matter,  (an  intimate  mixture  of  peat 
and  marl  or  shell-sand  would  answer  well,)  is  charred  in  close  ves- 
sels, and  is  then  mixed  at  intervals  with  repeated  portions  of  night 
soil  as  long  as  it  disinfects  it  or  removes  its  smell — and  to  this  mixture 
IS  added  4  or  5  per  cent,  of  clotted  and  partially  dried  blood.  This 
animalized  carbon  is  said  to  be  of  much  value  as  a  manure.  The 
main  objections  to  it  are  its  liability  to  adulteration  and  the  uncertain- 
ty to  which,  even  when  skilfully  and  conscientiously  prepared,  its 
composition  must  be  in  some  measure  liable. 

§  7.  Ofjish,  jish  refuse.,  ichale  blubber,  and  oil. 

1°.  Fish. — In  some  parts  of  the  world,  and  occasionally  on  the  shores 
of  England,  fish  are  met  with  in  such  abundance  that  they  can  be  econo- 
mically employed  as  a  manure  for  the  land.  They  are  either  spread  over 

*  The  refining  "  consists  in  putting  the  susar  into  a  larire  square  copper  cistern  along  with 
some  lime  water,  a  little  bullock's  blood,  and  from  5  to  20  per  cent,  of  bone  black,  and  in- 
jecting steam  through  the  mixture.  Instead  of  the  blood  many  refiners  employ  a  mixture 
of  gelatinous  alumina  and  gypsum,  called  finuigs,  prepared  by  adding  lime  water  to  a  so- 
lution of  alum,  and  collecting  the  precipitate"  (Ure.)  Hence  the  reason  why,  in  England 
«t  least,  the  refuse  charcoal  of  the  sugar  works  is  not  always  rich  in  blood. 


'454  OF  FISHj  FISH  REFUSE,  AND  OIL  ;   AND  THE  RELATIVE 

it  in  a  recent  state,  or — which  is  more  economical, — are  made  into  a  com- 
post chiefly  with  earth,  which  after  a  time  proves  rich  and  fertiUzing. 

The  bones  of  fish  are  similar  in  composition  to  those  of  terrestrial 
animals  (p.  447),  and  their  muscular  parts  are  nearly  identical  in  ele- 
mentary constitution  with  the  lean  part  of  beef  and  the  clot  of  blood. 
As  fertilizing  agents,  therefore,  the  parts  of  fishes  will  act  nearly  in 
the  same  way  as  the  blood  and  bodies  of  animals. 

2°.  Fish  refuse. — The  pilchards  of  Cornwall  and  the  herrings,  cod, 
and  ling  of  our  northern  coasts,  when  cleaned  for  salting,  yield  a 
large  quantity  of  refuse,  (fourteen  barrels  of  herrings  yield  one  of 
refuse,)  which  is  peculiarly  valuable  to  the  farmers  in  the  neighbor- 
hood of  the  principal  fishing  stations. 

In  the  North,  a  compost  prepared  from  this  fish  refuse,  is  generally 
esteemed  as  a  manure  for  barley  and  green  crops,  but  when  exten- 
sively used,  "  is  said  to  render  the  soil  unfit  for  the  production  of  oats.' 
Such  soil  is  said  to  be  poisoned  (Sinclair's  Statistical  Account  of 
Scotland,  vii.,  p.  201,  quoted  in  British  Husbandry,  I.,  p.  421.) 

3°.  Wtiale  blubber. — When  the  oil  is  expressed  from  whale  blub- 
ber, a  skinny  or  membraneous  refuse  remains,  which  has  hitherto 
been  employed  only  as  a  manure.  It  is  made  into  a  compost  with 
earth,  which  is  several  times  turned,  and  the  mixture  is  most  usefully 
employed  after  it  has  lain  not  less  than  9  or  12  months.  It  may  be 
applied  either  to  grass  or  to  arable  land. 

4°.  Whale  oil^  and  that  of  other  fish,  when  made  into  a  compost  with 
earth  and  a  little  lime  or  wood  ashes,  yields  a  manure  which  was  much 
recommended  by  the  late  Dr.  Hunter  of  York  (see  his  Georgical  Es- 
says, vols.  1,  2,  and  5.)  Merely  mixed  with  absorbent  earth,  and  ap- 
plied at  the  end  of  one  month,  impure  whale  oil,  at  the  rate  of  40  gallons 
per  acre,  gave  the  late  Mr.  Mason,  of  Chilton,  near  Durham,  a  crop  of 
23i  tons  of  turnips,  while  40  bushels  of  bones  gave  him  only  22  tons. 
More  recently,  also,  it  has  been  found  that  the  mixture  of  a  few  gallons 
of  oil  with  the  usual  quantity  of  bone-dust  increased  to  a  considerable 
degree  the  turnip  crop  to  which  it  was  applied.  In  a  theoretical  point 
of  view,  it  would  be  interesting  to  establish  me  fact,  that  pure  oil  is 
capable  of  promoting  in  a  large  degree  the  growth  and  produce  of 
our  cultivated  crops — though,  as  a  resource,  of  which  farmers  in  gene- 
ral can  avail  themselves  where  other  manure  is  scarce,  its  high  price 
will  probably  prevent  it  from  ever  becoming  extensively  useful. 

§  8.  Relative  fertilizing  value  of  the  animal  manures  already 
described. 

No  sufficiently  decisive  experiments  are  yet  upon  record,  from 
which  the  relative  value  of  the  several  animal  manures  above  des- 
cribed can  be  satisfactorily  deduced.  That  they  differ  in  fertihzing 
power  every  farmer  is  aware,  but  it  is  not  yet  decided  by  actual  trial, 
in  what  proportion  one  Of  them  exceeds  the  other. 

I  have  already  stated  to  you  (p.  440)  the  theoretical  opinion  enter- 
tained by  many,  that  the  efficacy  of  all  manures  is  in  proportion  to  the 
quantity  of  nitrogen  tJiey  co?itain.  Adopting  this  principle  as  true,  it 
IS  easy  to  assign  to  each  substance  its  proper  place  in  an  artificial  table. 
The  last  column  :n  the  following  table  shows  the  quantity  of  each 


FERTILIZING  VALUE  CF  VARIOUS  ANIMAL  MANURES.  455 

substance  in  its  ordinary  state  of  dryness,  which  will  be  necessary  to 
produce  the  same  effect  as  100  lbs.  of  common  farm-yard  manure, 
supposing  this  effect  to  be  determined  by  the  nitrogen  alone. 

Equal  effecls 
Water  per  cent.    Ash  per  cent.    Nitrogen  per  cent,    produced  by 

Farm-yard  manure..     80  ?  ^  100  lbs. 

Flesh 77  1  3§  14 

Fish 80  2  2i  20 

Blood 79to83  1  3  16 

Blood  dried* 12  to  20  3i  12  to  13  8 

Skin 58  i  8  12 

Wool,  hair,  and  horn.  9  to  11  1  to  2  16  6 

Bones 14  40  to  60    5  to  9  11  to  20 

Refuse    charcoal    of 

the  Sugar-works..     48  11  50 

Animalized  carbon. .     45  ?  1  50 

I  have  already  had  occasion  to  remark,  however,  that  this  mode  of 
classifying  manures  is  not  altogether  to  be  depended  upon.     Since — 

1°.  It  does  not  take  into  account  the  quantity  of  inorganic  matter 
they  severally  contain,  which  as  shewn  in  the  third  column  is  parti- 
cularly large  in  bones,  and  is  by  some  considered  as  the  (most  ?)  im- 
portant and  influential  constituent  of  this  manure.  Nor  is  any  effect 
ascribed  to  such  substances  as  the  sulphur,  which  in  hair  and  wool 
forms  nearly  5  per  cent,  of  their  whole  weight,  and  which  cannot  be 
wholly  without  influence  upon  the  plants,  by  which,  as  they  decay, 
the  elements  of  these  manures  fhay  happen  to  be  absorbed. 

2\  It  passes  by  the  practical  influence  of  the  quantity  of  water 
which  the  several  substances  contain.  Flesh,  fish,  blood,  and  skin,  in 
their  recent  state,  contain  so  much  water  that  they  begin  almost  im- 
mediately to  decompose,  and  thus  expend  most  of  their  fertilizing 
virtue  upon  the  first  crop  to  which  they  are  applied.  Hair  and  wool,  on 
the  other  hand,  retain  so  little  water  that  they  decay^iih  great  slo  w^ss. 
Hence,  the  true  amount  of  the  action  of  these  latter  substances  cannot 
be  estimated  in  a  single  year,  and  must  therefore  be  altogether  a  mat- 
ter of  theory  until  a  series  of  careful  observations,  made  in  consecu- 
tive years,  shall  afford  some  decisive  facts  upon  which  to  reason. 

3°.  This  is  confirmed  by  the  statement  of  Boussingault  and  Payen, 
{Annates  de  Chim.  et  de  Phys.^  3d  series,  iii.,  p.  94,)  that  the  effect 
of  the  animal  charcoal  of  the  sugar  refiners  and  of  the  animalized 
carbon  is,  by  experience.  Jive  times  greater  than  the  proportion  of  ni- 
trogen they  contain  would  indicate ;  and — 

4^.  If  pure  oil,  which  contains  no  nitrogen  at  all,  will  yet  produce 
an  enriching  manure  by  mere  mixture  with  the  soil  (p.  454),  or  will 
increase  greatly  the  effect  of  bones — we  must  obviously  seek  for 
some  other  principle  upon  which  to  account  for  the  effect  of  manures, 
besides  or  in  addition  to  the  proportion  of  nitrogen  they  contam.  It 
is  true  that  the  impure  or  refuse  whale  oil  used  for  composts  may 
contain  some  nitrogen,  but  we  can  scarcely  suppose  250  or  300  lbs. 
of  such  oil  to  hold  so  much  of  this  element  as  to  account  for  all  the 
effects  which  the  oil  is  said  to  have  produced. 

*  As  it  is  sold  for  manure  at  Paris  and  elsewhere,  p.  443. 


456  OP   THE    DROPPINGS    OF   BIRDS. 

While,  then,  we  put  so  much  faith  in  theory  as  to  believe  that  suo- 
stances  which  contain  much  nitrogen  are  very  likely  to  prove  valua- 
ble manures, — we  must  not  allow  ourselves  to  be  so  carried  away  by 
the  simplicity  of  the  principle  as  to  believe  either  that  their  relative 
effects  upon  our  crops  may  be  always  estimated  by  the  proportion  of 
nitrogen  they  contain,  or  that  a  substance  may  not  largely  increase 
the  produce  of  our  fields  in  which  no  nitrogen  is  present  at  all.  In- 
deed, the  effects  of  saline  substances  alone  are  sufficient  to  satisfy  us 
how  untrue  to  nature  this  latter  opinion  would  be. 

§  9.  Of  the  droppings  of  fowls — pigeons^  dung,  and  guano. 

The  droppings  of  birds  form  one  of  the  most  powerful  of  known  ma- 
nures. This  arises  in  part  from  the  circumstances  that  in  the  econo- 
my of  birds  there  is  no  final  separation  between  the  liquid  and  solid 
excretions.     Both  escape  mixed  together  from  the  same  aperture. 

1°.  Pigeons^  dung  is  much  prized  as  a  manure  wherever  it  can  be 
obtained  in  any  considerable  quantity.  In  Belgium  it  is  esteemed  as 
a  top-dressing  for  the  young  flax,  and  the  yearly  produce  of  100 
pigeons  is  sold  for  about  20s.  Its  immediate  effect  depends  upon  the 
quantity  of  soluble  matter  it  contains,  and  this  varies  much  accord- 
ing to  its  age  and  the  circumstances  under  which  it  has  been  pre- 
served. Thus  Davy  (Davy's  Agricultural  Chemistry,  Lecture  VI.,) 
and  Sprengel  obtainea  respectively  of 

Recent.  Six  months'  old.  After  fermentation. 

(Davy.)  (Sprengel)  (Davy.) 

Soluble  matter  in  )    ^3  ^g  g 

pigeons'  dung. .  ^         ^  ^  ^ 

The  soluble  matter  consists  of  uric  acid  in  small  quantity,  of  urate 
sulphate,  and  especially  of  carbonate  of  ammonia,  common  salt,  anc 
sulphate  of  potash  ; — the  insoluble  chiefly  of  phosphate  of  lime,  with 
a  little  phosphate  of  magnesia,  and  a  variable  admixture  of  sand  and 
other  earthy  matters  (  Sprengel's  Lehre  vom  Diinger,  p.  140.)  When 
ex^sed  to  moisture,  the  pigeons'  dung,  especially  if  recent,  undergoes 
fermentation,  loses  a  portion  of  its  ammoniacal  salts,  and  thus  be- 
comes less  valuable.  When  it  is  intended  to  be  kept  it  should  be 
mixed  with  a  dry  vegetable  soil,  or  made  into  a  compost  with  earth 
and  saw  dust,  with  a  portion  of  pulverized  or  charred  peat,  or  with 
such  a  disinfecting  charcoal  as  that  which  is  employed  in  the  manu- 
facture of  the  animalized  carbon  above  described. 

2^.  Hens^  dung  often  accumulates,  decomposes,  and  runs  to  waste 
in  poultry  yards,  when,  with  a  little  care,  it  might  be  collected  in 
considerable  quantities. 

3°.  Goose  dung  is  less  rich  than  that  of  hens  or  pigeons,  because 
this  bird  feeds  less  upon  grain,  and  derives  a  considerable  portion  of 
its  nourishment  from  the  grass  which  it  crops,  when  allowed  to  go  at 
liberty  over  the  fields.  Its  known  injurious  effects  upon  the  grass 
upon  which  it  falls  arise  from  its  being  in  too  concentrated  a  state. 
In  moist  weather,  or  where  rain  soon  succeeds,  it- does  no  injury,  and 
even  when  in  dry  weather  it  kills  the  blades  on  which  it  drops,  it 
brings  up  the  succeeding  shoots  with  increased  luxuriance. 

4°.  Rooks''  dung  unites  with  the  leaves  of  the  trees  among  which 
they  live,  in  enriching  the  pasture  beneath  them.  In  old  rookeries  the 
soil  JB  observed  also  to  be  slowly  elevated  above  the  surrounding  land. 


COMPOSITION    OF    GUANO.  457 

This  surface  soil  I  have  found  to  be  especially  rich  in  phosphate  of  lime, 
vvliich  has  gradually  accumulated  and  remained  in  it  while  the  volatile 
and  soluble  parts  of  the  droppings  of  the  birds  have  slowly  disappeared. 

5°.  Guano  is  the  name  given  to  the  accumulated  dung  chiefly  of 
sea  birds,  which  is  found  upon  the  rocky  promontories,  and  on  the  isl- 
ands that  skirt  the  coast  of  South  America,  from  the  13th  to  the  21st 
degree  of  south  latitude.  In  that  part  of  America,  the  climate  being 
very  dry,  the  droppings  of  the  birds  have  decomposed  with  exceeding 
slowness,  and  upon  some  spots  have  continued  to  accumulate  for  many 
centuries,  forming  layers,  more  or  less  extensive,  of  10,  20,  and  at  cer- 
tain places  it  is  said  even  60  (?)  feet  in  thickness.  In  some  places 
the  more  ancient  of  these  deposites  are  covered  bv  layers  of  drift 
sand,  which  tend  further  to  preserve  them  from  decay.  In  our  moist 
climate  the  dung  of  the  sea  fowl  is  readily  washed  away  by  the  rains, 
so  that  even  where  sea  birds  most  abound  no  considerable  quantity 
of  guaiio  can  ever  be  expected  to  collect. 

The  solid  part  of  the  droppings  of  birds  in  general,  when  recent,  con- 
sists chiefly  of  uric  acid,  with  a  little  urate  of  ammonia,  and  a  variable 
per-centage  of  phosphate  of  lime  and  other  saline  compounds.  The 
liquid  part,  like  the  urine  of  other  animal^  contains  much  urea,  with 
some  phosphates,  sulphates,  and  chlorides.  The  uric  acid  and  urea, 
however,  gradually  undergo  decomposition,  and  are  changed  into  car- 
bonate and  other  salts  of  ammonia.  If  applied  to  the  land  when  this 
stage  of  decomposition  is  attained,  they  form  an  active,  powerful,  and 
immediately  operating  manure  ;  but  if  allowed  to  remain'exposed  to 
the  air  for  a  lengthened  period  of  time,  the  salts  of  ammonia  gradually 
volatilize,  and  the  efficacy  of  what  remains  becomes  greatly  dimin- 
ished. Hence,  the  guano  which  is  imported  into  this  country  is  very 
variable  in  quality,  some  samples  being  capable  of  yielding  only  7 
per  cent,  of  ammonia,  while  others  are  said  to  give  as  much  as  25 
per  cent.  Of  two  portions  taken  by  myself  from  the  same  box,  the 
one  contained  8  per  cent,  and  the  other  only  1^  per  cent,  of  sand, 
while  their  other  constituents  were  as  follows : — 

1    •  percent-  '^   •  ^  percent 

Water,  salts  of  ammonia,  [Ammonia ' 7-0 

and  organic   matter   ex-  |  Uric  acid '. .        0-8 


pelled  by  a  red  heat 23-5 

Sulphate  of  soda 1-8 

Common  salt,  with  a  little 

phosphate  of  soda 30-3 

Phosphate  of  lime,  with  a  lit- 
tle phosphate  of  magnesia 
and  carbonate  of  lime 44-4 


100 


Water  and  carbonic  and  ox- 
ahc  acids,  &c.,  expelled 
by  a  red  heat 51-5 

Common  salt,  with  a  little 
sulphate  and  phosphate 
of  soda ...      11-4 

Phosphate  of  lime,  &c 29-3 


100 


On  the  other  hand,  Dr.  Ure  gives  the  following  as  the  average  re- 
sult of  his  analyses  of  genuine  guano  : — 

perc««t. 
Organic  matter  containing  nitrogen,  including  urate  of  ammo- 
nia, and  capable  of  aflfording  from  8  to  17  per  cent,  of  am- 
monia by  slow  decomposition  in  the  soil 50 

Water 11 


458  VALUE  OF  GUANO  AS  A  MANURE. 

per  cent. 

Phosphate  of  lime 25 

Ammonia,  phosphate  of  magnesia,  phosphate  of  ammonia,  &  ox- 
alate of  ammonia,  containing  from  4  to  9  per  cent,  of  ammonia.       13 
Siliceous  matter  from  the  crops  of  the  birds 1 

100* 
Others  have  found  sand  in  much  larger  proportion  than  was  pre? 
sent  in  the  samples  examined  by  myself— while  it  may,  I  think,  be 
taken  for  granted  that  very  little  of  what  comes  to  this  country  is  so 
rich  in  sokible  matter,  containing  ammonia  or  its  elements,  as  is  re- 
presented by  the  analyses  of  Dr.  Ure.f 

Variable  as  its  composition  is,  however,  there  is  now  no  doubt  that 
any  of  the  samples  yet  brought  into  the  English  market  may  be  ad- 
vantageously applied  as  a  manure  to  almost  any  crop.  From  the 
most  remote  period  guano  has  been  the  chief  manure  appHed  to  the 
land  on  the  parched  shores  of  Peru — and  at  the  present  day  it  is  not 
only  employed  for  the  same  purpose  in  the  provinces  which  lie  along 
the  coast,  but  it  is  also  carried  across  the  desert  of  Atacama  many 
leagues  inland,  "  on  the  backs  of  mules  over  rough  mountain  paths, 
ancTat  a  great  expense,  f^  the  use  of  the  agricultural  districts  of 
Peru  and  Bolivia"  (Silliman's  Journal,  xliv.,  p.  10.)  It  has  been 
estimated  that  a  hundred  thousand  quintals  (the  quintal  is  equal  to 
lOli  lbs.  avoirdupois)  are,  at  the  present  day,  annually  sold  in  Peru. 
There  also  the  quantity  and  the  price  vary — tbe  recent  white  guano 
selling  usually  at  3s.  6d.,  the  more  recent  red  and  grey  varieties  at 
2s.  3d.  per  cwt.  (Winterfeldt.)|  In  this  country,  the  latter — the  only 
variety  yet  imported — sells  at  present  (1843)  at  about  10s.  a  cwt. 

In  regard  to  the  effects  of  guano  upon  various  crops,  many  import- 
ant experimental  results,  obtained  in  1842,  will  be  found  in  the  Ap- 
pendix. I  here  insert  a  few  of  the  more  important  of  these,  along 
with  some  others  made  in  the  more  southern  counties,  which  appear 
to  be  highly  deserving  of  consideration. 

Swedish  Turnips. 

Produce  per  acre. 
"Top-dressed  with  tons.    cwt.  Locality. 

'°-^::r'.''^'fl'::t:  ll  ^^Baroch,„,„earPaisley. 

2°.  Farm-yard  dung.20    tons.  16  18  J 

Guano§ 2\  cwt.  17  4  >  Parish  of  Wraxal,  Somerset. 

Bones... 32   bush.  15  17) 

•  By  way  of  comparison,  I  insert  here  the  approximate  composition  of  the  solid  part  of 
the  excrements  of  four  different  varieties  of  eagle,  as  determined  by  Coindet : — 

American  American  Grand  Duke 

Senegal  Eagle.     Hunting  Eagle.    Fishing  Eagle.        of  Virginia. 

Uric  acid 89  79  9037  84  65  8871 

Ammonia 785  8-87  9  20  8-55 

Phosphate  of  lime 2-36  0i6  6  15  2*74 

100  100  100  100(a) 

(o)  Gmelin  Handbuch  der  Chemie,  II.,  p.  1456. 

tThe  presence  of  ammonia  in  guano  is  readily  ascertained  by  mixing  it  with  a  little 
slaked  lime— when  the  odour  of  ammonia  will  be  immediately  perceived,  and  will  be 
strong  in  proportion  to  the  quantity  contained  in  the  guano. 

t  For  further  particulars  regarding  guano  the  reader  is  referred  to  a  paper  in  the  Journal 
of  the  Royal  Agricultural  Society,  II.,  p.  301. 

§  Mixed  with  1  cwt.  of  charcoal  powder. 


ITS  ACTION  UPON  TURNIPS.  POTATOES,  WHEAT.  ETC. 


459 


Yellow  Turnips. 

Produce  per  acre. 
Top-dressed  with  tons.    cwt.  Locality. 

Guanof 5    cwt.     32      2  J 

Rape-dust 15    cwt.     24    11  VBarochan,  near  Paisley. 

Bone-dust 30    bush.   17      2  ) 


-.  Guano 3 

Rape-dust 1 

'.  Guano 4 

Rape-dust 1 

Bone-dust 45 

'.  Guano 4 

Rape-dust 1    ton. 

Bone-dust 45 


Potatoes. 

cwt.     18 

9^ 

ton.      12 

6 

cwt     14 

6 

ton.      10 

0 

bush.     9 

15 

cwt.      13 

14 

ton.      13 

0 

bush.   13 

14  J 

Barochan.  In  all  these  cases 
the  manures  were  put  in 
alone  with  the  potatoe  cut- 
tings, no  other  manure  be- 
ing afterwards  added  . 


As  a  top-dressing  to  the  young  potatoe  crop  at  Erskine,  in  1842,  one 
cwt.  of  guano  per  acre  produced  no  important  increase.  This  might, 
however,  be  owing  to  the  extreme  dryness  of  the  season  ^Appendix, 
No.  IX.) 

Wheat. 


Produce  per  acre. 

Top-dressed  with  bush.    lbs. 

1°.  Guano 1    cwt.  48 

Rape-dust 16    cwt.  51 

Undressed 47| 

2°.  Guano 3    cwt.  30 

Undressed 24 

3°.  Guano 2    cwt.  32 

Undressed^ 31 

4°.  Guano 1    cwt.  46 

Nitrate  of  Soda. .   1    cwt.  51 

Undressed 44 

5°.  Guano li  cwt.  45 

Nitrate  of  Soda.,   li  cwt.  41 

Undressed 39 


Locality. 

0  J  Lennox  Love,   near 
0  >     dington — 

rg  i  Barochan. 


Had- 


drought  very  great. 


Gadgirth,  near  Ayr. 


20 
31 
15  i 

18  V  Erskine.  Renfrewshire.il 
4) 

^) 

0  >  Seisdon,  Worcestershire.§ 

0) 


Barley. 

Guano 3    cwt     64      0 

Undressed 47     15 

Oats. 


Barochan. 


0  )  Lennox    Love,   near  Had- 
0  i     dington. 
16  . 

Erskine,  Renfrewshire. 


[6V 


1°.  Guano 2    cwt  70 

Undressed 52 

2°.  Guano 1    cwt  48 

Nitrate  of  Soda . .   1    cwt.  50 

Undressed 49 

t  Mixed  with  20  bushels  of  wood-ashes. 

t  The  undressed  grain  was  of  supprior  qualify,  yielding  76J  per  cent,  of  fine  flour,  whils 
that  dressed  with  guano  gave  only  68|  per  cent. 

I  The  grain  dressed  with  guano  weighed  half  a  pound  per  bushel  less  than  the  otherg. 

§  The  guano  gave  4  cwt.  more  straw  than  the  nitrate,  and  11  cwt.  more  than  the  undressed. 
The  undressed  grain  also  weighed  half  a  pound  less  per  bushel  than  either  of  the  other  two. 
20 


460  SOLID  MATTER  IN  THE  URINE  OF  DIFFERENT  ANIMALS. 

Beans. 

rroduce  per  acre. 
Top-dressed  with  bush.  Localily. 

Guano 2    cwt.      33.n 

Rape-dust 16    cwt.     35    (Lennox  Love,  near 

Nitrate  of  soda. .   1    cwt.      33    (      Haddington. 

Undressed 29|  J 

Hay. 

tons.  cwt. 

1°.  Guano li  cwt.        1     18  J 

Nitrate  of  Soda. .  li  cwt.       2     10  >  Barochan,  near  Paisley. 

Undressed 1       S) 

2°.  Guano U  cwt.       2      2  J 

Nitrateof  Soda. .   Ij  cwt.        1     17  >Erskine,  Renfrewshire. 

Undressed 1     10  ) 

An  inspection  of  the  above  results  appears  to  indicate  that  guano 
is  more  uniformly  successful  with  root  crops,  than  when  appHed  as  a 
top-dressing  to  corn  and  grass.  The  unusual  drought  which  pre- 
vailed in  1842  no  doubt  materially  diminished  its  action,  when  used 
as  a  top-dressing — and  the  results  upon  the  corn  crops  in  a  more  moist 
season  may  probably  prove  more  generally  favorable  to  its  use  as  an 
economical  manure. 

Some  experiments  seem  already  to  indicate  that  the  favorable  in- 
fluence of  guano  does  not  cease  with  the  first  season.  If  the  phos- 
phate of  lime  which  they  contain  operates  in  any  way  in  prolonging 
the  fertihzing  operation  of  bones,  the  large,  though  variable,  quanti- 
ty of  this  phosphate  contained  in  guano  should  render  this  latter 
substance  also  capable  of  permanently  improving  the  soil. 

By  exposure  to  the  air,  guano  gradually  gives  off  a  portion  of  its 
volatile  constituents ;  it  ought,  therefore,  to  be  kept  in  covered  ves- 
sels or  casks.  It  also  in  our  climate  absorbs  moisture  from  the  air, 
and  therefore  should  be  purchased  as  soon  as  possible  after  importa- 
tion. When  applied  as  a  top-dressing  it  may  be  conveniently  mixed 
with  an  equal  weight  of  gypsum  or  wood  ashes — with  charcoal  pow- 
der, or  with  fine  dry  soil. 

§  10,  Of  liquid  animal  manures — the  urine  of  Tnan,  of  the  cow, 
the  horse,  the  sheep,  and  the  pig. 

The  following  table  exhibits  the  average  proportions  of  water,  and 
of  the  solid  organic  and  inorganic  matters  contained  in  the  urine  of 
man  and  some  other  animals  in  their  healthy  state — and  the  average 
quantity  voided  by  each  in  a  day ; — 

Water.  Solid  matter  in  lOOt)  parts.  Average  quan- 

Urine  in  , -^ . »         tity  voided  in 

of  a  1000  parts.      Organic.        Inorcanic.        Total.  24  hours. 

Man 969*  23-4  7-6  31  3  'bs. 

Horse...  940  27  33  60  3  '■' 

Cow  . .  -  -930  50  20  70  40t 

Pig 926  56  18  74  ? 

6heep...960  28  12  40  ? 

•  Alfred  Becquerel.  See  Thomson's  Animal  Chemistry,  p.  477.  It  is  to  be  observed  that 
the  proportions  of  water  and  of  solid  matter  in  urine  vary  with  the  food,  and  with  a  great 
variety  of  circumstances. 

t  A  milk  cow  voids  leBS  than  this  in  a  proportion  which  varies  with  the  quantity  of  milk 


COMPOSITION   OF   HUMAN  URINE.  461 

Of  natural  liquid  manures,  the  most  important  and  valuable,  though 
the  most  neglected  and  the  most  wasted  also,  consists  of  the  urine  of 
man  and  of  the  animals  he  has  domesticated. 

The  efficacy  of  urine  as  a  manure  depends  upon  the  quantity  of 
solid  matter  which  it  holds  in  solution,  upon  the  nature  of  this  sohd 
matter,  and  especially  upon  the  rapid  changes  which  the  organic 
part  of  it  is  known  to  undergo. 

The  numbers  in  the  above  table  show  that  the  urine  of  the  cow, 
estimated  by  the  quantity  of  solid  matter  it  contains,  is  more  valu- 
able than  that  of  any  other  of  our  domestic  animals,  with  the  excep- 
tion of  the  pig.  But  the  quantity  voided  by  the  cow  must  be  so 
much  greater  than  by  the  pig,  that  in  annual  value  the  urine  of  one 
cow  must  greatly  exceed  that  of  many  pigs. 

It  might  be  supposed  at  first  that  in  all  animals  the  quantity  of 
urine  voided  would  have  a  close  connection  with  the  quantity  of  water 
which  each  was  in  the  habit  of  drinking.  But  this  is  by  no  means  the 
case.  Thus  it  is  the  result  of  experiment  that  in  man  the  drink  ex- 
ceeds the  urine  voided  by  about  one-tenth  part  only — while 

Of  watpr  id  24  hours.  Of  urine  in  24  hours. 

A  horse,  which  drank        35  lbs.        gave  only        3  lbs. 
A  cow,    which  drank       132  lbs.         gave  18  lbs.,  and 

19  lbs.  of  milk  (Boussingault). 
How  very  large  a  quantity  of  the  liquid  they  drink  must  escape 
from  the  horse  and  the  cow  in  the  form  of  insensible  perspiration ! 
That  this  should  be  very  much  greater  indeed  than  in  man,  we  are 
prepared  to  expect  from  the  greater  extent  of  surface  which  the  bo- 
dies of  these  animals  present. 

Let  us  now  examine  more  closely  the  composition  of  urine,  the 
changes  which  by  decomposition  it  readily  undergoes,  and  the  effect 
of  these  changes  upon  its  value  as  a  manure. 

1°.  Human  urine The  exact  composition  of  the  urine  of  a  healthy 

individual  in  its  usual  state  was  found  by  Berzelius  to  be  as  follows : — - 

Phosphate  of  soda 2-9 

Phosphate  of  ammonia 1-6 

Common  salt 4-5 

Sal-ammoniac 1-5 

Phosphates  of  lime  and  mag- 
nesia, with  a  trace  of  silica 
and  of  fluoride  of  calcium,       1-1 


Water 

933-0 

Urea         

30-1 

Uric  acid 

1-D 

Free  lactic  acid,  lactate  of 

ammonia ,    and    animal 

matter  not  separable. . . 

17-1 

Mucus  of  the  bladder 

0-3 

Sulphate  of  potash 

3-7 

Sulphate  of  soda 

3-2 

1000 
From  what  I  have  already  had  occasion  to  state  in  regard  to  the  ac- 
tion upon  living  plants  of  the  several  sulphates,  phosphates,  and  other 
saline  compounds,  mentioned  in  the  above  analysis,  you  will  see  that 
the  fertilizing  action  of  urine  would  be  considerable,  did  it  contain  no 
other  solid  constituents.  But  it  is  to  the  urea  which  exists  in  it  in  very 
much  larger  quantity  than  any  other  substance,  that  its  immediate 
and  marked  action  in  promoting  vegetation  is  chiefly  to  be  ascribed. 
This  urea,  which  is  a  white  salt-like  substance,  consists  of — 

she  gives.    Boussingault  found  a  milk  cow  to  yield  daily  18  lbs.  of  urine  and  19  lbs.  of 
milk..— Ann.  de  Chim.et  de  Phys.,  Ixxi.,  pp.  123, 124. 


462  URINE    OF   THE    COW — ITS    VALUE. 

Carbon 20-0  per  cent.  I  Nitrogen 46-7  per  cent. 

Hydrogen 6-6        "  |  Oxygen. .  .* 26-7        " 

100 

It  is,  therefore,  far  richer  in  nitrogen  than  flesh,  blood,  or  any  of 
Ihose  other  richly  fertiUzing  substances,  of  which  the  main  efficacy  is 
supposed  to  depend  upon  the  large  proportion  of  nitrogen  they  contain. 

But  urea  possesses  this  further  remarkable  property,  that  when 
urine  begins  to  ferment, — as  it  is  known  to  do  in  a  few  days  after  it  is 
voided — it  changes  entirely  into  carbonate  of  ammonia.*  Of  the  am- 
monia thus  formed  a  portion  soon  begins  to  escape  into  the  air,  and 
hence  the  strong  ammoniacal  odour  of  fermenting  urine.  This  escape 
of  ammonia  continues  for  a  long  period,  the  liquid  becoming  weaker 
and  weaker,  and  consequently  less  valuable  as  a  manure  every  day 
that  passes.  Experience  has  shown  that  recent  urine  exercises  in  gen- 
eral an  unfavorable  action  upon  growing  plants,  and  that  it  acts 
most  beneficially  after  fermentation  has  freely  begun,  but  the  longer 
time  we  suffer  to  elapse  after  it  has  reached  the  ripe  state,  the  great- 
er the  quantity  of  valuable  manure  we  permit  to  go  to  waste. 

2°.  The  urine  of  the  cow  hsi^  heen  analysed  in  several  states  by 
Sprengel,  with  the  following  results  in  1000  parts  : — 

Allowed  to  ferment  for  four  weeks 
Fresh.  in  the  open  air. 

A.  B. 

Water 926-2  954-4  934-8 

Urea 40-0  10-0  6-0 

Mucus 20  0-4  0-3 

Hippuric  and  lactic  acids. ..  6-1  7-5  6-2 

Carbonic  acid 2-1  1-7  15-3 

Ammonia 2-1  4-9  16-2 

Potash 6-6  6-6  6-6 

Soda 5-5  5-5  5-6 

Sulphuric  acid 4-0  3-9  3-3 

Phosphoric  acid 0-7  0-3  1-5 

Chlorine 2-7  2-7  -2-7 

Lime 0  6  trace  trace 

Magnesia 0-4  0-3  0-4 

Alumina,  oxide  of  iron,  and 

oxide  of  manganese 0*1  trace  — 

Silica 0-4  0.1  0-1 


1000  998-2  999-Ot 

The  first  variety  of  fermented  urine  (A.),  had  stood  four  weeks  in 
the  air  in  its  natural  state  of  dilution  ;  the  second  (B.),  had  been  mix- 
ed while  recent  with  an  equal  bulk  of  water— which  is  again  deducted 

•  This  takes  place  by  the  decomposition  at  the  same  time  of  two  atoms  of  the  water  In 
which  it  is  dissolved.  Thus  urea  is  represented  by  Ca  H4  Ns  Oa  ;  two  of  water  by  2H  O : 
and  carbonate  of  ammonia  by  N  Ha  +  C  O2  ;  and  the  change  is  thus  shown— 

2  of  2  of 

Urea.  Water.  Carbonate  of  Ammonia. 

C2  H4  Na  02  +  2  H  0  =  2  (N  H3  -H  C  O2) 
tThe  small  quantity  necessary  to  make  up  the  1000  parts  in  the  two  latter  analyses  con- 
sisted of  a  deposit  of  carbonate  and  phosphate  of  lime  and  other  earthy  matters  which 
had  gradually  been  formed,  and  of  a  trace  of  vinegar  aod  of  sulphuretted  hydioeen.- 
Bprengel,  Lehre  vom  Dilnger,  pp.  107  to  110. 


URINE  OF  THE  HORSE,  SHEEP,  AND  PIG.  463 

from  it  in  the  analysis — with  the  view  of  ascertaining  how  far  such 
an  admixture  would  tend  to  retain  the  volatile  ammonia  produced  by 
the  natural  decomposition  of  the  urea. 

An  inspection  of  these  tables  shows  three  facts  of  importance  to 
the  agriculturist — 

1°.  That  the  quantity  of  urea  in  the  urine  of  the  cow  is  considerably 
greater  than  in  that  of  man ;  2^.  That  as  the  urine  ferments,  the  quan- 
tity of  urea  diminishes,  while  that  of  ammonia  increases — owing,  as  I 
have  already  stated,  to  the  gradual  decomposition  of  the  urea  and  its 
conversion  into  carbonate  of  ammonia;  and  3^,.  That  by  dilution  with 
an  equal  bulk  of  water  the  loss  of  this  carbonate  of  ammonia,  which 
would  otherwise  naturally  take  place,  is  in  a  considerable  degree  pre- 
vented. Tke  quantity  of  ammonia  retained  by  the  urine^  after  dilu- 
tion, was  in  the  same  circumstances  nearly  three  times  as  great  as  when 
it  was  allowed  to  ferment  in  the  state  in  which  it  came  from  the  cow. 

But  even  by  this  dilution  the  whole  of  the  ammonia  is  not  saved. 
One  hundred  parts  of  urea  form  by  their  decomposition  56^  parts  of 
ammonia,  and  as  36  parts  of  the  urea  in  the  urine  B.  had  disappear- 
ed, there  ought  to  have  been  in  its  stead  19  parts  of  ammonia  in  ad- 
dition to  that  which  the  urine  contained  in  its  recent  state,  or  21  parts 
in  all — whereas  the  table  shows  it  to  have  contained  only  16  parts. 
Even  when  diluted  with  its  own  bulk  of  water,  therefore,  the  urine 
had  lost  by  fermentation  in  the  open  air  upwards  of  one-fourth  of 
the  ammonia  produced  in  it  during  that  period.  This  shows  the  ne- 
cessity of  causing  our  liquid  manures  to  ferment  in  covered  cisterns, 
or  of  adopting  some  other  means  by  which  the  above  serious  loss  of 
the  most  valuable  constituents  may  be  prevented. 

3^.  The  urine  of  the  horse,  sheep,  and  pig,  have  not  been  so  care- 
fully analysed  as  that  of  the  cow.  They  consist  essentially  of  the 
same  constituents,  and  the  specimens  which  have  been  examined 
were  found  to  contain  the  three  most  important  of  these  in  the  follow- 
ing proportions  : 

Horse.  Sheop.  Pig. 

Water 940  960  926 

Urea 7?  28  56 

Saline  substances . .       53  12  18 

1000  1000  1000 

Some  of  the  saline  substances  present  in  the  urine,  as  above  stated, 
contain  nitrogen.  This  is  especially  the  case  in  the  urine  of  the  horse, 
so  that  the  quantity  of  urea  above  given  is  not  to  be  considered  as  re- 
presenting the  true  ammonia-producing  power  of  the  urine  of  this  ani- 
mal. The  urine  of  the  pig,  if  the  above  analysis  is  to  be  relied  upon  as 
any  thing  like  an  average  result,  is  capable  of  producing  more  ammonia 
from  the  same  quantity  than  that  of  any  other  of  our  domestic  animals. 

§  11.  Of  the  waste  of  liquid  manure — ofurate^  and  ofsidphated  urine. 
1°.  Waste  of  human  urine. — The  quantity  of  solid  matter  contain- 
ed m  the  recent  urine  voided  in  a  year  by  a  man,  a  horse,  and  a  cow, 
and  the  weight  of  ammonia  they  are  respectively  capable  of  yielding, 
may  be  represented  as  follows : 


464  URATE,    AND    SULPHATED    URINE. 

Quantity  of  urine.    Solid  matter.    Containinor  of  urea.    And  yielding  of  ammonia. 

Man        1000  lbs.  67  lbs.  30  lbs.  17  lbs. 

Horse      1000    "  60    "  ?  1 

Cow       13000    "  900    "  400    "  230*  " 

How  much  of  all  this  enriching  matter  is  permitted  to  run  to  waste  ? 
The  sohd  substances  contained  in  urine,  if  all  added  to  the  land,  would 
be  more  fertilizing  than  guano,  which  now  sells  at  XIO  a  ton.  If  we 
estimate  the  urine  of  each  individual  on  an  average  at  only  600  lbs., 
then  there  arc  carried  into  the  common  sewers  of  a  city  of  15,000  in- 
habitants, a  yearly  weight  of  600,000  pounds,  or  270  tons,  of  manure, 
which,  at  the  present  price  of  guano,  is  worth  £2700, — which  would  no 
doubt  prove  more  fertilizing  than  its  own  weight  of  guano,  and  might  be 
expected  to  raise  an  increased  produce  of  not  less  than  1000  qrs.  of  grain. 

The  saving  of  all  this  manure  would  be  a  great  national  benefit, 
though  it  is  not  easy  to  see  by  what  means  it  could  be  effectually  ac- 
complished. What  is  thus  carried  off  by  the  sewers  and  conveyed 
ultimately  to  the  sea,  is  drawn  from  and  lost  by  the  land,  which  must, 
therefore,  to  a  certain  extent  be  impoverished.  Can  we  believe  that 
in  the  form  of  fish,  of  sea  tangle,  or  of  spray,  the  sea  ever  delivers 
back  a  tithe  of  the  enriching  matter  it  daily  receives  from  the  land  ? 

2°.  Urate. — In  order  to  prevent  a  portion  of  this  waste,  the  practice 
has  been  introduced  into  some  large  cities  of  collecting  the  urine,  add- 
ing to  it  one-seventh  of  its  weight  of  pov/dered  gypsum,  allowing 
the  whole  to  stand  for  some  days,  pouring  off  the  liquid  and  drying 
the  powder.  Under  the  name  of  urate  this  dry  powder  has  been  high- 
ly extolled,  but  it  can  contain  only  a  small  portion  of  what  is  really 
valuable  in  urine.  The  liquid  portion  poured  off  must  contain  most 
of  the  soluble  ammoniacal  and  other  salts,  and  even  were  the  whole 
evaporated  to  dryness,  the  gypsum  does  not  act  so  rapidly  in  fixing 
the  ammonia  as  to  prevent  a  considerable  escape  of  this  compound 
as  the  fermentation  of  the  urine  proceeds. 

3°.  Sulphated  urine A  method  of  more  apparent  promise  is  that 

now  practised  by  the  Messrs.  Turnbull  of  Glasgow,  of  adding  diluted 
sulphuric  acid  to  the  urine  as  the  ammonia  is  formed  in  it,  and  subse- 
quently evaporating  the  whole  to  dryness.  From  the  use  of  tl.is  sub- 
stance very  favorable  results  may  be  anticipated.!  Still  none  of  these 
preparations  will  ever  equal  the  urine  itself  part  of  the  efficacy  of 
which  depends  upon  the  perfect  state  of  solution  in  which  all  the  sub- 
stances it  contains  exist,  and  upon  the  readiness  with  which  in  this 
state  they  make  their  way  into  the  roots  of  plants. 

4°.  Loss  ofcouPs  urine. — When  left  to  ferment  for  five  or  six  weeks 

'The  numbers  given  above,  and  in  p.  40^1,  are  calculated  from  the  analysis  oi  the  urine 
of  tlie  horse  by  Fourcroy  and  Vauquelin,  and  ofthatof  the  cow  by  SpreJigel.  Boussingault, 
however,  obtained  very  different  results.  Thus  a  cow  and  a  horse,  on  which  his  experi- 
ments were  made,  yielded  a  quantity  of  urine  which  in  a  year  would  have  amounted  to, 
and  would  have  contaiiieil,  in  pounds — 

Containins  of  Capable  of  yicld- 

Quaniity.        Sulid  matter  (total).  Inor^ranic  matter.  Nitrogen,     ing  of  ammonia. 

Cow  6570  773  "  300  29  35 

Horse  HOC  243  m  30  36 

The  cow  yielded  at  the  same  lime  19  lb.«.   of  milk  each   day,   which   accounts  f()r  the 

smaller  proportion  of  urine  voided,  than  i.^  given  in  the  text.     It  is  remarkablp,  however, 

that  the  quantity  of  nitrogen  contained  in  an  equal  weight  of  the  urine  of  the  horse  was  in 

this  case  so  much  greater  than  that  of  the  cow— and  in  that  the  whole  amount  which  would 

have  been  yielded  by  that  of  a  cow  in  a  year  should  be  so  very  much  less  tlian  in  the  re- 


LOSS  OF  LiaUID  MANURi     N  THE  FARM-YARD.  465 

aloncj  and  with  the  addition  of  an  equal  bulk  of  v;ater,  the  urine  of 
the  cow  loses,  as  we  have  seen,  a  considerable  proportion  of  volatile 
matter,  and  in  these  several  states  will  yield  in  a  year — 

Solid  matter.        Yielding  of  ammonia. 

Recent  urine 900  lbs.  226  lbs. 

Mixed  with  water,  after  6  weeks. .  850    "  200    " 

Unmixed,  after  6  weeks 550    "  30    " 

Those  who  scrupulously  collect  in  tanks  and  preserve  the  hquid  ma- 
nure of  their  stables,  cow-houses,  and  fold-yards,  will  see,  from  the 
great  loss  which  it  undergoes  by  natural  fermentation,  the  propriety 
of  occasio'iially  washing  out  their  cow-houses  vi  ith  water,  and,  by  thus 
diluting  the  liquid  of  their  tanks,  of  preserving  the  immediately 
operating  constituents  of  their  hquid  manure  from  escaping  into  the 
air.  Even  when  thus  diluted  it  is  desirable  to  convey  it  on  to  the 
land  without  much  loss  of  time,  since  even  in  this  state  there  is  a  con- 
stant slow  escape,  by  which  its  value  is  daily  diminished.  Gypsum, 
sulphate  of  iron,  and  sulphuric  acid,  are,  by  some,  added  for  the  pur- 
pose o^  Jixmg  tiie  ammonia,  but  in  addition  to  diluting  it,  an  admix- 
ture of  rich  vegetable  soil,  and  especially  of  peat,  will  be  much  more 
economical,  and — except  in  so  far  as  the  gypsum  or  sulphuric  acid 
themselves  act  as  manures — nearly  as  effectual. 

But  these  remarks  apply  only  to  the  liquid  manure  when  collected. 
How  much  larger  a  waste  is  incurred  by  those  who  make  no  effort  to 
collect  the  urine  of  their  cow-houses  or  stables  !  The  recent  urine  of 
one  cow  is  valued  in  Flanders — where  liquid  manures  are  highly  es- 
teemed^ — at  40s.  a  year.  It  contains  on  an  average,  as  we  have  seen, 
900  lbs.  of  solid  matter,  and  this  estimated  at  the  price  of  guano  only, 
is  worth  at  present  £4  sterling.  Multiply  this  by  8  miUions,  the  num- 
ber of  cattle  said  to  exist  in  Uie  United  Kingdom,  and  we  have  32  mil- 
lions of  pounds  sterling,  as  the  value  of  the  urine,  supposing  it  to  be 
worth  no  more  than  the  foreign  guano.  It  is  impossible  to  estimate 
how  much  of  this  runs  to  waste,  but  1-lOth  of  it  will  amount  to  nearly 
as  much  as  the  whole  income-tax  recently  laid  upon  the  country.  The 
practical  farmer  who  uses  every  effort  to  collect  and  preserve  the  ma- 
nure which  nature  puts  within  his  reach,  is  deserving  of  praise  when 
he  expends  his  money  in  the  purchase  of  manures  brought  from  a  dis- 
tance, of  whatever  kind  they  may  be  ;  but  he,  on  the  other  hand,  is 
only  open  to  censure  who  puts  far  ward  the  purchase  of  foreign  ma- 
nures as  an  excuse  for  the  neglect  of  those  which  are  running  to 
waste  around  him.  Let  every  stock  farmer,  with  the  help  of  the 
facts  above  stated,  make  a  fair  calculation  of  what  is  lost  to  himself 
and  to  the  country  by  the  hitherto  unheeded  waste  of  the  urine  of 
his  cattle,  and  he  will  be  able  clearly  to  appreciate  the  importance  of 
taking  some  steps  for  preserving  it  in  future. 

suit  obtained  by  Sprencel.  The  milk  did  not  contain  nitrogen  sufficient  to  yield  more  than 
45  lbs.  of  ammonia,  and  this,  .-idded  to  the  35  lbs.  makes  only  80  Iba.  in  all — whereas 
Sprenspl  gives  230  lbs.  as  the  q'lantity  which  recent  urine  is  capable  of  yielding.  This  re- 
markable (iitference  must  be  ascribed  either  to  an  actual  loss  of  volatile  mtitter  by  the  urine 
analysed  by  Boussin^aiilt.  or— which  is  more  probable— to  a  difference  in  theqiiality  of  the 
food  on  wliich  the  two  animals  were  fed. 

'  The  Messr.a.  Turnbull  inform  me  that  with  this  sulphated  urine,  tinder  the  incorrect 
name  of  sulphate  (f  ammonia,  the  experiments  of  Mr.  Burnet  were  made  (p.  362),  as  well 
as  those  of  Mr.  Fleming  and  Mr.  Alexander,  detailed  in  the  Appendix. 


466  NIGHT  SOIL  READILY  :.  ECOMPOSES — ITS  COMPOSITION. 

§  12.  Of  solid  animal  manures— night  soil,  the  dung-  of  the  cov^    ife 
horse,  the  sheep,  and  the  pig. 

1°.  Night  soil  is  in  general  an  exceedingly  rich  and  valuable  ma- 
nure, but  its  disagreeable  odour  has  in  most  countries  rendered  its 
use  unpopular  among  practical  men.  This  unpleasant  smell  may  be 
in  a  great  measure  removed  by  mixing  it  with  powdered  charcoal  or 
with  half-charred  peat,— a  method  which  is  adopted  in  the  manufac- 
ture of  certain  artificial  manures.  Q,uick-lime  is  in  some  places  em- 
ployed for  the  same  purpose,  but  though  the  smell  is  thus  got  rid  of, 
a  large  portion  of  the  volatile  ammonia  produced  during  the  decom- 
position of  the  manure  is  at  the  same  time  driven  off  by  the  lime. 

In  general,  night  soil  contains  about  three-fourths  of  its  weight  of 
water,  and  when  exposed  to  the  air  undergoes  a  very  rapid  decompo- 
sition, gives  off  much  volatile  matter — consisting  of  ammonia,  of  car- 
bonic acid,  and  of  sulphuretted  and  phosphuretted  hydrogen  gases — 
and  finally  loses  its  smell.  In  the  neighborhood  of  many  large  cities,  the 
collected  night  soil  is  allowed  thus  naturally  to  ferment  and  lose  its  smell, 
and  is  then^dried  and  sold  for  manure,  under  the  name  of  poudrette. 

But  by  this  fermentation  a  very  large  pro'portion  of  valuable  matter 
is  permitted  to  escape  into  the  air.  To  retain  this,  gypsum  or  dilute 
sulphuric  acid  may  be  added  to  the  night  soil,  but  the  more  economi- 
cal and  generally  practicable  method  is  to  mix  it  with  earth  rich  in  ve- 
getable matter,  with  partially  dried  peat,  with  saw-dust,  or  with  some 
other  readily  accessible  absorbent  substance.  In  this  way  a  rich  and 
fertilizing  compost  will  be  obtained,  which  will  have  little  smell,  and 
yet  will  retain  most  of  the  virtues  of  the  original  manure. 

In  China  the  fresh  night  soil  is  mixed  up  with  clay  and  formed  into 
cakes,  which  when  dried  are  sold  under  the  name  of  Taffo,  and  form 
an  extensive  article  of  commerce  in  the  neighborhood  of  the  larger  cities. 

The  composition  of  night  soil,  and  consequently  its  value  as  a  ma- 
nure, varies  with  the  food,  and  with  many  other  circumstances  (p.  470). 
The  excrements  of  a  healthy  man  were  found  by  Berzelius  to  consist  of: 

Water 733  I  Mucilage,  fit,  and  other  ani- 

Albumen 9  |      mal  matters 167 

Bile 9  j  Undecomposed  food 70 

Sahne  matter 12  |  TOOO 

Of  the  excrement  when  freed  from  water  1000  parts  left  132  of  ash.viz. 

Carbonate  of  soda 8  1  Phosphate  of  lime  and  magne- 

Sulphate  of  soda,  with  a  little        [      sia,  and  a  trace  of  gypsum . .  100 

sulphate  of  potash,  and  phos-  Silica 16 

phate  of  soda 8  |  132 

2°.  Cow  dung  forms  by  for  the  largest  proportion  of  the  animal  ma- 
nure which  in  modern  agriculture  is  at  the  disposal  of  the  practical 
farmer.  It  ferments  more  slowly  than  night  soil,  or  than  the  dung  of 
the  horse  and  the  sheep.  In  fermenting  it  does  not  heat  much,  and  it 
gives  off  Httle  of  an  unpleasant  or  ammoniacal  odour.  Hence  it  acts 
more  slowly,  though  for  a  longer  period,  when  applied  to  the  soil. 

The  slowness  of  the  fermentation  arises  chiefly  from  the  smaller 
quantity  of  nitrogen,  or  of  substances  containing  nitrogen,  which  are 
present  in  cow  dung,  but  in  part  also  from  the  food  swallowed  by  the 
cow  being  less  perfectly  masticated  than  that  of  man  or  of  the  horse.  It 


HORSE  DUNG  SPEEDILY  FERMENTS,  AND  LOSES  WEIGHT.  487 

is  a  consequence  of  this  slower  fermentation,  that  the  same  evolution 
of  ammoniacal  vapours  is  not  perceived  from  the  droppings  of  the  cow 
as  from  night  soil  and  from  horse  dung.  Yet  by  exposure  to  the  air,  it 
undergoes  a  sensible  loss^  which  in  40  days  has  been  found  to  amount 
to  5  per  cent,  or  nearly  one-fifth  of  the  whole  solid  matter  which  re- 
cent cow  dung  contains.*  (Gazzeri.)  Although,  therefore,  the  compa- 
ratively slow  fermentation  as  well  as  the  softness  of  cow  dung  fits  it 
better  for  treading  among  the  straw  in  the  open  farm-yard,  yet  the 
serious  loss  which  it  ultimately  undergoes  will  satisfy  the  economical 
farmer  that  the  more  effectually  he  can  keep  it  covered  up,  or  the 
sooner  he  can  gather  his  mixed  dung  and  straw  into  heaps,  the  great- 
er proportion  of  this  valuable  manure  will  he  retain  for  the  future  en- 
riching of  his  fields. 

3°.  Horse  dung  is  of  a  warmer  nature  than  that  of  the  cow.  It 
heats  sooner,  and  evolves  much  ammonia,  not  merely  because  it  con- 
tains less  water  than  cow  dung,  but  because  it  is  generally  also  rich- 
er in  those  organic  compounds  of  which  nitrogen  forms  a  constituent 
part.  Even  when  fed  upon  the  same  food  the  dung  of  the  horse  will 
be  richer  than  that  of  the  cow,  because  of  the  greater  proportion  of 
the  food  of  the  latter  which  is  discharged  in  the  large  quantity  of  urine 
it  is  in  the  habit  of  voiding  (p.  470). 

In  the  short  period  of  24  hours,  horse  dung  heats  and  begins  to  suf- 
fer loss  by  fermentation.  If  left  in  a  heap  for  two  or  three  weeks,  scarce- 
ly seven-tenths  of  its  original  weight  will  remain.  Hence  the  propriety 
of  early  removing  it  from  the  stable,  and  of  mixing  it  as  soon  as  possi- 
ble with  some  other  material  by  which  the  volatile  substances  given 
off  may  be  absorbed  and  arrested.  The  colder  and  wetter  cow  or  pig's 
dang  will  answer  well  for  this  purpose,  or  soil  rich  in  vegetable  matter, 
or  peat,  or  saw-dust,  or  powdered  charcoal,  or  any  other  absorbent  sub- 
stance which  can  readily  be  obtained — or  if  a  chemical  agent  be  pre- 
ferred, moistened  gypsum  maybe  sprinkled  among  it,  or  diluted  sulphu- 
ric acid.  There  is  undoubtedly  great  loss  experienced  from  the  general 
neglect  of  night  soil,  but  in  most  cases  the  dung  of  the  horse  might  also 
be  rendered  a  source  of  much  greater  profit  than  it  has  hitherto  been. 

The  warmth  of  horse  dung  fits  it  admirably  for  bringing  other  sub- 
stances into  fermentation.  With  peat  or  saw-dust  it  will  form  a  rich 
compost  and  to  soils  which  contain  much  inert  vegetable  matter  it  can 
be  applied  with  great  advantage.  Horse  and  cow  dung,  in  the  dry 
state,  have  been  subjected  to  ultimate  analysis  by  Boussingaultf, 
(Ann.  de  Chim.,  Ixv.,  pp.  122,  134,)  with  the  following  results: — 

Dung  of  the  Horse.     Dung  of  a  Milk  Cow. 

Carbon 38-7  42-8 

Hydrogen 5-1  5-2 

Oxygen 37-7  37-7 

Nitrogen 2-2  2-3 

Ashes 16-3  12-0 

100  100 

Waterf 300  566 

400  666 

*  Cow  (lung  consisting  of  75  of  water  and  25  of  dry  solid  mailer,  of  which  latter  5  disappear 
t  Recent  hotse  dung  losing  76  per  cent,  of  water  bj'  drying  of  cow  dung  75  per  cent. 
20* 


468  THE  DUNG  OF  THE  ?IG  AND  THE  SHEEP.' 

The  proportion  of  nitrogen  contained  in  the  two  njanures,  according 
to  these  resuhs,  is  so  nearly  ahke — be.  ng  in  reaUty  greater  in  the  cow 
dung — that  were  we  to  consider  the  above  numbers  to  represent  the 
average  constitution  of  the  droppings  of  the  horse  and  cow,  Ave  should 
be  compelled  to  ascribe  the  difterence  in  their  qualities  solely  to  the 
different  states  in  which  the  elements  exist  in  the  two,  and  to  the  pro- 
portions of  water  they  respectively  contain.  But  the  nature  of  the 
food  and  other  circumstances  affect  the  quahty  of  these  manures  so 
much  (p.  470),  that  we  cannot  as  yet  draw  any  general  conclusion 
from  the  results  obtained  in  one  special  case. 

4°.  Pig''s  dung  is  still  colder  and  less  fermentable  than  that  o?  the 
cow.  It  is  characterized  by  an  exceedingly  unpleasant  odour,  which 
when  applied  to  the  land  alone  it  imparts  to  the  crops,  and  especially 
to  the  root  crops  which  are  manured  with  it.  Even  tobacco,  when 
maimred  with  pig's  dung,  is  said  to  be  so  much  tainted  that  the  leaves 
subsequently  collected  are  unfit  for  smoking  [Sprengel,  Lehre  vom 
Danger,  p.  38.]  It  is  a  good  manure  for  hemp  and  other  crops  not 
intended  for  food,  but  is  best  employed  in  a  state  of  mixture  with  tlie 
other  manures  of  the  farm-yard. 

5^.  Sheep^s  dung  is  a  rich  dry  manure,  which  ferments  more  readi- 
ly than  that  of  the  cow,  but  less  so  than  that  of  the  horse.  A  speci- 
men examined  by  Zierl  consisted  of— 

Water 68*0  per  cent. 

Animal  and  vegetable  matter 19-3         " 

Saline  matter,  or  ash 12-7         " 

100 

The  food  of  the  sheep  is  more  finely  masticated  than  that  of  the  cow, 
and  its  dung  contains  a  little  less  water,  and  is  probably  richer  in  nitro- 
gen ;  hence  its  more  rapid  fermentation.  When  crops  are  eaten  off 
by  sheep,  their  manure  is  more  evenly  spread  over  the  field,  and  is,  at 
the  same  time,  trodden  in.  When  thus  spread  it  decom.poses  more 
slowly  than  when  it  is  collected  into  heaps,  and  the  ammonia  and  other 
useful  products  of  the  decomposition  are  absorbed  in  great  part  by  the 
soil  as  they  are  produced.  Those  soils  in  which  a  considerable  quan- 
tity of  vegetable  m.atter  is  already  present,  are  said  to  be  most  bene- 
fitted by  sheep's  dung,  because  of  the  readiness  wilh  which  they  ab- 
sorb the  volatile  matters  it  so  soon  begins  to  give  off. 

Sheep's  dung  is  said  to  lengthen  the  straw  of  the  corn  crops,  and 
to  produce  a  grain  rich  in  gluten — and  unfit  therefore  for  seed,  for  the 
manufacture  of  starch,  or  for  the  purposes  of  the  brewer  and  the  dis- 
tiller (Sprengel.)  It  may  be  doubted,  however,  whether  these  can  as 
yet  be  safely  considered  as  the  universal  effects  of  sheep's  dung  upon 
every  soil,  and  when  the  animals  are  fed  upon  every  kind  of  food. 

§  13.  Of  tfie  quantity  of  manure  produced  from  the  same  kinds  of 
food  by  the  horse,  the  cow,  and  the  sheep. 

The  carefully  conducted  experiments  of  Block  give  the  following 
as  the  total  quantities  of  manure,  solid  and  liquid,  produced  from  100 
lbs.  of  the  different  kinds  of  food  by  the  cow,  the  horse,  and  the  sheep. 


MANURE  J  =TODUCED  BY  DIFFERENT  ANIMALS. 

Quantity  of  manure  in  lbs.,  prodliced  by 


Water  in 

From  ICK.>  lbs.  of                          tub  cow.  the  horse.  the  shkep.  the  manure, 

fresh,  dried,  fresh,  dried,  fresh,  dried.  per  cent. 

Rye —    —  212     53  —      —  75 

Oats —    —  204     51  —      —  75 

Rye  and  other  straws(chopped)2r.8    43  168     42  117      40  66  to  84 

Hay 275    44  172     43  123      42  do.    do. 

Potatoes  (containing  72  per  ct. 

of  water) : 87i  14  —      —  38      13  do.    do. 

Tumips  (containing  75  per  cent. 

of  water) 37*     6  —      —  —      —  84 

Carrots  (87  per  cent,  of  water)  37^     6  —      —  —      —  84 

Green  Clover  (79  per  ct,  water)  G5J     9^  —       —  —      —  86 

After  8  days.  After  3  weeks.  After  8  weeks. 

Rye  Straw  (used  for  bedding)  238    96  269     97  206      95  54  to  64 

One  important  theoretical  result  is  presented  in  this  table — that 
the  wanure  voided  by  an  animal  contains  very  much  less  solid  matter 
than  the  food  it  has  consumed.  We  shall  presently  see  how  this  fact 
is  to  be  explained  (p.  472),  and,  at  the  same  time,  what  light  it  throws 
upon  the  quality  of  the  manure  produced.  • 

The  most  valuable  practical  results  from  the  above  experiments  are — 

1^.  That  for  100  lbs.  of  dry  fodder  the  horse  or  cow  will  give  on 
an  average  216  lbs.  of  fresh  or  46  lbs.  of  dry  manure — the  sheep  128 
lbs.  moist  or  43  lbs.  dry. 

2°.  That  root  crops,  on  an  average,  give  about  half  their  weight 
of  fresh  or  one-twelfth  of  dry  manure — the  potatoe  giving  more  and. 
the  turnip  less. 

3^.  That  green  crops  give  about  half  their  weight  of  fresh  or  one- 
eighth  of  dry  manure. 
§  14.  Of  the  relative  fertilizing  values  of  different  animal  excretions. 

\°.  The  theoretical  value  of  different  animal  excretions  calculated 
solely  from  the  quantity  of  nitrogen  which  the  specimens  examined 
were  found  respectively  to  contain,  is  thus  given  by  Payen  and  Bous- 
singault.  The  numbers  opposite  to  each  substance  indicate  the  weights 
of  that  substance  which  ought  to  produce  an  equal  effect  with  100  lbs. 
of  farm-yard  manure  in  the  recent  and  in  the  dry  states  : — 

Equal  effects  ought  to  be  produced  by 
in  the  dry  state.        artificially  dried. 

Farm  yard  dung 100  lbs.  100  lbs. 

Cow 125    "  84    « 

Do.urine 91    «  51    « 

Horse 73    "  88    « 

Mixed  excrements  of  the — Pig 63    "  58    " 

Horse 54    "  64    " 

Sheep 36    "  65    " 

Pigeon 5    "  22*" 

Poudrette lOj  "  44    « 

Another  variety    26    «  73    « 

Too  much  reliance  is  not  in  any  case  to  be  placed  upon  the  princi- 
ple of  classifying  manures  solely  by  the  proportion  of  nitrogen  they 
contain  (pp.  441  &  454) — much  less  can  we  depend  upon  the  order  of 
value  it  assigns  to  substances  the  composition  of  which  is  liable  to 


470  FERTILIZING  VALUES  OF  .  \IMAL  EXCRETIONS. 

constant  change  from  the  escape  of  those  volatile  compounds  in  which 
the  nitrogen  principally  exists. 

2°.  A  series  of  experiments  made  by  Hemibstiidt  upon  the  quantity 
of  grain  of  different  kinds,  raised  in  the  same  circumstances  by  equal 
weights  of  different  manures,  gave  the  following  results  : 

Number  of  soads  reaped  from 
Manure  applied.  Wheat.        Barley.  Oals.  Rye. 

Oxblood 14  16  12i  14 

Nightsoil —  13  141  131 

Sheep's  dung 12  16  14"  13 ' 

Human  urine —  13|^  13  13 

Horsedung 10  13  14  11 

Pigeon  dung —  10  12  9 

Cow  dung 7  11  16  9 

Vegetable  matter 3             7  13  6 

Unmanured —              4  5  4 

If  the  results  contained  in  this  table  were  to  be  depended  upon,  it 
would  appea*  that,  in  so  far  as  the  quantity  of  the  produce  is  concern- 
ed, these  manures  severally  exercise  a  special  action  upon  certain 
crops — that  night-soil,  for  example,  is  most  propitious  to  rye,  cow 
dung  to  oats,  and  sheep's  dung  to  barley  and  wheat.  And  the  latter 
fact  would  seem  at  once  to  justify  and  to  recommend  the  eating  off 
with  sheep  preparatory  to  either  of  the  latter  crops. 

None  of  these  kinds  of  manure,  however,  is  constant  in  composition, 
and  the  following  observations  will  satisfy  ysu  that  implicit  rehance 
ought  not  to  be  placed  either  upon  the  relative  practical  values  of  the 
different  animal  manures  as  they  appear  in  the  latter  table,  nor  on 
their  theoretical  values  as  exhibited  in  the  former. 

§  15.  Influence  of  circwnstances  on  the  quality  of  animal  manures. 

The  quality  of  the  droppings  of  animals  considered  as  manures  is 
affected  by  a  great  variety  of  circumstances — such  as 

1°.  By  the  kind  of  food  upon  which  the  animal  is  fed. — Thus  night 
soil  is  more  valuable  in  those  countries  and  districts  in  which  much 
flesh  meat  is  consumed,  than  where  vegetable  food  forms  the  principal 
diet  of  the  people.  It  is  even  said  by  Sprengel,  that  in  the  neighborhood 
of  Hildesheim  the  farmers  give  a  higher  price  for  the  house  manure 
of  the  Lutheran  than  for  that  of  the  Roman  Catholic  families,  because 
of  the  numerous  fasts  which  the  latter  are  required  to  observe.  (Ijehre 
vom  Danger^  p.  142.)  Every  keeper  of  stock  also  knows  that  tJie  ma- 
nure in  his  farm-yard  is  richer  when  he  is  feeding  his  cattle  upon  oil- 
cake, than  when  he  gives  them  only  the  ordinary  produce  of  his  farm. — 
[12  loads  of  the  dung  of  animals  fed  (while  fattening)  chiefly  upon  oil- 
cake was  found  to  give  a  greater  produce  than  24  loads  from  store  stock 
fed  irfthe  straw  yard. —  Complete  Grazier^  6th  edit.,  p.  103.] 

2°.  By  the  quantity  of  urine  voided  by  the  animal. — Upon  the  unlike 
quantities  of  urine  they  produce  appears  mainly  to  depend  the  unhke 
richness  of  the  dung  of  the  horse  and  of  the  cow.  The  latter  animal, 
when  full  grown  and  not  in  milk,  voids  nearly  13  times  as  much  urine 
as  the  former  (p.  460),  and  though  an  equal  bulk  of  this  urine  is  poorer 
in  solid  matter,  yet  the  whole  quantity  contains  several  times  as  much 


ANIMAL  MANURES  AFFECTED  BY  MANY  CIRCUMSTANCES.         471 

as  IS  present  in  that  of  the  horse.  But  if  the  cow  discharges  more  in 
its  urine  it  must  void  less  in  its  solid  excretions.  Hence,  supposing  the 
food  of  a  full-grown  horse  and  of  a  cow  to  be  very  nearly  the  same, 
the  dung  of  the  former — the  less  urine-giving  animal — must  be  the 
richer,  the  warmer,  and  the  more  valuable— as  it  is  really  known  to  be. 

3°.  By  the  amount  of  exercise  or  labor  to  which  the  animal  is  sub-- 
jected. — The  greater  the  fatigue  ta  which  an  animal  is  subjected  the 
richer  the  urine  is  found  to  be  in  those  compounds  (urea  chiefly)  which 
yield  ammonia  by  their  decomposition  (Prout).  The  food  of  two 
animals,  therefore,  being  the  same — other  things  also  being  equal — 
the  solid  excretions  will  be  richer  and  more  fertilizing  in  that  which 
is  kept  in  the  stall  or  fold-yard,  the  urine  in  that  which  is  worked  in 
the  open  air  or  pastured  in  the  field. 

4°.  By  the  state  of  growth  to  which  the  animal  has  arrived. — A 
full-grown  animal  has  only  to  keep  up  its  weight  and  condition  by  the 
food  it  eats.  Every  thing  which  is  not  necessary  for  this  purpose, 
therefore,  it  rejects  either  in  its  solid  or  in  its  liquid  excretions.  A  young 
animal,  on  the  other  hand,  adds  to  and  increases  its  bone  and  muscle 
at  the  expense  of  its  food.  It  rejects,  therefore,  a  smaller  proportion 
of  what  it  eats.  Hence  the  manure  in  fold-yards,  where  young  cattle 
are  kept,  is  always  less  rich  than  where  full-grown  animals  are  fed. 

5°.  By  the  purpose  for  which  the  animal  is  fed. — Is  it  to  be  im- 
proved in  condition  ?  Then  the  food  must  supply  it  with  the  mate- 
rials for  increasing  the  size  and  strength  of  its  muscles — with  albu- 
men, or  fibrin,  or  other  substances  containing  nitrogen.  In  such  sub- 
stances, therefore,  or  in  nitrogen  derived  from  them,  the  droppings 
must  be  poorer,  and  as  a  manure,  less  valuable. 

Is  the  animal  to  be  fattened  ?  Then  its  food  must  supply  fatty  mat- 
ters, or  their  elements,  of  which  nitrogen  forms  no  part.  All  the  ni- 
trogen of  the  food,  therefore,  will  pass  off  in  the  excretions,  and  hence 
the  richest  manure  yielded  at  any  time  by  the  same  species  of  ani- 
mal is  that  which  is  obtained  when  it  is  full-grown,  and,  being  large- 
ly fed,  is  rapidly  fattening. 

Is  the  cow  kept  for  its  milk  ?  Then  the  milk  it  yields  is  a  daily 
drain  upon  the  food  it  eats.  Whatever  passes  into  the  udder  is  lost 
to  the  dung,  and  hence,  other  things  being  equal,  the  dung  of  a  milk 
cow  will  be  less  valuable  to  the  farmer  than  that  of  a  full-grown  ani- 
mal from  which  no  milk  is  expected,  or  than  that  of  the  same  animal 
when  it  is  only  laying-on  fat. 

6°.  By  the  length  cf  time  during  which  the  manure  has  been  kept. — 
In  24  hours,  as  we  have  seen,  the  dung  of  the  horse  begins  to  fer- 
ment and  to  lessen  in  weight.  All  rich  manures  in  like  manner — the 
dung  of  all  animals  especially — decompose  more  or  less  rapidly  and 
part  with  their  volatile  constituents.  The  value  we  assign  to  them 
to-day,  therefore,  will  not  apply  to  them  to-morrow,  and  hence  the 
droppings  of  the  same  animal  at  the  same  age,  and  fed  in  the  same 
way,  will  be  more  or  less  valuable  to  the  farmer  according  to  the 
length  of  time  during  which  they  have  been  permitted  to  ferment. 

7°.  Lastly.  By  the  way  in  which  the  manure  has  been  preserved. — 
The  mixed  dung  of  the  farm-yard  must  necessarily  be  less  valuable 
where  the  liquia  laanure  is  allowed  to  run  off— or  where  it  is  permitted 


472  CHANGES    PRODUCED   UPON    THE    FOOD 

to  stand  in  pools  and  ferment.  Twenty  cart-loads  of  such  dung  may 
hasten  the  growth  of  the  turnip  crop  in  a  less  degree  than  half  the 
weight  will  do,  where  the  liquid  manure  has  been  carefully  collected 
and  returned  upon  the  heaps — to  hasten  and  complete  their  fermenta- 
tion, and  to  saturate  them  with  enriching  matter. 


Since,  then,  the  quality  or  richness  of  the  dung  of  the  same  animal  is 
liable  to  be  affected  by  so  many  circumstances — it  is  obvious  that  no 
accurate  general  conclusions  can  be  drawn  in  regard  to  its  precise 
fertilizing  virtue  when  applied  to  this  or  to  that  crop,  or  to  its  relative 
fertilizing  value  when  compared  with  equal  weights  of  the  dung  of 
other  animals.  The  results  obtained  in  one  set  of  analyses,  as  in  that 
of  Boussingault,  or  in  one  series  of  practical  experiments,  as  in  that 
of  Hermbstadt  (p.  470),  will  not  agree  with  those  obtained  in  any 
other — because  the  substances  themselves  with  which  our  different 
experiments  are  made,  though  called  by  the  same  name,  are  yet  very 
unlike  in  their  chemical  properties  and  composition. 

§  16.  Of  the  c flanges  which  the  food  undergoes  in  passing  through 
the  bodies  of  animals. 

It  is  the  result  of  long  experience  that  vegetable  matter  is  more 
sensibly  active  as  a  manure,  after  it  has  passed  through  the  body  of  an 
animal,  than  if  applied  to  the  land  in  its  unmasticated  and  undigested 
state.  In  becoming  animalized,  therefore — as  it  has  been  called — 
vegetable  substances  have  been  supposed  to  undergo  some  mysteri- 
ous, because  not  very  obvious  or  intelligible,  internal  change,  by  which 
this  new  virtue  is  imparted  to  them.  Yet  the  change  is  very  simple, 
and  when  explained  is  not  more  satisfactory  than  it  is  beautiful. 

You  will  recollect,  as  I  have  already  stated  to  you  (p.  469),  that 
the  weight  of  dry  manure  voided  by  an  animal  is  always  considerably 
less  than  that  of  the  dry  food  eaten  by  it.  Upon  the  nature  and 
amount  of  this  loss  which  the  food  undergoes  depends  the  quality  of 
the  manure  obtained. 

This  you  will  readily  comprehend  from  the  following  statement : 

1°.  Every  thing  which  enters  into  the  body  in  the  form  of  food  must 
escape  from  the  body  in  one  or  other  of  three  different  forms.  It  must 
be  breathed  out  from  the  lungs,  perspired  by  the  skin,  or  rejected  in  the 
solid  or  hquid  excretions.  We  have  already  seen  (Lee.  VIII.,  §  3), 
that  the  function  of  the  lungs  is  to  give  off  carbon  in  the  form  of  car- 
bonic acid,  while  they  drink  in  oxygen  from  the  air — and  that  the  quan- 
tity of  carbon  thus  given  off  by  a  healthy  man  varies  from  5  to  13  or 
more  ounces  in  the  24  hours.  From  the  skin  also  carbon  escapes  along 
with  a  small  and  variable  proportion  of  saline  matter.  The  weight 
of  carbon  given  off  by  the  skin  has  not  been  accurately  ascertained. 
Let  us  leave  it  out  of  view  for  a  moment,  and  consider  solely  the  ef- 
fect of  respiration  upon  the  nature  of  the  solid  and  liquid  excretions. 

Suppose  a  healthy  man,  taking  a  moderate » degree  of  exercise,  to 
give  off  from  his  lungs  6  ounces  of  carbon  in  24  hours,  and  to  eat 
durmg  the  same  time  2  lbs.  ^f  potatoes,  half  a  pound  of  beef,  and 
half  a  pound  of  bread.    TheLi  he  has  taken  in  his  food — 


BY   PASSING   THROUGH   THE    BODIES    OF   ANIMALS.  473 

Carbon.  Nitrogen.        Saline  matter. 

In  the  potatoes 1716  grs.      47  grs.        196  grs. 

In  the  bread 1004    "         34   "  22    " 

In  the  beef 790    "       120   "  35  " 

^510  grs.     201  grs.        253"grs. 

And  he  has  given  off  in  respiration  2625    " 

Leaving  to  be  rejected  sooner  or 

later  in  the  excretions 885    "       201    "  253   " 

In  this  supposed  case,  therefore,  the  carbon,  nitrogen,  and  saline 

matter  were  to  each  other  nearly  as  the  numbers 

Carbon.        Nitrogen.  Saline  matter. 

•35  2  2h  in  the  food, 

and  as  9  2  2h  in  the  excretions : 

Or,  in  other  words,  the  carbon  being  in  great  part  sifted  out  of  the 
food  by  the  lungs,  the  excretions  are  necessarily  much  richer  in  ni- 
trogen and  in  saline  matter,  weight  for  weight,  than  the  mixed  vege- 
table and  animal  matters  on  which  the  man  has  lived. 

But  the  immediate  and  most  sensible  action  of  animal  and  vegetable 
substances,  as  manures,  depends  upon  the  proportion  of  nitrogen  and  sa- 
line matters  they  contain.  This  proportion,  then,  being  greater  in  the  ex- 
cretions than  in  the  crude  vegetables,  the  cause  of  the  higher  estimation 
in  which  the  former  are  held  by  the  practical  farmer  is  sufficiently  clear. 

2°.  In  the  above  case  I  have  supposed  the  allowance  of  food  to  be 
such  only  as  a  person  of  sedentary  habits  would  consume,  and  the 
quantity  of  carbon  given  off  from  the  lungs  to  be  such  as  his  habits 
would  occasion.  But  if  the  weight  of  carbon  given  off  from  the  lungs 
and  skin  together  amount,  as  it  often  does,  to  15  ounces,*  the  quantity 
of  food  must  be  greatly  increased  beyond  the  quantity  I  have  stated, 
if  the  health  and  strength  are  to  be  sustained.  By  such  an  increase 
of  food — the  carbon  being  removed  by  respiration — the  proportion  of 
nitrogen  and  of  saline  matters  in  the  excretions  may  be  still  further 
increased,  or  as  manures  they  may  become  still  richer  and  more  irrir- 
mediately  fertilizing. 

3*^.  Let  me  present  to  you  the  results  of  an  actual  experiment  made 
by  Boussingault  upon  a  horse  fed  with  hay  and  oats — and  of  which 
both  the  food  and  the  excretions  were  carefully  analysed. 

In  24  hours  the  horse  consumed — 

Carbon.  Nitrogen.      Saline  matter. 

Hay,  16i  lbs..t  containing 45,500  grs.  1,500  grs.     8,960  grs. 

Oats,  5  lbs..' 15,000    »        650    "      1,180   « 

Total  in  the  food 60,500    "    ~2,150    «     lO^lio"" « 

And  gave  off  from  the  lungs  &  skin  37,960    " 

Leaving  to  be  rejected  in  the  ex- 
cretions   22,540    "     2,150    "     10,140    " 

While  there  was  actually  found  in 
the  mixed  dung 22,540    «     1,770    "     10,540  " 

•  Liebig  estimates  the  quantity  of  carbon  which  escapes  from  the  lungs  and  skin  of  a 
healthy  man,  taking  moderate  exercise,  af,  13-93  ounces  (Hessian),  or  15>^  ounces  avoirdu- 
pois, in  24  hours. 

t  Each  containing  about  14  per  eant.  of  vf&ter.—AnTiales  <l*  Jhim.  et  de  Pht/s.,  Ixx!.,  p.  136. 


474  STATE  i.V  WHICH  FARM-YARD  MANURE  CAN  BE 

In  this  case,  then,  the  carbon,  nitrogen,  and  saline  matter  were  con- 
tained in  the  proportion  of — 

Carbon.  Nitrogen.  Saline  matter. 

28  1  5     in  the  food, 

and  of  10^  1  5     in  the  dung ; 

The  analysis  of  the  dung  itself  proving  that  in  passing  through  the 
body  of  an  animal,  the  food — 

a  diminishes  very  considerably  in  weight ; 

h  losing  a  large  but  variable  proportion  of  its  carbon, 

c  but  parting  with  scarcely  any  of  its  nitrogen  and  saline  matter — 
and  therefore 

d  that  the  fertilizing  virtues  of  the  dung  above  that  of  the  food  of 
animals — weight  for  weight — depends  mainly  upon  the  larger  pro- 
portion of  these  two  constituents  (the  nitrogen  and  the  saline  matter) 
which  the  dung  contains. 

I  have  only  further  to  remind  you  upon  this  subject  that  the  state 
of  combination  also  in  which  the  nitrogen  exists  in  the  excretions  has 
a  material  influence  in  rendering  their  action  more  immediate  and 
sensible  than  that  of  unchanged  vegetable  matter.  It  passes  off  for 
the  most  part  in  the  form  of  urea,  which  is  resolved  into  ammonia  and 
its  compounds  more  rapidly  than  the  albumen  of  the  dried  or  even  of 
the  recent  plant,  and  is  thus  enabled  sooner  to  exert  an  appreciable 
influence  upon  the  growing  crop. 

§  17.  Of  farm-yard  manure,  and  of  the  state  in  which  it  ought 
to  he  applied  to  the  land. 

The  manure  of  the  farm-yard  consists,  for  the  most  part,  of  cow- 
dung  and  straw  mixed  and  trodden  together,  in  order  that  the  latter 
may  be  brought  into  a  state  of  decomposition.  In  the  improved  hus- 
bandry, where  green  crops  are  extensively  grown  and  many  cattle 
are  kept,  the  horse-dung  forms  only  a  small  proportion  of  the  whole 
manure  of  the  farm-yard. 

On  an  average,  the  quantity  of  recent  manure  obtained  in  the  farm- 
yard amounts  to  a  little  more  than  twice  the  weight  of  the  dry  food  of 
the  cattle  and  of  the  straw  spread  in  the  farm-yard  or  in  the  stables 
(p.  469).  That  is  to  say,  for  every  10  cwt.  of  dry  fodder  and  bedding, 
20  to  23  cwt.  of  fresh  dung  nit,  y  be  calculated  upon.  But  if  green 
clover  or  turnips  (every  100  lbs.  of  which  contain  from  70  to  90  lbs. 
of  water)  be  given  to  the  cattle,  an  allowance  must  be  made  for  the 
water  they  contain — the  quantity  of  mixed  manure  to  be  expected 
being  from  2  to  2 J  times  the  weight  of  the  dry  food  and  fodder  only. 

But  the  recent  manure  loses  weight  by  lying  in  the  farm-yard.  The 
moisture  evaporates  and  volatile  matters  escape  by  fermentation.  By 
the  time  that  the  straw  is  half  rotten  this  loss  amounts  to  one  fourth  of 
the  whole  weight,  while  the  bulk  is  diminished  one-half  If  allowed  to 
lie  still  longer  the  loss  increases,  till  at  length  it  may  approach  lo  one- 
half  of  the  whole,  leaving  a  weight  of  dung  little  greater  than  that  of 
the  food  and  straw  which  have  been  consumed.  The  weight  of  com- 
mon mixed  farm-yard  dung,  therefore,  obtained  from  10  cwt.  of  dry  food 
and  straw,  at  different  periods,  may  be  thus  stated  approximately — 


M03T   ECONOMICALLY    APPLIED   TO    THE   LAND.  475 

10  owl.  of  dry  food  and  straw  y.eld  of  recent  dung  23  to  25  cwt. 

At  the  end  of  six  weeks 21  cwt. 

After  eight  weeks 20  cwt. 

When  half-rotten 15  to  17  cwt. 

When  fully-rotten 10  to  13  cwt.  * 

These  quantities,  you  will  observe,  are  supposed  to  be  obtained  in 
the  common  open  farm-yards,  with  the  ordinary  slow  process  of  fer- 
mentation. An  improved,  quicker,  or  more  economical  mode  of  fer- 
menting the  mixed  dung  and  straw  may  be  attended  with  less  loss 
and  may  give  a  larger  return  of  rich  and  fully-rotten  dung. 

A  knowledge  of  these  facts  shows  clearly  what  is  the  most  eco- 
nomical form  in  which  farm-yard  manure  can  be  applied  to  the  land. 

P.  The  more  recent  the  manure  from  a  given  quantity  of  food  and 
straw  is  ploughed  in,  the  greater  the  quantity  of  organic  matter  we 
add  to  the  land.  When  the  only  object  to  be  regarded,  therefore, 
is  the  general  enriching  of  the  soil,  this  is  the  most  economical  and 
the  most  expedient  form  of  employing  farm-yard  manure. 

2°.  But  where  the  soil  is  already  very  light  and  open,  the  plough- 
ing in  of  recent  manure  may  make  it  still  more  so,  and  may  thus  ma- 
terially injure  its  mechanical  condition.  In  such  a  case  the  least  of 
two  evils  must  be  chosen.  It  may  be  better  husbandry — that  is,  more 
economical — to  allow  the  manure  to  ferment  and  consolidate  in  the 
farm-yard  with  the  certainty  of  a  considerable  loss,  than  to  diminish 
the  solidity  of  the  land  by  ploughing  it  in  in  a  recent  state. 

3°.  Again — in  the  soil,  a  fermentation  and  decay  similar  to  that 
which  takes  place  in  the  farm-yard  will  slowly  ensue.  The  benetii 
which  generally  follows  from  causing  this  fermentation  to  take  place  in 
the  field  rather  than  in  the  open  yard  is,  that  the  products  of  the  decom- 
position are  taken  up  by  the  soil,  and  thus  waste  is  in  a  great  measure 
prevented.  But  in  very  light  and  open  soils,  this  absorption  of  the  pro- 
ducts of  decay  does  not  take  place  so  completely.  The  rains  wash  out 
some  portions,  while  others  escape  into  the  air,  and  thus  by  burying  the 
recent  manure  in  such  soils,  less  of  that  waste  is  prevented  which  when 
.ft1t  in  the  open  air  it  is  sure  to  undergo.  It  may  even  happen,  in  some 
cases,  that  the  waste  in  such  a  soil  will  not  be  greatly  inferior  to  that 
which  necessarily  takes  place  in  the  farm-yard.  The  practical  man, 
therefore,  may  question  whether,  as  a  general  rule,  it  would  not  be  safer 
in  farming  very  light  arable  lands,  to  keep  his  manure  in  heaps  till  it  is 
well  fermented,  and  to  adopt  those  means  for  preventing  waste  in  the 
heaps  themselves  which  science  and  practical  skill  point  out  to  him. 

It  may  be  regarded  indeed  as  a  prudent  and  general  opinion  to  hold 
— one,  however,  which  must  not  be  maintained  in  regard  to  any  par- 
ticular tract  of  land  in  opposition  to  the  results  of  enlightened  expe- 
rience— that  recent  farm-yard  manure  [Long  dung)  is  not  suited  to 
very  light  soils,  because  it  will  render  them  still  Hghter,  and  because 
m  them  the  manure  may  suffer  almost  as  Kuch  waste  as  in  the  farm- 

*  In  an  excellent  little  practical  work  printed  for  private  circulation,  under  the  title  of 
"  Notes  on  the  Culture  and  Cropping  of  Arable  LMnd,"  by  the  late  Dr.  Coventry,  of  Edin- 
burgh, the  reader  will  find  a  valuable  section  upon  manures.  The  most  complete  work 
now  in  existence  upon  the  general  subject  of  agricultural  statics,  is  that  of  Hlubek,  DieEV' 
ndhrung  der  PJlanzcn  une  die  iStatik  dea  Landbaues. 


476  AFFECTED    liY    THE    I^RPOSE    IT   IS   TO    SERVE. 

yard  ; — and,  therefore,  that  into  such  soils  it  should  be  ploughed  m 
the  compact  state  (short  dung)^  and  as  short  a  time  as  possible  be- 
fore the  sowing  of  the  crop  which  it  is  intended  to  benefit. 

4°.  But  Upon  loamy  and  clay  soils  the  contrary  practice  is  recom- 
mended. Such  soils  will  not  be  injured,  they  may  even  be  benefitted 
by  the  opening  tendency  of  the  unfermented  straw,  while  at  the  same 
time  the  products  of  its  decomposition  will  be  more  completely  re- 
tained— the  land  consequently  more  enriched,  and  the  future  crops 
more  improved  by  it.  On  such  soils,  the  recent  dung  ploughed  in,  in 
the  autumn,  has  been  found  greatly  more  influential  upon  the  crops 
of  corn  which  followed  it,  either  in  winter  or  in  spring,  than  a  propor- 
tional quantity  of  well  fermented  manure.  By  such  treatment,  in- 
deed, the  whole  surface  soil  is  converted  into  a  layer  of  compost,  in 
which  a  slow  fermentation  proceeds,  and  which  reaches  its  most  fer- 
tilizing condition  when  the  early  spring  causes  the  young  corn  to  seek 
for  larger  supplies  of  food. 

"5^.  But  the  nature  of  the  crop  he  is  about  to  raise  will  also  influ- 
ence the  skilful  farmer  in  his  application  of  long  or  short  dung  to  his 
land.  If  the  crop  is  one  which  quickly  springs  up,  runs  through  a 
short  life,  and  attains  an  early  maturity,  he  will  apply  his  manure  in 
such  an  advanced  state  of  fermentation  as  may  enable  it  immediately 
to  benefit  the  rapidly  growing  plant.  In  this  case,  also,  it  may  be 
better  to  lose  a  portion  by  fermenting  it  in  the  farm-yard,  than,  by  ap- 

E lying  his  manure  fresh,  to  allow  his  crop  to  reach  nearly  to  maturity 
efore  any  benefit  begins  to  be  derived  from  it. 
6°.  So  also  the  purpose  for  which  he  applies  his  manure  will  regu- 
late his  procedure.  In  manuring  his  turnips  the  farmer  has  two  dis- 
tinct objects  in  view.  He  wishes,  first,  to  force  the  young  plants  for- 
ward so  rapidly  that  they  may  get  into  the  second  leaf  soon  enough 
to  preserve  them  from  the  ravages  of  the  fly — and  afterwards  to  fur- 
nish them  with  such  supplies  of  food  as  shall  keep  them  growing  till 
they  have  attained  the  most  profitable  size.  For  the  former  purpose 
fermented  manure  appears  to  be  almost  indispensable — if  that  of  the 
farm-yard  is  employed  at  all — for  the  latter,  manure,  in  the  act  of  slow 
and  prolonged  decomposition,  is  the  most  suitable  and  expedient. 

It  is  because  bone-dust  is  admirably  adapted  for  both  purposes,  that 
it  has  become  so  favourite  a  manure  in  many  districts  for  the  turnip 
crop.  The  gelatine  of  the  outer  portion  of  the  bones  soon  heats,  fer- 
ments, and  gives  off  those  substances  by  which  the  young  plant  is 
benefitted — while  the  gelatine  in  the  interior  of  the  bone  decays,  lit- 
tle by  little,  and  during  the  entire  season  continues  to  feed  the  ma- 
turing bulb.  Rape-dust,  when  drilled  in,  acts  in  a  similar  manner,  if 
the  soil  be  sufiiciently  moist.  It  may  be  doubted,  however,  whether 
its  effects  are  so  permanent  as  those  of  bones. 

The  considerations  I  have  now  presented  will  satisfy  you  that  the 
disputes  which  have  prevailed  in  regard  to  the  use  of  long  and  short 
dung  have  arisen  from  not  keeping  sufficiently  distinct  the  two  ques- 
tions— what  is  theoretically  the  best  form  in  which  farm-yard  dung 
can  be  applied  in  general  7 — and  what  is  theoretically  and  practical- 
ly  the  best  form  in  which  it  can  be  applied  to  this  or  to  that  crop,  or 
for  this  or  for  that  special  object  ? 


TOP-DRESSING   WITH    FERMENTING    MANURES.  77 

§  18.   Of  top-dressing  with  fermenting  manures. 

If  so  large  a  waste  occur  in  the  farm-yard  where  the  manure  is 
left  long  to  ferment — can  it  be  good  husbandry  to  spread  fermenting 
manure  as  a  permanent  top-dressing  ov«r  the  surface  of  the  fields  ? 
This,  also,  is  a  question  in  regard  to  which  different  opinions  are 
entertained  by  practical  men. 

That  a  considerable  waste  must  attend  this  mode  of  application  there 
can  be  no  doubt.  Volatile  matters  will  escape  into  the  air  and  saline 
substances  may  be  washed  away  by  the  rains,  and  yet  there  are  many 
good  practical  farmers  who  consider  this  mode  of  applying  such  manure 
to  be  in  certain  cases  as  profitable  as  any  that  can  be  adopted.    Thus — 

1".  It  is  common  in  spring  to  apply  such  a  top-dressing  to  old  pas- 
ture or  meadow  lands,  and  the  increased  produce  of  food  in  the  form  of 
grass  or  hay  is  believed  to  be  equal,  at  least,  to  what  would  have  been 
obtained  from  the  same  quantity  of  manure  employed  in  the  raising 
of  turnips.  Where  such  is  really  the  case,  experience  decides  the 
question,  and  pronounces  that  notwithstanding  the  loss  which  must 
occur,  this  m.ode  of  applying  the  manure  is  consistent  with  good 
husbandry.  But  if  the  quantity  or  market  value  of  the  food  raised  by 
a  ton  of  manure  applied  in  this  way  is  not  equal  to  what  it  would 
have  raised  in  turnips  and  corn,  then  it  may  as  safely  be  said  that 
the  most  economical  method  of  employing  it  has  not  been  adopted. 

But  theory  also  throws  some  mteresting  light  upon  this  question. 

Old  grass  lands  can  only  be  manured  by  top-dressings.  And  if 
they  cannot  continue,  and  especially  such  as  are  meadowed,  to  yield 
an  average  produce,  unless  there  be  now  and  then  added  to  the  soil 
some  of  those  same  substances  which  are  carried  off  in  the  crop,  it 
appears  to  be  almost  necessary  that  farm-yard  dung  should  now  and 
then  be  applied  in  some  form  or  other.  It  is  true  that  hay  or  straw 
or  long  dung  contains  all  the  elements  which  the  growing  grass  re- 
quires, but  if  spread  on  the  surface  of  the  field  and  then  allowed  to 
ferment  and  decay,,  the  loss  would  probably  be  still  greater  than  when, 
for  this  purpose,  it  is  collected  into  heaps  or  strewed  in  the  farm-yard. 
Thus  the  usual  practice  of  laying  on  the  manure  in  a  highly  fer- 
mented state  may  be  the  most  economical. 

2°.  Again,  where  the  turnip  crop  is  raised  in  whole  or  in  part  by 
means  of  bones  only,  of  rape  dust,  or  of  other  artificial  manures,  as  they 
are  called^  it  is  usual  to  expend  a  large  proportion  of  the  farm-yard  dung 
in  top-dressing  the  succeeding  crop  of  clover.  Thus  the  land  obtains 
two  manurings  in  the  course  of  the  four  years'  rotation — bones  or  rape- 
dust  with  the  turnips — and  fermented  dung  with  the  clover.  This 
second  application  increases  the  clover  crop  in  some  districts  one-fourth 
and  the  after-crop  of  wheat  or  barley  very  considerably  also.  [Such 
is  the  case  upon  some  of  the  fiirms  in  the  Vale  of  the  Tame  (Stafford- 
shire,) where  the  turnips  are  raised  with  rape-dust,  and  wheat  follows 
the  clover.] 

Here,  also,  it  is  clear,  that  if  manure  be  necessary  to  the  clover,  it 
can  only  be  applied  in  the  form  of  a  top-dressing.  But  why  is  it  ne- 
cessary, as  experience  says,  and  why  should  farm-yard  manure,  which 
is  known  to  suffer  waste,  be  applied  as  a  top-dressing  rather  than 


478  EATING   OFF   COMPARED    WITH    GREEN    MANURING. 

rape-dust,  which  in  ordinary  seasons  is  not  so  Ukely  to  suffer  loss  1 
1  offer  you  the  following -explanation: — 

If  you  raise  your  turnip  crop  by  the  aid  of  the  bones  or  rape-dust  eJone 
you  add  to  the  soil  what,  in  most  cases,  may  be  sufficient  to  supply  near- 
ly all  the  wants  of  that  crop^ut  you  do  not  add  ail  which  the  succeed- 
ing crops  of  corn  and  clover  require.  Hence  if  these  crops  are  to  be 
grown  continuously,  and  for  a  length  of  time,  some  other  kind  of  ma- 
nure must  be  added — in  which  those  necessary  substances  or  kinds 
of  food  are  present  which  the  bones  and  rape-dust  cannot  supply. 
Farm-yard  manure  contains  them  all.  This  is  within  the  reach  of 
every  farmer.  It  is,  in  fact,  his  natural  resource  in  every  such  diffi- 
culty. He  has  tried  it  upon  his  clover  crop  in  the  circumstances  we 
are  considering,  and  has  necessarily  found  it  to  answer. 

Thus  to  explain  the  results  at  which  he  has  arrived  in  this  special 
case,  chemical  theory  only  refers  the  practical  man  to  the  general  prin- 
cipls  upon  which  all  scientific  manuring  depends — that  he  must  add  to 
the  soil  sufficient  supplies  of  every  thing  he  carries  off  in  his  crops — and, 
therefore,  without  some  such  dressing  as  he  actually  applies  to  his 
clover  crop,  he  could  not  long  continue  to  grow  good  crops  of  any  kind 
upon  his  land,  if  he  raise  his  turnips  with  bones  or  rape-dust  only. 

Ii  might,  I  think,  be  worthy  of  trial,  whether  the  use  of  the  fer- 
mented dung  for  the  turnips,  and  of  the  rape-dust  for  top-dressing  the 
after-crops,  would  not,  in  the  entire  rotation,  yield  a  larger  and  more 
remunerating  return. 

§  19.  Of  eating  off  witn,  sheep. 

The  practical  advantages  derived  from  eating  off  turnips  and  clover 
crops  with  sheep  are  mainly  of  two  kinds.  Light  lands  are  trodden 
down  and  solidified,  and  they  are  at  the  same  time  equably  and  more 
or  less  richly  manured.  With  this  latter  effect,  that  of  manuring, 
some  interesting  practical  facts  and  theoretical  considerations  are 
connected.     Thus — 

1°.  In  the  preceding  lecture  (p.  419)  I  mentioned  to  you  that  in  some 
parts  of  Germany,  spurry,  among  other  plants,  is  extensively  grown, 
and  with  much  profit,  for  ploughing  in  as  a  green  manure.  Now  it  is 
mentioned  that  the  crops  of  rye  which  follow  a  crop  of  spuriy  are  some- 
times quite  as  great  when  it  has  been  eaten  off  with  sheep  or  cattle  as 
when  it  has  been  ploughed  in  (Von  Voght,  Uber  Manche  Vortheile 
der  gruner  dungung.) 

2°.  In  accordance  with  this  statement  is  the  opinion  of  many  skil- 
ful practical  men  among  ourselves,  that  a  crop  of  clover  or  of  tares 
will  cause  a  larger  after-growth  of  corn,  if  it  be  eaten  off  with  sheep, 
than  if  it  be  ploughed  in  in  the  green  state. 

The  correctness  of  these  practical  observations  appears  from  a 
brief  consideration  of  one  of  those  interesting  theoretical  questions 
we  have  recently  been  discussing. 

When  a  crop  is  eaten  off  by  full-growm  animals,  it  returns  again  to 
the  soil,  deprived  of  a  portion  of  its  carbon  only  (p.  473.)  The  manure 
contains  all  the  nitrogen  and  saline  matter  of  the  green  vegetables,  and 
in  a  state  in  which  they  are  more  immediately  available  to  the  uses  of 
the  young  plant.     Thus  far,  then,  we  can  understand  that  in  certain 


IMPROVEMENT    OF   THE    SOIL    BY    IRRIGA''nON.  479 

cases  a  crop  may  appear  to  fertilize  the  land  more  after  it  has  been  eaten 
and  digested,  than  if  it  had  been  ploughed  in  green,  and  we  can  recog- 
nize the  correctness  of  the  opinion  at  which  practical  men  have  arrived. 

But  theory  does  not  forsake  us  here.  As  in  all  other  cases  in  which 
it  furnishes  a  true  explanation  of  known  facts,  it  points  to  new  facts  also, 
which  more  or  less  modify  our  received  opinions,  and  define  the  limits 
within  which  their  truth  can  be  rigorously  maintained.     Thus — 

1°.  Theory  says  that  if  the  animals  fed  upon  the  green  crop  be  in  a 
growing  state — if  they  be  increasing  in  muscle  or  in  bone — they  will 
not  only  dissipate  through  their  lungs  and  skin  a  portion  of  its  carbon, 
but  will  retain  also  a  part  of  its  nitrogen  and  saline  matter,  and  will 
thus  return  to  the  soil,  in  their  excretions,  a  smaller  quantity  of  these 
substances  than  the  crop  would  have  given  to  i*  if  ploughed  in  green. 
If,  therefore,  a  maximum  fertilizing  effect  is  to  ^e  produced  upon  a 
field  by  eating  off  a  green  crop,  it  is  not  altogetner  a  matter  of  indif- 
ference what  kind  of  animals  we  employ  as  digesters. 

2°.  Again,  the  practice  of  green  manuring  is  resorted  to  chiefly 
upon  soils  which  are  poor  in  organic  matter — to  which  the  carbon  of 
the  green  crop  is  of  consequence,  as  well  as  the  nitrogen  and  saline 
matter  it  contains.  But  when  eaten  off,  much  carbon  is  lost  to  the 
soil,  and  thus  the  supply  of  organic  matter  which  it  ultimately  gets  is 
considerably  less  than  if  the  crop  it  bore  had  been  ploughed  in  in  the 
green  state.  Such  soils,  then,  cannot  be  equally  enriched  by  the 
former  as  by  the  latter  method. 

This  case  presents  a  very  interesting  illustration,  and  one  which  you 
can  readily  appreciate,  of  the  kind  of  useful  information  which  thioreti- 
cal  chemistry  is  capable  of  imparting  upon  almost  every  branch  of  prac- 
tical agriculture.  It  says  to  the  farmer — yes,  you  may  in  some  cases, 
certainly,  eat  off  the  crop,  with  advantage — but  if  you  wish  to  do  most 
good  to  your  land  you  must  eat  it  off  with  fattening,  not  with  growing 
sheep — and  you  must  do  so -upon  soils  which  are  not  very  poor  in 
vegetable  matter.  And  that  explains  to  me  also,  says  the  practical 
man,  in  reply,  why  I  have  always  found  sheep-folding  to  be  most  be- 
neficial on  soils  which  are  rich  in  vegetable  matter*  (p.  468.) 

§  20.  Of  the  improvement  of  the  soil  by  irrigation. 

Irrigation,  as  it  is  practised  in  our  climate,  is  only  a  more  refined 
method  of  manuring  the  soil.  In  warm  climates,  where  the  parched 
plant  would  wither  and  die  unless  a  constant  supply  of  water  were 
artificially  afforded  to  it,  irrigation  may  act  beneficially  by  merely 
yielding  this  supply  to  the  growing  crops  ;  but  in  our  latitudes  only 
a  small  part  of  its  beneficial  effects  can  be  ascribed  to  this  cause.  It 
is  to  pasture  and  meadow  land  almost  solely  that  irrigation  is  applied 
by  British  farmers,  and  the  good  effect  it  produces  is  to  be  explained 
oy  a  reference  to  various  and  natural  causes. 

1°.  If  the  water  be  more  or  less  muddy,  bearing  with  it  solid  matter 
which  deposites  itself  in  still  places,  the  good  effects  which  follow  its 

*  Sprengel  explains  this  fact  by  alleging  that  the  humic  acid  of  the  vegetable  matter  re- 
tains more  effectually  the  ammonia  of  the  decomposing  dung.  There  may  be  something 
in  this,  but  more,  in  mcst  cases,  I  think,  in  the  fact  that  digestion  separates  much  of  the 
carbon  in  which  the  soils  abound,  but  returns  the  nitrogen  and  saline  matter  almost  en- 
tirely and  in  a  more  active  state. 


480  Tire    WATER    SHOULD    NOT    BE    STAGNANT. 

diJfTusion  over  the  soil  may  be  ascribed  to  the  layer  of  visible  manure 
which  it  leaves  everywhere  behind  it.  Thus  the  Nile  and  the  Ganges 
fertilize  the  lands  over  which  their  annual  floods  extend,  and  partly 
m  this  way  do  some  of  our  smaller  streams  improve  the  fields  over 
which  they  either  naturally  flow  or  are  artificially  led. 

2°.  Or  if  the  water  hold  in  solution,  as  the  hquid  manures  of  the 
farm-yard  do,  substances  on  which  plants  are  known  to  feed,  then  to 
diffuse  them  over  ilie  surface  is  a  simple  act  of  liquid  manuring,  from 
which  the  usual  benefits  foflow.  Such  is  the  irrigation  which  is  prac- 
tised in  the  neighborhood  of  our  large  towns,  where  the  contents  ol" 
the  common  sewers  are  discharged  into  the  waters  which  subsequent- 
ly spread  themselves  over  the  fields.  (For  an  interesting  account  of 
the  effects  of  such  irrigation  in  the  neighborhood  of  Edinburgh,  see 
Stephens,  On  IiTigaUon  and  Draining,  p.  75.)  In  so  far  also  as  any 
streams  can  be  supposed  to  hold  in  solution  the  washings  of  towns  or 
of  higher  lands — and  there  are  few  which  are  not  more  or  less  im- 
pregnated in  this  manner — so  far  may  their  beneficial  action,  when 
employed  for  purposes  of  irrigation,  be  ascribed  to  the  same  cause. 

3°.  But  spring  waters  which  have  run  only  a  short  way  from  their 
source  are  occasionally  found  to  be  valuable  irrigators.  In  such  cases, 
also,  the  good  effect  may  be  due  in  vihoie  or  in  part  to  substances  held 
in  solution  by  the  water.  Thus,  in  lime-stone  districts,  and  especially 
those  of  the  mountain  lime-stone  formation  (Lee.  XL,  §  8,) — in  which 
copious  springs  are  not  unfrequently  met  with — the  water  is  generally 
impregnated  with  much  carbonate  of  lime,  which  it  slowly  deposites  as 
it  flows  away  from  its  source.  To  irrigate  with  such  water  is,  in  a  re- 
fined sense,  to  lime  the  land,  and  at  the  same  time  to  place  within  the 
reach  of  the  growing  plants  an  abundant  supply  of  this  substance,  in  a 
form  in  which  it  can  readily  enter  into  their  roots.  (Some  of  the  water 
used  in  the  well-known  scientific  irrigations  at  Closeburn  Hall,  in 
Dumfries-shire,  appears  to  have  been  impregnated  with  lime.  See 
Stephens,  p.  43.) 

In  other  districts,  again,  the  springs  contain  gypsum  and  common 
salt,  and  sulphate  of  soda  and  sulphate  of  magnesia,  and  thus  are  ca- 
pable of  imparting  to  plants  many  of  those  inorganic  forms  of  matter, 
without  which,  as  we  have  seen,  they  cannot  exhibit  a  healthy  growth. 

4°.  Again,  it  is  observed  that  the  good  effects  of  irrigation  are  pro- 
duced only  by  running  watei — coarse  grasses  and  marsh  plants  spring- 
ing up  when  the  water  is  allowed  to  stagnate  (_Low's  Elements  of 
Agriculture^  3d  edition,  p.  472.)  This  is  explamed  in  part  by  the 
fact  that  a  given  quantity  of  water  will  soon  be  deprived  of  that  por- 
tion of  matter  held  in  solution,  of  which  the  plants  can  readily  avail 
themselves,  and  that  when  this  is  the  case  it  can  no  longer  contribute 
to  their  growth  in  an  equal  degree. 

But  there  is  another  virtue  in  running  water,  which  makes  it  more 
wholesome  in  the  living  plant.  It  comes  upon  the  field  charged  with 
gaseous  matter,  with  oxygen  and  nitrogen  and  carbonic  acid,  in  propor- 
tions very  different  from  those  in  which  these  gases  are  mixed  together 
in  the  air  (Lee.  II.,  §  6.)  To  the  root,  and  to  the  leaf  also,  it  carries 
these  gaseous  substances.  The  oxygen  is  worked  up  in  aiding  the 
decomposition  of  decaying  vegetable  matter.     The  carbonic  acid  is 


A  GOOD  DRAINAGE  NECESSARY.  48* 

absorbed  by  and  feeds  the  plant.  Let  the  same  water  remain  on  the 
same  spot,  and  its  supply  of  these  gaseous  substances  is  soon  ex- 
hausted. In  its  state  of  rest  it  re-absorbs  new  portions  from  the  air 
with  comparative  slowness.  But  let  it  flow  along  the  surface  of  the 
field,  exposing  every  moment  new  particles  to  the  moving  air,  and  it 
takes  in  the  carbonic  acid  especially  with  much  rapidity — and  as  it 
takes  it  from  the  air,  almost  as  readily  again  gives  it  up  to  the  leaf  or 
root  with  which  it  first  comes  in  contact.  This  is  no  doubt  one  of  the 
more  important  of  the  several  purposes  which  we  can  understand 
running  water  to  serve  when  used  for  irrigation. 

But  further,  if  water  be  allowed  to  stagnate  over  the  finer  grasses, 
they  soon  find  themselves  ih  circumstances  in  which  it  is  not  consist- 
ent with  their  nature  to  exhibit  a  healthy  growth.  They  droop, 
therefore,  and  die,  and  are  succeeded  by  new  races,  to  which  the  wet 
land  is  more  congenial. 

5^.  It  is  known  also,  that  even  running  water,  if  kept  flowing  with- 
out intermission  for  too  long  a  period,  will  injure  the  pasture.  This 
is  because  a  long  immersion  in  water  induces  a  decay  of  vegetable 
matter  in  the  soil  which  is  unfavorable  to  the  growth  of  the  grasses — 
producing  chemical  compounds  which  are  not  naturally  formed  in 
those  situations  in  which  the  grasses  delight  to  grow,  and  which  are 
unwholesome  .to  them.  Although,  therefore,  the  water  continues  to 
support  those  various  kinds  of  food  by  which  the  grasses  are  benefit- 
ted, yet  it  becomes  necessary  to  withdraw  it  for  a  time,  in  order  that 
other  injurious  consequences  may  be  avoided. 

6°.  Lastly. — Irrigation  is  most  beneficial  where  the  land  is  well 
drained  beneath — where  the  water,  after  the  irrigation  is  stopped,  can 
sink  and  find  a  ready  outlet.  The  same  benefits  indeed  flow  from  the 
draining  of  irrigated  as  from  that  of  arable  lands.  The  soil  and  sub- 
soil are  at  once  washed  free  of  any  noxious  substances  they  may 
naturally  contain,  or  may  have  derived  from  the  crops  they  have 
grown,  and  are  manured  and  opened  by  the  water  which  passes 
through  them.  As  the  water  descends  also,  the  air  follows  it,  to 
change  and  mellow  the  under-soil  itself 

Such  are  the  main  principles  upon  which  the  beneficial  action  of 
irrigation  depends,  and  they  appear  to  me  satisfactorily  to  account 
for  all  the  facts  upon  the  subject  with  which  I  am  acquainted.  I 
pass  over  the  alleged  beneficial  action  of  water  in  keeping  the  tem- 
perature of  irrigated  fields  from  sinking  too  low.  As  irrigation  is 
practised  in  our  islands,  little  of  the  good  done  to  watered  meadows 
can  be  properly  attributed  to  this  cause. 


1  have  now  drawn  your  attention  to  the  most  important  and  readily 
available  means,  mechanical  and  chemical,  for  improving  the  soil. 
Let  us  next  study  the  products  of  the  soil — their  composition,  their 
diflferences,  and  the  purposes  they  are  intended  to  serve  in  the  feed 
ing  and  nourishment  of  animals. 


LECTURES 

ON  THE 

APPLICATIONS  OF  CHEMISTRY  AND  GEOLOGY 

'^  *  TO 

AGRICULTURE. 


ON  THE  PRODUCTS  OF  THE  SOIL,  AND  THEIR 
USE  IN  THE  FEEDING  OF  ANIMALS, 


21 


LECTURE  XIX. 

Of  the  produce  of  the  soil.— Average  produce  of  England  and  Scotland.—Clrcumstanceg  by 
which  the  produce  of  the  land  is  affected.— Inlluence  of  climate,  of  season,  of  soil,  of  the 
kind  and  variety  of  crop,  of  the  method  of  culture,  and  of  the  course  of  cropping. — Theory 
of  the  rotation  of  crops.— Why  lands  become  tired  of  clover  (clover-sick)  and  other  special 
crops.— Theory  of  fallowrs.— Composition  of  wheat,  oats,  barley,  rye,  and  Indian  com.— In- 
fluence of  climate,  soil,  manure,  variety  of  seed,  mode  of  culture,  and  time  of  cutting,  upon 
the  composition  of  these  grains. — Effect  of  baking  upon  bread. — Supposed  relation  between 
the  weight  of  bread  and  the  proportion  of  gluten. — Effect  of  germination  (malting)  upon 
barley.— Composition  of  peas,  beans,  and  vetches.- Effects  of  soil,  &c.,  upon  the  boiling 
quality  of  pea.-?  —Composition  of  the  turnip,  the  carrot,  the  beet,  and  the  potatoe. — Effect 
of  soil,  age,  size,  rapidity  of  growth,  &c.,upon  their  composition. — Relative  proportions  of 
nutritive  matter  produced  by  different  crops  on  the  same  extent  of  ground. — Composition 
of  the  grasses  and  clovers.- Effect  of  soils,  manures,  time  of  cutting,  mode  of  drying,  «&c., 
upon  their  composition  and  nutritive  value. 

Having  now  considered  the  most  important  of  those  means  by  which 
tbe  soil  may  be  improved,  it  will  be  proper  to  direct  our  attention  to  that 
which  the  land  produces — to  the  chemical  nature  of  the  crops  you  raise, 
to  the  differences  which  exist  among  them,  and  to  the  purposes  they  are 
fitted  to  serve  in  the  feeding  of  man  and  other  animals. 

Agricultural  products  are  of  three  distinct  kinds  : 

1°.  Such  as  are  directly  reaped  from  the  soil  in  the  form  of  corn,  pota- 
toes, hay,  (fee. 

2°.  Such  as  are  the  result  of  a  kind  of  natural  process  of  manufacture, 
by  which  the  direct  produce  of  the  soil  is  more  economically  converted 
into  the  beef  and  mutton  of  the  feeder  of  stock. 

3°.  Such  as  are  the  results  of  a  further  conversion  at  the  hands  of  the 
dairy  farmer,  and  are  sent  to  market  in  the  form  of  butter  and  cheese. 

Thus  three  distinct  topics  of  consideration  present  themselves  in  con- 
nection, with  the  produce  of  the  soil, — the  nature  of  the  immediate  pro- 
ducts themselves — the  economy  of  the  feeding  of  stock — and  the  prepara- 
tion of  butter  and  cheese.  We  shall  study  these  several  topics  in  titair 
natiual  order. 

§  1.  Of  the  maximum  or  greatest  possible,  and  the  average  or  actual^ 
produce  of  the  land. 

There  is  a  wide  difference  in  most  countries  between  the  actual 
amount  of  food  produced  by  the  land,  and  that  which,  in  the  most  fa- 
vourable circumstances,  it  would  delight  to  yield. 

An  imperial  acre  of  land  in  our  island  has  been  known  to  yield  of 
wheat  70  bushels,*  barley  80  bushels,  oats  100  bushels,  potatoes  30 
tons, I  and  turnips  60  tons.  J 

The  average  produce  of  the  land,  however,  is  far  below  these  quanti- 
ties.    It  is  not  easy  to  arrive  it  a  tolerable  approximation  even  to  the 

•  In  the  county  of  Middlesex  the  produce  of  wheat  varies  from  12  to  68  bushels— of  bar- 
ley from  15  to  75— and  of  oats  from  32  to  96  bushels.— itfidd/e/on's  View  of  the  Agricul- 
ture of  Middlesex,  1798,  pp.  176,  183,  and  188. 

t  See  Mr.  Fleming's  experiments  upon  potatoes  in  the  Appendix. 

t  Perhaps  this  is  not  the  maximum.— In  iYve  Second  Report  of  the  Royal  Agricullurcd  Im- 
provement Society  of  Ireland^  p.  57,  a  crop  of  turnips  is  mentioned,  which  weighed  56  tons- 
tops  and  bulbs  amounting  together  to  76  tons. 


488  PRODUCE    OF    THE    LAND    IN    GREAT    BRITAIN. 

true  average  produce  of  the  island.     Mr.  Macculloch  estimates  that  of 
wheat  at  26  bushels  an  acre,  barley  at  32,  and  oats  at  36. 

Sir  Charles  Lemon  gives  for  the  average  produce  of  all  England,  and 
for  the  highest  and  lowest  county  averages,  the  following  numbers— 


Wlieat    -     ■ 
Barley    -     • 
Oats  -     -     ■ 

Average  for 
all  England 
in  bushels. 

-  -        21 

■     -       32| 

-  -       351 

Highest 
county  average 
in  bushels. 
26  NoHinghamsliire. 
40  Huntingdon. 
48  Lincolnshire. 

Lowest 

county  average 

in  bushels. 

16  Dorset. 
24  Devon. 
20  Gloucester. 

Potatoes  -     ■ 

•     -     241 

360  Cheshire. 

100  Durham. 

While  in  Scotland,  according  to  Mr.  Dudgeon,  the  average  produce 
of  corn  is — 

Good  land.  Lighter  land. 

Wheat     -     -     -     -   30  to  32  bushels.         22  to  26  bushels. 
Barley     -     -     -     -  40  to  44       do.  34  to  38       do. 

Oats 46  to  50       do.  36  to  43       do. 

If  these  numbers  of  Sir  Charles  Lemon  and  of  Mr.  Dudgeon  are  to  be 
depended  upon,  the  averages  for  the  whole  island  cannot  be  far  from 
wheat  24  bushels,  barley  34  bushels,  oats  37  bushels,  potatoes  6  tons, 
and  turnips  10  tons. 

Though  even  these,  especially  in  regard  to  the  root  crops,  must  be 
considered  as  in  a  considerable  degree  hypothetical.* 

What  is  the  cause  of  the  striking  differences  above  exhibited  between 
the  maximum  produce  of  certain  parts  of  the  island  and  the  average  pro- 
duce of  the  whole  ?  Are  such  differences  necessary  and  unavoidable  ? 
Can  the  less  productive  lands  not  be  made  to  yield  a  larger  return  ? 
Can  the  large  crops  of  the  richer  districts  not  be  further  increased,  and 
their  amount  kept  up  for  an  indefinite  succession  of  seasons  ? 

These  interesting  questions  lie  at  the  foundation  of  all  agricultural  im- 
provement— and  skill  and  science  answer  that,  though  differences  to 
a  certain  amount  are  unavoidable,  yet  that  means  are  already  known 
by  which  the  fertility  of  the  richer  lands  may  be  maintained,  and  the 
crops  of  the  less  productive  indefinitely  enlarged. 

§  2.  Of  the  circumstances  by  ivhich  the  produce  of  food  is  affected—' 
climate,  season,  soil,  S^-c. 

The  quantity  of  food  produced  by  a  given  extent  of  land  is  affected  by 
the  climate,  by  the  season,  by  the  soil,  by  the  nature  of  the  crop,  by  the 
variety  sown  or  planted,  by  the  geneidl  method  of  culture,  and  by  the  ro- 
tation or  course  of  cropping  that  is  adopted. 

1°.  Climate. — That  the  warmth  of  the  climate,  the  length  of  the  sum- 
mer, -and  the  quantity  of  rain  that  falls,  influence  in  a  remarkable  degree 
the  amount  of  food  which  a  district  of  country  is  fitted  to  raise,  is  fa- 
miliar to  every  one.  The  warmth  of  the  equatorial  regions  maintains  a 
perpetual  verdure,  while  the  short  northern  summers  afford  only  a  few 
months  of  pasture  to  the  stunted  cattle.  The  difference  of  latitude  be- 
tween the  extreme  ends  of  our  island  produces  a  similay  difference,  though 
in  a  less  degree.     The  almost  perennial  verdure  of  the  southern  counties 

•  In  1821,  Mr.  Wakefield  estimated  the  average  produce  of  wheat  in  all  England  at  17 
bushels  only— Devonshire  producing  an  average  of  20,  and  the  lands  netir  the  coast  of  Kent, 
Norfolk,  Suffolk,  and  Essex,  40  bushels  per  acre. 


INFLUENCTE    OF   CLIMATE,    SEASON,   AND   SOIL.  489 

cannot  be  hoped  for  in  the  north  of  Scotland,  and  yet  it  is  said  that  in 
parts  of  Ross-shire  the  com  and  turnip  crops  are  equal  to  those  of  the 
most  favoured  districts  of  Britain.  Is  this  to  be  regarded  solely  as  the 
triumph  of  skill  and  industry  over  the  ditficulties  presented  by  nature  ? 

2°.  Season. — The  influence  of  the  seasons,  wet  or  dry,  warm  or  cold, 
has  been  observed  by  the  farmer  in  all  ages,  and  it  cannot  be  entirely 
overcome.  The  heavy  crop  of  this  year  may  not  be  reaped  again  on 
the  next,  because  an  unusual  cold  may  arrest  its  growth.  And 
yet  good  husbandry  will  do  much  even  here — since  the  higher  the  farm- 
ing the  fewer  the  number  of  failures  which  the  intelligent  man  will 
have  occasion  to  lament. 

3°.  Soil. — Diversity  of  soil  is  held  to  be  a  sufficient  reason  for  diflfer- 
ence  both  in  kind  and  in  weight  of  crop.  A  poor  sand  is  not  expected  to 
give  the  same  return  as  a  rich  clay.  Yet  in  regard  to  the  capabilities  of 
soils  under  skilful  management,  practical  agriculture  appears  as  yet  to 
have  much  to  learn.  Is  there  any  method  hitherto  little  tried  by  which 
soils  of  known  poverty  may  be  compendiously  and  cheaply  doctored,  so 
as  to  produce  a  greatly  larger  return  ?  Science  seems  to  say  that  there  is, 
and  points  to  a  wide  field  of  experimental  research,  by  the  diligent  cul- 
ture of  which  we  may  hope  that  this  great  result  will  hereafter  be  at- 
tained. The  principles  upon  which  this  hope  rests  have  been  explained, 
for  the  most  part,  in. the  preceding  Lectures. 

4°.  Kind  of  crop. — The  amount  of  food,  either  for  man  or  beast, 
which  a  given  field  will  produce,  depends  considerably  upon  the  kind 
of  crop  which  is  raised.  Thus  a  crop  of  30  bushels  of  wheat  will  yield 
only  about  1400  lbs.  of  fine  flour,  while  a  crop  of  6  tons  of  potatoes  will 
give  about  4400  lbs.  of  an  agreeable,  dry,  and  mealy  food.  Thus  the 
gross  weight  of  food  for  man  is  in  the  one  case  three  times  what  it  is  in 
the  other.  So  it  is  said,  on  the  authority  of  the  Board  of  Agriculture, 
that  a  crop  of  clover,  of  tares,  of  rape,  of  potatoes,  turnips,  or  cabbages, 
will  furnish  at  least  thrice  as  much  food  for  cattle  as  one  of  pasture  grass 
of  medium  quality.* 

5°.  Variety  of  seed  sown. — The  variety  of  seed  sown  has  also  an  im- 
portant influence  on  the  amount  of  produce  reaped.  I  need  not  refer  to 
the  well  known  necessity  of  changing  the  seed  if  the  same  land  is  to 
continue  to  yield  good  crops — but  of  strange  seeds  of  the  same  species 
two  varieties  will  often  yield  very  unlike  weights  of  corn,  of  turnips,  or 
of  potatoes.  I  may  quote  as  an  illustration  the  experiments  of  Colonel 
Le  Couteur  upon  wheat.  He  found,  on  the  same  soil  and  under  the 
same  treatment,  that  the  varieties  known  by  the  name  of  the  White 
Downy  and  the  Jersey  Dantzic  yielded  respectively  : 

Grain.        Weight  pr  bush.    Straw.  Fine  flour.    Fine  do.  pr.ct 

White  Downy   -    48  bush.      62  lbs.      4557  lbs.      2402  lbs.      80|  lbs. 
Jersey  D^tzic   -   43^  bush.     63  lbs.      4681  lbs.      2161  lbs.      79|lbs. 
while  on  a  different  soil  and  treated  differently  from  the  above,  two  other 
varieties  yielded — 

Grain.  Weight  pr  bush.  Straw.  Fine  flour.  Fine  do.  pr.ct 
Whittington,  -  -  -  33  bush.  61  lbs.  7786  lbs.  1454  lbs.  72^1bg. 
BelleVueTalavera,    -  52bush.     61  lbs.     5480  lbs.     2485  lbs.  f  78^  Hw. 

*  Loudon's  Encyclopedia  of  Agriculture,  p.  910. 

t  Journal  of  the  Royal  Agricultural  Society  of  England,  L,  p.  123. 


490  INFLUENCE    OF  THE    METHOD    OF    CULTDRE, 

In  each  of  these  cases,  therefore,  and  especially  in  the  last,  a  striking 
difference  presented  itself  both  in  the  absolute  and  in  the  relative  weights 
of  grain  and  of  straw  reaped  under  precisely  similar  circumstances,  by 
the  use  of  different  varieties  of  the  same  species  of  seed.  Nor  are  the 
above  by  any  means  extreme  cases.  In  the  same  field  I  have  known 
the  Golden  Kent  and  the  Flanders  Red  varieties,  sown  in  the  sarne 
spring,  to  thrive  so  differently,  that,  while  the  former  was  an  excellent 
crop,  the  latter  was  almost  a  total  failure.  It  will  require  a  very  refined 
chemistry  to  explain  the  cause  of  such  diversities  as  tliese. 

§  3.  Influence  of  the  method  of  culture  upon  the  produce  of  food. 

In  addition  to  the  circumstances  above  alluded  to,  the  quantity  of  food 
tliat  is  raised  depends  very  much  upon  the  method  of  culture  which  is 
adopted.  Thus,  in  land  of  medium  quality,  our  opinion  in  regard  to  the 
quantity  of  food  it  is  likely  to  yield  would  be  greatly  affected  by  the 
answers  we  should  obtain  to  the  following  questions  ; — 

1°.  Is  the  land  in  permanent  pasture,  or  is  it  under  the  plough? — 
With  the  exception  of  rich  pasture,  it  is  said  that  land,  under  clover  or 
turnips,  will  produce  three  times  as  much  for  cattle  as  when  under  grass. 
If  such  a  green  crop  then  alternate  with  one  of  corn,  the  land  would 
every  two  years  produce  as  much  food  for  stock  as  it  would  during  three 
years  if  lying  in  grass,  besides  the  crop  of  corn  as  food  for  man,  and 
of  straw  for  the  production  of  manure. 

This  statement  may  possibly  be  a  little  exaggerated,  or  may  represent  tru- 
ly the  comparative  produce  of  food  in  special  cases  only — yet  there  seems 
sufficient  reason  for  believing,  as  a  general  rule,  that  a  very  much  larger 
amount  of  food  may  be  reaped  from  land  under  arable  culture,  than 
when  laid  away  to  permanent  pasture. 

2°.  What  kind  and  quality  of  manure  is  applied  1 — Every  practical 
man  knows  the  importance  of  manuring  his  land,  and  how  much  the 
abundance  of  every  crop  he  sows  depends  both  upon  the  quantity  and  upon 
the  kind  of  manure  he  is  able  to  add  to  it. 

3°.  In  what  way  is  it  applied  ? — But  much  depends  also  upon  the 
manner  in  which  the  manure  is  expended,  or  the  kind  of  crop  to  which 
it  is  applied. 

I  have  already  (p.  477)  directed  your  attention  to  the  loss  which  must 
necessarily  be  sustained  by  top-dressing  with  farm-yard  manure,  and  yet 
how  in  certain  modes  of  cropping  and  manuring  the  land,  it  may  be 
not  only  advisable  but  necessary  to  do  so.  Yet  the  comparative  return 
of  food  obtained  from  the  use  of  such  manure,  when  applied  as  a  top- 
dressing  to  grass  land  for  instance,  and  when  buried  with  the  turnip  crop 
in  the  usual  manner,  is  very  unlike. 

Thus,  suppose  an  acre  of  grass  land,  of  such  a  quality  as  to  produce 
annually  without  manure  1|  tons  of  hay,  to  be  top-dressed  ^ery  spring 
or  autumn  with  5  tons  of  farm-yard  manure  per  acre — and  suppose 
another  acre  of  the  same  land  in  arable  culture  to  be  manured  for  turnips 
with  20  tons  of  farm-yard  manure  at  once.  Then  the  grass  land,  by 
the  aid  of  the  manure,  would  not  produce  more  than  double  its  natural 
crop,  or  2^  tons  an  acre,  that  is,  10  tons  of  hay  in  the  four  years.  This,  I 
believe,  is  making  a  large  allowance  for  the  effect  of  the  manure. 

But  the  arable  land,  in  the  four  years,  if  of  the  same  quality,  may  be 


AND  OF  THE  MOEE  OF  APl-^flNG  THE  MANURE.       491 

expected  to  produce — turnips  20  tons,  barley  36  bushels,  clover  2^  tons, 
wheat  28  bushels  ;  besides  upwards  of  4  tons  of  straw. 

In  all  these  taken  together  there  must  be  much  more  food  than  in  the 
ten  tons  of  hay. 

If  we  consider  the  money  profit,  however,  to  the  farmer,  the  result 
may  be  different.  The  cost  of  raising  the  ten  tons  of  hay,  exclusive  of 
rent,  may  be  reckoned  at  one-half  the  produce,  and  of  the  several  crops 
in  the  four  years'  rotation  at  three-quarters  of  the  produce:  we  thus 
have  for  the  clear  return — 

In  the  one  case,  half  the  producers  tons  of  hay  ; 
In  the  other  case,  a  fourth  of  the  produce — 5  tons  of  turnips,  9  bushels 
of  barley,  i  t3n  of  clover,  7  bushels  of  wheat,  and  1  ton  of  straw. 

Let  the  clover  and  the  straw  together  equal  in  value  only  one  ton  of 
the  hay,  and  the  money  value  in  the  two  cases  will  stand  as  follows ; — 
Hay,  4  tons,  at  £5,  =  ^620     0     0 

Turnips,  5  tons,  at  10s.  =  <£2  10  0 
Barley,  9  bush.,  at  4s.  =  1  16  0 
Wheat,  7  bush.,  at    7s.   —     2       9     0 

6  15     0 


Leaving  a  gain  upon  the  grass  land  of  6£13     5     0 
Or,  d£3.  6s.  an  acre  every  year. 

Thus,  though  more  food  is  raised  by  converting  the  land  to  arable 
purposes,  and  more  people  may  be  sustained  by  it,  yet  more  money 
may  be  made  by  meadowing  the  land — ivhere  a  ready  market  exists 
for  the  hay,  where  it  is  allowed  to  be  sold  off  the  farm,  and  where  abun- 
dance of  manure  can  be  obtained  for  the  purpose  of  top-dressing  the  grass 
every  year.  It  is  only  in  the  neighbourhood  of  large  towns,  however, 
that  all  these  circumstances  usually  co-exist,  and  hence  one  cause  of  the 
value  of  grass  land  in  such  localities. 

The  farmer,  however,  is  never  prohibited  from  selling  his  corn  off  the 
farm,  or  his  fat  stock,  or  his  dairy  produce,  and  thus  at  a  distance  from 
large  towns  he  must  turn  his  attention  solely  to  the  raising  of  one  or  other 
of  these  kinds  of  produce. 

Of  the  two  ways  of  employing  his  grass  or  green  crops — in  rearing 
and  fattening  cattle,  namely,  and  in  the  production  of  butter  and  cheese 
— we  shall  hereafter  see  reason  to  believe  that  theoretically  the  latter 
ought  both  to  be  the  most  profitable  in  money  to  the  farmer,  and  at  the 
same  time  to  produce  the  greatest  amount  of  food  for  man. 

3°.  What  rotation  or  course  of  cropping  is  adopted? — If  the  land  be 
cropped  with  corn,  year  after  year,  the  produce  of  food  will  not  only  be 
less  than  if  an  alternate  husbandry  were  introduced — but  the  yearly  return 
of  corn,  even  on  the  richest  land,  must  sooner  or  later  diminish,  till  at 
length  the  crop  will  not  be  sufficient  to  defray  the  expense  of  cultivation. 
The  tillage  of  such  land  must  then  be  abandoned,  and  it  must  be  left  to 
a  slow  process  of  natural  restoration.  JNo  arable  land  will  produce  so 
much  food  if  year  by  year  it  be  made  to  raise  the  same  crop,  as  if  the 
crop  be  varied — and  especially  as  if  corn,  root,  and  leguminous  crops  be 
made  to  succeed  each  other  in  a  skilful  alternation. 

Upon  the  introduction  of  the  alternate  husbandry,  it  was  found  thai 
upon  lands  formerly  in  pasture,  not  only  could  one-third  more  stock  be 


492  THEORY    OF    THE    ROTATION    OF    CROPS. 

kept  continuously  than  before,  but  that  in  addition  a  crop  of  corn  could  be 
reaped  every  second  year.  On  the  other  hand,  those  which  had  been 
cropped  with  corn  alone,  or  which  after  two  white  crops  had  usually  been 
left  to  naked  fallow,  yielded  more  corn  in  a  given  number  of  years  than 
before,  while  a  green  crop  every  second  year  was  raised  on  them  besides. 
It  cannot  be  doubted,  therefore,  that  a  change  of  crojpjnng  influences,  in 
a  great  degree,  the  amount  of  food  which  the  same  piece  of  land  is  fitted 
to  produce. 

§  4.  Of  the  theory  of  the  rotation  of  crops. 

Upon  what  principles  do  the  beneficial  effects  of  this  change  of  crop- 
ping depend  ?     What  is  the  true  theory  of  a  rotation  of  cipps  ? 

It  was  supposed  by  Decandolle — 

1°.  That  the  roots  of  all  plants  gave  out  or  excreted  certain  substan- 
ces peculiar  to  themselves — and, 

2°.  That  these  substances  were  unfavourable  to  the  growth  of  those 
plants  from  the  roots  of  which  they  came,  but  were  capable  of  promo- 
ting the  growth  of  plants  of  other  species — that  the  excretions  of  one 
species  were  poisonous  to  itself,  but  nutritive  to  other  species. 

Upon  these  suppositions  he  explained  in  a  beautiful  and  apparently 
simple  and  convincing  manner  the  beneficial  effects  of  a  rotation  or  al- 
ternation of  different  crops.  If  wheat  refused  to  grow  after  wheat,  it  was 
because  the  first  crop  had  poisoned  the  land  to  plants  of  its  own  kind. 
If  after  an  intervening  naked  fallow  a  second  wheat  crop  could  be  safely 
grown,  it  was  because  during  the  year  of  rest  the  poisonous  matter  had 
time  to  decompose  and  become  again  fitted  to  feed  the  new  crop.  And 
if,  after  beans  or  turnips,  wheat  grew  well,  it  was  because  the  excretions  of 
these  plants  were  agreeable  to  the  young  wheat,  and  fitted  to  promote 
its  growth. 

Thus  easily  explained  were  the  benefits  both  of  a  rotation  of  crops 
and  of  naked  and  other  fallows — and  supported  at  once  by  its  own  beauty 
and  by  the  great  name  of  Decandolle,  this  explanation  obtained  for 
many  years  an  almost  universal  reception. 

But  though  there  seems  reason  enough  for  believing  (p.  82)  that  the 
roots  of  plants  really  do  give  out  certain  substances  into  the  soil — there  is 
no  evidence  that  these  excretions  take  place  to  the  extent  which  the 
theory  of  Decandolle  would  imply — none  of  a  satisfactory  kind  that 
they  are  noxious  to  the  plants  from  which  they  are  excreted* — and  none 
that  they  are  especially  nutritive  to  plants  of  other  species.  Being  un- 
supported by  decisive  facts  and  observations  therefore,  the  hypothesis  of 
Decandolle  must,  for  the  present,  be  in  a  great  measure  laid  aside,  and  we 
must  look  to  some  other  quarter  for  a  more  satisfactory  theory  of  rotation. 

Tlie  true  general  reason  why  a  second  or  third  crop  of  the  same  kind 
will  not  grow  well,  is — not  that  the  soil  contains  too  much  of  any,  but  that 
it  contains  too  little  of  one  or  more  kinds  of  matter.  If,  after  manuring, 
turnips  grow  luxuriantly,  it  is  because  the  soil  has  been  enriched  with 
all  that  the  crop  requires.  If  a  healthy  barley  crop  follow  the  turnips, 
it  is  because  the  soil  still  contains  all  the  food  of  this  new  plant.  If 
clover  thrive  after  this,  it  is  because  it  naturally  requires  certain  other 
kinds  of  nourishment  which  neither  of  the  former  crops  has  exhausted. 
If,  again,  luxuriant  wheat  succeeds,  it  is  because  the  soil  abounds  still  in 
•  See  page  81,  note. 


PRACTICAL    RULES    SU6GESTE1/    BY    THEORY.  493 

all  that  the  wheat  crop  needs — the  failing  vegetable  and  other  matters  of 
the  surface  being  increased  and  renewed  by  the  enriching  roots  of  the 
preceding  clover.  And  if  now,  turnips  refuse  again  to  give  a  fair  re- 
turn, it  is  because  you  have  not  added  to  the  soil  a  fresh  supply  of  that 
manure  without  which  they  cannot  thrive.  Add  the  manure,  and  the 
same  rotation  of  crops  may  again  ensue. 

We  have  already  had  frequent  occasion,  in  studying  the  inorganic 
constituents  of  plants,  to  observe  that  different  species  require  very  un- 
like proportions  of  the  several  kinds  of  inorganic  food  which  they  derive 
from  the  soil.  Some  require  a  large  proportion  of  one  kind,  some  of 
another  kind.  If  a  soil,  therefore,  abound  especially  in  one  of  these  va- 
rieties of  inorganic  food,  one  kind  of  plant  will  especially  flourish  upon 
it — while,  if  it  be  greatly  deficient  in  another  substance,  a  second  plant 
will  remarkably  languish  upon  it.  If  if  abound  in  both  substances,  then 
either  crop  will  succeed  which  we  may  choose  to  sow,  or  they  may  be 
alternately  cultivated  with  a  fair  return  from  each. 

Upon  this  principle  the  true  general  explanation  of  the  benefit  of  a 
rotation  of  crops  appears  to  depend.  There  may  be  special  cases  in 
which  peculiar  qualities  of  soil  or  climate  may  intervene  and  give  rise 
to  appearances,  or  cause  results  to  wliich  this  principle  does  not  apply, 
but  for  the  general  practice  it  seems  to  afford  a  satisfactory  explanation. 

It  may  be  said  that  this  explanation  seems  to  ira  ply  that  the  same 
kind  of  crop  maybe  reaped  from  the  same  soil  for  an  indefinite  number  of 
years,  by  simply  adding  to  it  what  the  crop  carries  off'.  This  is  certain- 
ly implied  in  the  principle — and  iftve  knew  exactly  ivhat  to  add  for  each 
crop,  we  might  possibly  attain  this  result,  except  in  cases  where  the  soil 
undergoes  some  gradual  chemical  alteration  within  itself,  which  it  may 
require  a  change  of  treatment  to  counteract.  At  all  events  it  does  not 
seem  impossible  to  obtain  crop  after  crop  of  the  same  kind — and  we  may 
hope  hereafter  not  only  to  be  able  to  etfect  this,  but  to  do  it  in  a  sutR- 
ciently  economical  manner. 

Two  practical  rules  are  suggested  by  the  fact  that  different  plants  require 
different  substances  to  abound  in  a  soil  in  which  they  shall  be  capable  of 
flourishing. 

1°.  To  grow  alternately  as  many  different  classes  or  families  of  plants 
as  possible — repeating  each  class  at  the  greatest  convenient  distance  of  time. 

In  this  country  we  grow  chiefly  root  crops,— corn  plants  ripened  for 
seed, — leguminous  plants  sometimes  for  seed  (peas  and  beans),  and 
sometimes  for  hay  or  fodder  (clover  and  tares), — and  grasses,  and  these 
in  alternate  years.  Every  four,  five,  or  six  years,  therefore,  the  culture 
of  the  same  class  of  plants  comes  round  again,  nnd  a  demand  is  made 
upon  the  soil  for  the  same  kinds  of  food  in  the  same  proportion. 

In  otlier  countries — tobacco — flax — rape,  poppy  or  madia,  cultivated  for 
their  oily  seeds — or  beet  for  its  sugar,  can  be  cultivated  with  profit,  and 
being  interposed  among  the  other  crops,  they  make  the  return  of  each 
class  of  plants  more  distant.  A  perfect  rotation  would  include  all  those 
classes  of  plants  which  the  soil,  climate,  and  otlier  circumstances  allow 
to  be  cultivated  with  a  profit. 

2°.  A  second  rule  is  to  repeat  the  same  species  of  plant  at  the  greatest 
convenient  distance  of  time.  In  corn  crops  there  is  not  much  choice, 
since  in  a  four  years'  course  two  corn  crops,  out  of  the  three  (barley, 
21* 


494  WHY    LAND    BECOMES    CLOVER-SICK. 

wheat,  oats)  usually  grown,  must  be  raised.  But  of  the  leguminous 
crops  we  have  the  choice  of  beans,  peas,  vetches,  and  clover — of  root 
crops,  turnips,  carrots,  beets,  and  potatoes — while  of  grasses,  there  is  a 
great  variety.  Instead,  therefore,  of  a  constant  repetition  of  the  turnip 
every  four  years,  theory  says — make  the  carrot  or  the  potatoe  take  its 
place  now  and  then,  and  instead  of  perpetual  clover,  let  tares  or  beans, 
or  peas,  occasionally  succeed  to  your  crops  of  corn.  The  land  loves  a 
change  of  crop,  because  it  is  better  prepared  with  that  food  which  the 
new  crop  will  relish,  than  with  such  as  the  plant  it  has  long  fed  before 
continues  to  require. 

It  is  for  this  reason  that  new  species  of  crop,  or  new  varieties,  when 
first  introduced,  succeed  remarkably  for  a  time,  and  give  great  and  en- 
couraging returns.  But  they  are  continued  too  long — till  the  soil  has 
been  exhausted  in  some  degree  of  those  substances  in  which  the  new 
crops  delighted.  They  cease  in  consequence  to  yield  as  before,  and  fall 
into  undeserved  disrepute.  Give  them  a  proper  place  in  a  long  rotation, 
and  they  will  not  disappoint  you. 

.  It  is  constant  variety  of  crops,  which,  with  rich  manuring,  makes  our 
market  gardens  so  productive — and  it  is  the  possibility  of  growing  in  the 
fields  many  diflferent  crops  in  succession,  that  gives  the  fertiUty  of  a  gar- 
den to  parts  of  Italy,  Flanders,  and  China.* 

§  5.   Why  land  becomes  tired  of  clover  {clover-sick). 

What  I  have  said  of  the  general  principle  might  be  supposed  to 
explain  fully  why  crops  fail  at  one  time  and  succeed  at  another — why 
the  soil  will  nourish  one  plant  well,  while  it  is  unable  adequately  to  sus- 
tain another.  But  a  brief  reference  to  the  case  of  the  clover  plant  will 
enable  us  to  see  how  modes  of  culture,  apparently  skilful  and  generous, 
may  yet  be  of  such  a  kind  as  to  lead,  sooner  or  later,  to  the  inevitable 
failure  of  a  particular  crop. 

It  is  known  that  upon  many  well  cultivated  famis  the  lands  become 
now  and  then  tired  or  sick  of  clover,  and  this  crop  failing,  the  wheat 
which  succeeds  it  in  a  great  measure  fails  also.  It  may  be  said  that  the 
soil  in  such  a  case  is  in  want  of  something,  and  so  it  is, — but  how  does 
this  deficiency  of  supply  arise  ?  The  land  is  skilfully  managed  and 
has  been  well  manured,  and  the  failure  of  the  clover  crop  is,  therefore,  a 
matter  of  surprise. 

If  farm-yard  manure  be  copiously  applied  previous  to  the  root  crop, 
the  land  has  received  a  certain  more  or  less  abundant  return  of  all  those 
substances  which  the  last  rotation  of  crops  had  carried  off  from  it, — and 
which  the  new  rotation  will  require  .or  food.  When  the  clover  comes 
round,  therefore,  a  supply  of  proper  food  is  ready  for  it,  as  well  as  for 
the  wheat  which  is  to  follow. 

But  if  ihe  turnip  crop  be  raised  by  means  of  bones  only,  the  lime 

*  A  method  of  superseding  in  some  measure  the  necessity  of  a  rotation  of  crops  is  de- 
scribed by  Mr.  James  Wilson  as  long  practised  in  Shetland,  in  the  neighbourhood  of  Ler- 
wick. "  It  is  known  that  bear  has  been  grown  in  the  same  patch  for  perhaps  100  years  suc- 
cessively, and  this  they  managed  by  scarifying  other  parts  of  the  ground  (the  out  field  por- 
tion), and  renovating  the  arable  patch  by  spreading  it  over  the  surface."  This  was  varying 
the  soil  instead  of  the  crop.  A  five  years'  rotation,  however,  is  now  getting  into  favour,  and 
the  average  produce,  after  liming,  is  found  to  be  increased  by  it  four-fold.  In  this  district 
much  herring  refuse  is  employed  as  a  manure,  and  the  improved  land  lets  at  aOs.  an  acre. 
—Wilson's  Voyage  round  the  Coast  of  Scotland,  II.,  p.  268. 


RESULT    OF    FREQUENT    MANURING    WITH    BONES.  495 

and  phosphoric  acid  which  the  earth  of  bones  contains  are  almost  the  only 
kinds  of  inorganic  f)od  required  by  plants  that  are  returL'^d  to  the  soil. 
By  the  aid  of  the  animal  matter  and  the  small  supply  of  other  substances 
in  the  bones,*  good  crops — and  especially  the  turnips  and  tlie  corn  which 
immediately  follows  them — may  be  raised  for  a  few  rotations,  but  at 
every  return  the  clover  and  wheat  will  become  more  unhealthy,  till  they 
at  length  appear  to  sicken  upon  the  land.  Neither  bones  nor  rape-dust 
nor  any  such  single  substance  can  replace  farm-yard  manure  for  an  in- 
definiie  period,  because  it  does  not  contain  all  the  substances  which  the 
entire  rotation  of  crops  requires. 

If  wood-ashes  be  used  along  with  the  bones,  the  bad  effects  I  have  des- 
cribed will  be  much  longer  delayed — they  may  even  be  delayed  indefi- 
nitely, since  wood-ashes  are  said  to  be  especially  favourable  to  the  growth 
of  clover  and  other  leguminous  plants,  (p.  353),  and  this  because  they 
contain  those  substances  which  the  clovers  require. 

It  thus  appears,  therefore,  that  while  the  failure,  upon  a  given  spot,  of 
a  crop  which  formerly  grew  well  there,  is  explained  generally  upon  the 
principle  that  the  soil  has  become  deficient  in  something  which  the  crop 
.  requires — the  cause  of  this  deficiency  may  not  unfrequently  be  found  in 
the  mode  of  culture,  or  in  the  species  of  manuring  which  the  land  has 
received.  The  cause  being  discovered,  the  remedy  is  easy.  Cease  to 
employ  exclusively  the  manure  with  which  your  land  has  hitherto  been 
dressed.  Mix  your  bones  or  rape-dust  with  wood-ashes,  with  gypsum, 
or  with  other  portable  manures  in  which  the  necessary  food  of  your 
crops  is  present — or  employ  farm-yard  manure  now  and  then  in  their 
stead,  and  you  will  apply  the  most  likely  remedy.  Unless  this  be  done, 
it  will  be  of  comparatively  little  service  to  vary  the  species, — to  substi- 
tute tares  or  beans  for  the  clover, — since  these  also  will  refuse  to  grow 
while  the  same  incorrect  system  of  manuring  is  persisted  in. 

I  have  already  drawn  your  attention  (p.  477)  to  the  falling  of  the 
clover  crops  in  certain  parts  of  Staffordshire,  where  the  turnips  are 
raised  by  means  of  rape-dust — and  of  the  mode  of  improving  them  by  a 
top-dressing  of  farm-yard  manure.  Were  this  manure  laid  in  with  the 
turnips,  the  after  top-dressing  would  most  probably  not  be  required. 

§  6.  Of  the  theory  of  fallows. 
,  By  fallowing,  it  has  been  known  in  all  ages  that  the  produce  of  the 
land  was  capable  of  being  increased.  How  is  this  increase  to  be  ac- 
counted for  ?  We  speak  of  leaving  the  land  to  rest,  but  it  can  never 
really  become  wearied  of  bearing  crops.  It  cannot,  through  fatigue,  lie 
in  need  of  repose.  In  what,  tlien,  does  the  efficacy  of  naked  fallowing 
consist  ? 

1°.  In  strong  clay  lands  one  gfeat  benefit  derived  from  a  naked  fallow 
is  the  opportunity  it  affords  for  keeping  the  land  clean.  In  such  soils  it 
is  believed  by  r^any  that  weeds  cannot  possibly  be  extirpated  without  an 
occasional  fallow.  It  is  certain  that  naked  fallows  are  had  recourse  to 
in  many  places  for  the  purpose  of  cleaning  the  land,  where  if  it  could 
easily  have  been  kept  so  by  other  means  they  would  not  have  been 
adopted.  Is  it  not  the  case  on  some  farms  that  a  neglect  of  other  avail- 
able methods  of  extirpating  weeds  has  rendered  necessary  the  assistance 
*  For  the  composition  of  bones,  see  page  446. 


496         FALLOWS  MAY  REPLACfc  DEEP  PLOUGHING  AND  DRAINING. 

of  a  naked  fallow,  while  on  similar  farms  in  the  same  neighhourhood 
they  can  easily  be  dispensed  with  ? 

2°.  In  a  naked  fallow,  whore  the  seeds  are  allowed  to  sprout,  and 
young  plants  to  shoot  up,  which  are  afterwards  ploughed  in,  the  land  is 
enriched  by  a  green  manuring  of  greater  or  less  extent.  If  weeds  abound, 
the  enriching  is  the  greater — if  they  are  more  scanty,  it  is  less — but  in 
almost  every  instance  where  land  lies  without  an  artificial  crop  during 
the  whole  summer,  a  crop  of  natural  herbage  springs  u}),  the  burying  of 
which  in  the  soil  must  be  productive  of  considerable  good. 

3°.  When  land  is  assiduously  cropped,  the  surface  in  which  the  roots 
chiefly  extend  themselves  becomes  especially  exhausted.  In  indiffer- 
ently worked  land  some  parts  of  this  surface  may  be  more  exhausted  than 
others.  By  leaving  such  soils  to  themselves,  the  rains  that  fall  and  more 
or  less  circulate  through  them  equalize  the  condition  of  the  whole  sur- 
face soil — in  so  far  as  the  soluble  substances  ii  contains  are  concerned. 
The  water  also,  which  in  dry  weather  ascends  from  beneath,  brings 
with  it  saline  and  other  soluble  compounds,  and  imparts  them  to  the  up- 
per layers  of  the  soil.  Thus,  by  lying  fallow,  the  land,  becomes  equa- 
bly furnished  over  its  whole  surface  with  all  those  substances  required  by 
plants  which  are  anywhere  to  be  found  in  it.  The  roots  of  the  crop, 
therefore,  can  more  readily  procure  them,  and  thus  the  plants  more 
readily  and  more  quickly  grow.  In  some  cases,  this  beneficial  action  of 
the  naked  fallow  will,  to  a  certain  extent,  make  up  for  shallow  ploughing^ 
ai^for  insufficient  working  of  the  land. 

4°.  It  is  known  that  the  subsoil  in  many  places  is  of  such  a  nature 
that  it  must  be  turned  up  to  the  surface,  and  exposed  for  a  considerable 
period  to  the  action  of  the  air,  before  k  can  be  safely  mixed  with  the  sur- 
face soil.  To  a  less  degree  stiff  clay  lands  acquire  this  noxious  quality 
during  the  ordinary  course  of  cropping.  Air  and  water  do  not  find  their 
way  through  them  in  sufficient  quantity  to  retain  them  in  a  healthy 
condition,  and  thus  they  require  an  occasional  fallow  with  repeated 
ploughings,  that  the  air  and  the  rains  may  have  access  to  their  inner- 
most parts.  I  do  not  detail  the  specific  chemical  changes  which  are  in- 
duced by  this  exposure  to  the  air  and  rain  ;  it  is  sufficient  that  they  are 
of  a  kind  to  render  the  soil  more  propitious  to  the  growth  of  crops,  to 
satisfy  us  that,  upon  very  stiff"  lands,  one  of  the  benefits  of  fallowing  is  to 
be  thus  accounted  for. 

We  have  seen  that  one  of  the  important  benefits  of  draining  is  the 
permeability  it  imparts  to  the  soil.  The  surface  water  is  permitted  to 
escape  downwards,  and  as  it  sinks  to  the  drain  the  air  follows  it,  so  that 
the  very  deepest  part  of  the  soil  from  which  the  water  runs  off",  is  ren- 
dered wholesome  by  the  frequent  admission  of  new  supplies  of  atmos- 
pheric air. 

It  thus  appears  that  in  a  certain  sense  draining  and  fallowing  may 
take  the  place  of  each  other — that  where  there  is  no  drainage,  fallowing 
is  more  necessary  and  will  partially  supply  its  place,  and  tliat  where  a 
good  drainage  exists,  the  use  of  naked  fallows  even  upon  stiff'clay  lands 
becomes  less  necessary. 

5°.  I  have  already  had  occasion  to  speak  of  the  existence  of  organic 
(animal  and  vegetable)  matter  in  the  soil,  in  a  so-called  inert  state — a 
state  in  which  it  undergoes  decay  veiy  slowly,  and  tluis  only  in  a  small 


THE  SOIL  IS  MANURED  BY  THE  SEA  AND  THE  AIR.  497 

degree  discharges  those  functions  for  wtiich  vegetable  matter  in  the  soil  is 
specially  destined.  In  stiff  clays  also,  the  roots  of  plants,  without  actu- 
ally attaining  this  inert  state,  yet  decay  with  extreme  slowness  in  conse- 
quence of  their  being  so  completely  sealed  up  from  the  access  of  the  air. 
In  both  cases  the  frecjuent  and  prolonged  exposure  which  a  naked  fallow 
occasions,  induces  a  more  rapid  decay  of  this  vegetable  matter,  or  brings 
it  into  a  state  in  which  its  elements  more  readily  assume  those  new 
forms  of  combination  which  are  capable  of  ministering  to  the  sustenance 
and  growth  of  plants. 

Among  the  other  compounds  which  are  produced  (p.  161)  during  this 
prolonged  exposure  and  more  rapid  decay  of  the  organic  matter  of  the 
soil,  nitric  acid  is  one  which  appears  to  exercise  a  considerable  in- 
fluence upon  the  future  fertility  of  the  land.  The  favourable  action  of 
the  nitrates  in  promoting  vegetable  growth  is  now  we-11  known,  and 
the  more  rapid  formation  of  these  compounds,  when  the  land  lies  na- 
ked to  the  action  of  the  sun  and  air,  must  not  be  neglected  among  the 
fertilizing  influences  of  the  sumnier  fallow. 

6°.  The  soil,  besides  the  clay,  (quartz)  sand  and  lime  of  which  it 
chiefly  consists,  contains  also  fragments  of  mineral  substances  of  a  com- 
pound nature — of  felspar,  of  mica,  of  hornblende — of  those  minerals 
which  constitute  or  which  occur  in  the  granitic  and  trap  rocks.  These 
slowly  decompose  in  the  soil — more  rapidly  also  the  more  freely  they 
are  exposed  to  the  air — and  the  substances  (potash,  soda,  lime,  magne- 
sia, silica,  &;c.*)  which  they  contain,  are  by  this  decomposition  difllised 
more  equably  and  brought  within  the  more  easy  reach  of  the  roots  of 
plants.  When  these  minerals,  therefore,  exist  in  the  soil,  and  when 
their  constituents  are  of  sucii  a  kind  as  to  favour  the  growth  of  any  given 
plant,  the  effect  of  a  naked  fallow  being  to  })roduce  an  accumulation  of 
their  constituent  substances  in  the  soil,  it  Avill  be  so  far  favourable  in  pre- 
paring the  land  for  an  after-crop  of  that  particular  species  of  plant. 
You  are  not  to  be  misled,  however,  by  any  broad  and  unguarded  state- 
ments of  scientitic  men,  so  as  to  imagine  for  a  moment  that  the  benefi- 
cial effects  of  fallowing  in  any  case  are  to  be  solely  ascribed  to  the  oper- 
ation of  this  one  cause. f 

7°.  The  rains  bring  down  upon  every  soil  periodical  supplies  of  ail 
those  saline  substances — common  salt,  gypsum,  salts  of  lime,  of  mag- 
nesia, and  of  potash  in  minute  quantity — which  exist  in  the  sea,  and  of 
nitrate  of  ammonia,  produced  or  present  in  the  air.  If  any  soil  be  defi- 
cient in  these,  then  a  year's  rest  from  cropping,  b3''  allowing  them  to  ac- 
cumulate, may  cause  the  succeeding  herbage  to  exhibit  a  more  luxuriant 
growth. 

8°.  The  same  remark  applies  to  soils  into  which  springs  frombenealJi 
bring  up  variable  quantities  of  lime  and  other  substances  which  the  wa- 
terSjhold  in  solution.  Such  springs  are,  no  doubt,  of  much  benefit  in 
some  districts,  and  when  the  supply  they  convey  is  scanty,  a  year's 
accumulation  may  impart  additional  fertility  to  the  fallowed  land. 

9°.  Besides  that  beneficial  action  of  the  air  to  which  I  have  already 
adverted  (4°  and  5°),  and  which  is  to  be  ascribed  mainly  to  the  influ- 

» 

•  For  the  constitution  of  these  mineral  substances,  see  pp.  257  to  260. 

t  Fallow  is  the  term  applied  to  land  left  atrest  for  further  disintegration.— lAQhxg^a  Organic 
Chemistry  applied  to  Agriculture,  p.  149. 


498  OF  GREEN  OR  FALLOW  CROPS. 

ence  of  the  oxygen  it  contains — the  exposure  of  the  naked  soil  to  the  at- 
mosphere for  a  length  of  time  is  said  by  some  to  be  productive  of  another 
good  effect.  The  atmosphere  contains  a  small  and  variable  portion  of 
ammonia  (p.  156).  Of  this  ammonia,  a  portion  is  brought  down  by  the 
rains  and  a  portion  is  probably  absorbed  by  the  leaves  of  plants  as  they 
spread  themselves  through  the  air.  But  the  clay,  the  oxide  of  iron,  and 
the  organic  matter  of  the  soil  are  supposed  also  to  have  the  power  of 
extracting  this  ammonia  from  the  atmosphere  and  retaining  it  in  their 
pores.  If  so,  the  more  the  soil  is  exposed,  and  for  the  longer  period 
to  the  air,  the  more  of  this  substance  will  it  extract  and  absorb.  If 
turned  over  by  frequent  ploughing,  it  will  be  able  to  drink  it  in  more 
abundantly,  from  the  greater  surface  it  can  present  to  the  passing  winds; 
and  if,  besides,  it  be  kept  naked  for  an  entire  year,  a  still  larger  accumu- 
lation must  take  place.  And  as  this  ammonia  is  known  in  many  cases 
to  be  favourable  in  a  high  degree  to  the  growth  of  plants,  it  is  not  im- 
reasonable  to  believe  that  if  thus  absorbed  in  quantity  from  the  air,  it  should 
be  one  source  at  least  of  the  augmented  fertility  of  fallowed  land. 

To  one  or  other — or  to  all  of  these  causes  combined — the  acknowledged 
benefit  of  naked  fallows  is  in  a  great  degree  to  be  ascribed. 

0[  green  or  fallow  crops  little  need  be  said  in  addition  to  what  I  have 
already  laid  before  you  in  reference  to  the  rotation  of  crops.  The  green 
crop  demands  a  comparatively  small  supply  only  of  those  inorganic  sub- 
stances which  the  corn  crops  specially  require.  During  its  growth, 
therefore,  these  latter  accumulate  in  the  same  way,  though  in  a  some- 
what less  degree  than  during  a  naked  fallow.  But  the  additional  vege- 
table matter  and  manure  which  the  gteen  crops  introduce  into  the  soil, 
and  the  large  supplies  of  inorganic  matter  which  such  of  them  as  are 
deep-rooted  bring  up  from  beneath,  amply  compensate  for  any  diminu- 
tion they  may  cause  in  the  benefits  which  are  usually  derived  from  the 
naked  fallow. 

§7.   Of  wheat  u,ad  wheaten  flour. 

The  grain  of  wheat  in  the  hands  of  the  miller  is  readily  separated  into 
two  portions — the  husk,  which  forms  the  bran,  and  the  greater  portion 
of  the  pollard — and  the  kernel,  which,  when  ground,  forms  the  wheaten 
flour.  The  relative  weights  of  these  two  parts  vary  very  much.  Some 
varieties  of  grain  are  much  smoother,  more  transparent,  and  thinner 
skinned  than  others,  and  yield  in  consequence  a  larger  return  of  the 
finest  flour.  In  good  wheat  the  husk  amounts  to  14  or  13  percent,  of 
the  whole  weight* — though  the  quantity  sei)arated  by  the  miller  is 
sometimes  not  more  than  ^th  (or  11  per  cent.)  of  the  weight  of  the 
wheat.  In  making  the  fine  white  flour  of  the  metropolis  and  other 
large  towns,  about  ^th  of  the  whole  is  separated  in  the  form  of  pollard 
and  bran.     The  proportion  of  the  husk  that  can  be  sifted  out  at  the  mil?. 

*  Boussingault  found  as  much  as  38,'^  per  cent,  of  husk  on  a  whiter  wheat  grown  in  the 
botanic  garden  of  Paris.    Three  lots  of  good  Englisli  wheat,  ground  at  Mr.  Robson's  mill  in 
.Jurham,  gave  per  cent.  respectively- 
Fine  flour 74-2  751  77  9 

Boxings 9  0  83  CI 

Sharps 5  8  6-6  5-6 

•       Bran 78  70  69 

Waste 32  30  35 

100  100  100 


RELAX  VE    WEIGHTS    OF    FLOUR  AND    BRAN.  499 

depends  considerably  upon  the  hardness  of  the  grain.  From  such  as  is 
soft  it  peels  off  in  flakes  under  the  stones,  whereas,  when  the  grain  and 
nusk  are  flinty,  much  of  the  latter  is  crushed  and  ground — adding  to  the 
weight  of  the  flour,  but  giving  it  a  darker  colour,  and  lowering  its  quality. 

The  country  millers  generally  separate  their  wheaten  flour  by  sifting 
into  four  parts  only — fine  flour,  boxings,  sharps  or  pollard,  and  bran. 
In  London  and  Paris  no  less  than  six  or  seven  qualities  are  manufac- 
tured and  sold  by  the  millers.*  The  value  of  the  wheat  to  the  miller 
depends  very  much  upon  the  quantity  of  fine  flour  it  will  yield,  though 
he  cannot  always  judge  accurately  of  this  point  by  simple  inspection. 

The  experimental  wheats  of  Mr.  Burnet,  of  Gadgirlli,f  raised  all  from 
the  same  seed  differently  manured,  gave  respectively  54|,  63^,  65|, 
66i,  68y,  and  76i  lbs.  of  fine  flour  from  100  of  wheat,  so  that  the  kind 
of  manure  applied  to  the  land  appears  materially  to  affect  the  relative 
proportions  of  flour  and  bran. 

Again,  Colonel  le  Couteur's  samples  of  wheat  (p. 489)  of  different  va- 
rieties, grown  under  the  same  circumstances,  gave  from  one  field  80| 
and  79|  lbs.,  and  from  another  72^  and  78^  lbs.  from  100  of  wheat — so 
that  wpon  the  variety  of  seed  sown  also,  though  in  a  less  degree,  the  quan- 
tity of  fine  flour  is  dependent. 

§  8.  Of  the  composition  of  wheaten  flour. 

1°.  Water. — When  wheat  is  kept  for  ayear  it  loses  a  little  water,  be- 
coming one  or  two  pounds  a  bushel  heavier  than  before.  When  put  into 
the  mill  and  ground  it  becomes  very  hot,  and  gives  off  so  much  watery 
vapour,  that  the  flour  and  bran,  though  together  nearly  twice  as  bulky, 
are  nearly  3  per  cent,  lighter  tlian  tlie  grain  before  it  was  ground.  A 
further  loss  of  weight  is  said  lo  take  place  when  the  flour  is  kept  long  in 
the  sack.  If  fine  flour  be  slowly  heated  to  a  temperature  not  higher 
than  220  for  several  hours,  it  loses  a  quantity  of  water,  which,  in  up- 
wards of  20  samples  of  English  flour  which  I  have  examined,  has  varied 
from  15  to  17  per  cent,  of  the  whole  weight.  It  may,  therefore,  be  as- 
sumed, that  English  flour  contains  nearly  a  sixth  part  of  its  weight  of 
water — or  every  six  pounds  of  fine  flour  contain  nearly  one  pound  of 
water. 

2°.  Gluten,  albumen,  caseine,  starch,  gum,  and  sugar. — When  the 
flour  of  wheat  is  made  into  dough,  and  is  then  washed  carefully  with 
successive  portions  of  water  upon  a  fine  gauze  or  hair  sieve,  as  long  as 
the  liquid  passes  through  milky,  the  flour  is  separated  into  two  portions — 
the  starch,  which  subsides  from  the  water,  and  the  gluten,  which  remains 
in  the  sieve  (p.  116).  If  the  water  be  poured  off',  after  the  starch  has 
subsided,  and  be  heated  nearly  to  boiling,  it  becomes  troubled,  and  flakes 
of  vegetable  albumen  (p.  117)  are  seen  to  float  in  it.     On  setting  aside  to 

•  These  are  called  respectively  in  London  and  Paris— 

London.  Paris.                        Called. 

Fine  flour.  White  flours,  1st  quality,  de  ble. 

Seconds.  do.           2d      do.      de  le  gruau. 

Fine  middling^s.  do.           3d      do.      de  2e  gruau. 

Coarse  middlings.  Brown  meals,  4th    do,      de  3e  gruau. 

Pollard.  do.            5th   /lo.      de  4e  gruau. 

Twentypenny.  Bran,  fine  and  coarse. 

Bran  Waste,  &c.,  Remoulage  and  Recoupe. 

.  Page  362,  and  Appendix,  pp.  54  and  70. 


600  STARCH,    SUGAR,    GUM,    AND    CIL,    IN    WHEAT. 

cool,  the  flaky  powder  falls  to  the  bottom,  and  may  l-e  collected,  dried, 
and  weighed.  If  the  water,  after  filtration,  be  CAaporated  to  dryness  on 
the  water  bath,  a  residue  will  be  obtained,  which  consists  chiefly  of  solu- 
ble sugar,  gum,  and  saline  matter,  with  a  little  fatty  matter,  and  sparingly 
soluble  caseine*  (p.  117). 

3°.  Gluiine  arid  oil. — \U  further,  the  crude  gluten  be  boiled  in  alco- 
hol, a  solution  is  obtained  which,  on  cooling,  deposits  a  w  bite  flocky  sub- 
stance, having  much  resemblance  to  caseine.  When  the  clear  solution  is 
concentrated  by  evaporation,  water  separates  from  it  an  adhesive  mass, 
which  consists  of  a  substance  to  which  the  name  of  giutine  is  given, 
mixed  with  a  little  oil.  By  digesting  the  mixed  mass  in  ether  the  oil  is 
dissolved  out  from  the  giutine,  and  may  be  obtained  in  a  pure  state  by 
evaporating  the  ethereal  solution.  This  oil  possesses  the  general  pro- 
perties of  the  fatty  oils,  or  of  butter.  As  it  is  partly  washed  out,  how- 
ever, along  with  the  starch,  the  whole  of  the  fatty  matter  of  the  flour  is 
best  obtained  by  boiling  it  in  a  considerable  quantity  of  ether. 

4°.  Vegetable  jihrine. — The  crude  gluten,  after  boiling  in  alcohol,  has 
much  resemblance  to  the  fibre  of  lean  beef,  and  has  therefore  been  named 
vegetable  fibrine.  When  burned,  it  leaves  behind  an  ash,  containing, 
among  other  substances,  the  phosphates  of  lime  and  magnesia,  which 
are  to  be  considered  also  as  among  the  usual  constituents  of  wheaten 
flour,  t 

Thus,  fine  wheaten  flour,  in  addition  to  the  water  it  contains,  and  to 
the  small  quantity  of  bran  which  is  ground  up  along  with  it,  consists  of 
vegetable  fibrine,  albumen,  caseine,  giutine,  starch,  sugar,  gum,  oil  or 
fat,  besides  the  saline  substances,  chiefly  phosphates,  which  remain  in 
the  form  of  ash,  when  the  flour  is  burned.  All  these  substances  vary  in 
quantity  in  different  samples  of  flour, — their  relative  proportions  appear- 
ing to  depend  upon  a  variety  of  circumstances  as  yet  little  understood. 
In  the  various  analyses  of  flour  that  have  hitherto  been  published,  little 
attention  has  been  paid  to  the  per-centage  of  oil,  of  giutine,  or  of  caseine, 
which  the  specimens  examined  have  severally  contained.  In  general, 
the  weight  of  the  crude  gluten  only  has  been  estimated,  without  extract- 
ing from  it  either  the  oil  or  the  giutine. 

The  following  table  exhibits  the  approximate  composition  of  some 
varieties  of  French  and  Odessa  flour  as  determined  many  years  ago  by 
VauquelinJ  : — 

*  This  caseine  begins  to  form  a  pellicle  on  the  surface,  when  the  liquid  is  concentrated  by 
evaporation,  and  though  it  is  generally  present  only  in  a  small  proportion  {X  to  1  per  cent.), 
yet  the  comparative  quantities  present  in  two  samples  of  flour  may  be  judged  of  by  the 
abundance  in  which  the  pellicle  is  formed. 

t  The  saline  and  other  inorganic  matter  of  grain  resides  chiefly  in  the  husk,  as  may  be 
seen  by  the  relative  quantities  of  ash  left  by  the  flour,  bran,  &c.,  of  several  samples  of  Eng- 
lish and  Foreign  wheat  as  determined  in  my  laboratory — 

wvTTrijn   rnnwN  ^^^  ^'^^'^   ^^^  CENT.    BY  DRY. 

WHERE    GROWN.  pj„g  pj^^j.        ^^^^^^^  ^h&X^s.  BraD. 

1°.  Sunderland  Bridge,  near  ^  ,.04  ..^  tQ  en 

Durham S 

2°.  Kimblesworth,  do 115  38  49  67 

30.  Houghall,  do 0-96  30  5-6  7-1 

40.  Plavvsworth,  do 093  27  5-5  76 

5°.  Stettin: '...  M  45  6-2  6-9 

6°.  Odessa 11  49  66  SO 

I  Dumas'  Traile  de  Chimie,  vi.  p.  388. 


ON    THE    COMPOSITIOIf    OF    VVHEATEN    FLOUR.  501 

COMPOSITION  OF   THE   FLOUR   OP 

French  Wheat.  Odessa  Wheat. 


Water 

l9t 

quality. 
....       100 

2(1 
quality. 

120 
7-3 

720 
5-4 
3  3 

Paris 
Bakers' 
Flour. 
100 
101 
72-8 
4-2 
2-8 

Flinty 
Wheat. 

120 

)4-6 

565 
8-5 
4-9 
23 

Soft  Wheat. 

1st          2d 

luality.  quality. 

100         8  0 

Gluten 

....      110 
....      715 

120        120 

620        70-8 

Sugar 

Gum   ..... 
Bran... 

....        4-7 
33 

7-4         4-9 
5-8         4-6 
1-2         — 

100-5         100         100  98-8         98-4     100-3 

§  9.  Of  the  influence  of  soil  and  climate  on  the  composition  of 
wheaten  flour. 

1°.  The  nature  of  the  soil  has  a  sensible  influence  upon  the  composi- 
tion of  the  grain  that  is  reaped  from  it.  The  proportion  of  gluten,  for 
example,  is  said  to  be  generally  greater  in  grain  which  is  reaped  from 
calcareous  soils,  or  from  such  as  abound  in  organic  matter.  In  the  north 
of  Ireland,  this  fact  has  been  observed  in  regard  to  the  wheat  grown  in 
the  limestone  districts  ;  and  the  millers  of  the  midland  counties  of  Eng- 
land (on  the  new  red  sandstone)  are  accustomed  to  mix,  with  their  native 
corn,  that  of  the  chalk  districts  to  the  east  and  south,  for  the  purpose  of 
giving  additional  strength  to  their  flour. 

Climate. — The  wheat  of  warm  climates  also  is  supposed  usually  to 
contain  more  gluten.  Thus  flour,  prepared  from  some  Eastern  wheats, 
compared  with  that  from  others  of  French  growth,  was  found  to  contain 
water  and  dry  gluten  in  the  following  proportions : 

Water,  Gluten, 

per  cent.  per  cent. 

.     15-1  12-7 

.     12-9  11-2 


French,  Saissette 
Roche!  le 
Brie  . 
Tuzelle 


Odessa 
Taganrog* 


The  quantity  of  gluten  contained 


.     13-5  10-7 

.     13-0  8-3 

.     13-0  15.0 

.     12-6  22-7 
n  English  flour  has  generally  been 

stated  much  too  high.  Thus,  Sir  Humphrey  Davyf  says  that  he  ob- 
tained from  the  flour  of — 

Gluten,  Gluten, 

per  cent.  per  cent. 

English  winter  wheat     19  Barbary  wheat     23 

'   English  spring  wheat     24  Sicilian  wheat     21 

— and  others  have  given  numbers  nearly  as  high.  But  the  gluten  is 
very  difficult  to  dry,  and  I  believe  that  the  large  per-centage  of  this  sub- 
stance assigned  by  previous  experimenters  has  arisen  from  the  water  not 
being  sufficiently  expelled  from  it  by  prolonged  heating  to  220°  F.  I 
select  the  following  from  a  greater  number  of  determinations,  carefully 
made  in  my  laboratory : — 

•  Taganrog,  at  the  head  of  the  sea  of  Asoph,  exports  the  produce  of  the  banks  of  the 
Don. 

•  Agricultural  Chemistry,  Lecture  III. 


502  INFLUENCE    OF   CLIMATE,    VARIETY    OF   SEED, 

Weight  Water 

per  in  Gluten. 

KiNP  OF  WHEAT,  bushel.  Flour.  where  grown. 

lbs.      per  ct.  per  ct. 
Red  English ... .    62^         17-5  81      At  Sunderland  Bridge,  near  Durham. 

"        "       ,...    62^         16-4  95      At  Kiniblesworth,  near  Durham. 

"        «       ....    63  150  8-5       At  Hougliall,  near  Durham. 

«        "       62|  16-8  9  9       Near  North  Deighton,  Yorkshire. 

White  "       ....    63  15  5  75       At  Flaw svvorth,  near  Durham. 

"        Scotch..     61^  16-3  9-4       At  Gadgirth,  near  Ayr  (Appendix,  p.  39.) 

Red  Stettin 63  14-6  8  6 

«    Odessa....     61  15-9        US 

In  all  these  cases  the  quantity  of  gluten  falls  far  short  of  that  assigned  to 
English  flour  by  Davy ;  yet  we  may  safely,  I  think,  conclude  from  them 
that  English  flour  seldom  contains  more  than  10  per  cent,  of  dry  gluten. 
The  flour  from  North  Deighton,  which  gave  9-9  per  cent,  was  grown 
upon  a  thin  limestone  soil,  and  may  perhaps  owe  its  larger  per-centage 
to  this  circumstance. 

But  these  numbers  do  not  indicate  the  exact  quantity  of  nitrogen-hold- 
ing food  which  these  flours  contained.  For  in  the  gluten  there  is  al- 
ways present  avariablequantity  of  fatty  matter  which  contains  no  nitrogen, 
and  which,  if  extracted,  would  lessen  considerably  the  weight  of  the  glu- 
ten in  some  of  the  flours.  On  the  other  hand,  however,  the  water  em- 
ployed in  washing  out  the  starch  holds  in  solution  some  albumen  and 
casein,  which,  having  the  same  composition,  might  be  added  to  the  glu- 
ten, and  would  sensibly  increase  its  weight.  Thus  in  a  sample  of  flour* 
grown  in  Ayrshire  I  found — 

Gluten  ....  9-3  per  cent. 
Albumen  ....  0-45  per  cent. 
Casein         ....         0*40  per  cent. 

Making  in  all  .  .  .        10-15  of  substances  which  contain 
nitrogen  in  nearly  equal  proportions. 

We  probably,  therefore,  do  not  greatly  err  in  general  in  estimating 
the  nutritive  value  of  wheaten  flour — in  so  far  as  it  depends  upon  these 
nitrogenous  compounds — by  the  per  centage  of  dry  gluten  which  a  care- 
ful washing  enables  us  to  separate  from  it.  Further  researches,  how- 
ever, which  are  now  in  progress,  will  throw  much  additional  light  upon 
this  subject. 

§  10.  Influence  of  variety  of  seed,  of  mode  of  culture,  of  time  of  cutting, 
and  of  special  manures,  on  the  composition  of  wheat. 
1°.  Variety  of  seed  and  mode  of  culture. — The  influence  of  these  two 
circumstances  upon  the  relative  proportions  of  bran  and  gluten  are  sjiown 
by  the  following  results  of  the  examination  by  Boussingaultf  of  several 
varieties  of  wheat  grown  in  the  Botanic  Garden  at  Paris — 

Husk  or  Bran  Flour  Water  Gluten,  &c. 

in  the  Grain,  in  the  Grain,  in  the  Flour,  in  the  Flour. 

per  cent.  per  cent  per  cent.  per  cent. 

Capewheat 19  81  7-0  20-6 

Russian  wheat 18  82  6-4  24-8 

Dantzic  wheat 24  76  73  25-8 

Red  Foix  wheat 185  815  9-3  26-1 

BaiTel  wheat 22  78  8-8  277 

Winter  wheat 38  62  141  33 

'  No.  2.  Appendix,  p.  171. 

t  Annalet  de  Chim.  et  de  Phya.  Izv.,  p.  311. 


TIME   CF    CUTTING,    AND    SPECIAL    MANURES.  503 

In  all  the  samples  the  bran  and  gluten  are  both  very  high,  but  they 
vary  much  in  the  several  varieties. 

The  gluten  includes  the  albumen  and  casein  and  other  substances  con- 
taining nitrogen,  but  even  though  grown  in  the  rich  soil  of  a  botanic  gar- 
den, I  fear  the  sum  of  these  has  been  estimated  much  too  high.*  The 
same  variety  of  wheat  grown  in  the  open  fields  in  Alsace  gave  17-3  of 
gluten,  and  in  the  Botanic  Garden  of  Paris,  26*7  of  gluten. 

2°.  The  time  of  cutting  affects  the  weight  of  produce,  as  well  as  the 
relative  proportions  of  flour,  bran,  and  gluten.  Thus  from  3  equal  patch- 
es of  the  same  field  of  wheat  upon  thin  limestone  soil  at  North  Deighton, 
in  Yorkshire,  cut  respectively  20  days  before  the  crop  was  fully  ripe,  10 
days  before  ripeness,  and  when  fully  ripe,  the  produce  was  in  gvain — 
20  days  before.  10  days  before.  Fully  ripe. 

166  lbs.  220  Itts.  209  lbs. 

and  the  per-centage  of  flour,  sharps,  and  bran,  yielded  by  each,  and  of 
water  and  gluten  in  the  flour,  was  as  follows  : — 

IN  THE  GRAIN  PER  CENT.    IN  THE  FLOUR  PER  CENT. 
WHEN  CUT.  , * ^-v   , ' , 

Flour.  Sharps.  Bran.  Water.  Gluten. 

20  days  before  it  was  ripe 747  72  17-5             157  9-3 

10  days  before 791  55  13-2             15-5  99 

Fully  ripe 72-2  110  160            15  9  9-6 

When  cut  a  fortnight  before  it  is  ripe,  therefore,  the  entire  produce  of 
grain  is  greater,  the  yield  of  flour  is  larger,  and  of  bran  considerably  less, 
while  the  proportion  of  gluten  contained  in  the  flour  appears  also  to  be 
in  favour  of  that  which  was  reaped  before  the  corn  was  fully  ripe.f 

3°.  Special  manures. — It  is  said  that  the  employment  of  manures 
which  are  rich  in  nitrogen  not  only  causes  a  larger  crop,  but  also  produ- 
ces a  grain  which  is  much  richer  in  gluten. .  The  experiments  which 
have  hitherto  been  chiefly  relied  upon  in  proof  of  this  result  are  those  of 
Hermbstadt.  On  ten  patches,  each  100  square  feet,  of  the  same  soil  (a 
sandy  loam)  manured  with  equal  weights  of  different  manures  in  the  dry 
state,  he  sowed  equal  quantities  (i  lb.)  of  the  same  wheat — collected, 
weighed,  and  analysed  the  produce.  TJis  results  are  represented  in  the 
following  table : — 

^  2  bo-"  *'s  gc  S°  ire  Si,  a  >  a  bc-s  g  "2 

OS  Zm  cot3  a-a  K  3  Kt3  Ph-3  O-a  >      S  &d 

Rtturn 14 fold.  14  fold.  12  fold.  12  fold.  12  fold.  10 fold.  9 fold.  7  fold.  5  fold.  3  fold. 

Water 4-3  42  4-2  43        4*2        4-3  4-3  42  4-2  4-2 

Gluten 34-2  339  329  32-9  35-1  137  12-2  12-0  96  92 

Albumen 1-0  1-3  1-3  1-3        1-4        M  09  1-0  08  0-7 

Starch 41-3  41-4  42-8  42-4  39-9  61-6  63*2  62-3  65-9  66-6 

Sugar 1-9  1-6  1*5  1-5        1-4        1*6  1-9  1-9  1-9  1-9 

Gum 1-8  1-6  1-5  1-5        1-6        1-6  1-9  1-9  1-6  1-8 

FattyOi! 0-9  M  1-0  09        1-0        1-0  0*9  I'O  10  10 

SolublePhosphates,&c.  0*5  0-6  0-7  07        0-9        0-6  0-5  05  0-5  0-3 

Husk  and  bran 13-9  14-0  138  14-2  14-2  14-0  14-0  14-9  14*0  14-0 

99'8      997      997      99-7      997      99-6      99-8      99-7      99-8      99-7 
The  large  per-centage  of  gluten  obtained  by  the  use  of  the  first  five 

*  In  these  flours  the  gluten  was  not  determined  by  washing  out  the  starch,  but  by  a  more 
refined  method  of  ultimate  analysis,  as  it  is  called,  by  which  the  per-centage  of  nitrogen  is 
determined,  and  the  proportion  of  gluten,  &c.,  calculated  from  this.  When  the  per-centaga 
of  nitrogen  is  small,  as  in  wheaten  flour,  this  method  is  open  to  many  sources  of  error. 

•  See  a  paper  by  Mr.  Jobn  Hannam,  Quarterly  Journal  of  Agriculture,  Iviii.,  p.  173. 


504  EFFECTS    OF    GERMINATION    M  ND    BAKING 

manures  is  very  striking,  if  the  determinations  are  really  to  be  depended 
upon.  They  are  certainly  interesting  in  a  theoretical  point  of  view,  and 
are  deserving  of  careful  repetition.  In  reference  to  their  bearing  upon 
practical  farming,  however,  it  must  not  be  forgotten,  that  the  results  of 
small  experiments  are  never  fully  bonie  out  when  they  are  repeated  on 
the  large  scale — that  the  relative  value  of  different  animal  manures  is 
materially  affected  by  the  kind  of  food  on  which  the  animal  has  lived^ — 
that  independent  of  manures,  there  are  circumstances  not  yet  made  out 
which  materially  affect  the  produce  of  single  patches* — and  that  it  will 
rarely  be  in  the  power  of  the  practical  farmer  to  apply  at  pleasure  to  his 
fields  the  relative  proportions  of  the  several  manures  used  by  Hermb- 
stadt.  Thus,  if  instead  of  20  tons  of  farm-yard  manure  he  wished  to 
try  blood  or  urine  alone,  he  must  apply  24  tons  of  the  former,  and  70 
tons  of  the  latter — quantities  which  it  might  be  both  difficult  to  procure 
and  inconvenient  to  apply. 

The  most  practically  useful  results  yet  published  in  regard  to  the  ac- 
tion of  the  different  manures  upon  the  weight  of  the  crop,  the  proportion 
of  flour  yielded  by  it,  and  of  gluten  in  the  flour,  are  those  of  Mr.  Burnet, 
to  which  I  have  already  had  occasion  to  draw  your  attention. f  These 
results  were  as  follow  : — 

KINI,OKM.K.KB.  ^f^l 

Nothing 31  i  bshls. 

Sulphated  urine  and  wood  ashes.    40      " 

Do.  and  sulphate  of  soda.    49       " 

Do.  and  common  salt.      .49      " 

Do.  and  nitrate  of  soda,  ..  48|     " 

We  perceive  here  a  slight  increase  in  the  per-centage  of  gluten  when 

the  manures  were  applied,  but  nothing  which  at  all  resembles  the  great 

differences  given  by  Hermbsatdt,  or  which  renders  it  probable  that  by 

skilful  management,  as   some   have   supposed,  we   may  hereafter  be 

able  to  raise  in  our  fields  whole  crops  of  corn  which  shall  yield  a  flour 

containing  20  or  30  per  cent,  of  gluten. 

§11.  Of  the  effects  of  germination,  and  of  baking,  upon  the  flour  of  wheat. 

The  effects  of  germination  and  of  baking  upon  the  flour  of  wheat  are 
very  analogous  to  each  other.  In  both  cases,  a  portion  of  the  starch  is 
changed  into  gum  and  sugar. 

1°.  Germination. — I  have  already  described  to  you  (p.  118),  the  very 
beautiful  change  which  takes  place  di  ring  the  sprouting  of  the  seeds  of 
plants — how  a  portion  of  their  gluten  s  changed  into  diastase,  and  how, 
by  the  agency  of  this  diastase,  the  starcli  of  the  seed  is  changed  into  gum 
and  sugar.  In  an  experiment  made  by  De  Saussure,  100  parts  of  the 
farina  of  wheat  had  by  germination  lost  6  parts  of  starch,  and  in  their 
stead  had  acquired  Sif  of  gum  and  2i  of  sugar.  The  eflTect  of  this 
change — which  proceeds  as  the  plant  continues  to  grow — is  to  make  the 
starch  soluble,  and  thus  capable  of  entering  into  the  circulation  of  the 
young  plant. 

2°.  Baking. — It  is  the  larger  proportion  of  gluten  usually  contained 
in  the  flour  of  wheat  that  renders  it  so  much  better  fitted  for  the  bakin?  of 

"  See  Appendix,  pp.  59  and  79.  T  See  p.  362  and  Appendix  pp.  49  and  71. 


Fine  Flour 

Gluten 

from  the  grain. 

in  the  flour. 

76f  lbs. 

9-4  per  cent. 

6Gi  " 

10-5      " 

63i  " 

9-7      " 

651  " 

9-6      " 

54|  " 

100      " 

UPON    THE    FLOUR    OF    WHEAT.  606 

bread  than  the  flour  of  any  other  grain.  If  the  gluten  be  washed  out  of 
the  flour,  and  put  alone  into  the  oven,  it  will  swell  up,  become  full  of 
pores,  and  assume  a  large  size.  The  comparative  baking  qualities 
of  ditferent  samples  of  flour  may  be  judged  of  by  the  height  to  v/hich,  in 
similar  vessels,  the  gluten  of  equal  weights  of  flour  is  thus  observed  to  riee. 

We  have  already  seen  that  by  heating  in  an  oven,  dry  starch  is  gra- 
dually changed  into  gum  {British  gum,  p.  113),  and  into  a  species  of 
sugar — becoming  completely  soluble  in  water.  Such  a  change  is  pro- 
duced upon  a  portion  of  the  starch  of  wheaten  flour  when  it  is  baked  in 
the  oven.  Thus  in  100  parts  of  the  flour,  and  of  the  bread  of  the  same 
wheat,  Vogel  found  respectively — 

Starch.  Sugar.  Gum. 

Flour         ...       68  5  — 

Bread        .         .         .       53i  3|  18 

So  that  a  very  considerable  portion  of  gum  had  been  produced  at  the  ex- 
pense of  the  starch. 

The  yeast  which  is  added  to  the  dough  in  baking,  acts  in  the  same 
way  as  when  it  is  added  to  the  sweet  wort  of  the  brewer.  It  induces  a 
fermentation  by  which  the  sugar  of  the  flour  is  changed  into  carbonic 
acid  and  alcohol.  The  carbonic  acid  is  liberated  in  the  form  of  minute 
bubbles  of  gas  throughout  the  whole  substance  of  the  dough  and  causes 
it  to  rise,  the  alcohol  is  distilled  off'  in  the  oven.  If  too  much  water 
have  been  added  to  the  dough — or  if  it  have  not  been  sufficiently  knead- 
ed—or if  the  flour  be  too  finely  ground — or  if  the  paste  be  not  sufficiently 
tenacious  in  its  nature,  these  niinute  bubbles  will  run  into  each  otlier, 
will  form  large  air  holes  in  the  heart  of  tlie  bread,  and  will  give  it  that 
open  irregularly  porous  appearance  so  much  disliked  by  the  skilful 
baker.  Good  bread  should  be  full  of  small  pores  and  uniformly  light. 
Such  bread  is  produced  by  a  strong  flour ;  that  is,  one  which  will  rise  well, 
will  retain  its  bulk,  and  will,  bear  the  largest  quantity  of  water. 

The  quantity  of  water  which  wheaten  flour  retains  when  baked  into 
bread  depends  in  some  degree  upon  the  (juality  of  the  flour.  In  the 
Acts  of  Parliament  relating  to  the  assize  of  bread,  it  is  assumed  that  a 
sack  of  flour  (280  lbs.)  will  produce  80  quartern  loaves,  or  320  lbs.  of 
bread.  According  to  this  calculation  the  flour  should  take  up  and  retain 
when  baked  one-seventh  of  its  weight  of  water.  But  the  quantity  of  water 
retained  by  the  flour  now  in  use  is  very  much  greater,  and  the  profit  to 
the  baker,  therefore,  very  much  more  than  this  calculation  supposes. 

This  is  shown  by  the  quantity  of  water  which  is  lost  by  wheaten 
bread,  whether  of  first  or  second  quality,  when  it  is  dried  by  prolonging 
heating,  at  a  temperature  not  exceeding  220°  F.  The  home-made 
bread  (white  and  brown)  baked  in  my  own  house,  and  in  two  other 
private  houses  in  Durham,  lost  of  water  by  drying  in  this  v/ay — 


How  long  baked. 

Water  per 

1°.    White 

24  hours. 

43-3 

Brown* 

24     do. 

44-0 

2°.   Brown 

42     do. 

44-1 

White        . 

36     do. 

42-9 

3°.   White 

9     do. 

44-1 

•  The  brown  bread  is  made  from  the  whole  grain  of  the  wheat  as  it  comes  from  the 
millstones— nothing  being  separated  by  sifling. 


606  WATER  TAKEN  UP  BY  FLOUR  IN  BAKING. 

So  that  wheaten  bread  one  day  old  contains  about  44,  and  two  days  oid» 
about  43  per  cent,  of  water.  Something,  however,  will  depend  upon 
the  size  of  the  loaves. 

This  proportion  is  almost  exactly  the  same  as  that  contained  in  the 
white  bread  of  Paris.  According  to  Dumas,  the  water  in  th«;  common 
white  bread  of  Paris  amounts  to — 

Hours  baked.  Water  per  cent. 

2 45-7 

4i 45-3 

10 43-0 

24 43-5 

We  may  assume,  therefore,  44  per  cent,  as  very  nearly  the  average 
quantity  of  water  contained  in  good  white  bread  both  in  England  and  in 
France.  Bread  baked  for  public  establishments  contains  more  water, — 
not  being  generally  so  well  fired,  or  being  baked  in  the  form  of  many 
loaves  stuck  together,  instead  of  in  separate  tins,  as  is  done  with  home- 
made bread.  Such  is  the  case  with  the  soldiers'  bread  of  our  own 
country,  and  the  barrack  bread  of  Paris  (pain  de  munition)  which  con- 
tains about  51  per  cent,  of  water. 

We  have  already  seen  (p.  499)  that  English  wheaten  flour  contains,  on 
an  average,  about  16  per  cent,  of  water.  If,  therefore,  the  bread  baked 
from  it,  as  it  comes  from  the  mill,  contain  44  per  cent.,  every  hundred 
pounds  consist  of — 

Dry  flour         .         .         .         .         .         ^^    l    661 
Water  in  the  flour  (naturally)  .         10^  J        2 

Water  added  by  the  baker        ....     33i 

100 
Or,  the  flour,  in  baking,  takes  up  half  its  weight  of  water.     A  hundred 
pounds  of  flour,  therefore,  as  it  comes  from  the  mill,  will  give  very 
nearly  150  pounds  of  bread.     Thus — 

Flour  contains  Bread  contains 

Dry  flour         ....  84  84 

Natural  water  ...  16  16 

Water  added  .   .    50 

100  

Weight  of  bread  150 
A  sack  of  flour,  therefore,  or  280  lbs.,  ought  to  give  about  420  lbs.  of 
well  baked  bread.  Something  must  be  deducted  from  this  for  the  loss 
by  fermentation,  and  for  the  dryness  of  the  crusts.  Allowing  5  percent, 
for  these,  a  sack  of  flour  should  give  400  lbs.  of  bread  of  the  best  quality,* 
or  100  quartern  loaves.  The  cost  of  fine  white  bread,  therefore,  com- 
]>ared  with  that  of  corn  and  flour,  ought  to  be  very  nearly  as  follows  : — 
Cost  of  Flour,  Cost  of  Bread,  Market  price  of 

per  sack.  per  stone.  per  quartern  loaf.  Grain  per  qr.t 

35s.  Is.  9d.  4]d.  47s. 

40s.  2s.  Od.  4id.  •  52s. 

'  Unmixed  with  potatoes,  which  are  employed  by  many  bakers  in  considerable  quantity 
Mixed  witn  the  yeast  they  are  said  to  make  the  bread  lijrhter. 

t  This  column  has  been  calculated  for  me,  from  the  price  of  the  flour,  ^y  my  friend  Mr. 
John  Robson,  miller,  in  Durham.  Tlie  practical  rule  is,  that  6  bushels  ot  corn  should  give 
one  sack  of  flour,  and  that  the  miller  should  have  the  offal  for  his  trouble. 


RELATIVE  COST  OF  CORN,  FLOUR,  AND  BREAD.        607 

Cost  of  Flour,  Cost  of  Bread,  Market  price  of 

per  sack.              per  stone.  per  quartern  loaf.  Grain  per  qr. 

45s.                 2s.  3d.  5|d.  60s. 

50s.                 2s.  6d.  6d.  67s. 

55s.                 2s.  9d.  6^d.  •         72s. 

60s.                 3s.  Od.  7|d.  80s. 

The  economy  of  baking  at  home,  therefore,  at  the  usual  prices  of 
bread,  seems  to  be  very  considerable. 

§  12.  Of  the  supposed  relation  between  the  per-centage  of  gluten  in 
flour,  and  the  weight  of  bread  obtained  from  it. 

It  has  been  assumed  by  recent  chemical  writers  that  the  quantity  of 
water  absorbed  by  flour,  and  consequently  the  weight  of  bread  obtained 
from  it,  depends,  in  whole  or  in  great  part,  upon  the  proportion  of  gluten 
which  the  flour  contains.  The  following  facts,  however,  do  not  accord 
with  this  supposition. 

1°.  Household  bread,  made  respectively  from  the  flour  of  a  French 
wheat  and  of  a  wlieat  from  Taganrog,  retained  nearly  the  same  per- 
centage of  water,  though  the  one  sample  contained  upwards  of  twice  as 
much  gluten  as  the  other.     Thus — 

Gluten  per  cent.  Water  per  cent, 

in  the  Flour.  in  tiie  Bread. 

Flour  of  Brie         .  .         .         10-7  47-4 

Flour  of  Taganrog  .         .         22-7  47-0 

This  one  fact  might  be  supposed  to  settle  the  question,  but  I  shall 
mention  others. 

2°.  The  flour  from  Odessa  wheat  contains  about  ^th  more  gluten  than 
French  flour  in  general,  and  j^et  it  absorbs  very  little  more  water  (Du- 
mas). This  Dumas  accounts  for  by  the  fact  that  the  starch  of  the 
Odessa  wheat  forms  hard  transparent  horny  particles,  which  take  less 
water  to  moisten  them  than  the  impalpable  powder  yielded  by  the  softer 
French  wheats — so  that  tlie  gluten  does  not  appear  to  produce  its  full 
effect.  I  do  not  know  how  far  this  explanation  is  consistent  with  the 
fact  that  the  hard  flinty  wheats  give  the  best  biscuit  flour — what  the 
baker  calls  the  strongest,  which  rises  best,  and  absorbs  the  most  water.* 

3°.  Rice  is  said  to  contain  very  little  gluten — not  estimated  by  any  to 
amount  to  more  than  6  or  7  per  cent. — and  yet  it  is  stated  as  the  result  of 
numerous  trials,  that  an  admixture  of  a  seventh  part  of  rice  flour  causes 
wheaten  flour  to  absorb  more  water. f 

4°.  If  the  hard  wheats  be  ground  too  fine  they  lose  a  part  of  their  ap- 
parent strength,  the  flour  becomes  dead,  as  it  is  sometimes  called,  and 
refuses  to  rise  as  it  would  do  if  sent  to  the  baker  in  a  more  gritty  and  less 
impalpable  state. 

6°.  Lastly,  the  admixture  of  very  minute  quantities  of  foreign  matter, 
by  way  of  adulteralioa,  is  said  to  have  a  remarkable  influence  upon  the 
quantity  of  water  which  the  flour  will  absorb.  In  some  parts  of  Belgium 
it  appears  to  have  been  the  practice  to  adulterate  the  bread  with  a  small 
quantity  of  sulphate  of  copper.J     This  salt  is  dissolved  in  water,  and 

•  That  such  Is  the  case  also  in  foreign  countries,  see  a  letter  from  the  British  Consul  at 
Lisbon,  in  Davy's  Agricultural  Chemistry,  Lecture  IIL 
t  Dumas'  Traite  de  Chimie,  vi.,  p.  396. 
t  Blue  vitriol— e  v'olent  poison. 


508  COMPOSITION    OF    BARLKY. 

the  solution  added  to  the  water  with  which  tlie  dough  is  to  be  made,  ia 
the  proportion  of  about  one  grain  to  two  pounds  of  flour.  It  gives  the 
bread  a  fairer  colour,  and  thus  permits  the  use  of  inferior  flour,  and  it  causes 
the  bread  to  retain  about  six  per  cent,  more  water  without  appearing  inoist- 
er.  Even  in  the  small  proportion  of  one  grain  of  the  sulpliate  to  G,  or 
7  lbs.  of  flour,  it  produces  a  very  sensible  effect  (Kuhlman). 

Other  adulterations  also  exercise  a  similar  influence.  Alum  improves 
the  colour  of  the  bread,  raises  it  well,  and  causes  it  to  keep  water,  but  it 
requires  to  be  added  in  larger  quantity  than  the  more  poisonous  sulphate 
of  copper.  Common  salt  likewise  makes  the  paste  stronger,  and 
causes  it  to  retain  more  water,  so  that  the  addition  of  salt  is  a  real  gain 
to  the  baker. 

From  all  these  facts,  therefore,  we  may  infer  that,  independent  of  the 
relative  proportions  of  gluten,  very  slight  differences  in  composition — 
8uch  as  have  not  yet  been  sought  for  or  appreciated — may  materially 
affect  the  relative  weights  of  bread  obtained  by  the  baker  from  different 
samples  of  wheaten  flour. 

§  13.  Of  the  composition  of  barley,  and  the  injiuence  of  different  manures 
upon  the  relative  proportions  of  its  several  constituents. 

The  grain  of  barley  consists  of  nearly  the  same  substances  as  that  of 
wheat,  but  in  proportions  somewhat  different.  These  proportions,  how- 
ever, are  aflfected  both  by  the  kind  of  manure  with  which  the  land  is 
dressed,  and  by  the  nature  of  the  soil  on  which  the  seed  is  sown. 

1°.  Manure. — The  effect  of  manure  appears  from  the  following  table, 
containing  the  results  of  Hermbstadt,  obtained  in  the  same  way  as  those 
with  wheat  already  described  (p.  503)  : — 

u  .       6  J:         u  -2  .  «       P'S 

KIND    OP  S  -^         3        h  A  E  rtp  ■B'i'E  ar^rS 

MANURE.  ^  3=£§5  3=  =       I -§  ^  O     «^S 

Ox  Blood 10-4  13-6  57  0-4  59-9  4-6  4-4  0  4  0-4  16 

Night-soil 10-2  13*6  5-8  0-5  59-6  4-5  4-3  0-5  0-6  13 

Sheep's  dnng...  10-3  13-5  5-7  0-4  599  4-6  4-4  0-4  0-3  16 

Goat'sdung 10-4  13-5  57  0-4  599  46  4-5  0-4  0-3  15 

Human  urine...  103  136  5-9  05  59-6  4-4  4-4  0-4  0-7  13i 

Horsedung 10-4  13-5  5-7  0-4  59-7  4-5  4-5  0-4  0-4  13 

Pigeon's  duiig  ..  10-4  13-5  5-6  0*4  598  46  45  0-4  0-4  10 

Cow'sdung 10-8  13*6  33  02  61-9  4'8  46  0-3  0-3  11 

Veget.  manure..  10-8  13-6  2-9  0-2  62-2  4-9  4-8  0-2  0-1  7 

No  manure 10  8  13-6  2-9  01  625  5-0  47  0-1  0-1  4 

In  so  far  as  reliance  is  to  be  placed  i^on  the  numbers  in  the  above 
table,  as  indicative  of  the  general  effect  of  the  several  manures  men- 
tioned, it  would  appear  that  the  relative  proportions  of  gluten,  albumen, 
and  starch  do  not  vary  very  much  until  we  come  to  cow-dung,  when  the 
former  two  substances  sensibly  diminish.  Further  experiments,  how- 
ever, are  required  upon  this  subject  (see  page  514). 

2°.  Soil. — The  effect  of  soil  upon  the  barley  crop  is  known  to  all 
practical  farmers — so  that  the  terms  barley-land  and  wheat-land  are  the 
usual  designations  for  light  and  heavy  soils  adapted  especially  to  the 
growth  of  these  several  crops.  On  clay  lands  the  produce  of  barley  is 
greater,  but  it  is  of  a  coarser  quality,  and  does  not  malt  so  well-^n 
loams  it  is  plump  and  full  of  meal — and  on  light  chalk  soils  the  crop  is 
ligtt,  but  the  grain  is  thin  in  the  skin,  of  a  rich  colour,  and  well  adapted 


EFFECT    OF    MALTING    UFOJN    BARLEY.  509 

for  malting.*  The  barley  of  the  light  lands  in  Norfolk  is  celebrated  in  the 
North  of  England  for  its  malting  properties — and  the  brewers  refuse  the 
barley  of  the  county  of  Durham,  even  at  a  lower  price,  when  Norfolk 
barley  is  in  the  market.  When  unfit  for  malting,  barley  affords  a  fat- 
tening food  for  pigs  and  for  some  other  kinds  of  stock. 

§  14.  Effect  of  malting  upon  barley. 

During  the  germination  good  barley  increases  in  bulk  one-half.  In 
order  that  it  may  do  so,  it  must  be  uniformly  ripe — a  quality  of  great 
value  to  the  maltster.  This  maximum  bulk  is  generally  acquired  in  24 
hours  after  it  has  been  moistened  and  laid  in  heaps.  In  drying,  how- 
ever, the  barley  again  diminishes  in  bulk,  so  that  the  dried  malt  rarely 
exceeds  by  more  than  njth  or  f^th  the  bulk  of  the  grain  as  it  came  from 
the  market.  The  well-dried  malt,  however,  is  lighter  by  |th  tnan  the 
barley  from  which  it  is  made — 100  lbs.  of  barley  yielding  about  80  lbs. 
of  malt.  This  is  not  all  loss  of  substance,  since  by  a  similar  drying  the 
barley  itself  before  malting  would  lose  about  12  per  cent  of  water.  The 
loss  of  substance,  therefore,  is  only  about  8  per  cent.  This  diminution 
of  solid  matter  arises  in  part  from  the  loss  of  the  little  roots  which  form 
the  malt-dust  {cumtnins),  of  which  I  have  already  spoken  (p.  436)  as 
being  a  valuable  manure,  and  of  which  4  or  5  bushels  are  obtained  from 
100  bushels  of  barley. 

The  colour  of  the  malt  varies  with  the  temperature  at  which  it  is  dried. 
If  the  heat  does  not  exceed  100°  F.  a  very  pale  malt  is  obtained,  which 
gives  a  very  white  beer.  A  heat  not  rising  above  180°  gives  an  amber 
coloured  malt — while  for  brown  malt  the  temperature  may  rise  as  high 
as  260°  F.  By  mixing  these  varieties  beer  of  any  colour  may  be  made. 
But  in  the  porter  breweries  it  is  usual  to  prepare  a  quantity  of  malt  of  a 
brownish  black  colour  {burned  malt),  by  adding  a  portion  of  which  any 
required  shade  of  colour  is  imparted  to  the  liquor. 

During  germination  a  variable  quantity  of  the  gluten  is  converted  into 
diastase  (p.  119),  and  about  two-fifths  (40  percent.)  of  its  starch  into 
sugar  or  gum  (dextrine).  The  quantity  of  diastase  produced  depends 
upon  the  extent  to  which  the  germination  has  proceeded.  It  is  greatest 
at  the  moment  when  the  gemmule  is  about  to  burst  from  the  seed,  and  to 
form  the  young  shoot. 

I  have  already  explained  the  beautiful  purpose  served  by  this  diastase 
in  converting  the  insoluble  starch  of  the  grain  into  soluble  sugar  and 
gum.  When  the  beer  is  to  be  made  wholly  from  malt,  it  is  unnecessary 
to  continue  the  germination  till  the  largest  quantity  of  diastase  is  pro- 
duced. It  is  sufficient  if  the  gemmule,  on  holding  up  a  grain  of  the 
barley,  be  seen  within  the  skin  to  have  attained  one-half  or  two-thirds  of 
the  length  of  the  seed.  The  diastase  then  produced  is  more  than  enough 
to  convert  the  whole  of  the  starch  of  the  grain  into  sugar  (p.  120).  But 
if  raw  grain,  as  in  some  of  our  distilleries,  is  to  be  added  to  the  malt, 
then  the  malting  should  be  prolonged  till  the  bud  is  about  to  burst  througli 
the  husk,  so  that  the  largest  possible  supply  of  diastase  may  be  contain- 
ed in  it.     In  this  way  ^so  malt  is  prepared  when  it  is  to  be  employed 

•  "  The  barley  on  the  compact  clays  (in  Hants)  is  of  a  coarser  quality,  but  produce  greater— 
on  the  light  chalk  soils  it  is  well  calculated  for  malting— the  skin  is  thin,  and  colour  rich  but 
light— in  fuUness  of  meal  and  plumpness  of  appearance  it  never  equals  the  barleys  grown  in 
Staflbrdshire,  and  upon  loamy  lands."— Mr.  Gawler  in  British  Husbandry,  ili.  p.  12. 

22 


510  COMPOSITION    OF    OATS    AND    RYE. 

in  the  manufacture  of  syrup  (glucose)  from  potatoe  flour — a  branch  of  in- 
dustry which  has  become  of  some  '.mportance  in  certain  parts  of  Frarce. 

§15.  Composition  of  oats,  and  effect  of  manures  in  m/)difying  that  composition. 

The  relative  proportions  of  husk  and  meal  in  the  several  varieties  of 
the  oat.  differ  in  a  greater  degree,  probably,  than  in  any  other  grain. 
Thus,  the  potatoe-oat  is  known  to  be  richer  in  meal,  the  Tartary-oat  in 
husk.  The  round  grain  of  the  former  is  chiefly  grown  in  Scotland,  for 
grinding  into  meal,  the  latter  in  England,  for  feeding  horses. 

But  even  the  round  potatoe-oat  varies  much  in  the  produce  of  meal 
which  it  gives.  Many  samples  yield  only  half  their  weight  of  oatmeal, 
others  9  stones  out  of  16,  while  some  give  as  much  as  12  stones  from  the 
same  quantity,  or  three-fourths  of  their  weight.  In  one  variety  of  oat 
Vogel  found  66  per  cent,  of  meal  and  34  of  husk,  which  is  equal  to  lOi 
stones  of  meal  from  16  of  grain.  He  also  extracted  from  the  meal  2  per 
cent,  of  oil,  and  59  of  starch,  and  observed  it  to  lose  by  drying  upwards 
of  20  per  cent,  of  water. 

Soil,  season,  climate,  variety  of  seed  sown,  and  the  kind  and  quantity 
of  manure  appKed — all  affect  the  amount  of  produce  and  the  chemical 
composition  of  the  oats  that  are  reaped.  According  to  Hermbstadt,  the 
effect  of  different  manures  in  modifying  the  composition  of  the  produce 
of  the  same  seed  are  represented  by  the  numbers  in  the  following  table : 

KIND   OF  «  -JgSfldSrtd  -^^S         S^-d 

MANCRB.  I  §^|S|^i:=         unci's 

OxBlood 120  19-3  5-0  0-4  53-1  3-8  5-5  03  04  12i 

Night-soil 12-1  19-2  4-6  0-4  53-3  38  5-4  0-3  0-5  14| 

Sheep's  dung...  12-6  133  40  05  540  52  5-5  03  0-4  14 

Goat'sdung 12-9  170  43  0-4  53-2  5-4  5-7  03  0-4  15 

Human  urine...  130  170  44  05  531  50  5-7  04  0-6  13 

Horsedung 13-1  160  40  05  545  52  5-6  0-3  0-5  14 

Pigeon's  dung..  12-3  183  3-2  0-3  532  50  68  03  0-3  12 

Cowdung 11-6  15-0  3'1  03  55-0  68  7-3  03  0-3  16 

Veget.  manure..  10-8  130  2-0  0-2  59-9  6-4  70  0-2  0-2  13 

Unmanured 10  8  12-0  1-9  02  600  6-4  70  03  0-1           5 

The  difTerences  in  this  table  are  very  striking  [see  p.  515]. 

§  16.  Composition  of  rye,  and  effect  of  different  manures  upon  its  composition. 
The  grain  of  rye  approaches  nearest  to  that  of  wheat  in  the  quantity 
of  gluten  it  contains,  and  in  the  consequent  fitness  of  its  flour  for  baking 
into  bread.  It  sometimes  also  contains  much  sugar — recent  rye-bread 
having  almost  invariably  a  sweet  taste — but  the  proportion  of  sugar  ap- 
pears to  be  by  no  means  constant.  Thus  Einhof  and  Greif  exhibit  the 
composition  of  a  sample  of  r^e-flour,  examined  by  each  of  them,  re- 
spectively as  follows  : — 

Einhof,  per  cent  Grief,  per  cent 

12-8 

3-0 

58-8 

10-4 

7-2 

7-8 

100  100 


Husk      . 

'6-4 

Gluten  (not  dried) 

9-5 

Albumen     . 

3-3 

Starch          .      . 

61-1 

Sugar 

3-3 

Gum 

111 

Loss 

5-3 

COMPOSITION    OF   RICE.  511 

Perhaps  no  great  degree  of  faith  is  to  be  placed  in  these  analyses.  If 
they  are  to  be  depended  upon,  they  show  that  very  remarkable  differ- 
ences indeed  may  exist  in  the  relative  proportions  of  some  of  the  consti- 
tuents of  rye  flour.  The  flour  of  rye  is  said  to  be  more  absorbent  of 
moisture  from  the  air  than  that  of  any  other  grain.* 

Rye  delights  in  a  sandy  soil,  and  is  cultivated  in  general  in  such  as 
are  poor  in  vegetable  matter,  and  to  which  manure  is  not  very  abun- 
dantly added.  The  experiments  of  Hermbstadt,  whose  results  are  ex- 
hibited in  the  following  table,  do  not  show  any  very  striking  difference 
to  have  been  produced  upon  the  composition  of  the  grain  by  the  use  of 
the  different  animal  manures  : — 

KIND    OP  fg  M  2        3  A        ii  c3e  -SoiS  3^T3 

MANURK.  ^  §  =||3  ^1=      l^^ci    Zu^ 

^        K  O*^  <B  9i  02OO     -KPLio,^  tf^oa 

OxBlood 10  1  10-4  120  3-6  62-2  36  6-2  1-0  08  14 

Night-soil 100  107  119  3-2  524  35  63  0-9  0-9  13i 

Sheep's  dung...  100  108  11-9  3-4  523  3-6  6-1  1-1  0-6  13 

Goat'sdung.   ...  10-0  10-8  11-9  3-4  522  3*5  6-0  1-0  0-9  12A 

Human  urine...  101  108  120  3-5  50-2  33  4-6  I'l  4-2  13 

Horsedung 100  10-7  119  28  512  40  4-6  1-0  3-6  11 

Pigeon's  dung..  101  10-5  11-6  3-7  522  3-7  4-7  09  2-3           9 

Cowdung 10-0  10-4  108  20  54-3  3-9  5-7  0-9  1-8           9 

Veget.  manure..  100  10-7  88  26  55-1  4-8  5-2  0-9  1-7           6 

Unmanured 10  0  101  86  26  56-3  4-7  5'4  0-9  1-3           4 

The  above  table  exhibits  a  larger  increase  in  the  return  or  produce 
from  some  of  the  animal  manures  than  from  others,  but  we  do  not  see 
any  of  those  remarkable  differences  in  the  composition  of  the  flour,  whix;h 
are  observable  in  the  results  obtained  by  the  application  of  different 
manures  to  the  wheat  crop. 

The  substance  extracted  from  rye,  and  called  gluten  by  Hermbstadt,  is 
different  from  the  gluten  of  wheat,  and  is  more  like  the  glutine  extracted 
from  the  latter  grain.  When  dough  made  of  rye  flour  is  washed  in 
water,  it  nearly  all  diffuses  itself  through  the  liquid,  leaving  little  more 
than  the  husk  or  bran  behind.  The  starch  deposits  itself  from  the  milky 
liquid,  or  may  be  separated  by  the  filter.  When  the  liquid  is  evaporated 
to  dryness,  and  the  dry  mass  boiled  in  alcohol,  the  so-called  gluten  is 
dissolved  out,  and  may  be  separated  from  the  alcohol  by  distillation.  It 
must  then  be  washed  with  water  to  free  it  from  sugar.  Like  the  gluten 
of  wheat,  it  is  now  insoluble  in  water,  and  is  less  cohesive  than  gluten. 
Both  of  these  forms  of  gluten  are  supposed  to  have  the  same  composi- 
tion as  vegetable  fibrin  and  albumen,  and  as  the  curd  of  mUk. 

§  17.   Composition  of  rice,,  maize  {Indian  corn),  and  buck-wheat. 

1°.  Rice  is  usually  supposed  to  differ  from  other  kinds  of  grain  by  the 
larger  proportion  of  starch  which  it  contains. 

The  large  quantities  of  rice  consumed  by  the  native  inhabitants  of 
India,  and  of  other  warm  countries,  has  often  appeared  surprizing  to 
foreigners.  Chemists  have  explained  this  alleged  fact  by  supposing  the 
small  per-centage  of  gluten  contained  in  rice,  as  shown  by  the  following 
analyses,  to  be  insufficient  for  the  sustenance  of  the  body — when  no 
pther  food  is  used — unless  this  grain  be  eaten  in  exceedingly  large  quan- 

*  A  sample  of  rye  meal,  dried  in  my  laboratory,  lost  only  14X  per  cent,  of  water,  and  of 
rye  bread  leavened  44,  and  yeaated  46  per  cent  This  rye  meal  may  possibly  have  been 
mixed. 


512 


OF  MAIZE  OR    INDIAN    CORN. 


titles.  It  is  probable,  however,  that  tlie  nitrogenous  constituents  of  rice 
are  stated  too  low  in  the  analyses  of  Braconnot,  and  that  it  contains  albu- 
men or  casein,  or  some  analogous  substance,  which  has  been  passed  over 
by  this  chemist.  A  scries  of  carefully  repeated  analyses  of  different 
varieties  of  rice,  if  it  did  not  modify,  would  at  least  fix  our  present  opin- 
ions in  regard  to  its  theoretical  value  as  food  for  man.* 

Two  samples  of  rice  examined  by  Braconnot,  were  found  by  him  to 
be  composed  of — 

•  Carolina.  Piedmont. 

5-0  7-0 

4-8  4-8 

3-6  3-6 

85-07  83-8 

0-3  0-05 

0-7  0-1 

0-13  0-25 

0-4  0-4 


w  aier     . 
Husk      . 

Gluten    . 

Starch     . 

Sugar     . 

Gum 

Oil     .     .     . 

Phosphates 

100  100 

2®.  Maize  or  Indian  corn  is  celebrated  for  the  large  return  of  focxl 
which  it  yields  from  a  given  extent  of  land,  and  for  its  remarkably  fat- 
tening qualities  when  given  to  poultry,  pigs,  and  cattle.  Buckwheat 
is  also  a  very  nourishing  grain.     They  consist  respectively  of — 

Dry  maize  (Payen).  Buckwheat  (Zenneck). 

5-0  26-9 

1-2  10-7 

7-1  52-3 

0-5  8-3 

8-9  0-4 

5-05  — 

1-8  ? 


Husk 

Gluten,  &c. 

Starch 

Sugar  and  gum 

Fatty  matter 

Colouring  matter 

Salts 


24-53f  98-6 

The  above  analysis  of  maize  must  be  incorrect,  as  it  supposes  the  fatty 
matter  to  amount  to  nearly  36  per  cent,  of  the  weight  of  the  corn. 
Dumas  has  lately  stated  it  at  8-9  per  cent. — instead  of  8-9  in  24-55  parts, 
as  found  by  Payen — and  Liebig  denies  that  Indian  corn  contains  more 
than  5  per  cent,  of  fatty  matter.  New  analyses,  therefore,  are  required 
of  this  grain  also.  Indeed  it  may  be  said  in  general  of  all  the  substances 
used,  especially  in  feeding  animals,  that  we  have  not  yet  the  requisite 
knowledge  to  enable  us  to  reason  accurately  in  regard  to  the  special  ope- 
ration of  each  in  sustaining  the  body  or  in  promoting  the  growth  of  fat.J 

•  Five  varieties  of  rice,  as  it  is  sold  in  the  shops,  examined  in  my  laboratory,  lost  of  water 
and  gave  of  ash  per  cent,  respectively— 

Water.  Ash,  Water.  Ash. 

Madras  rice    ....    13  5  0  58  I  Carolina  rice     .    .    .    130  0-33 

Bengal  rice     ....     131  0-45  Do.  flour .    .     146  035 

Patna  rice       ....     131  0-36  | 

The  water  in  these  samples  is  very  much  greater  than  in  those  examined  by  Braconnot.  By 
exposure  to  the  air  the  rice  in  a  few  days  re-absorbed  nearly  all  it  had  lost  by  drying.  The 
ash  of  rice  contains  more  alkaline  matter  than  that  of  wheat,  and  is  very  diflScuft  to  bim  white. 

t  Dumas,  Traite  de  Chitnie,  vi.,  p.  394. 

t  A  sample  of  Indian  corn  examined  in  my  laboratory,  lost  of  water  13-6  per  cent,  and 
leA  of  white  earthy  ash  1-3  per  cent. 


GENERAL   EFFECT    OF    MANURES.  513 

§  18.  On  the  alleged  general  effect  of  different  manures  in  modifying  the 
amount  of  gluten  and  albumen  in  wheat,  barley,  oats,  and  rye. 

Among  the  general  deductions  in  regard  to  the  Special  influence  of 
manures  upon  the  quality  of  the  grain  we  reap,  that  which  has  been  re- 
ceived with  the  greatest  confidence  is  this — that  the  richer  in  nitrogen  the 
manure  we  apply,  the  richer  in  gluten  the  grain  we  reap. 

The  only  experiments,  having  any  pretensions  to  accuracy,  by  which 
this  opinion  has  hitherto  been  supported,  are  those  of  Hermbstadt.  The 
results  of  these  experiments  are  contained  in  the  four  tables  to  which  I 
have  directed  your  attention  under  the  heads  of  wheat,  barley,  oats,  and 
rye.  As  the  opinion  founded  upon  them  is  one  which,  if  correct,  is  of 
great  practical  value, — it  will  be  proper  to  examine  the  experiments  them- 
selves a  little  more  narrowly.  Are  they  really  deserving  of  implicit 
credit  ?     Do  they  justify  the  conclusion  that  has  been  drawn  from  them  ? 

Turn  first  to  the  experiments  upon  wheat,  of  which  the  results  are 
embodied  in  the  following  table,  repeated  from  page  503 : — 


o  -ji,-;  0)=  eSc  «=  fee  SjC  Pc  tefS  5  O  £ 

OS  ZS  ^%  O-o  Ms  ffi-c  £•§  O-o  >      a  Ua 

Retui-n 14  fold.  14  fold.  12  fold.  12  fold.  12  fold.  10  fold.  9  fold.  7  fold.  5  fold.  3  fold. 

Water 4-3       42  4-2  43        42  4*3  43  42  4-2  4-2 

Gluten 34-2  339  329  32-9  361  13-7  122  12-0  96  92 

Albumen 10       1-3  r3  13        1-4  1-1  09  10  08  0*7 

Starch 413  414  42*8  42*4  39-9  61-6  632  623  659  66-6 

Sugar 1-9       1-6  1-5  15        14  1-6  19  1-9  1-9  19 

Gum 1-8       1-6  1-5  1*5        1-6  1-6  19  19  1  6  IB 

FattyOil 0-9       \i  10  09        10  1-0  09  TO  10  10 

SolublePhosphates,&c.  0-5       0-6  0*7  07        0-9  0-6  0-5  05  0-5  0-3 

Husk  and  bran 13-9  14-0  13-8  14-2  14-2  14-0  14*0  14-9  14-0  14-0 

99-8  99-7  99-7  997  99-7  99-6  99-8  99-7  99-8  997 
1°.  Water  present. — The  water  in  each  of  these  10  specimens  of  grain 
was  nearly  the  same,  about  4|  per  cent.  I  have  already  stated  the  quan- 
tity of  water  in  English  flour  to  amount  to  about  16  per  cent,  on  an  ave- 
rage. Many  samples  of  wheat  also  have  been  dried  in  my  laboratory. 
From  the  results  I  extract  the  following,  showing  the  water  lost  by  corn 
grown  in  four  different  parts  of  the  world  : — 

English,  Lammas  red 15-1  per  cent. 

Seminoff' wheat 13-2       *' 

St.  Petersburg 16-1        " 

Burletta  wheat 13-1       " 

This  weight  of  water  is  lost  when  the  grain,  as  it  is  sold  in  the  market, 
IS  crushed  and  then  heated  to  a  temperature  not  exceeding  220°  as  long 
as  it  loses  weight. 

The  above  quantities  of  water  are  very  much  greater  than  those  found 
in  the  wheats  of  Hermbstadt.  I  cannot  offer  these  results,  however,  as  a 
jsroq/' of  inaccuracy  on  the  part  of  this  experimenter,  as  I  have  not  had 
access  to  his  original  memoir.  It  is  only  fair  towards  him,  therefore,  to 
conclude  that,  before  they  were  subjected  to  analysis,  his  wheats  had  been 
artificially  dried  in  a  very  considerable  degree. 

2°.  Oil  in  the  different  samples. — Again,  it  appears  remarkable  that 
the  quantity  of  oil  in  all  the  samples  of  wheat  in  the  above  table  is  nearly 
identical,  and  is  also  very  small.  I  have  examined  the  fine  flour  yielded 
by  several  samples  of  tlie  same  wheat,  grown  by  Mr.  Burnet,  of  Gad- 


514  OIL    IN    DIFFERENT    SAMPLES    OF    WHEAT. 

• 

girth,  upon  the  same  field,  but  dressed  with  different  manures,  [Appen- 
dix, pp.  55  and  71,]  and  the  proportions  of  oil  which  they  yielded  in 
the  state  in  which  they  came  from  the  mill,  were  as  follows : — 

Per  cent 

1°.  From  the  undressed  soil ]-4 

2°.  Dressed  with  guano  and  wood-ash 1*9 

3°.  With  artificial  guano  and  wood-ash 2*2 

4°.  Sulphated  urine  and  wood-ash 2*2 

5°.  Do.  do.         and  sulphate  of  soda 2-0 

6°.  Do.  do.         and  common  salt 2*7 

7°.  Do.  do.         and  nitrate  of  soda 2'3 

The  two  facts — that  the  quantity  of  oil  in  nearly  all  the  above  sam- 
ples is  so  much  greater  than  was  found  by  Hermbstadt  in  any  of  his 
specimens,  and  that  the  proportion  varied  with  the  kind  of  manure  with 
which  the  wheat  had  been  dressed — these  two  facts,  I  think,  show  that 
the  analyses  of  Hermbstadt  have  not  been  made  with  such  a  degree  of 
accuracy  as  to  justify  us  in  relying  with  confidence  upon  the  general  de- 
ductions to  which  they  seem  to  lead. 

3°.  Relative  effects  of  these  manures  upon  different  crops. — If  we  com- 
pare together  the  relative  proportions  of  gluten  and  albumen  contained  in 
the  several  samples  of  wheat,  barley,  oats,  and  rye,  examined  by 
Hermbstadt,  and  exhibited  in  his  tab'es,  we  shall  find  that  the  effects  of 
his  manures  were  by  no  means  unifo-m  upon  the  several  crops.  Thus, 
when  manured  with — 

The  gluten  and  albumen  per  cent, 
taken  together  were  in  the 
Kind  of  Manure.  Wheat.      Barley.     Oats.      Rye. 

Ox  blood      .  .  "  ^  '  ' 

Night  soil    . 
Sheep's  dung 
Human  urine 
Horse  dung 
Pigeon's  dung     . 
Cow  dung  . 
Nothing 

Upon  the  numbers  in  this  table  I  offer  you  the  following  remarks  :— 
a.  Upon  the  wheat,  the  effect  of  the  horse  and  pigeon's  dung,   in  in- 
creasing the  amount  of  gluten  and  albumen,  was  little  more  than  one- 
fifth  of  that  produced  by  the  sheep's  dung.     Thus  the  wheat  contained 
of  gluten  and  albumen, — 

Per  cent.  Increase  of  gluten. 

Undressed 9*9  — 

With  sheep's  dung      .     .     .     34*1  24-2  per  cent. 

With  horse  dung    ....     14-7  4-8 

With  pigeon's  dung     .     .     .     13-1  3-2 

But  we  have  seen  (p.  470)  that  in  so  far  as  the  nitrogen  is  concerned^ 
dry  horse  and  sheep^s  dung  ought  to  produce  equal  effects,  while  pigeon's 
dung  should  have  three  times  the  effect  of  either.*  Whatever  be  the 
cause  of  the  increased  proportion  of  gluten  in  the  experimental  wheats 
of  Hermbstadt,  it  cannot,  therefore,  have  been  owing  solely  to  the  pro- 
portion of  nitrogen  in  the  manures  he  applied. 

•  22  of  dry  pigeon's  dung  are  equal  to  65  of  sheep's,  or  64  of  horse's  dung. 


35-2 

61 

54 

156 

352 

6'3 

50 

151 

34-2 

61 

45 

153 

36  5 

6-4 

4-9 

15-5 

14-8 

61 

45 

14-7 

131 

60 

3-5 

15-3 

130 

35 

3-4 

12-8 

9-9 

30 

21 

11-2 

DIFFERENT    PROPORTIONS    OF    GLUTEN.  515 

b.  Again,  upon  the  barley,  oats,  and  rye,  the  sheep's  dung  produced 
little  more  effect  than  the  horse's  dung.  It  might  be  said  that  this  was 
because  these  two  manures  contain  nearly  the  same  proportions  of  nitro- 
gen. But  if  so,  why  did  they  not  produce  like  effects  also  upon  the 
wheat  ? — and  why  did  pigeon's  dung  impart  less  gluten  than  either,  to 
all  these  varieties  of  grain  ? 

c.  The  unsatisfactory  nature  of  these  experiments  is  still  more  clearly 
seen  when  we  compare  the  relative  proportions  of  nitrogen,  contained  in 
the  several  manures  applied,  with  the  proportions  of  the  same  element 
contained  in  the  several  crops  to  which  these  manures  had  been  added. 

This  comparison  is  made  in  the  following  table — the  quantity  of  nitro- 
gen in  sheep's  dung  and  in  the  crops  manured  with  it  being  called 
100  :— 

Proportions  of       Proportions  of  nitrogen  added  to  the 

.r „  „ ,.„  .  nitrogen,  in  crop  by  earth  manure.* 

Manure  applied.         the  manure.    , ^^— . 

Wheat.    Barley.     Oats.         Rye. 
Sheep's  dung  ...         100  100        100        100        100 

Horse  dung    ...         102  16  75         100  66 

Pigeon's  dung     .     .        300  9  48  43  55 

Cow  dung       ...  97  6  1  66  22 

The  relation  which  exists  among  the  numbers  in  the  first  of  the  above 
columns,  is  totally  unlike  that  which  exists  among  those  in  any  of  the 
others.  In  none  of  the  crops  does  the  quantity  of  nitrogen  in  the  manure 
bear  a  perceptible  relation  to  that  contained  in  the  grain  that  was  reaped. 
The  theory,  therefore,  that  the  quantity  of  gluten  in  the  crop  is  always 
determined  by  that  in  the  manure,  and  that  the  amount  of  gluten  in  the 
grain  we  reap  may  at  pleasure  be  increased  by  the  use  of  manures 
which  are  rich  in  nitrogen — this  theory  derives  in  reality  no  solid  support 
from  the  experiments  of  Hermbstadt.  The  theory  may  indeed  be  correct, 
but  it  is  not  sustained  by  any  rigorous  experiments  hitfierto  made — and 
the  prudent  man  will  place  little  reliance  upon  it,  until  its  correctness 
shall  have  been  proved  by  future  and  more  rigorously  conducted  investi- 
gations. 

§  19.   Composition  of  peas,  beans,  and  vetches. 

The  seeds  of  leguminous  plants  in  general  contain  a  large  quantity  of 
a  substance — very  analogous  to  the  gluten  of  wheat — to  which  the  name 
of  legumin  has  been  given. 

To  extract  this  legumin,  bruised  beans,  peas,  or  vetches,  are  steeped 
in  tepid  water  for  some  hours,  then  rubbed  to  a  pulp  in  a  mortar  with 
their  own  weight  of  warm  water,  and,  after  an  hour,  strained  through 
linen.  The  strained  liquid  deposits,  at  first,  a  quantity  of  starch,  but  is 
obtained  nearly  clear  by  filtration.  To  the  filtered  solution  diluted 
acetic  acid  (vinegar)  or  sulphuric  acid  is  added  in  small  quantity,  when 
the  legumin  coagulates  and  falls  in  the  form  of  nearly  insoluble  flocks, 

•  These  columns  are  calculated  by  multiplying  together  the  increase  of  crop  and  the  ia- 
crease  in  the  per  centage  of  gluten  and  albumen.    Thus  in  the  case  of  wheat- 
Increase  of  crop.    Increase  of  gluten.    Product.    Proportions; 

Sheep's  dung 9  fold       X       24-3  per  cent.    =    218-7    =    100 

Horse  dung 7  fold        X         49  per  cent.    =      34-3    =      16 

Pigeon's  dung 6  fold       X         3-2  per  cient.    =      19  2    =       9 

Cow  dung 4  fold       X         31  per  cent.    =      124    =       8 


616  COMPOSITION    OF    PEAS,    BEANS    AND    LENTILS. 

which  are  easily  collected  on  a  filter.  The  addition  of  an  excess  of  acid 
will  re-dissolve  the  coagulated  Icgumin,  vvliich  is  again  thrown  down  by 
a  few  drops  of  a  solution  of  carbonate  of  soda  or  of  ammonia  ;  a  slight 
excess  of  either  of  the  latter,  however,  will  cause  the  precipitate  a  second 
time  to  disappear.  The  legumin  of  the  pea  and  bean,  therefore,  differs 
from  the  gluten  of  wheat,  in  being  soluble  in  water  (Dumas),  and  in  very 
dilute  acid  or  alcaiine  solutions. 

The  solution  of  legumin  in  water  is  coagulated  when  heated  nearly  to 
boiUng,  in  which  respect  it  resembles  albumen  (white  of  egg),  and  it  is  also 
coagulated  by  rennet,  in  which,  and  in  its  relations  to  acids  and  alcalies, 
it  resembles  casein,  the  curd  of  milit.  Legumin  has,  indeed,  by  Liebig, 
been  called  vegetable  casein,  from  an  impression  that  it  is  identical  in 
composition  and  properties  with  the  pure  curd  of  milk. 

The  semi-transparent  solution  of  legumin  in  water,  obtained  directly 
from  beans  or  peas,  gradually  becomes  opaque,  and  slowly  deposits  the 
legumin  in  an  insoluble  state.  This  is  owing  to  the  production  of  a 
small  quantity  of  acid  by  the  decomposition  of  the  sugar  or  other  sub- 
stances present  in  the  liquid.  This  acid  slowly  coagulates  the  legumin 
in  the  same  way  as  when  dilute  acids  are  artificially  added  to  the  solu- 
tion. It  is  proper  to  mention  that  other  chemists  consider  legumin,  like 
casein,  [see  the  following  lecture,]  to  be  nearly  insoluble  in  water,  and 
that  in  tlie  solutions  from  the  bean  and  the  pea  it  is  rendered  soluble  by 
the  presence  of  a  little  potash,  soda,  or  lime — the  liquid  becoiriing  turbid 
as  soon  as  a  quantity  of  acid  is  formed  to  combine  with  these  alcaiine 
substances.  According  to  Dumas,  pure  legumin  dried  in  vacuo  at  284° 
F.  consists  of — 


Fibrin 

Albumen 

Glutine 

Ca.sein 

Legumin. 

of 

of 

of 

of 

VvThe^. 

Wheat. 

Wheat. 

Wheat. 

Carbon  .     .     .     . 

.    50-4 

53-23 

53-74 

53  05 

53-46 

Hydrogen  .     .     . 

.      G-9 

701 

711 

7-17 

713 

Ni'trogen     .     .     . 

.     18-2 

16-41 

15-65 

15-94 

1604 

Oxygen,  sulphur, 

& 

phosph,  .     .     . 

.    24-5 

23-35 

23-50 

2J-84 

23-37 

100         100  100  100  100 

For  the  pur])ose  of  comparison,  I  have  inserted  the  composition,  ac- 
cording to  the  same  chemist,  of  the  several  nitrogenous  compounds  ex- 
isting in  wheat. 

If  these  analyses  be  correct,-  legumin  contains  more  nitrogen  than  the 
fibrin,  the  albumen,  the  glutine,  or  the  casein  of  wheat,  and  is  almost 
identical  with  the  gelatine  of  bones.  The  important  consequence  deduced 
from  this  fact,  by  Dumas,  in  reference  to  the  feeding  of  animals,  we  shall 
consider  in  a  subsequent  lecture. 

Above,  I  have  given  the  composition  of  legumin,  the  nitrogenous 
principles  contained  in  peas  and  beans,  as  found  by  Dumas,  from  which 
it  would  appear  to  contain  more  nitrogen  than  any  of  the  other  vegetable 
principles  hitherto  found  in  cultivated  grains.  The  legumin  analysed  by 
Dumas  was  extracted  from  sweet  almonds. 

Since  the  preceding  sheet  was  prepared  for  press,  a  further  analysis  of 
legumin,  extracted  from  beans,  has  been  published  by  Rochleder,*  which 

*  AnnaUn  der  Chem.  et  Pharmacie,  x\\i.,  p.  155. 


ANALYSIS    OF    LEGUMIN.  617 

does  not  agree  with  that  of  Dumas,  but  represents  this  legumin  as  iden- 
tical with  casein,  the  curd  of  milk  (see  the  following  lecture),  and  as  dif- 
fering in  properties  as  well  as  in  composition  from  that  of  the  almond. 

The  legumin  of  beans  and  peas  is  soluble  in  cold  water,  and  the  solu- 
tion, upon  evaporation,  forms  a  skin  on  the  surface  which  is  renewed  as 
often  as  it  is  removed.  It  is  not  coagulated  by  boiling,  but  is  immediately 
thrown  down  in  fine  flocks  by  acetic  acid,  which,  when  added  in  excess, 
does  not  redissolve  it  (Liebig). 

The  legumin  from  sweet  almonds  is  also  soluble  in  cold  water,  but, 
like  albumen,  falls  in  flocks  when  the  solution  is  heated  nearly  to  boil- 
ing. It  is  precipitated  also  by  diluted  acetic  acid,  and  is  again  dissolved 
when  an  excess  of  this  acid  is  added  (Dumas). 

The  two  substances,  therefore,  are  different  in  their  properties.  Their 
coiastitution  is  represented  respectively  by — 

LEGUMIN   PROM 

Beans  Sweet  almonda 
(Rochleder).  (Dumas). 

Carbon         ....         64-5  50-4 

Hydrogen    ....  7-4  6-9 

Nitrogen      ....         14-8  18-2 

Oxygen       ....         23-3  24-5 

100  100 

When  we  com^  to  consider  the  feeding  of  animals,  we  shall  find  that 
this  difference  in  the  composition  of  the  two  varieties  will  materially  af- 
fect the  view  we  must  take  in  regard  to  the  action  of  each  in  contributing 
to  the  support  of  the  various  parts  of  the  animal  body. 

The  approximate  composition  of  the  entire  peas  and  beans  is  thus 
stated  by  Einhof.     [Zierl  Kncydopadie,  ii.,  p.  52]. 

Composition  of  tlie  grain.  Composition  of  the  meal. 

Water.        Husk.       Meal.  Starch.  Legumin.  Gum,&c. 

Peas 14  0        10  5        755  65  0  23        12 

Field  Beans    .     .     .     155        16-2        C8  3  690  19        12 

A  series  of  rigorous  analyses  of  the  seeds  of  leguminous  plants  is  at 
present  much  to  be  desired.  According  to  those  of  Braconnot  and  Einhof, 
certain  species  examined  by  them  consisted  of — 

Kidney      Field  beans,      Lentils, 
Peas.  beans.         (Einhof.)         dried' 

(Einhof) 

Water •     125  230  156 

Husk        8  3  70  100  187 

Legumin,  albumen,  &c.  .    264  23-6  11-7  38-5 

Starch 43-6  430  50-1  32'8 

Sugur       2  0  0  2  q„  31 

Gum,  &c 40  1-5  ^'^  60 

Oil  and  fat 12  07  1  1 

Salts  and  loss    ....      20  1-0  4-4  09 

1000  1000  10^         lOOOt 

These  analyses  agree  in  showing  that  the  seeds  of  leguminous  plants 

•  By  drying,  the  lentils  lost  14  per  cent,  of  water. 

t  Dumas  Traite  de  Chimie,  vi.  p.  307,  comparad  with  Thomson's  Vegetable  Chemittrih 
p.  884,  Schiibler's  Agricultur  Chemie,  ii.,  p.  194,  and  Sprengel's  Chemie  fur  Landwirthe^  if., 
p.  368. 

22* 


618  "EFFECT    OF    SOILS    AND    MANURES    UPON    PEAS. 

are  especially  rich  in  substances  containing  nitrogen  (legumin  and  albu- 
men), and  are  therefore  fitted  to  contribute  much  to  the  nourishment  of 
those  animals  which,  in  consequence  of  the  state  of  their  growth  and 
health,  or  the  purposes  for  which  they  are  reared  and  maintained,  require 
a  large  supply  of  this  important  element. 

§  20.  Effect  of  soils  and  manures  upon  the  quality  of  peas  and  beans. 

The  quality  of  the  seeds  of  leguminous  plants  is  also  affected  by  the 
mode  of  culture  to  which  they  are  subjected,  and  by  the  kind  of  soil  in 
which  they  are  raised. 

1°.  Effect  of  animal  manures. — The  dung  "  of  sheep  or  horses  has 
been  found  to  impart  a  better  flavour  to  the  pea,  and  to  render  the  husk 
thinner  than  when  that  of  hogs  or  oxen  has  been  used."  [British  Hus- 
bandry, ii.,  p.  217.] 

2°.  Effect  of  mineral  manures. — The  effect  of  gypsum  and  of  other 
sulphates  upon  leguminous  plants  is  universally  known  (p.  482.)  The 
beneficial  influence  of  a  mixture  of  gypsum  and  common  salt  upon 
sickly  crops  of  beans  and  peas  is  very  strikingly  displayed  in  the  inter- 
esting experiments  of  Mr.  Alexander,  of  Southbar,  to  the  details  of  which 
1  have  already  had  occasion  to  draw  your  attention.     [See  Appendix,  p. 

3°.  Effect  of  lime. — Dr.  Anderson  says,  "  that  the  pea  cannot  be 
reared  to  perfection  in  any  field  which  has  not  been  either  naturally  or 
artificially  impregnated  with  some  calcareous  mattei^'  but  that  "  a  soil 
which  could  hardly  have  brought  a  single  pea  to  perfection,  although 
richly  manured  with  dung,  if  once  limed,  will  be  capable  of  producing 
abundant  crops  of  peas  ever  (?)  afterwards,  if  duly  prepared  in  other  re- 
spects."    [Essays,  ii.,  p.  302.] 

4°.  Boiling  or  melting  quality  of  peas. — ^But  the  most  singular  cir- 
cumstance in  connection  with  this  class  of  seeds,  to  which  the  agricul- 
tural chemist  has  hitherto  been  directed,  is  the  property  possessed  by 
peas  and  beans  of  boiling  soft  or  mouldering  into  a  pulp  more  or  less 
easily,  according  to  the  kind  of  land  in  which  they  are  raised  or  to  the 
species  of  manure  with  which  they  are  dressed.  The  observations, 
however,  which  I  have  found  upon  record  in  reference  to  this  point  are 
of  a  contradictory  character.     Thus — 

a.  Sprengel  says  "  that  peas  which  are  raised  after  liming  or  marling 
boil  sojt  more  easily,  and  are  more  agreeable  to  the  taste  than  when  raised 
after  manure."     [Die  Lehre  vom  Diinger,  p.  297.] 

6.  A  French  authority,  on  the  other  hand,  quoted  by  Loudon,  [Ency- 
clopaedia of  Agriculture,  p.  837,]  says,  that  "  stiff*  land  or  sandy  land 
that  has  been  limed  or  marled,  or  to  which  gypsum  has  been  appUed, 
produces  peas  that  vnll  not  melt  in  boiling,  no  matter  what  the  variety 
may  be.  The  same  effect  is  produced  on  the  seeds  and  pods  of  beans 
and  of  all  legumij^^s  plants.  To  counteract  this  fault  in  the  boihng,  it 
is  only  necessary  ^Rhrow  into  the  water  a  small  quantity  of  the  com- 
mon soda  of  the  shops." 

c.  The  author  of  the  British  Husbandry,  [ii.,  p.  217,]  says,  ^'  that 
shell  marl  or  lime  is  found  to  forward  this  crop  more  than  any  other 
mineral  manure,  though  it  is  said  to  communicate  a  degree  of  hardness 
to  the  grain  whicn  renders  it  unfit  for  boiling." 


SOME    PKAS    REFUSE    TO    BOIL    SOFT.  519 

Independently  of  all  api)lications  to  the  soil,  I  believe  it  is  generally 
observed  that  good  boilers  are  produced  ujjon  light,  sandy,  and  gravelly 
soils  ;  while  heavy,  wet,  undrained  (and  newly  broken  up  ?)  land  usually 
produces  bad  boiling  peas  and  beans.  Thus  melting  peas  {sidder  peas, 
as  they  are  locally  called)  for  the  Birmingham  market  are  grown  on  the 
slopes  of  the  gravelly  hill  of  Hopwas,  two  miles  from  Tamworth,  on 
ihe  Lichfield  road — the  red  clay  lands  of  the  vale  of  the  Tame  produc- 
ing in  general  pig*  peas  or  beans  only.  It  is  on  similar  soils  that  melt- 
ing barley  and  mealy  potatoes  are  produced,  and  the  effect  upon  the 
three  crops  may  probably  be  due  to  a  common  cause. 

At  all  events  it  is  probable — 

a.  That  the  boiling  quality  of  the  pea  crop  is  not  owing  to  the  qual- 
ity of  the  seed — since  peas  of  both  varieties  have  been  raised  from  the 
same  seed.f 

b.  That  it  is  not  generally  owing  to  the  seasons,  since  some  land  pro- 
duces hard  peas  every  year.  If  the  wetness  of  the  soil  indeed  have  any 
influence,  a  rainy  season  may  cause  the  production  of  bad  boilers  upon 
land  from  which  soft  peas  are  usually  reaped. 

4°.  Chemical  difference  between  the  two  varieties  of  pea. — Why  does 
one  of  these  varieties  of  pea  melt  more  readily  than  the  other  ?  For 
the  same  reason  very  nearly  that  one  potatoe  boils  mealy,  and  another 
waxy,  and  that  one  sample  of  barley  melts  better  in  the  mash-tub  than 
another.  Melting  peas  and  barley  and  mealy  potatoes  contain  a  larger 
proportion  of  starch  tlian  samples  which  are  possessed  of  an  opposite 
quality. 

The  pea,  as  we  have  seen,  consists  essentially  of  legumin  and  starch. 
The  former  coagulates  and  contracts,  or  runs  together  into  a  mass  by 
boiling, — the  latter,  on  the  contrary,  expands,*  becomes  more  bulky,  tends 
to  burst  the  husk,  and  to  separate  into  single  grains.  If  the  tendency  to 
contract  and  cohere  be  greater  than  the  disposition  to  expand  and  sepa- 
rate— in  other  words,  if  the  legumin  predominate — the  pea  does  not  melt, 
while  if  the  starch  be  abundant  the  pea  boils  well.  It  is  possible  that 
the  addition  of  a  little  soda  may  cause  hard  peas  to  melt,  since  legumin 
is  soluble  in  a  solution  of  soda,  but  in  waters  impregnated  with  lime  all 
peas  are  said  to  boil  soft  much  less  readily  than  in  such  as  are  free  from 
that  ingredient.     [Dumas,  Traite  de  Chimie,  vi.] 

It  is  only  when  peas  and  beans  are  raised  for  the  food  of  man  that  the 
possession  of  the  melting  property  becomes  a  matter  of  importance.  It 
is  rather  because  they  are  more  agreeable  to  the  palate  than  because  they 
are  ascertained  to  be  more  nutritive,  that  they  are  preferred  in  this  state. 
When  wo  come  to  consider  the  feeding  of  stock,  we  shall  see  that,  ac- 
cording to  the  present  state  of  our  knowledge,  the  opinion  may  rea- 
sonably be  entertained  that  insoluble  peas  are  really  better  adapted  for  the 
feeding  and  fattening  pigs  and  other  stock — the  purpose  for  which  they 
are  employed — than  those  which  are  possessed  of  the  melting  quality. 

It  is  a  difference  in  the  chemical  composition  of  the  seeds  of  legumi- 
nous plants  that  makes  them  melt  more  or  less  easily — but  by  what 

*  Much  used  for  the  feeding  of  pigs. 

t  Some  however  suppose  it  to  depend  upon  the  age  of  the  seed,  or  the  time  of  aowing. 
•^British  Husbandry,  ii.,  p.  217. 


D»0  COMPOSITION    or    POTATOES. 

quality  in  the  soil  or  manure  is  this  difference  in  composition  produced  ? 
In  regard  to  lime  the  evidence  is  contradictory.  Gypsum  may  render 
them  harder  since  legmnin  contains  sulphur,  and  a  portion  of  the  effect 
of  gypsum  upon  leguminous  crops  is  supposed  to  .arise  from  its  yielding 
sulphur  to  the  growing  plants,  and  thus  promoting  the  production  of  le- 
gumin.  "Wet  and  clay  lands  also  favour  the  production  of  legumin 
more  than  that  of  starch — but  in  what  way,  we  are  not  yet  in  possession 
of  experimental  results  of  sufficient  accuracy  to  enable  us  to  say. 

§  21.  Of  the  composition  of  potatoes,  and  the  effect  of  circumstances  in 
modifying  their  composition. 

1°.  Composition  of  potatoes. — Potatoes,  in  addition  to  much  water, 
consist  of  starch,  gum,  woody  fibre,  and  albumen.  The  proportions  of 
these  several  constituents  are  very  variable.  Thus,  according  to 
Einhof  and  Lampadius,  the  following  kinds  of  potatoe  consisted  in  100 
parts  of — 

2°.  Influence  of  the  state  of  ripeness. — According  to  Korte  the  quan- 
tity of  dry  solid  matter  contained  in  the  potatoe  depends  very  much  upon 
the  state  of  ripeness  to  which  it  has  attained.  The  ripest  leave  30  to  32 
per  cent,  of  dry  matter,  the  least  ripe  only  24  per  cent.  The  per 
centage  of  starch  varies  from  8  to  16  per  cent.  The  mean  result  of  his 
examination  of  55  varieties  of  potatoe  gave  him  for  the  solid  matter  24-9, 
and  for  the  starch  11*85  per  cent.  [Schiibler,  Agricuhur  Chemie,  ii.,  p. 
213.] 

3°.  Influence  of  variety. — Much  appears  also  to  depend  upon  the 
variety  of  potatoe.  Thus  the  following  varieties  of  potatoe  grown  at 
Barrochan  in  Renfrewshire,  in  1842,  yielded  respectively — 

Connaught  cups         ....         21     per  cent,  of  starch. 

Irish  blacks IGg-  *' 

White  dons 13  " 

Red  dons 10| 

— while,  according  to  a  starch  manufacturer  in  the  neighbourhood,  11^ 
per  cent,  has  been  the  average  quantity  obtained  from  the  common 
rough  red  of  good  quality  during  the  last  four  years. 

The  difference  in  the  quantity  of  starch  yielded  by  the  above-named 
varieties  is  the  more  striking  when  taken  in  connection  with  the  weight 
of  each  per  acre,  raised  from  the  same  land,  treated  in  the  same  way. 
These  weights  were  as  follows  : — 


Containing  of 

Manure. 

Produce  per  acre. 

starch. 

Cups,              with  4  cwt.  of  guano 

13|  tons 

2-9  tons. 

Red  Dons,      with  4  cwt.  of  guano 

141      " 

1-5      " 

White  Dons,  with  3  cwt.  of  guano 

isj-   " 

24      " 

So  that,  of  these  three  crops,  that  of  cups,  which  weighed  the  least, 
gave  the  largest  produce  of  starch.  It  yielded  nearly  twice  as  much  as 
the  red  dons,  which  were  half  a  ton  heavier,  and  one-fifth  more  than 
even  the  white  dons,  the  crop  of  which  was  greater  by  five  tons  an  acre. 
Such  differences  as  these,  in  the  relative  quantities  of  starch,  which  may 
be  obtained  from  an  acre  of  the  same  land  by  the  growth  of  different  va- 
rieties of  potatoe  are  deserving  of  the  attentive  consideration  of  the  prac- 
tical man. 

See  Appendix,  p.  61. 


THE   PROPORTION    OF   STARCH   VARIES    VERT    MUCH.  521 

Larger  quantities  of  starch  than  any  of  those  above  stated  have  been 
obtained  from  potatoes  by  some  experimenters.     Thus  from  the 

Per  cent,  of  starch. 

Kidney  potatoe,  Dr.  Pearson  obtained         .         .         .       28  to  32 

Apple        do.       Sir  H.  Davy 18  to  20 

Shaw         do.       Vauquelin 18-8 

L'Orpheline  do.  ^ 24-4 

The  first  and  last  of  these  proportions  are  probably  very  rare  in  oui 
climate. 

4°.  Effect  of  keeping. — Those  potatoes  are  said  to  keep  best  in  which 
the  starch  is  most  abundant,  but  in  general  keeping  has  an  effect — 

a.  On  the  proportion  of  starch. — ^By  keeping  till  the  spring,  potatoes 
lose  from  4  to  7  per  cent,  of  their  weight,  and  the  quantity  of  starch  they 
are  capable  of  yielding  suffers  a  considerable  diminution.     Thus,  ac- 
cording to  Pay  en,  the  same  variety  of  potatoe  yielded  of  starch  in 
October,         17-2  per  cent.  January,      15-5  per  cent. 

November,    16-8         "  February,     16'2  " 

December,     15-6         "  March,  15-0  " 

April,  14-5  " 

This  diminution  is  probably  owing  to  the  conversion  of  a  portion  of  the 
starch  into  sugar  and  gum.  When  potatoes  are  rendered  unfit  for  food 
by  being  frozen  and  suddenly  thawed,  the  quantity  of  starch  which  they 
are  capable  of  yielding  is  said  to  have  undergone  no  diminution. 

6.  On  the  proportion  of  gluten. — The  proportion  of  gluten  also  ap- 
pears to  become  less  when  potatoes  are  kept.  Thus,  in  new  potatoes 
Boussingault  found  the  gluten  amount  to  2|-  per  cent.,  but  in  old  potatoes 
to  only  1|  per  cent,  of  their  weight.  To  this  natural  diminution  of  the 
proportion  of  starch  and  gluten,  is  probably  to  be  ascribed  the  smaller 
value  in  the  feeding  of  stock,  which  experience  has  shown  very  old  po- 
tatoes to  possess. 

5°.  Effect  of  soils  and  manures. — The  potatoe  thrives  best  on  a  light 
loamy  soil — neither  too  dry,  nor  too  moist.  The  most  agreeably  flavour- 
ed table  potatoes  are  almost  always  produced  from  newly  broken  up 
pasture  ground,  not  manured,  or  from  any  new  soil.  [Loudon's  Ency- 
clopaedia of  Agriculture,  p.  847.]  When  the  soil  is  suitable,  they  delight 
in  much  rain,  and  hence  the  large  crops  of  potatoes  obtained  in  Ireland, 
in  Lancashire,  and  in  the  west  of  Scotland.  No  skill  will  enable 
the  farmer  to  produce  crops  of  equal  weight  on  the  east  coast  where 
rains  are  less  abundant.  It  has  not  been  shown,  however,  that  the  weighs 
of  starch  produced  in  the  less  rainy  districts  is  defective  in  an  equal  de- 
gree. Warm  climates  and  dry  seasons,  as  well  as  dry  soils,  appear  to 
increase  the  per-centage  of  starch. 

Potatoes  are  considered  by  the  farmer  to  be  an  exhausting  crop,  and 
they  require  a  plentiful  supply  of  manure.  By  abundantly  manuring, 
however,  the  land  in  the  neighbourhood  of  some  of  our  large  towns, 
where  this  crop  is  valuable,  have  been  made  to  produce  potatoes  and 
corn  every  other  year,  for  a  very  long  period. 

6°.  Influence  of  saline  manures. — I  have  already  drawn  your  attention 
to  the  remarkable  influence  of  certain  saline  substances  in  promoting  the 
growth  of  the  potatoe  crop  in  some  localities.  The  most  striking  effects 
of  this  kind  hitherto  observed  in  our  island  have  been  produced  by  mix- 


522  OCCASIONAL   FAILURE  OF   SEED   POTATOES. 

tures  of  the  nitrate  of  soda  with  the  sulphate  of  soda  or  with  the  sulphate 
of  magnesia.*  The  effect  of  such  mixtures  affords  a  beautiful  illustration 
of  the  principle  I  have  frequently  before  had  occasion  to  press  upon  your 
attention — that  plants  require  for  their  healthy  growth  a  constant  supply 
of  a  considerable  number  of  different  organic  and  inorganic  substances. 
Thus  upon  a  field  of  potatoes,  the  whole  of  which  was  manured  alike 
with  40  cart  loads  of  dung,  the  addition  of—  ^ 

a.     Nitrate  of  soda  alone  gave  an  increase  of  3|^  tons. 

Sulphate  of  soda  alone  gave      ...       0       '*     ' 

While  one  half  of  each  gave 


h.     Sulphate  of  ammonia. alone  gave 

Sulphate  of  soda 

But  one  half  of  each  gave      .     . 


c.  Nitrate  of  soda  alone  gave  .  . 
Sulphate  of  magnesia  alone  gave 
And  one  half  of  each  gave     .     . 

These  results  are  very  interesting,  and  when  confirmed  by  future  re- 
petitions of  such  experiments — and  followed  up  by  an  examination  of 
the  quality  and  composition  of  the  several  samples  of  potatoes  produced — 
cannot  fail  to  lead  to  very  important  practical  conclusions- 

7°.  Occasional  failure  of  seed  potatoes. — The  seeds  of  all  cultivated 
plants  are  known  at  times  to  fail,  and  the  necessity  of  an  occasional 
change  of  seed  is  recognised  in  almost  every  district.  In  the  Lowlands 
of  Scotland  potatoes  brought  from  the  Highlands  are  generally  pre- 
ferred for  seed,  and  on  the  banks  of  the  Tyne  Scottish  potatoes  bring  a 
higher  price  for  seed  than  those  of  native  growth.  This  superior  quality 
is  supposed  by  some  to  arise  from  the  less  perfect  ripening  of  the  upland 
potatoes,  and  in  conformity  with  this  view  the  extensive  failures  which 
have  taken  place  during  the  present  summer  (1643)  have  been  ascribeo 
to  the  unusual  degree  of  ripeness  attained  by  the  potatoes  during  the 
warm  dry  autumn  of  the  past  year. 

This  may  in  part  be  a  true  explanation  of  the  fact,  if — as  is  said — the 
ripest  potatoes  always  contain  the  largest  proportion  of  starch — since 
some  very  interesting  observations  of  Mr.  Stirrat,  of  Paisley,  would 
seem  to  indicate  that  whatever  increases  the  per-centage  of  starch,  in- 
creases also  the  risk  of  failure  in  potatoes  that  are  to  be  used  for  seed.f 
This  subject  is  highly  deserving  of  further  investigation. 

'  For  the  particulars  of  these  experiments  see  the  Appendix. 

t  I  insert  Mr.  Stirrat's  letter  upon  this  subject,  not  only  because  his  observations  are  in- 
teresting in  themselves,  but  because  they  are  really  deserving  of  the  careful  attention  'of 
practical  men : — 

"Sir,— The  following  experiment  with  potatoes  was  tried  with  the  view  of  discovering  the 
cause  of  so  many  failures  in  the  crops  of  late  years,  from  the  seed  not  vegetating,  and  rotting 
in  the  ground.  I  had  an  idea  that  the  vegetative  principle  of  the  plant  might  become  weak 
In  consequence  of  being  grown  on  land  that  had  been  a  long  time  subjected  to  cropping,  and 
not  allowed  any  length  of  lime  to  lie  at  rest.  I,  therefore,  raised  a  few  bolls  on  land  that  liad 
Iain  lea  for  70  years  (being  part  of  my  bleach  green),  and  found  that  these  on  being  planted 
Bgain  the  following  year  were  remarlcably  strong  and  healthy,  and  not  a  plant  gave  way,  and 
I  have  continued  the  same  method  for  the  last  six  years,  and  the  result  has,  in  every  instance, 
been  equally  favourable.  Four  years  ago,  one  boll  of  my  seed  potatoes  was  planted  along 
with  some  others  in  a  field  of  about  an  acre,  the  other  seed  was  grown  on  the  farm,  and  the 
•eed  all  gave  way  ezceptiog  that  got  from  me.    They  were  all  planted  at  the  same  time  and 


EFFECT   OF   SALINE    SUBSTANCES  523 

8°.  Effect  of  saline  top-dressings  on  the  quality  of  the  seed. — It  may 
be  doubted,  however,  whether  the  relative  proportions  of  starch  are  to  be 
considered  as  the  cause  of  the  relative  vahies  of  different  samples  of  seed 
potatoes.  This  proportion  may  prove  a  valuable  test  of  the  probable 
success  of  two  samples  when  planted,  without  being  itself  the  reason  of 
the  greater  or  less  amount  of  failures.  With  the  increase  of  the  starch 
it  is  probable  that  both  the  albumen  and  the  saline  matter  of  the  potatoe 
will  in  some  degree  diminish,  and  both  of  these  are  necessary  to  its  fruit 
fulness  when  used  for  seed. 

The  value  of  the  saline  matter  is  beautifully  illustrated  by  the  obser- 
vation of  Mr.  Fleming,  that  the  potatoes  top-dressed  with  sulphate  and 
pitrate  of  soda  in  1841,  and  used  for  seed  in  1842,  "  presented  a  remark- 
able contrast  to  the  same  vanety  of  potatoe,  planted  alongside  of  them, 
but  which  had  not  been  so  top-dressed  in  the  previous  season.  These 
last  came  away  weak,  and  of  a  yellowish  colour,  and  under  the  same 
treatment  in  every  respect  did  not  produce  so  good  a  crop  by  fifteen  bolls 
(3|  tons)  an  acre."  This  observation,  made  in  1 842,  is  confirmed  by  the 
appearance  of  the  crops  now  growing  (July,  1843)  upon  Mr.  Fleming's 
experimental  fields.  The  prosecution  of  the  enq-uiry  opened  up  by  his 
experiments  promises  to  lead  to  the  most  valuable  practical  results.*  They 
may  teach  us  how  to  secure  at  all  times  a  fruitful  seed,  and  thus  to  dis- 
pense with  supplies  of  imported  produce. 

§  22.   The  composition  of  the  turnip,  the  carrot,  the  beet,  and  the  parsnip. 

1°.  Composition. — The  potatoe  is  characterised  by  containing  a  large 
proportion  of  starch  in  connection  with  a  small  quantity  of  albumen — the 
turnip  and  carrot  by  containing,  in  place  of  the  starch,  a  variable  pro- 

with  the  same  manure.  From  these  circumstances,  I  am  of  opinion,  that  if  farmers  were 
careful  in  raising  their  own  seed  potatoes  from  land  that  has  lain  long  in  a  state  of  rest  (a) — or 
where  that  cannot  be  had,  the  same  object  can  be  obtained  by  bringing  new  soil  to  the  sur- 
face by  trenching  as  much  as  is  necessary,  or  by  the  use  of  the  subsoil-plough — failures  of 
the  potatoe  crop  from  the  seed  not  being  good,  would  become  much  less  frequent.  I  am 
somewhat  confirmed  in  this  opinion  by  the  fact,  that  it  has  been  found  for  the  last  dozen  of 

J 'ears  that  generally  the  best  seed  potatoes  have  been  got  from  farms  in  the  moors  or  high 
ands  of  the  country.  The  reason  of  this  may  be  that  these  high  lands  have  been  but  of  late 
brought  under  crops  of  any  kind,  and  many  of  them  but  newly  brought  from  a  state  of  nature, 
and  the  superiority  of  seed  potatoes  from  these  high  lands  may  not  at  all  arise  (as  is  gene- 
rally supposed)  from  a  change  of  soil  or  climate. 

"  Potatoes  raised  on  new  soil,  or  on  ground  that  has  been  long  lying  lea,  are  not  so  good 
for  the  table  as  the  others,  being  mostly  very  soft,  and,  by  the  following  experiment,  it  would 
appear  that  they  contain  a  much  less  quantity  of  farina  than  those  which  are  raised  from 
land  that  has  been  some  time  under  crop,  and,  perhaps,  this  is  the  reason  why  they  arc  better 
for  seed.  From  one  peck  of  potatoes,  grown  on  land  near  Paisley,  which  has  been  almost 
constantly  under  crop  for  the  last  30  years,  I  obtained  nearly  7  lbs.  of  flour  or  starch;  and 
from  the  other  peck,  grown  on  my  bleach  green,  the  quantity  obtained  was  under  4  lbs.,  from 
which  it  would  seem  that  as  the  vegetative  principle  of  the  plant  is  strengthened,  the  farina- 
ceous principle  is  weakened,  and  vice  versa.  Jas.  Stirkat." 

Paisley,  22d  November,  1842. 

(a)  Mr.  Finnie,  of  Swanstone,  informs  me  that  the  growing  of  potatoes  intended  for  seed  upon 
new  land,  has  long  been  practised  by  good  farmers.  Mr.  Little,  of  Carlesgill,  near  Langholm, 
writes  me  that  in  Dumfriesshire,  they  obtain  the  best  change  of  potatoe  seed  from  mossy 
land — of  oats  and  barley  from  the  warmer  and  drier  climate  of  Roxburghshire.  The  grains, 
he  adds,  degenerate  by  once  sc/twJhg-,  still  looking  plump  when  dry,  but  having  a  thicker  husk, 
and  weighing  two  or  three  powids  less  per  busiiei.  The  deterioration  of  seeds,  in  general, 
is  a  cAemfco-physiological  sut^ect  of  great  interest  and  importance,  and  will  doubtles.s  soon 
be  taken  up  and  investigated. 

*  In  the  Appendix,  p,  47,  the  experiments  are  recorded,  and  in  p.  66  I  have  more  fully  ad- 
verted to  the  interesting  results  likely  to  be  derived  from  the  continuance  of  auch  experimenta. 


524  COMPOSITION    OF    THE    TURNIP,    CARROT,    AND    BEET. 

portion  of  sugar,  and  of  a  gelatinous  gummy-like  substance,  to  which 
the  name  o^ pectin  has  been  given.  In  the  Swedish  turnip  and  in  beet- 
root the  sugar  ])redominates,  in  the  white  turnip  and  in  the  carrot  tlie 
pectin  is  usually  present  in  the  larger  quantity. 

The  composition  of  the  turnip,  the  carrot,  and  the  beet  varies  very  much, 
and  is  influenced  by  a  great  variety  of  circumstances.  We  are  not  in 
possession  of  any  recent  detailed  analyses  of  these  rootB.  The  following 
table  exhibits  the  component  parts  of  several  varieties,  as  they  have  been 
given  chiefly  by  Hermbstadt,  [Schiibler,  Ag.  Chem.,  ii.,  p.  207]  : — 


Variety  of  Turnips. 

Sugar 

Common 

beet 

Parsni 

White.  Swedish.  Cabbage. 

Carrot. 

(Payen). 

(Crome 

Water     .     .     . 

.    790        800        780 

800 

850 

79-4 

Starch  and  fibre 

.      7-2          5-3          60 

90 

30 

6-9 

Gum  (pectin  ?) 

.      2-5          30          3-5 

1-75 

20 

61 

Sugar      .     .     . 

.      80          90          90 

7-8 

100 

5-5 

Albumen     .     . 

.      2-5          20          2.5 

11 

1 

21 

Salts  .... 

.      0-5          0-5          0-5 



1 

? 

Loss  .... 

.      0-3          0?          05 

oil  0  35 

... 

— 

100         100         100         100        100        100 
These  analyses  are  very  defective,  and  apply  with  any  degree  of  cor- 
rectness only  to  the  specimens  actually  operated  upon.     Any  reasonings, 
therefore,  which  are  founded  upon  them  can  only  lead  to  probable  or  ap- 
proximate conclusions. 

2°.  The  proportion  of  sugar  contained  in  the  sap  of  these  roots  is 
greatest  when  they  are  young,  and  diminishes  as  they  ripen.  In  the 
beet,  it  has  been  observed  that  the  nitrates  of  potash  and  ammonia  are 
present  in  considerable  quantity,  and  that  in  the  old  beet  these  nitrates 
become  more  abundant  as  the  sugar  diminishes.  In  the  beet,  also,  when 
raised  by  the  aid  of  rich  manure,  the  production  of  nitrates  is  increased 
more  than  that  of  sugar.*  The  same  may  possibly  be  the  case  with  the 
common  cultivated  turnips.  It  would  not  be  without  interest,  both  theo- 
retically and  practically,  to  ascertain  by  experiment,  the  relative  com- 
position of  the  same  variety  of  turnip,  grown  on  the  same  soil,  by  the 
aid  of  rich  fann-yard  manure,  and  by  the  aid  of  bones  or  of  rape-dust. 
The  one  may  produce  more  sugar,  the  other  more  albumen  or  nitrates. 
Such  differences  may  materially  affect  the  value  of  the  crop,  either  in 
the  feeding  of  stock  or  in  the  production  of  an  enriching  manure.  It  is 
in  suggesting  and  carrying  on  enquiries  of  this  kind  that  the  joint  labours 
of  the  practical  farmer  and  of  the  theoretical  chemist  are  likely,  among 
other  ways,  to  promote  the  advancement  of  a  rational  and  scientific  agri- 
culture. 

3°.  Effect  of  soils  and  manures. — These  roots  delight  in  a  rich,  open, 
and  loamy  soil — and  the  weight  of  produce  varies  much  with  the  kind 
of  manure  that  may  have  been  applied  to  them.  [See,  for  many  in- 
structive illustrations  of  this  fact,  the  experiments  upon  turnips,  detailed 
in  the  Appendix,  pp.  43  et  seq.]  No  experiments,  however,  have  yet 
been  made  to  determine  the  relative  proportions  of  water  and  of  their 
other  constituents  which  the  same  turnips  contain,  when  raised  by  the 

*  According  to  Payen,  the  beet,  w*ien  raised  with  street  manure,  contains  20  times  a* 
mucb  saltpetre  as  when  raised  in  the  ordinary  manner. 


WATER    IN    DIFFERENT    VARIETIES    OF    TURNIP.  525 

aid  of  diffbrent  manures,  nor,  consequently,  the  true  effect  of  these 
manures  upon  the  relative  values  of  the  several  crops. 

4°.  Quantity  of  water  in  different  varieties  of  turnip. — The  same  re- 
mark may  be  made  in  regard  to  the  several  varieties  of  turnip.  All 
those  examined  by  Hermbstadt,  as  appears  from  the  above  tables,  con- 
tained 20  to  22  per  cent,  of  solid  matter  (78  to  80  of  water),  while  other 
experimenters  have  found  as  little  as  from  8  to  15  of  solid  matter  in  tur- 
nips, and  generally  less  in  the  white  and  large  globe  turnip  than  in  the 
yellow  and  more  solid  Swede. 

Thus,  four  varieties  of  the  above  roots^ contain  of  water  and  solid  mat- 
ter, according  to  three  different  experimenters  : — 

WATER  PEH  CENT.  DRY  MATTER  PER  CENT. 

Einhof.  Playfair.  ^^^ermb-        Eiuhof.  Playfair.  ^Jf|S!"" 
White  turnip        92        90        79  '  8        11        21 

Swedish  do.  87^      85        80  12|      15        20 

Cabbagedo.  8G        —        78  14        —        22 

white. 
Carrot  .     .  86        87        80  14        13        20 

The  above  differences  are  very  great,  especially  when  we  look  to  the 
relative  proportions  of  dry  matter  in  which  the  nutritive  power  resides. 
They  are  of  much  importance,  therefore,  to  the  feeding  of  stock,  and 
the  circumstances  under  which  they  occur,  are  deserving  of  a  careful  in- 
vestigation. 

5°.  Relative  nutritive  properties  of  the  potatoe  and  the  turnip. — The 
potatoe  is  usually  considered  more  nutritive  than  the  turnip,  weight  for 
weight,  and  no  doubt  it  generally  is  so.  But  if  we  compare  together  the 
quantities  of  solid  matter  which  the  two  roots  may  contain,  we  shall  see 
how  very  far  wrong  our  estimate  may  be  in  any  special  case.  Thus — 
The  turnip  contains  of  solid  matter  from  8  to  22  per  cent. 

The  potatoe  do.  do.  24  to  32         " 

— so  that,  while  the  driest  turnips  may  contain  four  times  as  much  solid 
matter  as  the  most  watery  potatoes,  very  dry  potatoes  m.ay  contain 
nearly  as  much  as  very  jiiicy  turnips.  It  is  impossible,  therefore,  with- 
out an  actual  examination  of  the  samples,  to  pronounce  upon  the  relative 
amount  of  food  which  is  likely  to  be  contained  in  any  equal  weights  of 
turnips  and  potatoes.  The  very  discordant  estimates  which  different 
feeders  of  stock  have  formed  in  regard  to  the  relative  value  of  these 
crops  in  the  production  of  beef  or  mutton  is  partly  owing  to  this  cause. 
[Other  causes  for  these  discordant  estimates  will  be  .stated  in  Lecture 
XXL]  Until  the  effects  of  equal  weights  of  the  different  kinds  of  food, 
estimated  in  the  dry  state,  are  carefully  ascertained,  it  will  be  impossible 
to  obtain  results  of-  a  general  kind  or  upon  which  any  real  confidence 
can  be  placed. 

§  23.  Of  the  composition  of  the  green  stems  of  peas,  vetches,  clover,  spurry^ 
and  huck-wheat. 
The  stems  and  leaves  of  plants  which  are  given  as  green  food  to 
animals  differ  much  in  composition,  according  to  the  age  they  have  at- 
tained, to  the  rapidity  of  their  growth,  to  the  nature  of  the  soil,  the 
season,  and  the  mode  of  culture.  They  are  generally  supposed  to  be 
richest  in  nutritive  matter  when  the  plant  has  just  come  into  flower: 


526  COMPOSITION    OF    THE   GREEN    STEMS    OP    PEAS,    ETC. 

The  following  table  exhibits  the  approximate    composition  of  the 

freen  stems  of  some  clovers  and  vetches,  as  they  have  been  given  by 
linhof  and  Crome  : — 


^ 

^ 

^    ^ 

•s 

J5-N 

_o  a 

6 

£6 

«5 

III 

u 

2  « 

•1? 

1 

1 

2 

1 

a 
a. 
00 

on 

1 

r 

Water      . 

800 

760 

800 

750 

770 

82-5 

77-5 

79-5 

860 

Starch      . 

3-40 

1-4 

•10 

2-2 

•2-3 

4-7 

26 

38 

1-3 

Woody  fibre    . 

•1031 

13-9 

11-5 

143 

120 

100 

104 

11-5 

70 

Sugar 
Albumen 

4-55 

21 

1-5 

0-8 

— 

— 

— 

— 

— 

0-90 

20 

15 

1-9 

2-3 

0-2 

1-9 

0-7 

1-8 

Extractive  matter  and 

gum      . 

0-65 

35 

34 

44 

bU 

2-6 

76 

3-6 

2-9 

Phosphate  of  lime     . 

019 

10 

0-8 

0-8 

0-8 

1 

— 

— 

— 

Wax  and  Resin 

— 

01 

02 

0-6 

1 

1 

] 

0-9 

10 

100     100       99-9  100       99-6  100     100     100     100 

§  24.   Of  the  composition  of  the  grasses  when  made  into  hay. 

1°.  An  elaborate  examination  of  the  grasses  of  this  country,  in  the 
dry  state,  with  the  view  of  determining  their  relative  nutritive  proper- 
ties, was  made  by  the  late  Mr.  Sinclair,  gardener  to  the  Duke  of  Bed- 
ford. His  method  was  to  boil  in  water  equal  weights  of  each  species  of 
hay  till  every  thing  soluble  was  taken  up,  and  to  evaporate  the  solution 
to  dryness.  The  weights  of  the  dry  matter  thus  obtained  he  considered 
to  represent  the  nutritive  values  of  the  grasses  from  which  the  several 
samples  of  hay  were  made. 

The  results  of  Mr.  Sinclair,  however,  have  lost  much  of  their  value, 
since  it  has  been  satisfactorily  ascertained — 

a.  That  the  proportion  of  soluble  matter  yielded  by  any  species  of 
grass,  when  made  into  hay,  varies  not  only  with  the  age  of  the  grass, 
when  cut,  but  with  the  soil,  the  climate,  the  season,  the  rapidity  of 
growth,  the  variety  of  seed  sown,  and  with  many  other  circumstances 
which  are  susceptible  of  constant  variation. 

h.  That  animals  have  the  power  of  digesting  a  greater  or  less  propor- 
tion of  that  part  of  their  food  which  is  insoluble  in  water.  Even  the 
woody  fibre  of  the  hay  is  not  entirely  useless  as  an  article  of  nourish- 
iiiont — experiment  having  shown  that  the  manure  often  contains  less 
of  this  insoluble  matter  than  was  present  in  the  food  consumed.*    (Spren- 

c.  That  some  of  the  substances  which  are  of  the  greatest  importance 
lii  the  nutrition  of  animals — such  as  vegetable  fibrin,  albumen,  casein, 
and  legumin — are  either  wholly  insoluble  in  water  or  are  more  or  less 
pcrfectl}'^  coagulated  and  rendered  insoluble  by  boiling  with  water.  Mr. 
Sinclair,  therefore,  must  have  left  behind,  among  the  insoluble  parts  of 

*  This  will  not  appear  surprising  when  it  is  recollectcxl  that,  by  prolonged  digestion  in 

"  iltd  sulphuric  acid,  insoluble  woody  fibre  naay  be  slowly  changed  into  sohible  gum  or 

iu-  (see  p.  112).     The  proportion  of  Ihe  woody  fibre  which  will  be  thus  worked  up  in  the 


dilultd  sulphuric  acid,  insoluble  woody  fibre  xnay  be  slowly  changed  into  soluble  gum  or 
[see  p.  112).     The  proportion  of  lh( 
iriach  of^an  animal  will  depend,  ainonft  other  circumstances,  upon  the  constitution  of  the 


aiiinuil  itself,  upon  the  abundance  of  food  supplied  to  it,  and  upon  the  more  or  less  perfect 
niaiiiication  to  which  the  food  is  subjected. 


WOODY    FIBRE    AND    GLUTEN    IN    THE    GRASSES.  527 

ah  hay,  tlie  greater  proportion  of  these  important  substances.  Hence, 
the  nature  and  weight  of  the  dry  extracts  he  obtained  could  not  fairly  re- 
present either  the  kind  or  quantity  of  the  nutritive  matters  which  the 
hay  was  likely  to  yield  when  introduced  into  the  stomach  of  an  animal. 

For  these  reasons  I  do  not  think  it  necessary  to  dwell  upon  the  results 
of  his  experiments.* 

2°.  Woody  fibre  in  the  grasses. — In  the  stems  of  the  grasses  (in  hay 
and  straw),  woody  fibre  is  the  predominating  ingredient.  They  are  not 
destitute  of  starch,  gum,  and  sugar,  but  they  are  distinguisjied  from  all 
the  other  usual  forms  of  animal  food,  by  the  large  (luantity  of  woody 
fibre,  and  of  saline  or  earthy  matter  which  tliey  contain.  The  propor- 
tion of  woody  fibre  in  the  more  common  grasses,  in  their  usual  state  of 
dryness  when  made  into  hay  and  straw,  is  thus  given  by  Sprengel  (see 
p.  106):— 

Per  cent.  Per  cent 

Wheat  straw,  ripe   ....     52 


Barley  straw,  do 50 

Oat  straw,  do.      .....  40 

Rye  straw,  do 48 

Indian  corn,  do 24 


Pea  straw,  ripe 30 

Bean  straw,  do 51 

Vetch  hay,  do "42 

Red  clover,  do 28 

Rye  grass,  do 35 


The  proportions  of  woody  fibre  here  given,  however,  can  be  considered 
only  as  approximations,  l^he  riper  the  straw  or  grass,  the  less  soluble 
matter  does  it  contain,  and  every  farmer  knows  how  much  soil,  season, 
and  manure,  affect  the  quality  of  his  artificial  grasses.  One  field  will 
grow  a  hard  wiry  rye-grass,  while  another  will  produce  a  soft  and  flexi- 
ble plant,  and  a  highly  nutritious  hay. 

3°.  Gluten  in  the  grasses. — Boussingault,  who  considers  the  relative 
nutritive  value  of  the  vegetable  substances  employed  for  fodder  to  be  in- 
dicated by  the  proportions  of  nitrogen  ihey  severally  contain,  has  arranged 
grass  and  clover  hays  and  the  straws  of  the  corn  plants,  in  their  usual 
state  of  dryness,  in  the  following  order  :- 


Or  tluten, 

Equal  effects 

Nitrosen 

&c., 

should  be 

per  cent. 

per  cent. 

produced  by 

Hay  from  mixed 

grasses 

{       115 

)      104 

154 

7-1 
G-4 

1 

100  lbs. 

Do.    aftermath  . 

93 

75t  " 

Do.   from  clover 

in  flower         15 

93 

75    " 

Pea  straw    . 

1-95 

12-3 

64t  " 

Lentil  straw 

101 

6-4 

114    " 

Indian  corn  straw 

054 

b-4 

240    " 

Wheat  straw 

— 

— 

520    " 

Barley  straw 

— 

— 

520    " 

Oat  straw    . 

— 

— 

550    " 

We   shall   liave   occasion  to 

compare 

the   above 

theoretical 

values 
{equivalents)  assigned  to  the  several  kinds  of  fodder,  with  the  results  of 

•  They  will  be  foumi  at  lenpih  in  the  Appendix  to  Davy's  Agricultusral  Chemiatry,  or  in  a 
tabulated  form  in  Sehiibler's  Agricultur  Chemie,  ii.,  p.  208. 

t  It  is  usually  supposed  that  the  aftermath  is  not  so  valuable  as  tiie  first  produce.  Schwertz, 
however,  considers  it  more  nourishing  by  one-tenth  part. 

X  "The  value  of  all  straw  for  fodder  must  depend  on  the  mode  in  which  it  is  harvested. 
In  Scotland,  the  order  in  which  the  farmer  places  his  straw  for  fodder  is — 1st,  pea ;  2nd, 
bean  ;  3d,  oat ;  4th,  wheat ;  5th,  barley.  While  in  England,  where  the  bean  is  quite  withered 
before  it  is  cut,  it  stands  last  in  the  scale."— Mr.  IlyeJt,  Royal  AgricuUurai  Jmtrmd,  iv.,p.  148. 


623  COMPOSITION    OF   HEMP   AND    LINT   SEEDS. 

practical  experience,  when  we  come  to  direct  our  attention  more  parti- 
cularly to  the  feeding  of  stock. 

4°.  Fatty  matter  in  the  grasses. — Besides  woody  fibre,  starch,  gum, 
and  gluten,  dry  hay  and  straw  contain  also  a  variable  proportion  of  fatty 
matter.  According  to  Liebig,  it  does  not  exceed  1-56  per  cent,  in  hay, 
while,  according  to  Dumas  and  Boussingault,  as  much  as  3,  4,  or  even  5 
per  cent,  of  tat  can  be  extracted  from  it.  To  this  fact  we  shall  also  re 
turn  when  considering  the  methods  of  fattening  stock. 

5°.  Inorganic  matter  in  the  grasses. — The  proportion  of  saline  and 
earthy  matter  contained  in  the  grasses  is  an  important  feature  in  their 
composition.  This,  as  I  have  already  said,  is  much  larger  than  in  any 
of  the  other  kinds  of  food  usually  given  to  animals,  being  seldom  less 
than  5,  and  occasionally  amounting  to  as  much  as  10  per  cent,  of  their 
weight  when  in  the  state  of  hay  or  straw.  A  large  proportion  of  the  ash 
left  by  the  stems  of  the  corn  plants,  and  by  many  grasses,  consists  of 
silica.  The  straw  of  the  bean,  pea,  and  vetch,  and  the  different  kinds 
of  clover  hay,  contain  little  silica,  its  place  in  these  plants  being  supplied 
by  a  large  quantity  of  lime  and  magnesia. 

§  25.  Of  hemp,  line,  rape,  and  other  oil-bearing  seeds. 

The  oily  seeds  are  important  to  the  agriculturist  from  their  long  ac- 
knowledged value  in  the  feeding  and  fattening  of  cattle.  Lintseed  is  ex- 
tensively used  for  the  latter  purpose,  both  in  its  entire  state  and  in  the 
form  o^cake — when  the  greater  part  of  the  oil  has  already  been  expressed 
from  it.  All  these  seeds,  however,  are  not  cfjually  palatable  to  cattle. 
Some  varieties  they  even  refuse  to  eat.  Among  these  is  the  rape-seed, 
from  which  so  much  oil  is  expressed,  and  the  cake  left  by  which  is  now 
so  extensively  employed  as  a  manure. 

These  seeds  are  distinguished  from  those  of  the  corn  plants,  by  con- 
taining, instead  of  starch  or  sugar,  a  predominating  proportion  of  oil;  and 
instead  of  their  gluten  a  substance  soluble  in  water,  which  possesses  many 
of  the  properties  of  the  curd  of  cheese  {casein). 

We  are  in  possession  of  a  somewhat  imperfect  analysis  of  hemp  seed 
and  of  the  seed  of  the  common  lint,  according  to  which  the  varieties  ex- 
amined consisted  in  100  parts  of — 

Hemp  seed  Lime  seed 

(Bucholz).  (Leo  Meier) 

Oil 19-1  11-3 

Husk,  &c 38-3  44-4 

Woody  fibre  and  starch  .     .  6'0  1*5 

Sugar,  &c 1-6  10-8 

Gum 9-0  7-1 

Soluble  albumen  (Casein  ?)  .  24-7  15-1 

Insoluble     do —  3*7 

Wax  and  resin     ....  1'6  3-1 

Loss 0-7  3-0 

100  100 

These  analyses  show  that,  besides  the  oil,  these  seeds  contain  consi- 
derable proportions  of  gum  and  sugar  and  a  large  (piantity  of  a  substance 
here  called  soluble  albumen,  of  whicli  nitrogen  is  a  constituent  part,  but 


Oil  per  cent. 

Sun-flower  seed   . 

.    15 

Walnut  kernels    .     . 

.    40  to  70 

Hazel-nut  do. 

.     .    60 

Beech-nut  do. 

.     .   15  to  17 

Plum  stone  do.    . 

.     .    33 

Sweet  almond  do. 

.   40  to  54 

Bitter     do.        do. 

.    28  to  46 

PROPORTION    OF    OIL   IN    DIFFERENT    SEEDS.  529 

which  differs  in  its  properties  from  the  gluten  and  albumen  of  the  seeds 
of  the  corn-bearing  plants,  and  has  much  resemblance  to  the  curd  of 
milk.  Besides  their  fattening  properties,  therefore — which  these  seeds 
probably  owe  in  a  great  measure  to  the  oil  they  contain — this  peculiar 
albuminous  matter  ought  to  render  them  very  nourishing  also  ; — capable 
of  promoting  the  growth  of  the  growing,  and  of  sustaining  the  strength 
of  the  matured,  animal. 

The  quantity  of  oil  contained  in  different  seeds  of  this  class,  and  even 
in  the  same  species  of  seed  when  raised  in  different  circumstances,  is 
very  variable.  These  facts  will  appear  from  the  following  table,  which 
represents  the  proportions  of  oil  that  have  been  found  in  100  lbs.  of  some 
of  the  more  common  seeds : — 

Oil  per  cent. 

Line  seed 11  to  22 

Hemp  seed 14  to  25 

Rape  seed 40  to  70 

Poppy  seed      .     .     .     .     36  to  53 
White  mustard  do.     .     .     36  to  38 
Black       do.      do.     .     .     15 
Swedish  turnip  do.    .     .     34 

It  seems  to  be  a  provision  of  nature,  that  the  seeds  of  nearly  all  plants 
should  contain  a  greater  or  less  proportion  of  oil,  which  is  lodged  for  the 
most  part  in,  or  immediately  beneath,  the  husk,  and,  among  other  pur- 
poses, may  be  intended  to  aid  in  preserving  the  seed.  We  shall  here- 
after «ee  that  this  oily  constituent  is  of  much  importance  also  to  the  prac- 
tical agriculturist. 

§  26.  General  differences  in  composition  among  the  different  kinds  of 
vegetable  food. 

It  may  be  useful  shortly  to  recapitulate  the  leading  differences  in 
chemical  constitution  which  exist  among  the  different  kinds  of  vegetable 
food  to  which  I  have  directed  your  attention  in  the  present  lecture. 

We  have  seen  that  each  of  the  varieties  of  food  contains  a  greater  or 
less  proportion  of  three  different  classes  of  chemical  substances — an 
organic  substance  containing  nitrogen,  an  organic .  substance  containing 
no  nitrogen,  and  an  in-organic  substance.  But  it  is  interesting  to  mark 
how  in  each  class  of  those  vegetable  products  which  we  gather  from  the 
earth  for  our  sustenance,  the  organic  substances  vary  either  in  composition 
or  in  chemical  characters,  while  the  inorganic  matter  alters  also  either  in 
kind  or  quantity.     Thus — 

1°.  In  the  seeds  of  the  com  plants — wheat,  oats,  &c. — the  predomi- 
nating ingredient  is  starch,  in  connection  with  a  considerable  proportion 
of  gluten,  and  a  small  quantity  of  saline  matter  consisting  chiefly  of  the 
phosphates  of  potash  and  of  magnesia,  and  in  the  case  of  barley  of  a 
considerable  proportion  of  lime. 

2°.  In  the  seeds  of  leguminous  plants — the  pea,  the  bean,  the  vetch, 
6cc. — starch  is  still  the  predominating  ingredient,  but  it  is  connected  with 
a  large  quantity  of  legumin,  and  with  a  greater  proportion  of  inorganic 
Blatter — in  which  phosphate  of  lime  also  is  more  abundant. 

3°.  In  the  oil-beanng  seeds — those  of  hemp,  lint,  dec — oil  is  often  the 


530  SPECIAL   DIFFERENCES    AMONG    SEEDS    AND    ROOTS. 

predominating  ingredient,  and  it  is  connected  with  a  large  proportion  of  a 
nitrogenous  substance,  resembling  the  curd  of  milk  {casein),  and  with  a 
quantity  of  ash  about  equal  to  that  in  tlie  pea,  hut  in  which  the  phos- 
phate of  lime  is  said  to  be  still  more  abundant. 

4°.  In  the  potaioe — starch  is  the  greatly  predominating  ingredient,  but 
it  is  united  with  albumen  nearly  in  the  same  proportion  as  it  is  with 
gluten  in  wheat.  The  inorganic  matter  is  nearly  in  the  same  proportion 
to  the  dry  organic  matter,  as  in  the  pea  and  the  bean,  but  is  much 
more  rich  in  potash  and  soda.  Still  it  is  more  rich  in  the  earthy  phos- 
phates than  the  ash  left  by  wheat  and  oats,  and  is  inferior  in  this  respect 
only  to  that  of  barley. 

5°.  In  the  turnip — sugar  and  pectin  take  the  place  of  the  starch,  and 
these  are  associated  with  albumen,  and  with  a  proportion  of  inorganic 
matter  about  equal  to  that  of  the  potatoe,  abounding  like  it  in  potash  and 
soda,  but  more  rich  in  the  phosphates  of  lime  and  of  magnesia. 

6°.  In  the  stems  of  the  grasses  and  clovers — woody  Jibre  becomes  the 
predominating  ingredient,  associated  apparently  with  albumen,  and  with 
a  larger  proportion  of  inorganic  matter  than  in  any  of  the  other  crops. 
In  the  straws  and  in  some  of  the  grasses  which  are  cut  for  hay,  silica 
forms  a  large  portion  of  this  inorganic  matter.  In  the  clovers,  lime  and 
magnesia  take  its  place. 

The  natural  differences  above  described  not  only  exercise  an  important 
influence  upon  the  mode  of  culture  by  which  the  different  crops  may  be 
most  successfully  and  most  abundantly  raised,  but  also  upon  the  way 
in  which  they  can  be  most  skilfully  and  economically  employed  in  the 
feeding  of  stock.     To  tliis  latter  point  we  shall  return  hereafter. 

§  27.  Average  composition  and  produce  of  nutritive  matter  per  acre,  by 
each  of  the  usually  cultivated  crops. 

1°.  Average  composition. — The  relative  proportions  of  the  several  most 
important  constituents  contained  in  our  cultivated  crops  vary,  as  we  have 
seen,  with  a  great  number  of  circumstances.  The  following  table  exhi- 
bits the  average  composition  of  ]  00  parts  of  the  more  common  grains, 
roots,  and  grasses,  as  nearly  as  the  present  state  of  our  knowledge  upon 
the  subject  enables  us  to  represent  it.    (See  table  at  top  of  next  page.) 

In  drawing  up  this  table,  I  have  adopted  the  proportions  of  gluten,  for 
the  most  part,  from  Boussingault.  Some  of  them,  however,  appear  to 
be  very  doubtful.  The  proportions  of  fatty  matter  are  also  very  uncer- 
tain. With  a  few  exceptions,  those  above  given  have  been  taken  from 
Sprengel,  and  they  are,  in  general,  stated  considerably  too  low. 

It  is  an  interesting  fact,  that  the  proportion  of  fatty  matter  in  and  im- 
mediately under  the  husk  of  the  grains  of  corn,  is  generally  much  greater 
than  in  the  substance  of  the  corn  itself.  Thus  I  have  found  the  pollard 
of  wheat  to  yield  more  than  twice  as  much  oil  as  the  fine  flour  obtained 
from  the  same  sample  of  grain  ;*  and  Dumas  states  that  the  husk  of  oats 
sometimes  yields  as  much  as  5  or  6  per  cent,  of  oil.  We  shall  perceive 
the  practical  value  of  this  fact  when  we  come  to  consider  the  uSe  of  bran 
and  pollard  in  the  fattening  of  pigs  and  other  kinds  of  stock. 

*  Thus  the  four  portions  separated  by  the  miller  from  a  superior  sample  of  wheat  grown 
in  the  neighbourhood  of  Durham,  gave  of  oil  respectively  :-^fine  flour,  1-5  per  cent ;  poUard, 
2*4 ;  boxings,  3-6;  and  bran,  3-3  per  cent. 


AVERAGE    COMPOSITION    OF   THE   DIFFERENT   CROPS. 


531 


Husk  or 

starch, 

Gluten,  al- 

Fatty 
matter. 

Saline 
matter. 

Water. 

woody 
fibre. 

gum,  and 
sugar. 

bumen,  le- 
gumin,«&c. 

Wheat      .    . 

16 

15 

55 

10tol5 

2  to  4  J 

20 

Barley       .     . 

15 

15 

60 

121 

2-5  J 

20 

Oats      .     .     . 

16 

20 

50 

14-51 

56  J 

3-5 

Rye       ... 

12 

10 

60 

14-5 

30 

10 

Indian  corn  . 

14 

151 

50 

120 

5  to  9  D. 

1-5 

Buckwheat    . 

16-? 

25  7 

50 

14-5 

0-41 

1-5 

Beans  .    .    . 

16 

10 

40 

280 

2  + 

30 

Peas     .     .     . 

.        13 

8 

50 

24-0 

2-81 

2-8 

Potatoes    .     . 

751 

51 

121 

225 

0-3 

0-8  to  1 

Turnips    .     . 

.        85 

3 

10 

1-2 

1 

0-8  to  1 

Carrots      .    . 

85 

3 

10 

20 

0-4 

10 

Meadow  hay 

14 

30 

40 

71 

2to5D. 

5  to  10 

Clover  hay    . 

14 

25 

40 

93 

30 

9 

Pea  straw 

10tol5 

25 

45 

123 

1-5 

5 

Oat    do.   .     . 

12 

45 

35 

1-3 

0-8 

6 

Wheat  do.     . 

12tol5 

50 

30 

13 

0-5 

5 

Barley  do. 

do. 

50 

30 

13 

0-8 

5 

Rye  do.    .    . 

do. 

45 

38 

1-3 

05 

3 

Indian  com  do. 

12 

25 

52 

30 

1-7 

4 

2°.  Gross  produce  per  acre. — The  gross  produce,  per  acre,  of  the  dif- 
ferent crops  varies  as  we  have  already  seen  (p.  487)  in  different  districts 
of  the  country.  The  weight  of  each  crop  in  pounds,  however,  will,  in 
general,  approach  to  one  or  other  of  tlie  quantities  represented  by  the  num- 
bers in  the  following  table  : — 

Produce  Weight  Total  weight 

per  acre.  per  bushel.  in  pounds. 

Wheat     .....  25  bush.  60  lbs.  1500 

—        30  *'  1800 

Barley 35  "  53  lbs.  1855 

—        40  "  2120 

Oats 40  "  42  lbs.  1680 

—        50  "  2100 

Rye 25  "  54  lbs.  1350 

—        30  "  1620 

Indian  com ....  30  "  60  lbs.  1800 

Buckwheat  ....  30  "  46  lbs.  1380 

Beans 25  "  64  lbs.  1600 

—        30  "  1920 

Peas        ..*...  25  "  66  lbs.  1650 

• 


Potatoes  . 
Turnips  . 


Weight  of  produce. 

.     6  tons. 

12  tons. 

.  20  tons. 

30  tons. 


Carrots     . 
Meadow  hay 
Clover  hay 


Weight  of  producer 
.  25  tons. 
.  1^  tons. 
.     2  tons. 


PRODUCE    PER    ACRE. 


Weight  of  produce. 

Weight  of  produce. 

Wheat  straw 

.  3000  lbs. 

Rye  straw 

. 

4000  lbs. 

3600    " 

4800    " 

Barley  straw 

.2100    " 

Bean  str^iw     . 

. 

2700    "? 

2500    " 

3200   " 

Oat  straw     . 

.  2700    " 

Pea  straw 

. 

2700   "? 

3500    " 

3°.  Average  produce  of  nutritive  matter  per  acre. — In  the  gross  pro- 
duce above  given,  there  are  contained,  according  to  the  first  table,  the  fol- 
lowing average  proportions  of  nutritive  matter  of  various  ki..'ds  : — 

AVERAGE  PRODUCE  OF    NUTRITIVE  MATTER  OF  DIFFERENT  KINDS    FROM 
AN  ACRE  OF  THE  USUALLY  CULTIVATED  CROPS. 


Gross  produce. 

Husk,  or 

woody 
fibre. 

lbs. 

Starch, 
sugar,  &c. 

lbs. 

Gluten, 
d,c. 

lbs. 

Oil  or  fat. 
lbs. 

Saline 
matter. 

bush. 

lbs. 

lbs. 

Wheat  . 

25 

1,500 

225 

825 

150  to  220 

30  to  60 

30 

30 

1,800 

270 

990 

180  to  260 

36  to  72 

36 

Barley   . 

35 

1,800 

270 

1080 

216 

45  + 

36 

40 

2,100 

315 

1260 

252 

52-^ 

42 

Oats 

40 

1,700 

340 

850 

2301 

95 

60 

50 

2,100 

420 

1050 

290? 

118 

75 

Rye  .     , 

25 

1,300 

130 

780 

190 

40 

13 

30 

1,600 

160 

960 

230 

48 

16 

Indian  corr 

I      30 

1,800 

270 

900 

216 

90  to  170 

27 

Buck  whea 

t     30 

1,300 

3201 

650 

180 

5  + 

21 

Beans    . 

25 

1,600 

160 

640 

450 

32  + 

48 

30 

1,900 

190 

760 

530 

36  + 

57 

Peas      . 

.      25 

1,600 

130 

800 

380 

45 

45 

Potatoes 

tons. 
6 

13,500 

675 

1620 

300 

45 

120 

.       12 

27,000 

1350 

3240 

600 

90 

240 

Turnips 

20 

45,000 

1350 

4500 

5401 

1 

400 



.      30 

67,000 

2010 

6700 

8001 

i 

600 

Carrots 

25 

56,000 

1680 

5600 

11201 

200 

560 

Meadow  h 

ay  n 

3,400 

1020 

1360 

240 

70  to  170 

220 

Clover  hay 

2 

4,500 

1120 

1800 

420 

135  to  225 

400 

Pea  straw 

— 

2,700 

675 

1200 

330 

40 

135 

Wheat  stra 

w   — 

3,000 

1500 

900 

40 

15 

150 

— 

3,600 

1800 

1080 

48 

18 

180 

Oat  straw 

— 

2,700 

1210 

950 

36 

20 

135 



3,500 

1570 

1200 

48 

28 

175 

Barley  stra 

w     

2,100 

1050 

630 

28  . 

16 

105 



— 

2,500 

1250 

750 

33 

20 

125 

Rye^i^raw 



4,000 

1800 

1500 

53 

20 

120 



— 

4,800 

2200 

1800 

64 

24 

144 

The  most  uncertain  column  in  this  table  is  that  which  represents  the 
quantity  of  oil  or  fat  contained  in  the  several  kinds  of  produce.  The 
importance  ot  the  whole  table  to  the  practical  man  will  appear  more 
clearly  when  we  come  to  treat  of  tbs  feeding  of  stock. 


LECTURE  XX. 

Of  milk  and  its  products.— Properties  and  composition  of  the  milk  of  different  animals.— 
Circumstances  which  aflFect  the  quality  and  quantity  of  milk— species,  size,  variety,  age, 
health,  and  constitution  of  the  animal,  time  of  milking,  kind  of  food,  &c.— Mode  of  sepa- 
rating and  estimating  the  several  constituents  of  milk. — Sugar  of  milk,  and  acid  of  milk 
(Lactic  acid),  their  composition  and  properties. — Souring  of  milk,  cause  of. — Cream — 
composition  and  variable  proportions  of— mode  of  estimating  iis  quantity — the  gaiactome- 
ter. — Churning  of  milk  and  cream. — Composition  of  butter. — ButKr-milk. — The  solid  and 
liquid  fats  contained  in  butter — margarin  and  butter-oil — their  separation  and  properties- — 
Rancidity  and  preservation  of  butter.— Composition  and  propertits  of  the  curd  ^casein). — 
Curdling  of  milk,  natural  and  artificial — by  acids  and  by  animal  membranes. — Making  and 
action  of  rennet — how  explained. — Manufacture  of  cheese. — Varieties  of  cheese. — Aver- 
age produce  of  butter  and  cheese.— Colouring  of  butter  and  cheese.— The  whey.— Saline 
matter  in  the  whey. — Nature  of  the  saline  constituents  of  milk. — Fermentation  of  milk. — 
Intoxicating  liquor  from  milk. — Milk  vinegar. — Purposes  served  by  milk  in  tlie  economy 
of  nature. 

Or  the  indirect  products  of  agriculture,  milk,  and  the  butter  and 
cheese  manufactured  from  it,  are  among  the  most  important.  In  our 
large  towns  these  substances  may  almost  be  considered  as  necessaries  of 
life,  and  many  extensive  agricultural  districts  are  entirely  devoted  to  the 
production  of  them.  The  branch  of  dairy  husbandry  also  presents  many 
curious  and  interesting  questions  to  the  scientific  enquirer,  and  upon 
these  questions  modem  chemistry  has  thrown  much  light.  To  the  con- 
sideration of  this  subject,  therefore,  it  is  my  intention  to  devote  the  pre- 
sent lecture. 

§  1.  Of  the  ]noperties  and  composition  of  milk. 
1°.  Properties  of  milk. — The  milk  of  most  animals  is  a  white  opaque 
liquid,  having  a  slight  but  peculiar  odour — which  becomes  more  distinct 
when  the  milk  is  warmed — and  an  agreeable  sweetish  taste.  It  is 
heavier  than  water — usually  in  the  proportion  of  about  103  to  100.* 
When  newly  taken  from  the  animal,  cow's  milk  is  almost  always 
slightly  alcaline.  It  speedily  loses  this  character,  however,  when  ex- 
posed to  the  air,  and  hence  even  new  milk  often  exhibits  a  slight  degree 
of  acidity. f  When  left  at  rest  for  a  number  of  hours,  it  separates  into 
two  portions,  throwing  up  the  lighter  part  to  the  surface  in  the  form  of 
cream.  If  the  whole  milk,  or  the  cream  alone,  be  agitated  in  a  proper 
vessel  (a  churn),  the  temperature  of  the  liquid  undergoes  a  slight  increase, 
it  becomes  distinctly  sour,  and  the  fatty  matter  separates  in  the  form  of 
butter.  If  a  little  acid,  such  as  vinegar  or  diluted  muriatic  acid,  be  add- 
ed to  milk  warmed  to  about  100°  F.,  it  immediately  coagulates  and  se- 
parates into  a  solid  and  a  liquid  part — the  curd  and  the  whey.  The 
same  effect  is  produced  by  the  addition  of  rennet  or  of  sour  milk — and 
it  takes  place  naturally  when  milk  is  left  to  itself  until  it  becomes  sour. 
At  a  very  low  temperature,  or  when  kept  in  a  cool  place,  milk  remains 
sweet  for  a  considerable  time.     At  the  temperature  of  60°  F.  it  soon 

*  Or  it  has  a  specific  gravity  of  1020  in  woman's  milk,  to  1041  in  sheep's  milk ;  water  being 
1000. 

t  It  is  said  that  if  the  animal  remain  long  unmilked,  the  milk  will  begin  to  sour  in  ttie 
udder,  and  that  hence  it  is  sometimes  slightly  acicTwhen  fresh  drawn  from  tbe  cow. 
23 


634  PROPERTIES    AND    COMPOSITION    OF    MILK. 

turns  or  acquires  a  sour  taste,  and  at  70°  or  80°  it  sours  with  still  greater 
rapidity.  If  sour  milk  be  gently  warmed  it  undergoes  fermentation,  and 
may  be  made  to  yield  an  intoxicating  liquor.  By  longer  exposure  to  the 
air  it  gradually  begins  to  putrify,  becomes  disagreeable  to  the  taste, 
emits  an  unpleasant  odour,  and  ceases  to  be  a  wholesome  article  of 
food. 

The  milk  of  each  species  of  animal  is  distinguished  by  some  charac- 
ters peculiar  to  itself. 

Ewe's  milk  does  not  differ  in  appearance  from  that  of  the  cow,  but  it 
is  generally  more  dense  and  thicker,  and  gives  a  pale  yellow  butter, 
which  is  soft,  and  soon  becomes  rancid.  The  curd  is  separated  from 
this  milk  with  greater  difficulty  than  from  that  of  the  cow. 

Goafs  milk  generally  possesses  a  characteristic  unpleasant  odour  and 
taste,  which  is  said  to  be  less  marked  in  animals  of  a  white  colour  or 
that  are  destitute  of  horns.  The  butter  is  always  white  and  hard,  and 
keeps  long  fresh.  The  milk  is  considered  to  be  very  wholesome,  and  is 
often  recommended  to  invalids. 

Ass's  milk  has  much  resemblance  to  that  of  the  woman.  It  yields 
little  cream,  and  the  butter  is  white  and  light,  and  soon  becomes  rancid. 
It  contains  much  sugar,  and  hence  soon  passes  to  the  state  of  fermenta- 
tion. 

2°.  Composition  of  milk. — Milk,  like  the  numerous  vegetable  products 
we  have  had  occasion  to  consider,  consists,  besides  water,  of  organic  sub- 
stances destitute  of  nitrogen — sugar  and  butter ;  of  an  organic  substance 
containing  nitrogen  in  considerable  quantity — the  curd  or  casein  ;  and 
of  inorganic  or  saline  matter,  partly  soluble  and  partly  insoluble  in  pure 
water. 

The  proportions  of  these  several  cc  stituents  vary  in  different  animals. 
This  appears  in  the  following  table,  which  exhibits  the  composition  of 
the  milk  of  several  animals  in  its  ordinary  state,  as  found  by  Henry  and 
Chevallier : — 

Woman. 

Casein  (cheese)     .     .     1-52 

Butter 3-55 

Milk  sugar       .     .     .     6-50 

Saline  matter  .     .     .     0-45 

Water 87-98 


Cow. 

Ass. 

Goat. 

Ewe. 

4-48 

1.82 

4-08 

4-50 

3-13 

0-11 

3-32 

420 

4-77 

6-08 

5-23 

5-00 

0-60 

0-34 

0-58 

0-68 

87-02 

91-65 

86-80 

88-62 

100         100  100  100  100 

From  the  numbers  in  the  above  table,  it  appears  that  the  milk  of  the 
cow,  the  goat,  and  the  ewe,  contains  much  more  cheesy  matter  than  that 
of  the  woman  or  the  ass.  It  is  probably  this  similarity  of  asses'  milk  to 
that  of  the  human  species,  together  with  its  deficiency  in  butter,  which, 
from  the  most  remote  times,  has  recommended  it  to  invalids,  as  a  light 
and  easily  digested  drink. 

§  2.  Of  the  circumstances  by  which  the  composition  or  quality  of  the  milk 
is  modified. 
^  But  the  composition  or  quality  of  milk  varies  with  a  great  variety  of 
circumstances.     Let  me  direct  your  attention  to  a  few  of  these. 

1°.  Distance  from  the  time  of  calving. — The  most  remarkable  depar- 


INFLUENCE  OF  THE  HEALTH  OF  THE  ANIMAL.        535 

ture  from  the  ordinary  composition  of  milk  is  observed  in  the  heistingSy 
colostrum  or  first  milk,  yielded  by  the  animal  after  the  birth  of  its  young. 
This  milk  is  thicker  and  yellower  than  ordinary  milk,  coagulates  by 
heating,  and  contains  an  unusually  large  quantity  of  casein  or  cheesy 
matter.  Thus  the  first  milk  of  the  cow,  the  ass,  and  the  goat,  consisted, 
in  some  specimens  examined  by  Henry  and  Chevallier,  of — 

Cow.  Ass.  Goat. 


Casein 

15-1 

11-6 

24-5 

Butter 

2-6 

0-6 

5-2 

Milk  sugar 

— 

4-3 

3-2 

Mucus 

2-0 

0-7 

3-0 

Water 

80-3 

82-8 

64-3 

100  100  100 

The  increase  in  the  proportion  of  cheese  is  peculiarly  great  in  the  first 
nilk  of  the  ass  and  the  goat. 

This  state  of  the  milk,  however,  does  not  long  continue.  It  gradually 
assumes  its  ordinary  qualities.  After  ten  or  twelve  days  from  the  time 
of  calving,  its  peculiarities  disappear,  though  in  tlie  celebrated  dairy  dis- 
tricts of  Italy  it  is  considered  that  the  milk  does  not  reach  perfection  until 
about  eight  months  after  calving.  [Cataneo,  11  iatte  e  i  suoi  prodoUi,  p. 
27.] 

2°.  Age  of  the  anim.al. — It  is  observed  that  milk  of  the  best  quality  is 
given  only  by  cows  which  have  been  already  three  or  four  times  in  calf. 
Such  animals  continue  to  give  excellent  milk  till  they  are  ten  or  twelve 
years  of  age,  and  have  had  seven  or  eight  calves,  when  they  are 
generally  fattened  for  the  butcher. 

3°.  Climate  and  season  of  the  year. — Moist  and  temperate  climates 
are  favourable  to  the  production  of  milk  in  large  quantity.  In  hot  coun- 
tries, and  in  dry  seasons,  the  quantity  is  less,  but  the  average  quality  is 
richer.  Cool  weather  favours  the  production  of  cheese  and  sugar  in  the 
milk,  while  hot  weather  increases  the  yield  of  butter,  [Sprengel,  Che- 
mie  fiir  Landwirthe,  ii.,  p.  620.] 

In  spring  the  milk  is  more  abundant  and  of  finer  flavour.  In  autumn 
and  winter,  other  things  being  equal,  it  yields  less  cheese,  but  a  larger 
return  of  butter.*  Where  cattle  are  fed  upon  pasture  grass  only,  this 
observed  difference  may  be  derived  from  a  natural  difference  in  the 
quality  of  the  herbage  upon  which  the  cow  is  fed. 

4°.  Health  and  general  state  of  the  animal. — It  is  obvious  that  the 
quality  of  the  milk  must  be  affected  by  almost  every  change  in  the  health 
of  the  animal.  It  is  sensibly  less  rich  in  cream  also,  as  soon  as  the  cow 
becomes  pregnant,  and  the  same  is  observed  to  be  the  case  when  it  shows 
a  tendency  to  fatten.  The  poorer  the  apparent  condition  of  the  cow, 
good  food  being  given,  the  richer  in  general  is  the  milk. 

5°.  Time  and  frequency  of  milking. — If  the  cow  be  milked  only  once 
a  day,  the  milk  will  yield  a  seventh  part  more  butter  than  an  equal 
quantity  of  that  which  is  obtained  by  two  milkings  in  the  day.  When 
the  milk  is  drawn  three  times  a  day,  it  is  more  abundant  but  still  less 

*  British  Husbandry,  ii.,  p.  404.  This  opinion  seems  to  contradict  that  o-f  Sprengel  in  the 
preceding  paragraph.  Does  this  difference  arise  from  the  locality  and  other  unlike  circum 
stanceB  in  which  the  observations  of  the  two  writers  were  severally  made — or  are  there  no 
accurate  experiments  upon  the  subject  from  which  a  correct  result  can  be  drawn  7 


536  INFLUENCE    OF    THE    BREED    ON    THE    QUALITY    OF   MILK. 

rich.  It  is  also  universally  remarked,  that  the  morning's  milk  is  of  bet- 
ter quality  than  that  obtained  in  the  evening. 

6°.  Period  at  which  it  is  taken,  during  the  milking. — The  milk  in  the 
udder  of  the  cow  is  not  uniform  in  quality.  That  which  is  first  drawn 
off  is  thin  and  poor,  and  gives  little  cream.  That  which  is  last  drawn — 
the  stroakings,  strippings,  or  afterings — is  rich  in  (luality,  and  yields 
much  cream.  Compared  with  the  first  milk,  the  same  measure  of  the 
last  will  give  at  least  eight  and  often  sixteen  times  as  much  cream  (An- 
derson). The  quality  of  the  cream  also,  and  of  the  milk  when  skimmed, 
is  much  better  in  the  later  than  in  the  earlier  drawn  portions  of  the  milk. 

7°.  Treatment  and  moral  state  of  the  animal. — A  state  of  comparative 
repose  is  favourable  to  the  performance  of  all  the  important  functions  in 
a  healthy  animal.  Any  thing  which  frets,  disturbs,  torments,  or  renders 
it  uneasy,  affects  these  functions,  and,  among  other  results,  lessens  tlie 
quantity  or  changes  the  quality  of  the  milk.  Such  is  observed  to  be  the 
case  when  the  cow  has  been  newly  deprived  of  her  calf — when  she  is 
taken  from  her  companions  in  the  pasture  field — when  her  usual  place 
ki  the  cow-house  is  changed — when  she  is  kept  long  in  the  house  after 
the  spring  has  arrived — when  she  is  hunted  in  the  field  or  tormented  by 
insects— or  when  any  other  circumstance  occurs  by  which  irritation  or 
restlessness  is  caused,  either  of  a  temporary  or  of  a  permanent  kind.  I 
do  not  enquire  at  present  into  the  physiological  nature  of  the  changes 
which  ensue — to  the  dairy  farmer  it  is  of  importance  chiefly  to  be  familiar 
with  the  facts. 

8°.  The  race  or  breed  and  size  of  the  animal. — The  quality  of  the  milk 
depends  much  upon  the  race  and  size  of  the  cow.  As  a  general 
rule,  small  races,  or  small  individuals  of  the  larger  races,  give  the  richest 
milk  from  the  same  kind  of  food.  Thus  the  small  Highland  cow  gives 
a  richer  milk  than  the  Ayrshire.  The  small  Alderneys  give  a  richer 
cream  than  any  other  breed  in  common  use  in  this  country.*  The  small 
Kerry  cow  is  said  to  equal  the  Alderney  in  this  respect,  while  the  small 
Shetlander  has  been  found  in  the  north  of  Scotland  to  give  from  the  same 
food  a  more  profitable  return  of  rich  milk  than  any  of  the  larger  races. 
AU  these  breeds  are  hardy,  and  will  pick  up  a  subsistence  from  pastures 
on  which  other  breeds  would  starve. 

The  old  Yorkshire  stock,  a  cross  between  the  short-horn  and  the 
Holderness,  is  preferred  by  the  London  cow-keepers  as  giving  the  Zar^c*i 
quantity  of  milk,  though  poor  in  quahty. 

The  long-horns  are  preferred  in  Cheshire  and  Lancashire  because  of 
their  producing  a  greater  quantity  of  cheese.  The  Ayrshire  kyloe,  on 
ordinary  pasture,  is  said  to  be  unrivalled  for  abundant  produce  (Ayton) 
— though  the  milk  is  not  so  rich  as  that  of  the  small  breeds.  Va"rious 
crosses  have  been  tried  in  different  parts  of  the  island — and* in  almost 
every  district  it  has  been  found  that  the  produce  of  some  particular  stock 
is  best  adapted  to  the  chmate,  the  soil,  the  natural  grasses,  the  prevailing 
husbandry,  or  to  the  kind  of  dairy  produce  which  it  is  the  interest  of  the 
farmer  to  raise  in  his  own  peculiar  neighbourhood. 

'  A  very  striking  illustration  of  the  difference  in  the  quality  of  tiie  milk  of  two  breeds,  in 
the  same  circumstances,  is  given  by  Mr.  Malcolm,  in  his  Compendium  of  Modem  litis- 
bandry.  He  kept  an  Alderney  and  a  Suffolk  cow,  the  latter  the  best  he  ever  saw.  During 
seven  years,  the  milk  and  butfer  being  kept  separate,  it  was  found,  year  after  year,  that  the 
value  of  the  Alderney  exceeded  that  of  the  Suffolk,  though  the  latter  gave  more  than 
double  the  quantity  of  milk  at  a  meal— BrtrtsA  Husbandry,  ii.,  p.  397. 


Butter. 

yielded  by 

38^  OZ. 

12  quarts  of  milk. 

25    " 

12 

28    " 

9f 

34    " 

9i 

EXPERIMENTS    WITH    DIFFERENT    KINDS    OP    FOOD.  537 

In  the  South  of  Europe,  ihe  Swiss  breeds  are  considered  the  best  for 
dairy  purposes,  and  of  these  that  of  the  Canton  of  Schweitz,  which,  in 
size,  is  intermediate  between  the  large  cattle  of  Fribourg  and  Berne,  and 
the  small  breed  of  Hasti.  They  have  enormous  udders  and  give  much 
milk,  but  like  that  of  the  Suffolk  cows  it  is  less  rich  in  butter  and  chee.sc. 

The  influence  of  breed  alone  upon  the  quality  of  the  milk  is  well  il- 
lustrated by  the  resuh  of  a  series  of  trials  made  at  Bradley  Hall,  in 
Derbyshire.  During  the  height  of  the  season,  and  when  fed  upon  the 
same  pasture,  cows  of  four  ditferent  breeds  gave  per  day — 

Or  1  lb.  of  butter  was 
Breed.  Milk. 

Holderness     .     .     29  quarts,  and 

Aldemey  ...     19         " 

Devon       ...     17         " 

Ayrshire  ...  20  " 
The  Ayrshire  cows  gave  the  richest  milk  and  a  larger  quantity  of  both 
milk  and  butter  than  the  Alderneys  or  Devons,  but  the  Holderness  breed 
surpassed  them  all.  It  gave  \  lb.  more  butter  than  the  Ayrshire,  and 
nearly  one-half  more  milk.  It  would  appear,  therefore,  to  be  admirably 
adapted  to  the  purposes  of  the  town  dairyman,  whose  profit  arises  from 
milk  and  cream  only.  It  does  not  appear  what  is  the  relative  value  of 
this  breed  in  the  production  of  cheese. 

9°.  The  kind  of  food. — But  tbe  kind  of  food  has  probably  more  in- 
fluence upon  the  quality  of  the  milk  than  any  other  circumstance.  It  is 
familiar  to  every  dairy  farmer  that  the  taste  and  colour  of  his  milk  and 
cream  are  affected  by  the  plants  on  which  his  cows  feed,  and  by  the  food 
he  gives  them  in  the  stall.  The  taste  of  the  wild  onion  and  of  the  turnip, 
when  eaten  by  the  cow,  are  often  perceptible  both  in  the  milk  and  in  the 
butter.  If  madder  be  given  to  cows  the  milk  is  red,  if  they  eat  safiron 
it  becomes  yellow.  It  has  also  been  observed  from  the  most  remote 
times,  that  when  fed  upon  one  pasture  a  cow  will  yield  more  cheese, 
upon  another  more  butter.  From  this  has  arisen  the  practice  more  or 
less  observed  in  all  dairy  districts  of  varying  the  food  of  the  cattle — of 
giving  some  artificial  food  in  addition  to  that  obtained  in  the  natural  pas- 
tures— of  leaving  the  animal  at  liberty  to  roam  over  wide  pastures  and 
thus  to  seek  out  for  itself,  as  the  sheep  does  on  extensive  sheep-walks, 
those  different  kinds  of  herbage  which  are  necessary  to  the  production 
©f  a  rich  and  valuable  milk — or  in  more  inclosed  districts,  and  where 
different  soils  exist  on  the  same  farm,  of  turning  them  during  the  former 
part  of  the  day  into  one  field,  and  during  the  latter  part  into  another. 

Various  sets  of  experiments  have  been  made  with  the  view  of  deter- 
mining the  relative  quantities  of  butter  and  cheese  produced  by  the  same 
animals,  when  fed  upon  different  kinds  of  food.  Much,  however,  re- 
mains yet  to  be  done  both  by  the  practical  dairy  farmer  and  by  the  fui- 
alytical  chemist,  before  this  subject  can  be  fully  cleared  up.  According 
to  theory,  as  I  shall  more  fully  explain  in  my  next  lecture,  the  legumi- 
nous plants — clover,  tares,  &c.,  and  the  cultivated  seeds  of  such  plants — 
peas  and  beans,  ought  to  promote  the  production  of  cheese  ;  while  oil- 
cake, oats,  and  other  kinds  of  food  which  contain  much  oily  matter, 
ought  to  favour  the  yield  of  butter.  The  most  recent  experiments  we 
possess,  however,  do  not  lend  any  disided  confirmation  to  these  theoreti- 


538  EXPERIMENTS    WITH    DIFFERENT    KIiNDS    OF    FOOD. 

cal  views.  The  most  extensive  series  of  trials  lately  published  is  that 
of  Boussingault,  [Annales  de  Chini.  et  de  Phys.,  Ixxi.,  p.  79,,]  from 
which  I  select  the  following  : — 

FIRST  SERIKS  MADE  ON  A  FRENCH  COW. 
Tta„=»f»/>..  Quarts  Composition  of  the  milk  per  cent. 

^^iljni        Kind  of  food.  of       , > 

^**^^"S.  njijk.    Casein.     Butter.    Sugar.      Salts.      Water. 

200  Hay    ....  5  30  45  47  01  8T7 

207  Turnips  ...  5i  30  42  50  02  87-6 

215  Beet     ....  5  34  40  53  02  871 

229  Potatoes  ...  4f  34  40  5-9  02  865 

302  Hay  and  oil-cake  2^  34  36  60  02  868 

SECOND  SERIES  MADE    ON  A   SWISS  COW. 

176    Potatoes  and  hay      8}        33        48        51         03        865 

182     Hay  and  clover         7j        40        45        4  0        03        872 

193    Clover      ...        8f        40        22        47        03        888 

204    Do.  in  flower    .        6j        37        35        5  2        02        874 

In  the  first  series  of  experiments  the  proportion  of  cheesy  matter  and 

of  sugar  was  greatest  when  beets,  potatoes,  and  oil-cake  were  given, 

while  the  largest  proportion  of  butter  was  obtained  from  the  use  of  hay 

and  the  least  from  oil-cake. 

In  the  second  series  the  proportion  both  of  cheese  and  of  butter  de- 
creased by  the  use  of  clover,  while  the  quantity  of  milk  was  not  per- 
manently increased. 

These  two  series  of  experiments  may  appear  to  be  deserving  of  less 
reliance  because  they  were  not  made  on  successive  days,  but  at  varying 
intervals  of  time.  But  some  recent  experiments,  made  in  Lancashire 
by  Dr.  Playfair,  are  little  more  satisfactory.  These  were  made  upon  a 
short-horned  cow,  which  was  fed  one  day  in  the  field  on  after-gra.ss,  and 
during  the  four  succeeding  days  in  the  stall,  upon  weighed  quantities  of 
different  kinds  of  food.     [Memoirs  of  the  Chemical  Society,  i.,  p.  174.] 

Composition  of  the  milk. 

Day's  Food.  Qts.  , ■ > 

Casein.    Butter.    Sugar.     Salts.    Water. 

lo     Aftor^vocc  S  Evening's  milk..     4         5-4         3-7         3-8         0-6         86-6 

X   .  Alter-grass ^Morning's     do..     4^        3-9         5-6         3-0         0-5         87-0 

2°.  281bs.Hay ;  Evening's     do..     ^       4-9         5-1  3-8         0-5         85-7 

2ilbs.  Oatmeal S  Morning's     do,.     4         5-4  3-9         4-8         0-5         85-4 

'°-  -lbs  "oJtmeaV-;  Evening's  do..  4  -  -  _  -            - 

ribs  Bean  Flour:  :^>I°"""g'«  ^-"  ^^  3-9  4-G  4-5  0-7  86-3 

^°-?im«^H!.v°^'"--     Evening's  do..  5  3-9  6-7  4-6  0-6  81-2 

8lb?BeanVlour::S^«™''«'«  ^o..  4  2-7  4-9  5-0  0-5  86-9 

6°.  141bs.Hay ;  Evening's  do..  Gj  3-9  4-6  3-9  0-5  87-1 

301bs.   Potatoes...  S  Morning's  do..  4f  3-5  4-9  3-8  0-5  87*3 

In  these  experiments  there  appears  an  increase  in  the  proportion  of  but- 
ter and  sugar,  and  in  the  quantity  of  milk  on  the  fourth  day,  when  the 
potatoes,  hay,  and  bean  flour  were  given  together.  On  the  fifth,  when 
potatoes  and  hay  only  were  given,  the  (piantity  of  milk  went  on  increas- 
ing, but  it  was  poorer  in  quality.  Could  we  infer  any  thing,  then,  from 
a  single  day's  trial,  it  would  be  that  the  bean  meal  had  aided  in  tbe  pro- 
duction of  butter  and  sugar — instead  of  cheese,  as  theory  would  indicate 
— while  the  steamed  potatoes  had  added  to  the  quantity  of  the  milk. 
But  no  sensible  results  can  justly  be  expucted  in  regard  to  the  influence 


Albumen 

2d  day  eat 

2}j  lbs. 

3d       " 

5     " 

4th      " 

4      " 

5th      " 

1-7" 

INFLUENCE    OF    THE   STATE    OF    PREGNANCY.  539 

of  this  or  that  food,  except  by  a  much  more  prolonged  series  of  careful 
observations. 

If  we  compare  the  quantity  of  albumen  and  casein  contained  in  the 
food,  with  that  yielded  in  the  milk  during  the  four  days'  experiments  of 
Dr.  Playfair,  we  shall  find  no  perceptible  relation  between  the  two  quan- 
tities.    Thus,  the  cow  on  the — 

Of  Casein 

and  yielded  0-93  lbs. 

1-0     " 
0-75  " 
«;  0-94  " 

So  that,  whether,  as  on  the  third  day  double  the  quantity  was  eaten,  or, 
as  on  the  fifth,  little  more  than  half  as  much  as  was  consumed  on  the 
second  day,  the  produce  of  cheesy  matter  in  the  milk  was  sensibly  the 
same,  on  each  of  the  three  days. 

We  must  not,  however,  from  these  experiments,  infer  that  the  kind  of 
food  really  has  no  influence  upon  the  quality  of  the  milk — for  this  con- 
clusion is  contradicted  by  general  experience.  We  must  wait  rather  for 
renewed  and  more  extended  practical  researches,  by  which  both  our 
theory  and  practice  may  probably  be  amended,  and  by  which  the  con- 
clusions may  be  reconciled  to  which  they  respectively  lead  us.  [See  the 
following  Lecture  "  On  the  feeding  of  stock.*^] 

10°.  State  of  pregnancy. — I  have  already  stated  (p.  535),  that  the 
richness  in  cream  diminishes  as  soon  as  the  cow  becomes  pregnant.  The 
same  is  no  doubt  true  also  of  the  amount  of  cheese  which  the  same 
volume  of  milk  will  be  capable  of  yielding.  It  must  become  poorer  in 
every  respect,  or  else  considerably  less  in  quantity  (p.  541),  as  soon  as  the 
cow  is  with  calf,  since  a  portion  of  the  food  which  might  otherwise  have 
been  employed  in  the  production  of  milk,  must  now  be  directed  to  the 
nourishment  of  the  young  animal  in  the  womb  of  the  mother.  In  the 
experiments  to  which  I  have  just  directed  your  attention  in  regard  to  the 
effect  of  the  kind  of  food  upon  the  quaUty  of  the  milk,  the  state  of  preg- 
nancy of  the  animal  was  not  taken  into  consideration,  though,  as  I  have 
already  said,  this  must  necessarily  exercise  an  important  influence  upon 
the  quality  of  the  milk,  whatever  be  the  kind  of  food  upon  which  the 
animal  may  have  been  fed.*  To  this  the  want  of  accordance  between 
theory  and  experiment  is  probably  in  part  to  be  ascribed. 

11°.  Individual  fonn  and  constitution  of  the  animal. — But  it  is  well 
known  that  animals  of  the  same  breed,  fed  on  the  same  food,  will  yield 
milk  not  only  in  different  quantities,  but  also  of  very  different  quality. 
In  regard  to  the  form,  Mr.  Youatt  states  that  the  "  Milch  cow  should 
have  a  long  thin  head,  with  a  brisk  but  placid  eye, — should  be  thin  and 
hollow  in  the  neck,  narrow  in  the  breast  and  point  of  the  shoulder,  and 
altogether  light  in  the  forequarter — but  wide  in  the  loins,  with  little  dew- 
lap, and  neither  too  full  fleshed  along  the  chine,  nor  shewing  in  any  part 
an  inclination  to  put  on  much  fat.  The  udder  should  especially  be 
large,  round,  and  full,  with  the  milk  veins  protruding,  yet  thin  skinned, 
but  not  hanging  loose  or  tending  far  behind.  The  teats  should  also  stand 
square,  all  pointing  out  at  equal  distances  and  of  the  same  size,  and  al- 

'  Both  of  the  cows  experimented  upon  by  Boussingault  were  with  calf,  Dr  Piayfoir  doe» 
not  mention  whether  his  was  w  or  not. 


540  EFFECT    OF    INDIVIDUAL    FORM    AXI)    CONSTITUTION. 

though  neither  very  large  nor  thick  towards  the  udder,  yet  long  and 
tapering  towards  a  point.  A  cow  with  a  large  head,  a  high  backbone,  a 
small  udder  and  teats,  and  drawn  up  in  the  belly,  will,  beyond  all  doubt, 
be  found  a  bad  milker."  [Youatt's  Cattle,  p.  244,  quoted  in  British  Hus- 
bandry, ii.,  p.  397.]  Thus,  while  much  depends  upon  the  breed,  the 
form  of  the  individual  also  has  much  influence  upon  its  value  as  a 
milker. 

But  independent  of  form,  the  quality  of  the  milk  is  greatl}'  affected  by 
the  individual  constitution  of  every  cow  we  feed.  Thus  in  a  report  of 
the  produce  of  butter  yielded  by  each  cow  of  a  drove  of  22,  chiefly  of  the 
Ayrshire  breed — all  of  which  we  may  presume  to  have  been  selected 
for  dairy  purposes  with  equal  regard  to  their  forms — and  which  were 
all  fed  upon  the  same  pastures  in  Lanarkshire,  the  yield  of  milk  and 
butter  by  four  of  the  cows  in  the  same  week  is  given  as  follows  : — 
Milk.  Butter. 

A  yielded     ...     84  quarts,  which  gave     .     .     .     .     3|  lbs. 

F  and  R  each      .     86       "  "         " 5|  lbs. 

G  yielded    ...     88       "  "        " 7    lbs.* 

Showing  that,  though  the  breed,  the  lood,  and  the  yield  of  milk  was 
nearly  the  same,  the  cow  G  produced  twice  as  much  butter  as  the  cow 
A — or  its  milk  was  twice  as  rich.  This  result  would  have  been  still 
more  interesting  had  we  known  the  relative  quantities  of  grass  consumed 
by  these  two  cows  respectively. 

I  will  not  insist  upon  other  causes  by  which  the  quality  of  the  milk  is 
more  or  less  materially  affected.  It  is  said  that  when  stall  fed  the  same 
cow  will  yield  more  butter  than  when  pastured  in  the  field — that  the  age 
of  the  pasture  also  influences  the  yield  of  butter — an  i  that  salt  mingled 
with  the  food  improves  both  the  quantity  and  the  quality  of  the  milk. 
There  are,  probably,  few  circumstances  which  are  capable  in  any  way 
of  affecting  the  comfort  of  the  animal  which  will  not  also  modify  the 
quality  of  the  milk  it  yields. 

§  3.   Of  the  circumstances  which  affect  the  quantity  of  the  milk. 

The  epithet  good-milker  applied  to  a  cow  has  very  different  significa- 
tions in  different  districts  and  countries.  Thus  the  experiments  of 
Boussingault  upon  the  effect  of  different  kinds  of  food  on  the  quality  of 
the  milk  (p.  538)  were  made  upon  a  French  cow  which  was  considered 
a  gT?od  milker,  and  yet  when  in  best  condition  never  gave  more  than  11 
quarts  a  day.  Two,  or  even  two  and  a  half,  times  that  quantity  is  not 
considered  extraordinary  in  the  height  of  the  season  in  many  parts  of  our 
island. 

There  are  three  circumstances  which  principally  affect  the  quantity  of 
milk — namely,  the  breed,  the  kind  of  food  or  pasture,  and  the  distance 
from  the  time  of  calving. 

1°.  The  breed. — The  smaller  breeds  of  cattle  yiekl,  as  is  to  be  ex- 
pected, a  smaller  daily  produce  of  milk — though  from  the  same  weight 
of  food  they  occasionally  give  even  a  greater  volume  of  milk  than  the 
larger  breeds. 

Good  ordinary  cows  in  this  country  yield,  on  an  average,  from  8  to  12 

'  Prize  Essays  of  t'Ki  JEgfdand  Society,  New  Series,  ii.,  p.  258. 


.CIRCUMSTANCES    AFFECT    THE    QUANTITY    OF   MILK.  541 

quarts  a  day.     The  county  surveys  state  the  average  daily  produce  3f 
dairy  cows  to  be,  in — 

Devonshire     ...     12  qts.  I  Lancas)iire  .     .     .     8  to  9  qts. 

Cheshire    ....       8  "     |  Ayrshire 8  " 

But  the  best  Ayrshire  kyloes  will  yield  an  average  of  12|  quarts  daily, 
during  10  months  of  the  year  (Ayton). 
The  yearly  produce  of  the  best  Ayrshire  kyloes  is  stated  by  Mr. 

Ayton  at 4000  qts 

Of  average  Ayrshire  stock 2400  '* 

Good  short-horns,  grazed  in  summer,  and  fed  on  hay  and  tur- 
nips in  winter  (Dickson) 4000  ** 

Mixed  breeds  in  Lancashire  (Dickson) 3500  " 

Large  dairy  of  mixed  long  and  short-horns,   at  Workington 

Hall,  taking  an  average  of  4  years  (Mr.  Curwen)       .         .  3700  " 
Crossed  breeds  in  many  localities  are  found  more  productive  in  milk 
than  pure  stock  of  any  of  the  native  races  of  cattle. 

2°.  Food  and  pasture. — In  the  same  animal  the  quantity  of  milk  is 
known  to  be  greatly  influenced  by  the  kind  of  food.  This  is  best  under- 
stood in  the  neighbourhood  of  large  towns  where  the  profit  of  the  dairy- 
man is  dependent  upon  the  quantity*  rather  than  upon  the  quality  of  his 
milk.  Hence  the  value  of  highly  succulent  foods — of  the  grass  (/f  irri- 
gated meadows — of  mashed  and  steamed  food — of  brewers'  grains — ot 
turnips,  potatoes  and  beets — and  of  other  similar  vegetable  productions 
which  contain  much  water  intimately  mixed  with  nutritive  matter,  and 
thus  tend  both  to  aid  in  tlie  production  of  milk  and  to  increase  its  quan- 
tity. 

3°.  Distance  from  the  time  of  calving. — It  is  a  well-known  fact  that 
cows  in  general  after  the  first  two  months  from  the  time  of  calving, 
though  fed  upon  the  same  food  in  equal  quantity,  begin  gradually  to  give 
less  milk,  till  at  the  end  of  about  10  months  they  become  altogether,  or 
nearly,  dry.  In  the  best  Ayrshire  kyloes,  the  rate  of  this  decrease  is  thus 
represented  by  Mr.  Ayton  : — 

First  fifty  days,  24  qts.  per  day, — or  in  all,  1200  qts. 
Second     do.         20     "         "  "  1000  " 

Third       do.         14     "         "  "  700  " 

Fourth     do.  8     "         "  "  400  " 

Fifth        do.  8     "         "  "  400  '* 

Sixth        do.  6     "         "  "  300  " 

Some  cows  indeed  do  not  run  dry  throughout  the  whole  year,  but  these 
may  be  considered  as  exceptions  to  the  general  rule.  By  feeding  them 
upon  brewer's  grains,  mashes,  and  succulent  grass,  the  milk-sellers  near 
our  large  towns  occasionally  keep  the  same  cow  in  profitable  milking 
condition  for  three  years  and  upwards. f  Such  cows  are  generally  fat- 
tened after  they  have  become  dry — indeed  as  they  cease  to  give  milk, 
they  generally  lay  on  fat  in  its  stead — and,  as  soon  as  they  are  consider- 
ed ripe,  are  sold  ofi'  to  the  butcher. 

*  It  is  quoted,  even  by  foreign  writers,  as  a  fair  joke  against  the  dairy  establishments  of 
our  large  towns,  that  among  the  advantages  possessed  by  one  which  was  advertised  for  sale, 
much  stress  was  laid  upon  a  never-failing  puvip. — See  II  latte  e  i  auoi  prodotti.  p.  07. 

t  Even  on  shipboard  1  have  heard  of  a  cow  being  kept  in  milk  during  the  whole  of  a  three 
years'  cruise — the  food  being  principally  a  kind  of  pease  soup.    After  the  first  year,  how- 
ever, the  milk  is  said  to  become  thinner  and  more  watery. 
23* 


542     MODE  OF  SEPARATING  THE  CONSTITUENTS  OF  MILK. 

§  4.  O/*  the  mode  of  separating  and  estimating  the  several  constituents 

of  milk. 

1°.  If  a  weighed  quantity  of  milk  be  allowed  to  stand  for  a  sufficient 
length  of  time,  the  cream  will  rise  to  the  top,  and  may  be  easily  skim- 
med off.  If  this  creatn  be  gently  heated  the  butter  in  an  oily  form  will 
collect  upon  the  surface,  and  when  cold  may  be  separated  from  the 
water  beneath,  and  its  weight  determined. 

2°.  If  the  skimmed  milk  be  gently  warmed,  and  a  little  vinegar  or 
rennet  then  added  to  it,  the  curd  will  separate,  and  may  be  collected  in  a 
cloth,  pressed,  dried,  and  weighed. 

3*^.  If  a  second  equal  portion  of  the  milk  be  weighed  and  then  evap- 
orated to  dryness  by  a  gentle  heat  and  again  weighed,  the  loss  will  be 
the  (juantity  of  water  which  the  milk  contained. 

4^^.  If  now  the  dried  milk  be  burned  in  the  air  till  all  the  combustible 
matter  disappears,  and  the  residue  be  weighed,  the  quantity  of  inorganic 
saline  matter  will  be  determined. 

5°.  Supposing  those  processes  to  be  performed  with  tolerable  accuracy, 
the  difference  between  the  sum  of  the  weight  of  the  water,  butter,  curd, 
and  ash,  and  the  weight  of  the  milk  employed,  will  nearly  represent 
that  of  the  sugar  contained  in  the  given  quantity  of  milk. 

For  many  purposes  a  rude  examination  of  milk  after  this  mahner  may 
be  sufficient,  but  where  any  thing  like  an  accurate  analysis  is  required, 
more  refined  methods  must  be  adopted.  In  such  cases,  the  following 
appears  to  be  the  best  which  has  hitherto  been  recommended.  [Haid- 
len,  Annal.  der  Chem.  &  Phar.,  xlv.,  p.  263.] 

a.  The  butter. — The  weighed  quantity  of  milk  is  mixed  with  one- 
sixth  of  its  weight  of  common  unburnt  gypsum  previously  reduced  to  a 
very  fine  powder.  The  whole  is  then  evaporated  to  dryness  with  fre- 
quent stirring  at  the  heat  of  boiling  water  (212°  F.)  A  brittle  mass  is 
obtained,  which  is  reduced  to  fine  powder.  By  digesting  this  powder  in 
ether,  the  whole  of  the  butter  is  dissolved  out,  and  by  evaporating  the 
ether,  may  be  obtained  in  a  pure  state  and  weighed.  Or  the  powder 
itself,  after  being  treated  with  ether,  may  be  dried  and  weighed.  The 
butter  is  then  estimated  by  the  loss. 

6.  The  sugar. — After  the  removal  of  the  butter,  alcohol  is  poured  upon 
the  powder  and  digested  with  it.  This  takes  up  the  sugar  with  a  little 
saline  matter  soluble  in  alcohol.  By  evaporating  this  solution  and 
weighing  the  dry  residue,  the  quantity  of  sugar  is  determined.  Or,  as 
before,  the  powder  itself  may  be  dried  and  weighed  and  the  sugar  esti- 
mated by  the  loss.  If  we  wish  to  estimate  the  small  quantity  of  inor- 
ganic saline  matter  which  has  been  taken  up  along  with  the  sugar,  it 
may  be  done  by  burning  the  latter  in  the  air,  and  weighing  the  residue. 

c.  The  saline  matter. — A  second  weighed  portion  of  milk  is  now  evap- 
orated carefully  to  dryness  and  again  weighed.  The  loss  is  the  water. 
The  dried  milk  is  then  burned  in  the  air.  The  weight  of  the  incombus- 
tible ash  indicates  the  proportion  of  inorganic  saline  matter  contained  in 
the  milk. 

d.  The  casein. — The  weight  of  the  butter,  sugar,  saline  matter  and 
water  being  thus  known  and  added  together,  the  deficiency  is  the  weight 
of  the  casein. 


PROPERTIES  OF  THE  SUGAR  OF  MILK.  543, 

§  5.   Of  the  sugar  of  milk,  and  of  the  acid  of  milk  or  lactic  acid. 

Before  I  can  hope  to  make  you  understand  the  nature  of  the  changes 
which  take  place  during  the  souring,  the  churning,  and  the  curdling  of 
milk,  it  will  be  necessary  to  make  you  acquainted  with  the  sugar  of 
milk,  and  with  lactic  acid  or  the  acid  of  milk. 

1°.  Sugar  of  milk. — When  the  curd  is  separated  from  milk,  the  raw 
whey  afterwards  boiled — with  or  without  the  addition  of  new  and  butter 
milk — and  the  floating  churd  skimmed  off  or  separated  by  straining 
through  a  cloth,  the  whey  is  obtained  nearly  free  from  butter  and  cheese. 
By  mixing  it  while  hot  with  well  beat  white  of  egg,  the  remainder  of  the 
curd  is  coagulated,  and  may  be  removed  by  again  straining  through 
cloth.  If  the  clear  whey,  thus  obtained,  be  boiled  down  in  a  pan  to  one 
fourth  of  its  bulk,  then  poured  into  an  earthen  dish,  and  set  aside  for  a 
few  days  in  a  cool  place,  minute  hard  white  crystals  gradually  de- 
posit themselves  upon  the  sides  and  bottom  of  the  vessel.  These  crystals 
are  sugar  of  milk.  A  second  portion  may  be  obtained  by  evaporating 
the  remaining  whey  still  further,  and  again  setting  aside.  If  the  whey 
be  at  once  evaporated  to  dryness  a  white  mass  of  impure  sugar  is  pre- 
pared, which  in  many  places  is  used  as  an  article  of  food.  Of  the  purer 
variety  large  quantities  are  extracted  from  milk  by  the  Swiss  shepherds, 
and  in  their  country  it  forms  an  important  article  of  commerce. 

The  sugar  of  milk  is  less  sweet  than  that  of  the  grape,  or  of  the  sugar 
cane.  It  is  harder  also,  and  much  less  soluble  in  water,  and  is  gritty 
between  the  teeth.  This  sugar  undergoes  no  change  when  exposed  to 
the  air,  either  in  the  dry  state  or  when  dissolved  in  water.  But  if  a  little 
of  the  curd  of  milk  (casein)  be  introduced  into  the  solution  it  gradually  be- 
comes sour,  lactic  acid  is  formed,  and  the  lifjuid  begins  to  ferment.  Car- 
bonic acid  is  given  oti^— as  is  the  case  during  the  fermentation  of  other 
liquids — and  alcohol  is  produced.  In  milk  the  two  substances  are  na- 
turally intermixed,  and  it  is  the  presence  of  the  cheesy  matter,  as  we 
shall  hereafter  see,  which  at  favourable  temperatures  always  causes  milk 
of  every  kind  first  to  become  sour  and  then  to  ferment. 

The  gluten  of  wheat  and  animal  membranes  of  various  kinds  produce 
a  similar  effect  upon  solutions  of  sugar  of  milk.  A  piece  of  bladder,  or 
of  the  gut  or  stomach  of  an  animal,  immersed  into  a  solution  of  the  sugar, 
changes  it  by  degrees  into  lactic  acid,  and  upon  this  influence  depends 
the  effect  of  the  calf's  stomach,  in  the  form  of  rennet,  in  the  curdling  of 
milk.  The  effect  of  such  membranes  is  more  speedy  after  they  have 
been  some  time  taken  from  the  body  of  the  animal,  a  fact  which  also  ac- 
cords with  the  long  experience  of  the  dairy  districts  in  the  preparation  of 
rennet. 

When  a  little  sulphuric  or  muriatic  acid  is  added  to  a  solution  of  milk 
sugar,  it  is  slowly  converted  into  grape  sugar.  This  change  is  hastened 
very  much  by  boiling  it  with  the  acid.  It  is  supposed  that  previous  to 
the  fermentation  of  milk  the  sugar  it  contains  undergoes  a  similar  change 
into  the  sugar  of  grapes. 

Milk  sugar  has  not  hitherto  been  formed  by  art.  It  exists  in  the  milk 
of  all  mammiferous  animals,  and  from  this  source  alone  have  we  hith- 
erto been  able  to  obtain  it. 

2°.  The  acid  of  milk — lactic  acid. — When  milk  is  exposed  to  the  air 
for  a  length  of  time  it  acquires  a  sour  taste,  which  gradually  increases  in 


544  THK    ACID    OF    MILK,    OR    LACTIC    ACID. 

intensity  till  at  length  the  whole  heghis  to  ferment.  This  sour  taste  is 
owing  to  tlie  production  of  a  jieculiar  acid,  to  which  the  name  of  acid 
of  milk  or  lactic  acid  has  been  given.  The  same  acid  is  formed  during 
the  fermentation  of  the  juices  of  the  beet,  and  of  the  turnip,  in  sour  cab- 
bage {sauer  kraut),  and  sour  malt,  in  brewers'  grains  which  have  become 
sour,  in  the  sour  vegetable  mixtures  with  which  cattle  are  often  fed,  in 
the  waste  liquor  of  the  tanners,  in  the  fermented  extract  of  rice,  and  in 
large  quantity  during  the  fermentation  of  the  gluten  in  the  manufacture 
of  starch  from  wlieaten  flour,  or  of  a  mixture  of  oat-meal  or  bean- 
meal  with  water,  which  is  allowed  to  stand  and  become  sour. 

The  acid,  therefore,  differs  from  the  sugar  of  milk  in  so  far  that  it  can 
readily  be  formed,  and  in  any  quantity,  by  anificial  means.  As  it  is 
not  employed  for  any  economical  purposes,  I  shall  not  trouble  you  with 
the  methods  by  which  this  acid  is  obtained  in  a  state  of  purity. 

It  is  rarely  found  in  milk  when  first  drawn  from  the  cow,  but  it  very 
soon  begins  to  be  formed  in  it.  It  is  produced  from  the  sugar,  through 
the  influence  of  the  cheesy  matter  of  the  milk.  The  pure  acid  may  be 
mixed  with  cold  milk  without  causing  it  to  curdle,  but  if  the  mixture  be 
heated,  the  curd  forms  and  speedily  separates.  It  is  for  the  sarne  reason 
that  milk  may  be  distinctly  sour  to  the  taste,  and  yet  may  not  coagulate. 
But  if  such  milk  be  heated  it  will  curdle  immediately.  So  cream  when 
sour  may  not  appear  so,  till  it  is  poured  into  hot  tea,  when  it  will  break 
and  leave  its  cheesy  matter  floating  on  the  surface. 

§  6.  Of  the  mutual  relations  which  exist  between  lactic  acid  and  the  cane^ 
grape,  and  milk  sugars. 

It  is  important,  and  I  think  it  will  prove  interesting  to  you,  to  under- 
stand the  beautifully  simple  relation  which  exists  between  the  sugar  of 
milk  and  this  lactic  acid,  which  plays  so  important  a  part  in  nearly  all 
your  daily  operations- 
Cane  sugar,  grape  sugar,  milk  sugar,  and  lactic  acid,  as  they  exist  in 
solution  in  water  or  in  milk,  may  all  be  represented  as  compounds  of  car- 
bon with  water — or  of  carbon  with  hydrogen  and  oxygen  in  the  propor- 
tions in  which  they  exist  in  water.     Thus  they  consist  respectively  of — 

12  Carbon  +  12  Water 
12H  +   120     or     12C  +   12HO* 

12  Carbon  +  14  Water 

14H  4-   140     or     12C  +   14HO 

24  Carbon  -|-  24  Water 
24H  4-   240     or     24C  -f   24HO 

6  Carbon  +  6  Water 
6H  +     60     or       6C  +     6HO 

4  Carbon  +  3  Water 
3H  +     30     or       4C  -|-     3HO 

I  have  added  acetic  acid  to  this  list,  to  show  you  that  the  lactic  acid 
bears  a  similar  relation  to  the  sugars  as  this  acid  does.  You  will  recol- 
lect that  starch,  gum,  and  woody  fibre,  have  also  a  similar  relation  to 
the  sugars — and  tliat  by  certain  apparently  simple  transformations  these 

•  C,  H,  and  O,  as  in  our  former  lectures,  representing  respectively  carbon,  hydrogen,  and 
^Jtygen,  and  HO  watpr— a  compound  of  hydrogen  with  oxygen. 


Cane  sugar    .     .     . 

12C 

+ 

Grape  sugar      .     . 

12C 

+ 

Milk  sugar    .     .     . 

24C 

+ 

Lactic  acid    .     .     . 

6C  + 

Acetic  acid  {vinegar) 

4C 

+ 

CHANGE    Of    mils:    SUSAR    INTO    LACTIC    ACID.  645 

several  substances  are  capable  of  being  converted  into  grape  sugar.'  In 
like  manner  all  these  sugars  by  a  similar  simple  transformation  are 
readily  converted  into  one  or  other  of  the  two  acids  above  named.  Starch, 
gum,  and  woody  fibre  in  favourable  circumstances  are  transformed  intc 
sugar,  (see  Lecture  VI.,  p.  Ill) — the  sugars,  in  favourable  circum- 
stances, are  further  transformed  into  the  lactic  or  the  acetic  acids. 

We  have  seen  that  animal  membranes  or  the  curd  of  milk  have  the 
property  of  changing  these  su^rs  into  lactic  acid.  This  they  do,  though 
excluded  from  the  action  of  the  air,  and  without  the  escape  of  any  gas. 
The  above  formulae  show  with  what  apparent  simplicity  this  may  be 
accomplished. 

In  fact,  cane  sugar,  milk  sugar,  and  lactic  acid,  as  above  represented, 
consist  of  the  same  elements  united  together  in  the  same  proportions.  It 
is  easy  to  conceive  therefore  in  what  way  the  one  may  be  transformed 
into  the  other. 

1°.  Two  of  lactic  acid  are  represented  by  12C  +  12H  +  120,  which 
is  the  formula  for  cane  sugar.  The  transforming  action  of  the  animal 
membrane,  or  of  the  casein  in  its  state  of  incipient  decay,  is  therefore 
simply  to  cause  the  elemeu»:;s  of  the  sugar  to  assume  a  new  arrangement 
—in  which  instead  of  cane  sugar  they  form  a  substance  having  the  very 
different  properties  of  lactic  acid. 

2°.  Again,  milk  sugar  is  represented  by  24C  +  24H  +  240,  and  4 
of  lactic  acid  are  also  equal  to  24C  +  24H  +  240 ;  the  change  which 
takes  place  when  milk  becomes  sour,  therefore,  is  easily  understood 
Under  the  influence  of  the  casein  the  elements  of  a  portion  of  the  milk 
sugar  are  made  to  assume  a  new  arrang(3ment,  and  the  sour  lactic  acid 
is  the  result.  There  is  no  loss  of  matter,  no  new  elements  are  called  into 
play,  nothing  is  absorbed  from  the  air  or  given  off  into  it — but  a  simple 
transposition  of  the  elements  of  the  sugar  takes  place,  and  the  new  acid 
compound  is  produced. 

These  changes  appear  very  simple,  and  yet  how  difficult  it  is  to  con- 
ceive by  what  mysterious  influence  the  mere  contact  of  this  decaying 
membrane  or  of  the  casein  of  the  milk,  can  cause  the  elements  of  the 
sugar  to  break  up  their  old  connexion,  and  to  arrange  themselves  anew 
in  another  prescribed  order,  so  as  to  form  a  compound  endowed  with 
properties  so  very  diflerent  as  those  of  lactic  acid.  It  is  beautiful  to  see 
the  simple  means  by  which  in  nature  so  many  important  ends  are  ac- 
complished— to  observe  how  they  are  all  veiled  to  the  uni-nstructed — and 
how  every  slight  accession  to  our  knowledge  opens  up  new  v/onders  to 
us  even  in  those  ordinary  operations  with  which  during  our  whole  lives 
we  have  been  most  familiar. 

From  these  intellectual,  in  addition  to  other  rev/ards,  which  constantly 
follow  the  study  of  nature,  you  will  with  me  draw  the  conclusion — 
which  is  ever  pressing  itself  upon  our  attention — that  it  is  the  will  and 
intention  of  the  Deity,  that  all  his  works  shall  be  thoroughly  studied  and 
investigated.  But  you  will,  I  think,  agree  with  me  in  drawing  this  con- 
clusion, because  of  the  further  and  higher  moral  effect  also  which  such 
investigations  tend  to  produce  upon  the  mind.  Every  fresh  discovery, 
as  it  opens  up  new  fields  of  knowledge,  forces  upon  us  more  distinctly  the 
sense  of  our  own  ignorance.  In  the  case  before  us  we  are  delighted  by 
the  apparent  simplicity  which  the  several  transformations  of  starch  into 


546  SOURING    AND    PRESERVING    OF    MILK. 

sugar,  and  of  the  latter  into  lactic  acid,  may  be  brought  about,  and  seem 
almost  to  understand  liow  it  is  done,  since  it  can  be  effected  by  a  simple 
transposition  of  their  elements.  But  the  after-thought  occurs — by  what 
kind  of  power  is  this  change  effected  ?  The  materials  are  certainly  pre- 
sent, but  how  are  they  made  to  shift  their  relative  positions,  and  move 
into  their  new  places  ?  We  have  concpiered  one  intellectual  difficulty 
only  to  encounter  another  apparently  still  harder  to  overcome. 

It  was  said  first,  I  believe  by  Priesl*ey,  [Experiments  and  Obser- 
vations, ii.,  p.  ix.,  edition  1781,]  "  that  the  greater  the  circle  of  light, 
the  greater  is  the  boundary  of  darkness  by  which  it  is  confined."  Thus 
they  who  know  the  most  are  the  most  strongly  impressed  with  the  sense 
of  their  own  want  of  knowledge.  What  a  fine  result  this  is  of  large 
acquirements  !  And  how  touchingly  it  was  expressed  by  Sir  Isaac  New- 
ton, when  he  likened  his  great  discoveries  to  the  gathering  of  a  few  peb- 
bles along  the  sea-shore — the  vast  ocean  of  natural  knowledge  lying  still 
unexplored  before  him  I 

§  7.   Of  the  souring  and  preserving  of  milk. 

The  natural  souring  of  milk  requires  now  little  explanation.  It  arises 
from  the  gradual  conversion  of  the  sugar  into  the  acid  of  milk  by  the 
action  of  the  casein.  There  are,  however,  one  or  two  circumstances  con- 
nected with  it  to  which  it  may  be  proper  to  advert. 

1°.  If  milk  be  kept  at  a  low  temperature,  it  may  be  preserved  for  se- 
veral days  without  becoming  sensibly  sour.  This  is  effected  in  Switzer- 
land by  immersing  the  milk  vessels  in  a  shallow  trough  of  cool  water, 
which,  by  means  of  a  running  stream,  can  at  any  time  be  renewed.  In 
such  circumstances  the  action  of  the  cheesy  matter  in  converting  the 
sugar  into  lactic  acid  is  very  slow. 

2°.  But  if  the  milk  be  kept  at  the  temperature  of  65°  or  70°  F.  it  be- 
comes sour  with  great  rapidity,  and  if  afterwards  raised  to  the  boiling 
point  curdles  immediately.  An  easy  way  of  preserving  milk  or  cream 
sweet  for  a  longer  time,  or  of  removing  the  sourness  when  it  has  already 
come  on,  is  to  add  to  it  a  small  quantity  of  the  common  soda,  pearl  ash, 
or  magnesia  of  the  shops.  Enough  is  added,  when  a  little  of  the  milk 
poured  into  boiling  water  no  longer  throws  up  any  curd.  As  the  small 
quantity  of  soda  or  magnesia  thus  added  is  not  unwholesome,  cream 
may  in  this  way  be  kept  sweet  for  a  considerable  time,  or  may  have  its 
sweetness  restored  when  it  has  already  become  sour. 

3°.  I  have  already  observed  to  you  that  animal  membrane,  the  curd  of 
milk,  or  any  of  tlv/se  substances  which  possess  tlie  power  of  changing  sugar 
into  lactic  acid,  loose  that  power  if  the  solution  in  which  they  are  present 
be  raised  to  the  boiling  temperature.  Hence  if  milk  be  introduced  into 
bottles,  be  then  well  corked,  put  into  a  pan  with  cold  water,  and  gradually 
raised  to  the  boiling  point,  and  after  being  allowed  to  cool  be  taken  out 
and  set  away  in  a  cool  place,  the  milk  may  be  preserved  perfectly 
sweet  for  upwards  of  half  a-year. 

I  mentioned  also  that  if  the  solution  containing  the  sugar  and  cheesy 
matter  be  again  exposed  to  the  air  after  boiling,  it  will  gradually  resume 
the  property  of  transforming  the  sugar  into  lactic  acid.  Hence,  if  milk 
be  boiled,  it  is  preserved  sweet  for  a  longer  period  of  time,  but  the 
casein  gradually  resumes  its  transforming  property,  and  at  the  end  of  a 


SEPARATION    OF    CREAM    FROM    THE    MILK.  547 

few  days  turns  it  sour.  If,  however,  the  milk  be  boiled  every  morning 
or  every  second  morning,  the  souring  property  of  the  casein  is  at  every 
boiling  destroyed  again,  and  the  milk  may  thus  be  kept  fresh  for  two 
months  or  more. 

4°.  Another  mode  of  preserving  milk  is  to  evaporate  it  to  dryness  by 
a  gentle  heat,  and  under  constant  stirring.  By  this  means  a  dry  mass  is 
obtained  which  may  be  preserved  for  a  length  of  time,  and  which  when 
dissolved  in  water  is  said  to  possess  all  the  properties  of  the  most  excel- 
lent milk.  It  is  known  in  Italy  by  the  name  of  latteina.  [II  latte  e  i 
suoi  prodotti,  p.  19.] 

§  8.   Of  the  separation  and  measureinent  of  cream,  the  galaciometer,  the 
composition  of  cream,  and  the  preparation  of  cream-cheese. 

1°.  Separation  of  cream. — The  fatty  part  of  the  milk  which  exists  in 
the  cream,  and  which  forms  the  butter,  is  merely  mixed  with  and  held  in 
suspension  by  the  water  of  which  the  milk  chiefly  consists.  In  the 
udder  of  the  cow  it  is  in  some  measure  separated  from,  and  floats  on,  the 
surface  of  the  milk,  the  later  drawn  portions  being  always  the  richest  in 
cream.  During  the  milking,  the  rich  and  poor  portions  are  usually 
mixed  intimately  tojgether  again,  and  thus  the  after-separation  is  render- 
ed slower,  more  difficult,  and  less  com|)lete.  That  this  is  really  so,  is 
proved  by  two  facts — first,  that  if  milk  be  well  shaken  or  stirred,  so 
as  to  mix  its  parts  intimately  together  before  it  is  set  aside,  the  cream 
will  be  considerably  longer  in  rising  to  the  surface — and  second,  that 
more  cream  is  obtained  by  keeping  the  milk  in  separate  portions  as  it  is 
drawn,  and  setting  these  aside  to  throw  up  their  cream  in  separate  ves- 
sels, than  when  the  whole  milking  is  mixed  together.  When  the  collec- 
tion of  cream,  therefore,  is  the  principal  object,  economy  suggests  that 
the  first,  second,  third,  and  last  drawn  portions  of  the  milk  should  be 
kept  apart  from  each  other.  Even  in  large  dairies  this  could  easily  be 
effected  by  having  three  or  four  pails,  in  one  of  which  the  first,  in 
another  the  second  milk,  and  so  on,  might  be  collected. 

Cream  does  not  readily  rise  through  any  considerable  depth  of  milk  ; 
it  is  usual,  therefore,  to  set  it  aside  in  broad  shallow  vessels  in  which  the 
milk  stands  at  a  deptli  of  not  more  than  two  or  three  inches.  By  this 
means  the  cream  can  be  more  effectually  separated  witliin  a  given  time. 

But  the  temperature  of  the  surrounding  air  materially  affects  the 
quantity  of  cream  which  milk  will  yield,  or  the  rapidity  with  which  it 
rises  to  the  surface  and  can  be  separated.  Thus  it  is  said  that  from  the 
same  milk  an  equal  quantity  of  cream  may  be  extracted  in  a  much 
shorter  time  during  warm  than  during  cold  weather — that,  for  example, 
milk  may  be  perfectly  creamed  in — 

36  hours,  v/hen  the  temperature  of  the  air  is 
24       u  .i  u 

18  to  20  hours   "  ''  " 

10  to  12 

— while,  at  a  temperature  of  34°  to  37*^  F.,  milk  may  be  kept  for  three 
weeks,  without  throwing  up  any  notable  quantity  of  cream  (Sprengel). 

The  reason  of  this  is  that  the  fatty  matter  of  the  milk  becomes  partially 
solidified  in  cold  weather,  and  is  thus  unable  to  rise  to  the  surface  of  ihd 
milk  so  readily  as  it  does  when  in  a  warm  and  perrisctly  fluid  state- 


50° 

F. 

55° 

F. 

68° 

F. 

77° 

F. 

548  CCi-  POSITION    OF    CREAM. 

The  abov«  remarks  apply  to  milk  of  ordinary  quality  and  consistency. 
In  ve^y  thin  ?r  poor  milk,  in  which  little  cheesy  matter  is  contained,  the 
cream  will  rise  more  quickly. 

2°.  Measurement  of  cream — the  galactometer. — The  richness  of  milk 
is  very  generally  estimated  by  the  bulk  of  cream  which  rises  to  its 
surface  in  a  given  time.  For  the  purpose  of  testing  this  richness,  a 
simple  instrument,  dignified  by  the  learned  name  of  a  galactometer 
(milk-gauge),  has  been  recommenJed  and  may  often  be  useful.  It  con- 
sists of  a  narrow  cylindrical  vessel  or  long  tube  of  glass,  divided  or  gra- 
duated  into  100  equal  parts.  This  vessel  is  filled  up  to  100  with  the 
milk  to  be  tested,  and  at  the  end  of  24  or  36  hours,  the  quantity  of  cream 
which  has  risen  is  estimated  by  the  number  of  degrees  of  space  which  it 
occupies  at  the  top  of  the  milk.  If  it  cover  3  degrees  the  milk  yields 
3  per  cent.,  if  7  degrees  7  per  cent,  of  cream.  This  instrument,  how- 
ever, will  give  a  result  which  will  be  generally  less  than  the  truth,  be- 
cause the  cream  will  always  rise  slowly  through  5  or  6  inches  of  milk — 
the  smallest  length  which  the  instrument  can  conveniently  be — and  most 
slowly  in  the  richest  and  thickest  milk.  Unless  considerable  care  be 
taken,  therefore,  this  milk-gauge  may  easily  lead  to  erroneous  con- 
clusions in  regard  to  the  relative  degrees  of  richness  of  different  samples 
of  milk. 

3°.  Composition  of  cream. — Cream  does  not  consist  wholly  of  fatty 
matter  (butter),  but  the  globules  of  fat  as  they  rise  bring  up  with  them  a 
variable  proportion  of  the  casein  or  curd  of  the  milk,  and  also  some  of  the 
milk  sugar.  It  is  owing  to  the  presence  of  sugar  that  cream  is  capable 
of  becoming  sour,  while  the  casein  gives  it  the  prop*erty  of  curdling  when 
mixed  with  acid  liquids  or  with  acid  fruits. 

The  proportion  of  cheesy  matter  present  in  cream  depends  upon  the 
richness  of  the  milk  and  upon  the  temperature  at  wliich  the  milk  is  kept 
during  the  rising  of  the  cream.  In  cool  weather  the  fatty  matter  will 
bring  up  with  it  a  larger  quantity  of  the  curd,  and  form  a  thicker  cream, 
containing  a  greater  propouion  of  cheesy  matter.  The  composition  of 
cream,  therefore,  is  very  variable — much  more  so  than  that  of  milk — 
and  depends  very  much  upon  the  mode  in  which  it  is  collected. 

A  specimen  of  cream,  examined  by  Berzelius,  which  had  a  density 
(specific  gravity)  of  1*0244,  consisted  of — 

Butter,  separated  by  agitation 4*5  per  cent. 

Cheesy  matter,  separated  by  coagulating  the  butter- 
milk    3-5         " 

Whey 92-0 

100 
Some  of  the  butter  remained,  as  is  usually  the  case,  in  the  butter- 
milk, and  added  a  little  to  the  weight  of  the  curd  which  was  afterwards 
separated,  but  the  result  of  this  analysis  is  sutlicient  to  show  that  cream 
in  general  contains  a  very  considerable  proportion  of  cheesy  matter- 
sometimes  almost  as  much  cheese  as  butter.* 

*  The  clouted  cream  of  Devonshire  and  other  Western  counties,  as  well  as  the  butter  pre- 
pared from  it,  probably  contains  an  nnusually  large  quantity  of  cheese.  It  is  prepared  by 
straining  the  warm  milk  into  large  shallow  pans  into  which  a  little  water  has  previously  been 
put,  allowing  these  to  stand  from  6  to  12  hours,  and  then  carefully  heatin,  them  over  a  slow 
fire,  or  on  a  hot  plate,  till  the  milk  approaches  the  boiling  point.    The  n  Jlk,  however,  muat 


CREAM-CHEESE    AND    MASCARPONI.  549 

I  would  remark,  however,  that,  this  cream  examined  by  Berzelius 
must  have  been  of  an  exceedingly  poor  quality — little  richer,  indeed, 
than  common  milk,  since  100  lbs.  of  it  would  only  have  yielded  4^  lbs. 
of  butter.  Cream  of  good  quality  in  this  country,  when  skilfully 
churned,  will  yield  about  one-fourth  of  its  weight  of  butter,  or  one  wine 
gallon  of  cream,  weighing  8|  lbs.,  will  give  nearly  2  lbs  of  butter.* 

4°.  Cream-cheese. — You  will  now  readily  understand  the  nature  of 
what  is  called  cream-cheese — how  it  dilfers  from  ordinary  cheese  and 
from  butter,  and  why  it  so  soon  becomes  first  sour,  and  then  rancid. 

In  preparing  this  cheese  the  cream  in  this  country  is  generally,  I  be- 
lieve, either  tied  up  in  a  cloth  or  put  into  a  shallow  cheese  vat,  and  al- 
lowed to  curdle  and  drain  without  any  addition.  The  cheesy  matter  and 
butter  remain  thus  intimately  intermixed,  and  it  is  more  or  less  rich,  ac- 
cording as  the  proportion  of  butter  to  the  cheesy  matter  in  the  cream  is 
greater  or  less.  This  cheese  becomes  soon  rancid  and  unpleasant  to  the 
taste,  because  the  moist  curd,  after  a  certain  length  of  exposure  to  the 
air,  not  only  decomposes  and  becomes  unpleasant  of  itself,  but  acquires 
the  property  of  changing  the  butter  also  and  of  imparting  to  it  a  dis- 
agreeable taste  and  smell. 

In  Italy,  cream-cheeses,  called  mascarponi,  are  made  by  heating  the 
cream  nearly  to  boiling,  and  adding  a  little  sour  whey  as  the  oily  matter 
begins  to  separate.  The  whole  then  coagulates,  and  the  curd  is  taken 
out  and  set  to  drain  in  shapes.  As  the  sour  whey  is  apt  to  give  this 
cheese  an  unpleasant  flavour  or  a  yellow  colour,  it  is  said  to  be  better  to 
take  20  grains  of  Tartaric  acid  for  each  quart  of  cream,  to  dissolve  it  in 
a  little  water,  and  to  add  this,  instead  of  the  sour  whey,  to  the  hot  cream. 
The  acid  runs  oflf  in  the  whey  of  the  cream,  and  the  cheese  is  colour- 
less and  free  from  foreign  flavour.  The  mascarponi,  like  the  English 
cream-cheeses,  are  covered  with  leaves  or  straw,  are  littled  pressed  or 
handled,  and  must  be  eaten  fresh. 

§  9.   O/"  the  separation  of  butter  by  churning  or  otherwise. 

Milk  is  a  kind  of  natural  emulsion  in  which  the  fatty  matter  exists  in 
the  state  of  very  minute  globules,  suspended  in  a  solution  of  casein  and 
sugar.  Cream  is  a  similar  emulsion,  ditfering  from  milk  chiefly  in  con- 
taining a  greater  number  of  oily  globules  and  a  much  smaller  proportion 
of  water.  In  milk  and  cream  these  globules  appear  to  be  surrounded 
Wth  a  thin  white  shell  or  covering,  probably  of  casein,  by  which  they 
are  prevented  from  running  into  one  another,  and  collecting  into  larger 
oily  drops. 

But  when  cream  is  heated  for  a  length  of  time,  these  globules,  by  their 
lightness,  rise  to  the  surface,  press  nearer  to  each  other,  break  through 

not  actually  boil,  nor  must  the  skin  of  the  cream  be  broken.  The  dishes  are  now  removed 
into  the  dairy,  and  allowed  to  cool.  In  summer  the  cream  should  be  churned  on  thr;  fol- 
lowing day — ill  winter  it  may  stand  over  two  days.  The  quantity  of  cream  obtained  is  said 
to  be  one-fourth  greater  by  this  method,  and  the  milk  which  is  left  is  proportionably  poor. 
When  milk  on  which  no  cream  floats  is  heated  nearly  to  boiling  in  the  air,  a  pellicle  of 
cheesy  matter  forms  on  its  surface.  Such  a  pellicle  may  form  in  a  less  degree  in  the  scald- 
ding  process  of  Devonshire,  and  may  thus  increase  the  bulk  of  the  cream.  The  Corstor- 
phine  cream  of  Mid-Lothian  resembles  the  clouted  cream  very  much,  and  is  made  in  a  very 
similar  way. 

*  A  series  of  analyses  of  cream,  collected  under  diffferent  circumstances,  might  throw  some 
useful  light  upon  the  manufacture  and  preservation  >f  butter. 


S60  OF  THE  SEPARATION  OF  BUTTER. 

their  coverings,  and  unite  into  a  film  of  melted  fat.  In  like  manner, 
when  milk  and  cream  are  strongly  agitated  by  any  mechanical  means, 
the  temperature  is  found  to  rise,  the  coverings  of  the  globules  are  broken 
or  separated,  and  the  fatty  matter  unites  into  small  grains,  and  finally 
into  lumps,  wliich  form  our  ordinary  butter.  This  union  of  the  globules 
appears  to  be  greatly  promoted  by  the  presence  of  a  small  quantity  of 
acid — since  in  the  practice  of  churning  it  never  takes  place  until  the 
milk  or  cream  has  become  somewhat  sour. 

These  two  facts  afford  an  explanation  of  the  various  methods  which 
are  in  different  places  adopted  for  the  preparation  of  butter. 

1°.  Byheatm^  the  cream. — When  rich  cream  is  heated  nearly  to  boil- 
ing, and  is  kept  f()r  some  time  at  that  temperature,  the  butter  gradually 
rises  and  collects  on  the  surface  in  tbe  form  of  a  fluid  oil.  On  cooling,  this 
oil  becomes  solid,  and  may  be  readily  removed  from  the  water  and  curd 
beneath.  The  fatty  matter  of  the  niilk  is  thus  obtained  in  a  purer  fonn 
than  when  butter  is  prepared  in  the  usual  way.  It  may,  therefore,  be 
kept  for  a  longer  period  without  salt  and  without  becoming  rancid,  but  it 
has  neither  the  agreeable  flavour  nor  the  consistence  of  churned  butter, 
and  is,  therefore,  scarcely  known  in  our  climate  as  an  article  of  f(X)d.* 

The  same  oily  kind  of  butter  may  also  be  obtained  by  melting  the 
churned  butter  and  pouring  off  the  trans})areut  li(iuid  part  which  floats 
upon  the  top.  This  is  the  only  form  in  which  sweet  butter  is  known  in 
many  parts  of  Russia.  In  warm  weather  it  has  the  consistence  of  a 
thick  oil,  is  used  instead  of  oil  for  many  culinary  purposes,  and  is  de- 
noted, indeed,  by  the  same  Russian  word.  It  may  be  kept  for  a  consi- 
derable time  without  salt. 

2°.  By  ckurning  the  cream — a.  Sour  cream. — Cream  for  the  purpose 
of  churning  is  usually  allowed  to  become  sour.  It  ought  to  be  at  least 
one  day  old,  but  may  with  advantage  be  kept  several  days  in  cool 
weather — if  it  be  previously  well  freed  from  milk  and  be  frequently 
stirred  to  keep  it  from  curdling. 

This  sour  cream  is  put  into  the  churn  and  worked  in  the  usual  way 
till  the  butter  separates.  This  is  collected  into  lumps,  well  beat  and 
squeezed  free  from  the  milk,  and  in  some  dairies  is  washed  with  pure 
cold  water  as  long  as  the  water  is  rendered  milky.  In  other  localities 
the  butter  is  not  washed,  but,  after  being  well  beat,  is  carefully  freed 
from  the  remaining  milk  by  repeated  squeezings  and  dryings  with  a  clean 
cloth.  Both  methods,  no  doubt,  have  "their  advantages.  In  the  same 
circumstances  the  washed  butter  ma^'^  be  more  easily  preserved  in  the 
fresh  state,  while  the  unwashed  butter  will  probably  possess  a  higher 
flavour. 

b.  Sweet  cream. — If  sweet  cream  be  put  into  the  churn  the  butter  may 
be  obtained,  but  in  most  cases  it  requires  more  labour  and  longer  time, 
without,  in  the  opinion  of  good  judges,  aflbrding  in  general  a  finer 
quality  of  butter.  In  all  cases  the  cream  becomes  sour  during  the  agi- 
tation and  before  the  butter  begins  distinctlj^  to  form  (see  p.  554.) 

c.  Clouted  cream. — The  churning  of  the  clouted  cream  of  this  and 
other  countries  forms  an  exception  to  the  general  rule  just  stated,  that 
more  time  is  required  in  the  churning  of  sweet  creams.     Clouted  cream 

"  It  is  said,  that  when  melted  butter  is  poured  into  very  cold  water,  it  acquires  the  consig' 
tency  and  appearance  of  common  butter. 


ClIUK>i.<a    XHK    WHOLE    MILK.  -  551 

may  be  churne^l  in  llie  morning  after  it  is  made,  that  is,  within  24  Iiours 
of  the  time  when  the  milk  was  taken  from  the  cow — and  from  such 
cream  it  is  well  known  that  the  butter  separates  with  very  great  ease.  But 
in  this  case  the  heating  of  the  cream  has  already  disposed  the  oily  matter 
to  cohere,  an  incipient  running  together  of  the  globules  has  probably  taken 
place  before  the  cream  is  removed  from  the  milk,  and  hence  the  com- 
parative ease  with  which  the  churning  is  effected.  I  suppose  there  is 
something  peculiar  in  butter  prepared  in  this  way,  as  it  is  known  in 
other  counties  by  the  name  of  Bohemian  butter.  It  is  said  to  be  *^ery 
agreeable  in  flavour,  but  it  must  contain  more  cheesy  matter  than  the 
butter  from  ordinary  cream. 

3°.  Churning  the  whole  milk. — Butter  in  very  many  districts  is  pre- 
pared from  the  whole  milk.  This  is  a  much  more  laborious  method — 
from  the  difficulty  of  keeping  in  motion  such  large  quantities  of  fluid. 
It  lias  the  advantage,  however,  it  is  said,  of  giving  a  larger  quantity  of 
butter  ;  and  in  the  neighbourhood  of  the  towns  in  Scotland  and  Ireland 
the  ready  sale  obtained  for  the  butter-milk  is  another  inducement  for  the 
continuance  of  the  practice. 

At  Rennes,  in  Brittany,  the  milk  of  the  previous  evening  is  poured 
into  the  churn  along  with  the  warm  morning's  milk,  and  the  mixture  is 
allowed  to  stand  for  some  hours,  when  the  whole  is  churned.  In  this 
way  it  is  said  that  a  larger  quantity  of  butter  is  obtained,  and  oi'  a  more 
delicate  flavour.    [II  latte  e  i  suoi  prodotti,  p.  112.] 

In  the  neighbourhood  of  Glasgow,  according  to  Mr.  Ayton,*  the  milk 
is  allowed  to  stand  6,  12,  or  24  hours  in  the  dairy  till  the  whole  has 
cooled,  and  the  cream  has  risen  to  the  surface.  Two  or  three  milkings, 
still  sweet,  are  then  poured,  together  with  their  cr-aam,  into  a  largo  ves- 
sel, and  are  left  undisturbed  till  the  whole  has  become  distinctly  sour, 
and  is  completely  coagulated.  The  proper  sourness  is  indicated  by  the 
formation  of  a  stitr6ra^  upon  the  surface  which  has  become  imeven  (Bal- 
lanfyne).  Great  care  must  be  taken,  however,  to  keep  the  brat  and 
curd  unbroken  until  the  milk  is  about  to  be  churned,  for  if  any  of  the 
whey  be  separated  the  air  gains  admission  to  it  and  to  the  curd,  and 
fermentation  is  induced.  By  this  fermentation  the  quality  of  the  buttei 
may  or  may  not  be  affected,  but  that  of  the  butter-milk  is  almost  sure  to 
be  injured. 

In  Holland  the  practice  is  a  little  different.  The.  cream  is  not  allow 
ed  to  rise  to  the  surface  at  all,  but  the  milk  is  stirred  two  or  three  times  a 
day,  till  it  gets  sour,  and  so  thick  that  a  wooden  spoon  will  stand  in  it. 
It  is  then  put  into  the  churn,  and  the  working  or  the  separation  of  the 
butter  is  assisted  by  the  addition  of  a  quantity  of  cold  water. 

By  churning  the  sour  milk  in  one  or  other  of  tliese  ways,  the  butter 
is  said  to  bs  "  rich,  sound,  and  well-flavoured."  If  it  be  greater  in 
quantity — which  appears  to  be  the  opinion  of  those  who  practise  it  in 
this  country,  in  Germany,  and  in  Holland — it  is,  according  to  Sjirengel, 
because  the  fatty  matter  carries  with  it  from  the  milk  a  larger  quantity  of 
casein  than  it  does  in  most  cases  from  the  cream  alone  (  ?). 

§  10.   Of  the  composition  of  butter. 
Butter  prepared  by  any  of  the  usual  methods  contains  more  or  less  of 
•  In  his  Dairy  Hiiabandrt/,  a  work  much  praised,  and  which  I  regret  that  I  huve  never  seen. 


552  COMPOSITION    OF    BUTTER. 

all  the  ingredients  which  exist  in  milli.  It  consists,  however,  essentinlly 
of  the  fat  of  milk  intimately  mixed  with  a  more  or  less  considerable 
proportion  of  casein  and  water,  and  with  a  small  (luantity  of  sugar  of 
milk.  Fresh  butter  is  said  to  contain  about  one-sixtli  of  its  weiglit  (16 
per  cent.)  of  these  latter  substances,  and  five-sixths  of  pure  fat  (Chev- 
reul).  How  much  of  the  16  per  cent,  usually  consists  of  cheesy  matter 
has  not  yet  been  determined.* 

It  is  probable,  however,  that  the  proportion  of  cheesy  matter  contained 
in  butter  varies  very  much.  The  thickness  and  richness  of  the  milk— - 
the  mode  of  preparing  the  butter,  whether  from  the  whole  milk  or  from 
the  cream — the  way  in  wfjich  the  cream  is  se})arated  from  the  milk, 
whether  by  clouting  or  otherwise — and  ths  nature  of  the  food  and  pas- 
ture, must  all  affect  in  a  very  considerable  degree  the  relative  pro- 
portions of  the  fatty  and  cheesy  matters  of  which  our  domestic  butter 
consists. 

Besides  the  casein  and  sugar,  butter  also  usually  contains  some  colour- 
ing substance  derived  from  the  plants  on  which  the  .cow  has  fed,  and 
some  aromatic  or  other  similar  ingredients  to  wliich  its  peculiar  flavour 
is  owing,  and  which  are  also  derived  from  the  food  on  which  the  animal 
lives. 

The  fat  of  butter  may  be  readily  separated  from  all  these  substances, 
and  obtained  in  a  nearly  pure  state.  Fresh  newly-churned  butter  is 
melted  in  a  cylindrical  jar  at  a  temperature  of  140°  to  180°  F.,  the 
fluid  oil  poured  off"  into  water  heated  to  the  same  temperature,  and  re- 
peatedly shaken  with  fresh  portions  as  long  as  any  thing  soluble  is  taken 
up.  When  left  at  rest  in  a  warm  place,  the  melted  fat  rises  to  the  sur- 
face in  the  form  of  a  nearly  colourless  transparent  oil,  which,  on  cooling, 
hardens  into  a  colourless  mass. 

This  pure  fat  may  be  preserved  for  a  much  longer  time  without  be- 
coming rancid  (Thenard).  It  is  the  various  substances  with  which  its 
fatty  matter  is  mixed  that  give  to  common  butter  its  tendency  to  become 
so  speedily  rancid  and  to  acquire  an  unpleasant  taste.  To  the  nume- 
rous precautions  which  have  been  adopted  with  the  view  of  counteract- 
ing this  tendency,  and  of  preserving  the  sweet  taste  of  butter,  I  shall  pre- 
sently direct  your  attention. 

§  11.  Of  the  average  ^quqnlity  cf  butter  yielded  by  milk  and  cream,  and 
of  the  yearly  yroduce  of  a  cow. 

1  have  already  made  you  acquainted  with  some  of  those  numerous 
circumstances  by  which  the  quality  of  milk  is  affected.  These  same 
circumstances  will  necessarily  more  or  less  affect  the  quantity  of  butter 
also,  which  a  given  weight  or  measure  of  milk  can  be  made  to  yield. 

Thus  in  the  King  William's  town  dairy  (County  Kerry),  the  average 
quantity  of  milk  and  butter  yielded  by  the  Kerry  and  Ayrshire  breeds 
respectively  was,  in  a  whole  year — 

Ayrshire  cow,  1328  quarts,  of  which  9^  to  Qf^  quarts  gave  1  lb.  of  but- 
ter. 

*  Since  the  above  was  written,  two  samples  of  fresh  butter,  from  cream,  examined  in  my 
laboralory,  have  yielded  only  0-5  and  07  per  cent,  respectively  of  cheesy  mutter.  This  is 
certainly  a  much  smaller  quantity  than  I  had  expected.  Does  butter  from  the  tchole  milk 
contain  morel    A  series  of  such  examinations  would  prove  not  iminteresting. 


QUANTITY    OF    BUTTER    YIELDED    BY    MILK.  553 

Kerry  coio,  1264  quarts,  of  which  from  8  quarts  to  8}  gave  1  Ih.  of 
Dutter. 

Showing,  as  I  have  before  stated,  (p.  536),  that  the  small  Kerry  cow, 
upon  the  same  pasture,  will  give  a  richer  milk  even  than  the  Ayrshire. 

In  Holstein  and  Lunenburg  again,  it  is  considered,  on  an  average, 
that  15  quarts  of  milk  will  yield  1  lb.  of  butter.  The  milk  in  that 
country,  therefore,  must  be  very  much  poorer  in  butter.  [Journal  of  the 
Royal  Agricultural  Society,  I.  p.  386.] 

The  result  of  numerous  trials,  however,  made  upon  the  milk  and 
cream  of  cows  considered  as  good  butter-givers,  in  this  country,  has 
established  the  following  average  relation  between  milk,  cream,  and  but- 
ler : — 

Milk.  Cream.  Butter. 

18  to  21  lb$.  )  .   1  ,  W  lbs.     }  T  ,, 

9tollqts.$  y^^^^  j2qts.M  ^' ^  ^^' 

The  cow,  therefore,  that  yields  3000  quarts  of  milk  should  produce, 
where  butter  is  the  principal  object  of  the  farmer,  about  300  lbs.  of  but- 
ter, or  1  lb.  a  day  for  300  days  in  the  year. 

This  is  not  a  large  daily  produce,  since  some  cows  have  been  known 
to  give  for  a  limited  time  as  much  as  two  or  even  three  pounds  of  butter 
in  a  single  day.  It  is  a  large  quantity  however,  taken  as  the  average  of 
a  lengthened  period  of  time,  and  hence  such  cases  as  that  of  Mr.  Cramp's 
cow,  which  for  four  years  continuously  yielded  nearly  a  pound  and  a 
half  of  butterf  every  day,  are  naturally  quoted  as  extraordinary. 

In  most  districts  the  average  of  the  whole  year  is  much  less  than  a 
pound  a  day,  even  for  ten  months  only.  In  Devon,  for  the  first  twenty 
weeks  after  calving,  a  good  cow  will  yield  12  quarts  of  milk  a  day,  from 
which,  by  the  method  of  scalding,  a  pound  and  a  quarter  of  butter  can  be 
extracted. 

In  South  Holland,  [Loudon's  Encyclopasdia,]  a  good  cow  will  pro- 
duce during  the  summer  njpnths  about  76  lbs.  of  butter.  In  the  high 
pastures  of  Scaria  in  Switzerland,  a  cow  will  yield  during  the  ninety 
days  of  summer  about  40  lbs.  of  butter,  or  less  than  half  a  pound  a  day. 
In  Holstein  and  Lunenburg  it  is  considered  a  fair  return  if  a  cow  yields 
100  lbs.  of  butter,  and  even  in  England,  [British  Husbandry,  II.,  p. 
404,]  160  to  180  lbs.  is  reckoned  a  fair  annual  produce  for  a  cow,  or  from 
8  to  9  ounces  a  day  for  ten  months  in  the  year. 

§  12.  Of  the  circumstances  which  affect  the  quality  of  butter. 
It  is  known  that  the  butter  produced  in  one  district  of  the  country,  dif- 
fers often  in  quality  from  that  produced  in  another,  even  though  the  same 
method  of  manufacture  be  adopted.  In  different  seasons  also  the  same 
farm  will  produce  different  qualities  of  butter — thus  it  is  said  that  cows 
which  are  pastured  yield  the  most  pleasant  butter  in  May,  when  the  first 
green  fodder  comes  in — that  the  finest  flavoured  is  given  by  cows  fed  upon 
spurrey  (Sprengel) — that  it  is  generally  the  hardest  when  the  animal 
lives  upon  dry  food — and  that  autumn  butter  is  best  for  long  keeping. 

*  The  quarts  spoken  of  in  this  lecture  are  old  wine  quarts,  of  which  5  make  an  intperuU 
pallon.  A  wine  gallon  of  milk  or  cream  weighs  about  8  lbs.  4  oz.,  an  imperial  gallon  about 
10  lbs.  5  oz.    About  two  imperial  gallons,  therefore,  should  yield  a  pound  of  butter. 

t  It  gave  in  four  years  2132  lbs.  of  butter  from  23,559  quarts  of  milk,  or  16  quarts  a  day,  of 
which  11  quarts  gave  apound  of  butter.  ..„,,^_  -iiv--  «-«,'«• 


654  FIRST    AND    SECOND    BIII.X    AND    CREAM. 

These  differences  may  all  be  ascribed  to  varieties  or  natural  differences 
in  the  pasture  or  fodder  upon  wliicli  the  cow  is  fed.*  The  constitution  ot 
the  animal  also  is  known  to  affect  the  quality  of  the  butter — since  there 
are  some  animals  which  with  the  best  food  will  never  give  first-rate  but- 
ter. 

In  all  such  cases  as  these,  however,  the  quality  of  the  butter  is  almost 
entirely  dependent  upon  that  of  the  milk  from  which  it  is  made,  so  that 
whatever  affects  the  quality  of  the  milk  must  influence  also  that  of  the 
butter  prepared  from  it.  But  as  I  have  already  considered  the  circum- 
stances by  which  the  quality  of  the  milk  is  principally  modified  (p. 
534),  I  shall  not  further  advert  to  this  subject  at  present. 

But  from  the  same  milk,  and  even  from  the  same  cream,  by  different 
modes  of  procedure,  very  different  qualities  of  butter  may  be  obtained. 
The  mode  of  making  or  extracting  butter,  therefore,  is  highly  worthy  of 
your  attention.  Let  us  consider  a  few  of  the  more  important  circimi- 
stances  under  which  different  qualities  of  butter  may  be  extracted  from 
the  same  quality  of  milk  or  cream. 

1°.  First  and  second  drawn  milk. — If  the  milk  be  collected  in  two  or 
three  successive  portions,  as  it  comes  from  the  cow,  we  have  already 
seen  (p.  536),  that  the  last  drawn  portion  will  be  much  richer  than  that 
which  has  been  taken  first.  The  cream  yielded  by  it  will  also  be  richer, 
and  of  a  finer  and  higher  flavour.  Whether,  therefore,  the  butter  be  ex- 
tracted directly  from  the  whole  milk,  or  from  the  cream,  the  butter  ob- 
tained from  the  three  successive  portions  will  differ  in  quality  almost  as 
much  as  the  several  portions  of  milk  themselves. 

A  practical  application  of  this  fact  is  made  in  some  of  the  Highland 
counties  of  Scotland,  and  in  other  districts,  where  the  calves  are  allowed 
to  suck,  or  are  fed  with,  the  first  half  of  the  milk  as  it  comes  from  the 
cow — the  latter  and  richest  half  only  being  reserved  for  dairy  purposes. 
This  second  milk  is  found  to  afford  an  exquisite  butter. 

2'^,  First  and  second  cream. — In  like  marfher  the  first  cream  that  rises 
upon  any  milk  is  always  the  richest,  and  gives  the  finest  flavoured  but- 
ter. The  after-creamings  are  not  only  poorer  in  butter,  but  yield  it  of  a 
whiter  colour  and  of  inferior  quality. 

This  fact  again  is  well  understood,  and  has  been  long  practically  ap- 
plied in  the  neighbourhood  of  Epping,  which  is  celebrated  for  the  excel- 
lence of  its  butter.  The  cream  of  the  first  24  hours  is  set  aside  and 
churned  by  itself.  The  second  and  third  creams  produce  a  pale,  less 
pleasant  butter,  which  always  sells  for  an  inferior  price.  Any  admix- 
ture of  the  after-creamings  causes  a  corresponding  diminution  in  the  value 
of  the  butter  produced.  To  produce  the  most  exquisite  butter  the  cream 
of  the  first  eight  hours  only  ought  to  be  taken. 

3^.  Mode  of  creaming.— The  rapidity  with  which  cream  rises  to  the 
surface,  either  naturally  or  when  influenced  by  art,  affects  the  quality  of 
the  cream,  and  consequently  that  of  the  butter  made  from  it.  In  warm 
weather  it  rises  more  quickly  than  in  cold,  and  more  quickly  still  when 
the  milk  is  heated,  as  in  the  preparation  of  clouted  cream.     The  butter 

*  The  influence  of  the  food  given  in  the  stall  and  of  the  plants  eaten  in  the  pasture,  upon 
the  colour  and  flavour  of  the  butter,  is  familiar  fo  all  practical  men.  The  turnipy  taste  of 
the  butter  in  winter — the  garlic  taste  in  summer,  where  the  wild  onion  grows  in  the  pastures 
— and  the  alleged  effect  of  raw  potatoes  in  winter,  in  giving  a  rich  colour  to  the  butter,  are 
•emmon  examples  of  this  kind. 


TOO    RAPID    OR    CTER-CIIUR.N'ING.  655 

(Bohemiau  butter)  obtain Qd  from  such  crean:i — from  cream  thus  rapidly- 
brought  to  the  surface — may  be  expected  to  differ  both  in  flavour,  in  con- 
sistency, and  in  composition,  from  that  yielded  by  the  cream  of  the  same 
milk  when  allowed  to  rise  in  the  usual  manner. 

4°.  Sourness  of  the  cream. — F6r  the  production  of  the  best  butter  it  is 
necessary  that  the  cream  should  be  sufficiently  sour  before  it  is  put  into 
the  churn.  Butter  made  from  sweet  cream  (not  clouted),  is  neither  good 
in  quality  nor  large  in  quantity,  and  longer  time  is  required  in  churning. 
It  is  an  unprofitable  method  (Ballantyne). 

5°.  Quickness  in  churning. — The  more  quickly  milk  or  cream  is 
churned,  the  paler,  the  softer,  and  the  less  rich  the  butter.  Cream,  ac- 
cording to  Mr.  Ayton,  may  be  safely  churned  in  an  hour  and  a  half, 
while  milk  ought  to  obtain  from  two  to  three  hours.  The  churning 
ought  also  to  be  regular,  slower  in  warm  weather  that  the  butter  may 
not  be  soft  and  white,  and  quicker  in  winter  that  the  proper  temperature 
may  be  kept  up. 

Mr.  Blacker  has  lately  introduced  into  this  country  a  barrel-churn  in- 
vented by  a  Mr.  Valcourt,  which,  being  placed  in  a  trough  of  water  of 
the  proper  temperature,  readily  imparts  the  degree  of  heat  required  by 
the  milk  or  cream  without  the  necessity  of  adding  warm  water  to  the 
milk,  and  churns  the  whole  in  ten  or  twelve  minutes.  It  is  said  also  to 
give  a  larger  weight  of  butter  from  the  same  quantity  of  milk.  If  the 
quality  be  really  as  good  by  this  quick  churning,  the  alleged  inferiority 
in  the  quality  of  butter  churned  quickly  in  the  coirimon  churn  can  not 
be  due  to  the  mere  rapidity  of  churning  alone. 

6°.  Over- churning. — When  the  process  of  churning  is  continued  after 
the  full  separation  of  the  butter,  it  loses  its  fine  yellowish,  waxy  ap- 
pearance, and  becomes  soft  and  light  coloured.  The  weight  of  the  butter, 
however,  is  said  to  be  considerably  increased ;  and  hence  that  in  Lan- 
cashire over-churning  is  frequently  practised  in  the  manufacture  of  fresh 
butter  for  immediate  sale  (Dr.  Traill.) 

7°.  Temperature  of  the  miik  or  cream. — Much  also  depends  upon  the 
temperature  of  the  milk  or  cream  when  the  churning  is  commenced. 
Cream  when  put  into  the  churn  should  never  be  warmer  than  53°  to  55° 
F.  It  rises  during  the  churning  from  4°  to  10°  F.  above  its  original 
temperature.  When  the  whole  milk  is  churned,  tne  temperature  should 
be  raised  to  65°  F.,  which  is  best  done  by  pouring  in  hot  water  into  the 
churn  while  the  milk  is  kept  in  motion.* 

The  importance  of  attending  to  the  temperature  and  to  the  quickness 
of  churning,  when  the  best  quality  of  butter  is  required,  is  shown  by  the 
two  following  series  of  results  obtained  in  the  churning  of  cream  at  dif- 
ferent temperatures  and  with  different  degrees  of  rapidity. 

The  first  series  was  obtained  in  the  August  ar-jd  September  of  1823,  by 
Dr.  Barclay  and  Mr.  Allan.  The  quantity  of  cream  churned  in  each 
experiment  was  15  wine  gallons,  weighing  from  8  lbs.  to  8^  lbs.  per  gal- 
lon. 

Ballantyne,  Transactions  of  the  Highland  Society,  New  Series,  I.,  p.  24.  Some  object  to 
this  method  of  adding  hot  water,  saying  that  it  renders  the  butter  pale  and  less  valuable  in  the 
market.  This  is  by  no  means  universally  the  case,  and  the  keeping  the  milk  in  motion, 
while  the  water  is  added,  may  possibly,  in  some  cages,  make  the  difference.  lu  other  caees. 
maybe  owing  to  natural  differences  in  the  quality  of  the  milks  operated  upon. 


Temperature. 

Quantity  of 

Time  in       Butter 

So. 

^^^'"-      End  ' 

Churning,  per  gallon. 

ning.        ^'^'^• 

Hours.        lb.    oz. 

1 

50°          60° 

4          1     15i 

2 

55°        65° 

3i        1     15» 
3          1     14' 

3 

58°        67° 

4 

60°        68° 

3          1     121 

5 

66°        75° 

2J        1     lOi 

556  TEMPERATURE   OF    THE   MILK   OR   CREAM. 


Quality  of  the  Butter. 

Very  best,  rich,  firm,  well  tasted. 
Not  sensibly  superior  to  the  former. 
(jrood,  but  softer. 
Soft  and  spongy. 
Inferior  in  every  respect. 

The  results  of  these  experiments  prescribe  the  temperature  of  50  to  55** 
F.  for  the  cream  when  put  into  the  churn,  and  from  3A  to  4  hours  as  the 
most  eligible  for  producing  butter,  both  in  the  largest  quantity  and  of  the 
finest  quality.  Something,  however,  appears  to  depend  upon  the  quality 
of  the  cream  ;  since  the  indications  of  the  next  series  of  experiments  dif- 
fer considerably  from  the  above,  in  so  far  at  least  as  regards  the  length 
of  time  expended  in  churning. 

The  follovv^ing  experiments  were  made  in  Edinburgh,  by  Mr.  Ballan 
tyne,  between  June  and  August,  1825.     Tlie  quantity  of  cream  he  used 
at  each  churning  was  8  wine  gallons — weighing  8  lbs.  to  the  gallon,  ex- 
fcept  hat  of  the  fourth  experiment,  which  weighed  4  ounces  less. 

Temperature.    Time  in  Quantity  of 
Churn-         " 


No.    Of  the  When  but-      ing.        per  gallon.  Quality  of  the  butter, 

cream,  ter  came.    Hours.        lbs.  oz. 

1  56°F.     60°F,         li  2     1       Inferior;  white  and  softer  than  No.  2. 

2  52°        56°  2  2    0)    The  flavour  and  quality  of  the'se  two 

3  52°        56  2  2    0  J        butters  could  not  be  surpassed. 

4  65°        67°  h  1  15      Soft,  white,  and  milky. 

5  50°        53  J°  3  1  15  J     Good— evidently  injured  by  long  churn- 

ing. 

6  53 J°      57i°  U  2    0§     Most  excellent.     High  in  flavour  and 

colour,  and  solid  as  wax. 

To  obtain   butter  from  cream,   therefore,  both  finest  in  quality  and 
largest  in  quantity,  these  two  series  of  experiments  prescribe  the  follow- 
ing temperatures  of  the  cream,  and  times  in  the  churning  — 
Temperature.  Time. 

First     ...     50°  to  55° 

Second      .     .     53i°  1^  to  1| 

In  the  temperature  both  agree.  It  is  probable  that  the  nature  of  the 
cream  obtained  at  different  seasons  or  in  different  localities  may  render 
a  longer  time  necessary  in  the  churning  on  some  occasions  or  in  some 
places  than  in  others.  It  is  certain  that  the  sourer  the  cream,  the  sooner 
generally  will  the  butter  come.* 

8°.  Churning  the  entire  milk. — It  is  in  connection  with  the  tempera- 
ture at  which  milk  and  cream  may  respectively  be  best  and  most  eco- 
nomically churned,  that  the  chances  of  obtaining  a  butter  of  good  quality 
at  every  season  of  the  year  appear  to  be  greater  when  the  whole  raiilk  is 
used,  than  when  the  cream  only  is  put  into  the  churn. 

Cream,  when  the  churning  commences,  should  not  be  warmer  than 
65°  F. — milk  ought  to  be  raised  to  65°  F.  In  winter,  either  of  these  tem- 
peratures may  be  easily  attained.     In  cold  weather  it  is  often  necessary 

*  In  sweet  cream,  when  the  butter  is  long  in  coming,  the  addition  of  a  little  vinegar,  brandy, 
or  whiskey,  will  hasten  the  chuniing. 


ADVAiNTAGE    OF    CFIURMi\G    THE    WHOLE    MILK.  557 

10  add  hot  water  to  the  cream  to  raise  it  even  to  55°.  But  in  summer, 
and  ('.specially  in  hot  weather,  it  is  difficult,  even  in  cool  and  well  or- 
dered dairies,  to  keep  the  cream  down  to  this  comparatively  low  temper- 
ature. Hence  if  the  cream  he  then  churned,  a  second  rate  butter,  at  best, 
is  all  that  can  be  obtained. 

Milk,  on  the  other  hand,  requires  a  temperature  of  65*^ — ten  degrees 
higher  than  cream — and  therefore  neither  summer  nor  winter  weather 
materially  affects  t^ie  ease  of  churning  it.  In  winter,  its  temperature  is 
raised  by  hot  water,  as  that  of  cream  is,  and  even  in  summer  there  can 
be  few  days  in  our  climate — where  the  milk  is  kept  in  a  well  contrived 
dairy — in  which  it  will  not  be  necessary  to  add  more  or  less  hot  water  in 
order  to  raise  the  milk  to  65°  F.  Thus,  where  the  entire  milk  is  churned, 
the  same  regular  method  or  system  of  churning  can  be  carried  on  through- 
out the  whole  year.  No  difficulty  is  to  be  apprehended  from  the  state 
of  the  weather,  nor,  so  long  as  the  quality  of  the  milk  remains  the  same, 
is  there  reason  to  apprehend  any  chaftige  in  the  quality  of  the  butter. 
The  winter  butter  and  the  summer  butter  may  be  alike  j5rm,  finely  fla 
voured,  and  rich  in  colour. 

The  alleged  advantages  of  churning  the  entire  milk  rather  than  the 
cream  may  be  thus  stated  : — 

a.  The  proper  temperature  can  be  readily  obtained  both  in  winter  and 
in  summer. 

6.  A  hundred  gallons  of  entire  milk  will  give  in  summer  five  per  cent, 
more  butter  than  the  cream  from  the  same  quantity  of  milk  will  give 
(Ballantyne). 

c.  Butter  of  the  best  quality  can  be  obtained  without  difficulty  both 
in  winter  and  in  summer. 

d.  No  special  attention  to  circumstances  or  change  of  method  is  at 
any  time  required.  The  churning  in  winter  and  summer  is  alike  simple 
and  easy. 

e.  The  butter  is  not  only  of  the  best  quality  while  fresh,  but  is  also 
best  for  long  keeping,  when  properly  cured  or  salted  (Ballantyne). 

To  these  advantages  it  is  set  off,  that  except  in  the  neighbourhood  of 
large  towns,  the  butter-milk  is  of  little  value — while  from  the  skimmed- 
milk,  a  marketable  cheese  can  always  be  manufactured.  But  this  ought 
to  be  no  objection,  where  churning  the  whole  milk  would  otherwise  be 
preferred,  since  it  is  little  more  difficult  to  make  cheese  from  the  sour 
butter-milk  than  from  the  sweet  skimmed-milk.  To  this  point  I  shall 
direct  your  attention  hereafter. 

9°.  Cleanliness. — It  seems  almost  unnecessary  for  me  to  allude  to 
cleanliness  as  peculiarly  necessary  to  the  manufacture  of  good  butter. 
But  I  do  so  to  bring  under  your  notice  the  fact,  that  cream  is  remarkable 
for  the  rapidity  with  which  it  absorbs  and  becomes  tainted  by  any  un- 
pleasant odours.  It  is  very  necessary  thai  the  air  of  the  dairy  should  be 
sweet,  that  it  should  be  often  renewed,  and  that  it  should  be  open  in  no 
direction  from  which  bad  odours  can  come. 

§  13.   Of  the  fatty  substances  of  which  butter  consists,  and  of  the  acid  of 
butter  {butyric  acid,)  and  the  capric  and  caproic  acids. 
1°.  Butter  fat. — I  have  already  mentioned  to  you  that  if  the  butter  as 
it  is  taken  from  the  churn  be  melted  in  water  of  a  temperature  not  ex- 
24 


558  THE  FATTY  SUBSTANCES  IN  BUTTER- 

ceeding  180°  F.,  and  be  then  washed  with  repeated  portions  of  warm 
water,  a  nearly  colourless  fluid  oil  is  obtained,  which,  if  not  transpar- 
ent, becomes  so  when  filtered  through  paper,  and  when  cool  congeals  into 
a  more  or  less  pure  white  solid  fat.  If  this  fat  be  put  into  a  linen  cloth 
and  be  submitted  to  a  strong  pressure  in  a  hydraulic  or  other  press  at  the 
temperature  of  60°  F.,  a  slightly  yellow,  transparent  oil  will  flow  out, 
and  a  solid  white  fat  will  remain  behind  in  the  linen  cloth.  The  solid 
fat  is  known  to  chemists  by  the  name  of  margarine.  The  liquid  oil  is 
peculiar  to  butter,  at  least  it  has  not  hitherto  been  found  in  any  other  sub- 
stance ;  it  is  therefore  called  the  oleinc  of  butter,  or  simply  butter-oil. 

The  pure  fat  of  butter  consists  almost  entirely  of  these  two  substances, 
there  being  generally^present  in  it  only  a  small  quantity  of  certain  fatiy 
acids,  which  I  shall  presently  introduce  to  your  notice.  Thus  a  speci- 
men of  butter  made  in  the  month  of  May  gave  a  fat  which  was  found 
by  Bromeis  to  consist  of  about — 

Margarine * 68  per  cent. 

Butter  oil 30         " 

Butyric,  caproic,  and  capric  acids     ....       2         '* 

100* 
But  the  proportion  of  the  solid  and  fluid  fats  in  butter  varies  very  much. 
ft  is  familiar  in  every  dairy  that  the  butter  is  harder  and  firmer  at 
one  time  and  with  one  mode  of  churning  than  with  another, — and  this 
greater  firmness  depends  mainly  upon  the  presence  of  the  solid  fat  {mar- 
garine) in  larger  proportion.  According  to  Braconnot,  summer  butter 
contains  much  more  of  the  butter-oil  than  winter  butter  does ;  and  he 
states  their  relative  proportions  in  these  two  seasons,  in  the  butter  of  the 
Vosges,  which  he  examined,  to  be  as  follows  : — 

Summer.  Winter. 

Margarine 40  65 

Butter  oil 60  35 

100  100 

Of  course  these  proportions  ire  not  to  be  considered  as  constant.  In- 
deed, the  proportion  of  oil  here  given  for  summer  butter  is  much  greater 
than  in  the  butter  examined  by  Bromeis.  It  is  probable,  therefore,  that 
the  relative  proportions  of  the  two  fats  are  affected  by  climate,  by  sea- 
son, by  the  race,  the  food,  and  the  constitution  of  the  animal;  by  the  way 
in  which  the  butter  is  made,  by  the  manner  in  which  it  is  kept,  and  by 
other  circumstances  not  hitherto  investigated. 

2°.  Margarine. — This  solid  fat,  which  exists  so  largely  in  butter,  is 
also  the  solid  ingredient  in  olive  oil,  and  in  goose  and  human  fat.  But- 
ter, therefore,  appears  to  be  a  most  natural  food  for  the  human  race,  since 
it  contains  so  large  a  proportion  of  one  of  those  substances  which  enter 
directly  into  the  constitution  of  the  human  frame. 

Margarine  is  white,  hard,  and  brittle,  and  melts  at  118°  F.  In  the 
pure  state  it  may  be  kept  for  a  length  of  time  without  undergoing  any 
sensible  change,  but  in  the  state  of  mixture  in  which  it  exists  in  milk  and 
butter  it  is  apt  to  absorb  oxygen  from  the  atmosphere,  and  to  be  partially 

*  Annal.  der  Chem.  und  Phar.,  xlii.,  p.  70. 


PROPERTIES    OF    THE    SUGAR    OF    MILK.  559 

changed  into  butter  oil,  and  into  one  or  other  of  those  fatty  acic  s  which 
are  present  in  butter  in  smaller  quantity. 

3°.  Margaric  acid. — When  this  fat  (Margarine)  is  introduced  into  a 
hot  solution  of  caustic  potash,  it  readily  dissolves  and  forms  a  soap.  If 
the  solution  of  this  soap  in  water  be  decomposed  by  the  addition  of  diluted 
sulphuric  acid  a  white  fatty  substance  separates,  which,  after  being  col- 
lected, dried,  and  dissolved  in  hot  alcohol,  crystallizes  as  the  solution 
cools,  in  the  form  of  pearly  scales.  This  substance  is  known  by  the 
name  of  the  margaric  (or  pearly)  acid.  Margarine  consists  of  this  acid 
in  combination  with  a  sweet  substance  known  by  the  name  of  glycerine, 
or  oil  sugar,* 

Margaric  acid  is  represented  by  the  formula  34  C  +  34  H  +  4  O,  or 
C34  H34  O4.  To  this  formula  it  will  be  necessary  in  a  few  minutes  to 
revert. 

Butter  oil. — The  liquid  fat  expressed  from  butter  has  the  appearance 
of  an  oil,  sometimes  colourless,  but  often  tinged  of  a  yellow  colour.  It 
has  the  taste  and  smell  of  butter — mixes  readily  with  alcohol,  and  be- 
comes solid  when  cooled  down  to  32 '^  F. — the  freezing  point  of  water. 
It  dissolves  without  difficulty  in  a  solution  of  caustic  potash,  and  forms 
a  soap. 

Acid  of  bulter-oil — oleic  acid  of  butter. — When  the  solution  of  the  oil 
in  caustic  potash  is  diluted  with  much  water,  and  decomposed  by  the  ad- 
dition of  diluted  sulphuric  acid,  an  oily  substance  is  separated,  which  is 
different  from  the  original  oil  of  butter,  possesses  acid  properties,  and  is 
known  by  the  name  of  the  oleic  acid  of  butter.  This  fatty  acid  has 
never  hitherto  been  obtained  from  any  other  substance  than  the  oil  of 
butter,  and  the  oil  consists  of  the  acid  in  combination  with  oil-sugar. 
You  will  recollect  that  margarine  consists  of  margaric  acid  in  combination 
with  the  same  sugar  (p.  558.) 

*  Such  is  the  apparent  composition  of  the  two  fatty  substances,  margarine  and  butter-oil, 

inasmuch  as  when  they  are  dissolved  in  a  solution  of  caustic  potash,  and  their  solutions 

afterwards  decomposed  by  an  acid,  tlioy  are  resolved  respectively — 
Margarine — into  margaric  acid  and  oil-sugar ; 
Butter- oil— into  butter  oleic  acid  and  oil-sugar. 
But,  for  the  benefit  of  my  chemical  readers  (my  other  readers  will  please  to  pass  ovct 

this  note),  it  is  necessary  to  state- 
to.  That  a  compound  is  supposed  to  exist,  consisting  of  3  atoms  of  carbon  united  to  2  o 

hydrogen— Cii  H:^,  to  which  the  name  odipyle  is  given. 
2°.  That  this  radical  Cs  H2  unites  with  an  atom  of  oxygen,  forming  C3  H2  O,  or  oxide  of 

3°.  That  in  neutral  fatty  bodies,  such  as  margarine,  this  oxide  exists  in  combination 
with  a  fatty  acid.    Thus,  for  example,  that— 

,  _  .  ,       f  S  1   of  margaric  acid =  C34  H34  O4 

Mcrganne  consists  ofji  ^f  ^^.^%  ^f  ,ipy,g =  C3  Ha  O 

Forming,  together,  1  of  margarine =:C37H36  05 

And  r   ,.„.,  „f  SI  of  oleic  acid  of  butter =  C34  H31  05 

butter-otl  of  J  J  ^f  ^^.^^  ^f  lipy,g =  C3  H2  O 

Forming,  together,  1  of  butter-oil =  C37  H33  Os 

4°.  And  that  when  this  oxide  of  lipyle  is  separated  from  its  combination  with  the  fatty 
acids  it  unites  with  a  quantity  of  water,  and  forms  glycerine  or  oil-sugar.    Thus— 

2  of  oxide  of  lipyle =  Ce  H4  O2  united  to 

3  of  water =        H3  O3  give 

1  of  glycerine  (oil-sugar)   .    .    •    .     .    .    .    =:  Ce  H?  O5 
5".  The  above  is  the  view  of  Berzelius,  but  Redtenbacher  has  recently  suggested,  [Annai! 
der  Chem.  und  Phar,  XLVII.,  p.  141,]  that  a  known  substancF  palled  acrolein  exists  in  the 


560  CHANGE    OF    MARGARINE    INTO    OLEIC    ACID. 

When  pure,  ihis  oily  ncid  is  colourless  and  transparent,  and  is  re- 
markahle  for  the   lapidi  y  with  which  it  absorbs  oxygen  from  the  atmos- 
phere, and  becoines  convirted  into  new  chemical  compounds.     It  is  re- 
presented by  the  formula  34C  +  31H  -f  50,  or  C34  H31  O5. 
Let  us  compare  this  formula  with  that  of  the  marg;aric  acid  : 

Margaric  acid =  C34  H34  O4 

Butter  oleic  acid       .     .     .     .     =  C34  Hu  O5 

Ditference +H3 — Oi 

or,  if  3  of  hydrogen  be  taken  from  the  margaric  acid  and  1  of  oxygen 
added  to  it,  it  will  be  converted  in(o  tlie  oleic  acid. 

Now  this  may  be  etlected  by  simply  sup[)()sing  one  atom  of  margaric 
acid  to  absorb  four  atoms  of  oxygen  from  the  atmosphere.     Thus — 

1  of  margaric  acid  =  C34  H34  O4 

4  of  oxygen     .     .   =  O4 

•  1  of  oleic  acid     +    3  of  water. 

C;m  H34  Os  ,     or    C34  H31  O5     +        3HO. 

So  that  either  in  the  body  of  the  animal,  in  the  milk  while  it  remains 
in  the  udder,  or  when  it  is  exposed  to  the  air  after  being  drawn  from  the 
cow,  or  even  in  the  churn  itself,  it  may  happen  that  a  portion  of  the 
margaric  acid  may  absorb  oxygen  and  become  changed  into  the  oleic 
acid.  It  may  also  be  that  this  change,  this  absorption  of  oxygen,  is  pro- 
moted by  warm  and  retarded  by  cold  weather,  and  that  thus  the  butter 
is  rendered  generally  softer  in  the  summer  and  harder  in  the  winter  sea- 
son. But  these  are  as  yet  only  conjectures  ;  for,  after  all,  the  relative  pro- 
portions of  the  soft  and  hard  fat  in  butter  at  different  times  of  the  year 
may  depend  upon  natural  differences  in  the  herbage  at  the  several 
seasons,  or  upon  some  other  causes  which  have  not  as  yet  been  in 
vestigated. 

6°.  Butyric,  capric,  and  caproic  acids. — These  substances,  as  I  have 
already  stated  to  you,  exist  in  butter  only  in  small  quantity — to  the 
amount  of  2  or  3  per  cent.  To  these  acids,  and  especially  to  the  capric 
and  caproic,  butter  owes  its  disagreeable  smell  when  it  becomes  rancid. 
They  do  not  exist,  naturally,  to  any  unpleasant  extent  in  perfectly  fresh 
butter — they  are  gradually  formed  in  it,  however,  when  fresh  butter 
is  exposed  to  the  air.  I  do  not  enter  into  any  detail  of  their  proper- 
ties, or  of  the  mode  of  extracting  them  from  butter,  because  these  points 

fats  in  combination  with  the  fatty  acid.  Ttiis  acrolein  is  represented  by  C6  H4  O2,  which 
is  exactly  the  constitution  of  2  of  lipyle.  So  that  according  to  this  view  the  solid  fat  of  but- 
ter would  consist  of— 

2  of  margaric  acid    .     .     .     .    =  CC8 1168  OS 

1  of  acrolein =  Cr,    H4  .O2 

2  of  margaric  acid    .     ,     .    .     =  C74  II72  Oio 

and,  by  a  like  substitution  of  acrolein  for  oxide  of  lipyle,  may  the  constitution  of  butter-oil 
be  represented. 

The  principal  known  fact  in  favour  of  this  view  of  Redtenbacher  is,  that  when  glycerine  is 
distilled  with  anhydrous  phosphoric  acid,  acrolein  is  produced.  He  supposes  that  the  acid 
takes  the  elements  of  3  atoms  of  water  from  glycerine,  forming  acrolein :  since  if  from — 

1  of  glycerine =  C6  H7  05  we  take 

3  of  water =        Hg  O3 

Acrolein  remains :=  Cs  H4  O2 

The  convsrsion  of  acrolein  into  glycerine,  when  it  is  separated  from  the  fatty  acids,  is  sup- 
posed to  proceed,  as  in  the  case  of  lipyle,  from  its  combination  with  the  water  at  the  moment 
of  extrication.    Further  r^archss  are  yet  required  to  clear  up  this  subject. 


PROPERTIES    OF    THE    CURD    OF    MILK.  561 

are  of  less  interest  or  importance  to  you.  It  is  necessary  only,  to  a 
clear  understanding  of  the  kind  of  changes  which  take  place  when  butter 
becomes  rancid,  that  I  should  exhibit  to  you  the  formulae  by  which  these 
acid  bodies  are  severally  represented  : — 

Butyric  acid  =  Cg    Ug    O4 

Caproic  acid  =  C12  Ho    O3 

Capric  acid    =  Cis  H14  O3 
We  shall  see  how  these  substances  are  produced  from  the  solid  and 
fluid  fats  of  butter,  when  we  come  to  treat  of  the  preservation  of  butter. 

§  14.   Of  casein  or  the  curd  of  milk  and  its  properties. 

The  casein  or  cheesy  matter  of  milk  may  be  obtained  nearly  pure  by 
the  following  process  : — Heat  a  quantity  of  milk  which  has  stood  for  5 
or  6  hours,  jis  if  you  intended  to  prepare  clouted  cream  (p.  548),  let  it 
cool,  and  separate  the  cream  completely.  Add  now  to  the  milk  a  little 
vinegar  and  heat  it  gently.  The  whole  will  coagulate,  and  the  curd  will 
separate.  Pour  off"  the  whey,  and  wash  the  curd  well  by  kneading  it 
with  repeated  portions  of  water.  When  pressed  and  dried,  this  will  be 
casein  sufficiently  pure  for  ordinary  purposes.  It  may  be  made  still 
more  pure  by  dissolving  it  in  a  weak  solution  of  carbonate  of  soda,  al- 
lowing the  solution  to  stand  for  12  hours  in  a  shallow  vessel,  separating 
any  cream  that  may  rise  to  the  surface,  again  throwing  down  the  curd 
by  vinegar,  washing  it  frequently,  and  occasionally  boiling  it  with  pure 
wat'='-r.  By  repeating  this  process  two  or  three  times,  it  may  be  obtained 
almost  entirely  free  from  the  fatty  and  saline  matters  of  the  milk. 

Casein  thus  prepared,  reddens  vegetable  blues,  and  is  therefore  a 
slightly  acid  substance.  It  is  very  sparingly  soluble  in  water — 400  lbs. 
of  cold  water  dissolving  only  1  lb.  of  pure  casein  (Rochleder).  It  dis- 
solves readily,  however,  and  in  large  quantity,  in  a  weak  solution  of  the 
carbonate  of  potash  or  of  soda,  and  to  some  extent  even  in  lime-water. 
These  solutions  are  coagulated  by  the  addition  of  an  acid — of  sulphuric 
acid,  of  vinegar,  or  of  lactic  acid — and  the  curd  readily  separates  on  the 
application  of  a  gentle  heat.  If  a  large  quantity  of  acid  be  added,  a  por- 
tion of  the  casein  is  re-dissolved.  This  property  of  dissolving  in  weak 
alcaline  (potash  or  soda)  solutions,  satisfactorily  explains  what  takes 
place  during  the  curdling  of  milk,  as  we  shall  hereafter  see  (p.  567). 

The  casein  of  milk  is  identical  in  chemical  constitution  with  the  fibrm 
of  wheat,  the  legumin  of  the  pea  and  bean,*  and  the  albumen  of  the 
egg  or  of  vegetahle  substances.  Hence  the  opinion  has  naturally  arisen 
among  chemists,  that  the  cheesy  matter  contained  in  an  animal's  milk  is 
derived  directly,  and  without  change,  from  the  food  on  which  it  lives. 
The  probability  of  this  opinion  will  cx)me  naturally  under  our  considera- 
tion in  the  following  lecture.  (See  next  lecture,  "  On  the  feeding  of 
stock.'') 

Casein  possesses  still  one  property  more  remarliable  than  any  of  its 

•  In  page  394  it  is  stated,  on  the  authority  of  Dumas,  that  the  legumin  of  the  pea  and  bean 
differs  in  composition  from  fibrin  and  albiin>en  Since  that  sheet  was  published,  it  appears, 
from  the  experiments  of  Rochleder  (Annal.  dor  Cheni.  und  Pharm.,  xlvi.,  p.  162),  that  the 
legumin  which  Dumas  extracted  from  the  almond,  analysed,  and  supposed  to  be  identical 
with  the  legumin  of  the  bean  and  pea,  is  not  so,  but  is  in  reality  a  different  substance  ;  an4 
thatlhe  legumin  of  peas  does  agree  in  composition  with  the  casein  of  milk. 


562  ACTION.  OF  CASEIN  UPON  SUGAR. 

Others,  and   exceedingly  interesting  to  the  practical  agriculturist.     Let 
me  explain  this  property  a  little  more  in  detail. 

§  15.   Of  the  relations  of  casein  to  the  sugars  and  the  fats. 

1°.  Relation  to  the  sugars.— a.  Production  of  lactic  acid. — I  have 
already  adverted  (p.  543)  to  the  remarkable  property  which  casein  pos- 
sesses of  gradually  converting  milk  or  other  sugars  into  lactic  acid.  If 
a  small  quantity  c^  this  substance,  either  in  the  state  of  fresh  curd  or  in 
the  purer  form  juSt  iescriijed,  be  introduced  into  a  solution  of  cane-sugar, 
or  of  sugar  of  milk,  lactic  acid  begins  very  soon  to  be  formed.  Thus 
the  casein  it  contains  is  the  cause  of  the  souring  of  milk.  In  like  man- 
ner it  is  the  casein  contained  in  bean  or  pea-meal  v^^hich  makes  it  so 
soon  become  sour  when  mixed  with  water. 

h.  Production  of  butyric  acid. — But  the  transforming  action  of  casein 
doos  not  end  when  this  change  is  produced.  After  a  longer  time  a 
further  alteration  is  ^ected  by  its  means.  A  fermentation  commences, 
during  wdiich  carbonic  acid  and  pure  hydrogen  gases  are  given  off,  and 
butyric  acid  is  produced  (Pelouze  and  Gelis).  Let  us  consider  the 
nature  of  this  new^  change. 

Butyric  acid  is  represented  by  Cs  Hs  O4  ;  and  lactic  acid,  as  we  have 
seen,  by  Ce  He  Oe  ;  therefore — 

4  of  lactic  acid =  C24  H24  O24  and 

3  of  butyric  acid =  C24  H24  O12 

Difference O12 

That  is  to  say,  that  4  of  lactic  acid,  in  order  to  be  converted  into  3  of 
butyric  acid,  must  give  off  12  of  oxygen.  But 'during  the  fermentation 
which  accompanies  the  change  no  oxygen  is  given  off.  The  gases 
which  escape  are  carbonic  acid  and  hydrogen.  The  oxygen  given  off 
by  one  portion  of  the  lactic  acid,  therefore,  must  combine  with  the  ele- 
ments of  another  portion,  and  convert  it  into  these  gases.  Thus  to — 
1|  of  lactic  acid  .  .  =  C9  H9  O9 
Add  12  of  oxygen    .     .     =  O12 

9  of  carbo-       ,       6  of  liy-       ,     3  of 
nic  acid        "*"      drogen       "*    water. 

And  we  have  .  .  .  Cg  H9  O21  =  9  C  O2  +  6H  -f  3  HO  ; 
or,  while  4  atoms  of  lactic  acid  are  converted  into  3  of  butyric  acid,  1^ 
of  lactic  acid  are  at  the  same  time  converted  into  9  of  carbonic  acid  gas, 
6  of  hydrogen  gas,  and  3  of  water.  The  gases  escape  and  cause  the  fer- 
mentation, while  the  water  remains  in  the  solution.* 

*  I  have  taken  in  the  text  the  smallest  numbers  by  which  the  general  change  could  be  re- 
presented in  the  simplest  way.  According  to  Pelouze  and  Gelis,  however,  the  hydrogen 
given  off  is  sensibly  one-third  of  the  bulk  of  the  carbonic  acid  when  the  butyric  fermenta- 
tion is  in  its  vigour.  To  satisfy  this  condition,  therefore,  much  higher  numbers  must  be 
taken  ;  such  as  the  following: — 

20  of  lactic  acid        =  Cf^o  H|'A  O120  are  converted  into 

15  of  butyric  acid =  Cl'^^o  Hiio  Oeo 

Giving  off =  Oeo 

And  these  CO  of  oxygen  decompose  6  of  lactic  acid,  as  above  described.    Thus  to — 

6  of  lactic C36  H;j6  (m 

Add  60  of  oxygen     .     .  Ogo 

6  of  carbonic  acid  -1-  12  hydrogen  +  24  water. 

And  we  have      .    .     C36  H36  09C  z=  36COJ  +  ]2Ii  +  24HO, 

where  the  carbonic  acid  gas  i?  exactly  three  times  the  bulk  of  the  Hydrogen  gaj  produced. 


OF    THE    RANCIDITY    OF    BUTTER.  663 

The  outyric  acid  thus  produced  is  a  colourless  transparent  volatile 
liquid,  which  emits  a  mingled  odour  of  vinegar  and  of  rancid  butter. 
To  the  production  and  presence  of  this  acid,  therefore,  in  the  milk  or 
cream  or  in  the  manufactured  butter,  the  rancidity  of  this  important 
dairy  product  is  partly  to  be  ascribed. 

2°.  Relation  to  the  fatty  bodies. — It  is  probable  that  in  certain  cir- 
cumstances the  casein  of  milk  is  capable  of  inducing  chemical  changes 
in  the  fatty  bodies  as  well  as  in  the  sugars,  but  this  conjecture  has  not, 
as  yet,  been  verified  by  rigorous  experimental  investigation. 

3°.  Relation  to  fats  and  sugars  mixed. — It  is  known,  however,  to  act 
upon  fatty  bodies  when  mixed  with  sugar.  Thus,  if  a  small  quantity 
of  casein  be  added  to  a  solution  of  sugar,  lactic  acid  is  produced  for  a 
certain  length  of  time,  but  it  ceases  to  be  sensibly  formed  before  the 
whole  of  the  sugar  is  transformed  into  this  acid.  If  now  a  quantity  of 
oily  matter  be  added  to  the  mixture,  the  production  of  lactic  acid  will  re- 
commence, and  may  continue  till  all  the  sugar  is  changed.  If  more 
sugar  be  added  by  degrees,  the  formation  of  acid  will  go  on  again,  and, 
after  a  while,  will  cease.  The  introduction  of  a  little  more  oil  will  again 
give  rise  to  the  production  of  acid,  and,  at  length,  the  acid  will  cease  to 
be  formed,  while  both  sugar  and  oil  are  present.  The  casein  originally 
added  has  now  produced  its  full  effect  (Lehmann). 

It  appears,  therefore,  that  in  the  presence  of  sugar,  casein  is  capable 
of  changing  or  decomposing  the  fatty  bodies  also,  and  of  giving  birth  to 
oily  acids  of  various  kinds.  Now,  in  milk,  in  cream,  and  in  butter,  the 
casein  is  mixed  with  the  sugar  of  the  milk  and  the  fats  of  the  butter,  and 
thus  is  in  a  condition  for  (^hanging  at  one  and  the  same  time  both  the 
sugar  into  lactic  or  butyric  acid,  and  the  butter  into  other  acids  of  a 
fatty  kind.  Among  those  latter  into  which  the  butter-oil  is  convertible 
may  probably  be  reckoned  the  capric  and  c;aproic  acids,  which  are  still 
more  unpleasant  to  the  smell  and  taste  than  the  butyric  acid,  and  which 
are  known  to  be  present  in  rancid  butter- 

§  16.   Of  the  rancidity  and  preservation  of  butter. 

We  are  now  prepared,  in  some  measure,  to  understand  the. changes 
that  take  place  when  butter  becomes  rancid — and  the  way  in  which  those 
substances  act  which  are  usually  employed  for  preserving  it  in  a  sweet 
and  natural  state.  '  • 

1°.  When  butter  becomes  rancid,  there  are  two  substances  which 
change — the  fatty  matters  and  the  milk  sugar  with  which  they  are  mixed. 
There  are  also  two  agencies  by  which  these  changes  are  induced — the 
casein  present  in  butter,  and  the  oxygen  of  the  atmosphere.  The  quantity 
of  casein  or  cheesy  matter  which  butter  usually  contains  is  very  small, 
but,  as  we  have  seen,  it  is  the  singular  property  of  this  substance  to  in- 
duce chemical  changes  of  a  very  remarkable  kind,  upon  other  compound 
bodies,  even  when  mixed  with  them  in  very  minute  quantity. 

2°.  As  it  comes  from  the  cow,  this  substance,  casein,  produces  no 
change  on  the  sugar  or  on  the  fatty  matters  of  the  milk.     But  after  a 

Every  chemist  is  aware,  however,  that  in  decompositions  of  this  kind,  it  is  seldom 
that  one  single  product  is  obtained  aloma.  Though  the  above  formula,  therefore,  represents 
truly  how  butyric  acid  may  be  produced  from  lactic  acid  under  the  circumstances,  yet 
other  substances  are  not  unfrequenily  formed  during  the  actual  experiment,  by  which  the 
result  is  more  or  less  complicated. 


564  INFLUENCE    OF    THE    CHEESY    MATTER. 

short  exposure  to  the  air  it  alters  in  some  degree,  and  acquires  the  power 
of  transforming  milk  sugar  into  lactic  acid.  Hence,  as  we  have  seen,  the 
milk  ])egins  speedily  to  become  sour.  Further  changes  follow,  and, 
among  other  substances,  butyric  acid  is  formed. 

In  butter  the  same  changes  take  place.  The  casein  alters  the  suga? 
and  the  fatty  matters,  producing  the  butyric  and  other  acids,  lo  which  its 
rancid  taste  and  smell  are  lo  be  ascribed. 

In  the  manufacture  of  butter,  therefore,  it  is  of  consequence  to  free  it  as 
completely  as  possible  from  the  curd  and  sugar  of  milk.  This  is  done 
in  some  dairies  by  kneading  and  pressing  only ;  in  others,  by  washing 
with  cold  water  as  long  as  the  latter  comes  off' milky.  The  washing 
must  be  th«  most  effective  method,  and  is  very  generally  recommended 
for  butter  that  is  to  be  eaten  fresh.  In  some  dairies,  however,  it  is  care- 
fully abstained  from,  in  the  case  of  butter  which  is  to  be  salted  for  long 
keeping. 

There  are  two  circumstances  which,  in  the  case  of  butter  that  is  to  be 
kept  for  a  length  of  time,  may  render  it  inexpedient  to  adopt  the  method 
of  washing.  The  water  may  not  be  of  the  purest  kind,  and  thus  may 
be  fitted  to  promote  the  future  decomposition  of  the  butter.  Sprengel 
says  that  the  water  ought  to  contain  as  little  lime  as  possible,  because 
the  butter  retains  the  lime  and  acquires  a  bad  taste  from  it. 

But  the  water  may  also  contain  organic  substances  in  solution — vege- 
table or  animal  matters  not  visible  perhaps,  yet  usually  present  even  in 
spring  water.  These  the  butter  is  sure  to  extract,  and  they  may  mate- 
rially contribute  to  its  after-decay,  and  to  the  difficulty  of  preserving  it 
from  rancidity. 

Again,  the  washing  with  water  exposes  the  particles  of  the  butter  to 
the  action  of  the  oxygen  of  tha  atmosphere  much  more  than  when  the 
butter  is  merely  well  squeezed.  The  effect  of  this  oxygen,  in  altering 
either  the  fatty  matters  themselves  or  the  small  quantity  of  casein  which 
remains  mixed  with  them,  may,  no  doubt,  contribute  to  render  some  but- 
ters more  susceptible  of  decay. 

3°.  But  the  casein,  after  it  has  been  a  still  longer  time  or  more  fully 
exposed  to  the  air,  undergoes  a  second  alteration,  by  which  its  tendency 
to  transform  the  substances  with  which  it  may  be  in  contact,  is  consi- 
derably increased.  It  acquires  the  property  also  of  inducing  chemical 
changes  of  an(^er  kind,  and  it  is  not  improbable  that  the  more  un- 
pleasant smelling  capric  and  caproic  acids  may  be  produced  during  this 
period  of  its  action. 

In  the  preservation  of  butter,  therefore,  for  a  length  of  time,  it  is  of 
indispensable  necessity  that  the  air  should  be  excktded  from  it  as  com- 
pletely as  possible.  In  butter  that  is  to  be  salted  also,  it  is  obvious  that 
the  sooner  the  salt  is  applied  and  the  whole  packed  close,  the  better  and 
sweeter  the  butter  is  likely  to  remain. 

4°.  The  action  of  this  cheesy  matter,  and  its  tendency  to  decay,  are 
arrested  or  greatly  retarded  by  the  presence  o^  saturated  solutions  of  cer- 
tain saline  and  other  substances.  Of  this  kind  is  common  salt,  which  is 
most  usually  employed  for  the  purpose  of  preserving  butter.  Saltpetre, 
also,  possesses  this  property  in  a  less  degree,  and  is  said  to  impart  to  the 
butter  an  agreeable  flavour.  A  syrup  or  strong  solution  of  sugar  will 
likewise  prevent  both  meat  and  butter  from  becoming  rancid.     liike  salt- 


HOW    TO    PURIFY    SALT    FOR   BUTTER.  565 

petre,  however^  it  is  seldom  used  alone,  but  it  is  not  uncommon  to  em- 
ploy a  mixture  (;f  common  salt,  saltpetre,  and  sugar,  for  the  preservation 
of  butter.  Where  the  butter  has  been  washed,  this  admixture  of  cane- 
sugar  may  supply  the  place  of  the  milk-sugar  which  the  butter  originally 
contained,  and  may  impart  to  it  a  sweeter  taste. 

The  salt  should  be  as  pure  as  possible,  as  free,  at  least,  from  lime  and 
magnesia  as  it  can  be  obtained,  since  these  substances  are  apt  to  give 
it  a  bitter  or  other  disagreeable  taste.  It  is  easy,  however,  to  purify  the 
common  salt  of  the  shops  from  these  impurities  by  pouring  a  couple  of 
quarts  of  boiling  water  upon  a  stone  or  two  of  salt,  stirring  the  whole 
well  about,  now  and  then,  for  a  couple  of  hours,  and  afterwards  straining 
it  through  a  clean  cloth.  The  water  which  runs  through  is  a  saturated 
solution  of  salt,  and  contains  all  the  impurities,  but  may  be  used  for  com- 
mon culinary  purposes  or  may  be  mixed  with  the  food  of  the  cattle. 
The  salt  which  remains  on  the  cloth  is  free  from  the  soluble  salts  of  lime 
and  magnesia,  and  may  be  hung  up  in  the  cloth  till  it  is  dry  enough  to 
be  used  for  mixing  with  the  butter  or  with  cheese. 

The  quantity  of  salt  usually  employed  is  from  g^^th  to  3-3  th  part  of  the 
weight  of  the  butter — with  which  it  ought  to  be  well  and  thoroughly  in- 
corporated. The  first  sensible  effect  of  the  salt  is  to  make  the  butter 
shrink  and  diminish  in  bulk.  It  becomes  more  solid  and  squeezes  out  a 
portion  of  the  water — with  which  part  of  the  salt  also  flows  away.  It  is 
not  known  that  the  casein  actually  combines  with  the  salt,  nor,  if  it  did, 
considering  the  very  small  (juantity  of  this  substance  which  is  present  in 
butter,  could  much  salt  be  required  for  this  purpose.  But  the  points  to 
attend  to  in  the  salting  of  butter  are  to  take  care  that  all  the  water  which 
remains  in  the  butter  shall  be  fully  saturated  with  salt — that  is  to  say, 
shall  have  dissolved  as  much  as  it  can  possibly  take  up — and  that  in  no 
part  of  the  butter  shall  there  be  a  particle  of  cheesy  matter  which  is  not 
also  in  contact  with  salt.  If  you  exclude  the  air,  the  presence  of  a  sat- 
urated solution  of  salt  will  not  only  preserve  this  cheesy  matter  from  it- 
self undergoing  decay,  but  will  i-ender  it  unable  also  to  induce  decay  in 
the  sugar  and  fat  which  are  in  contact  with  it.* 

It  is  really  extraordinary  that  such  rigid  precautions  should  be  neces- 
sary to  prevent  the  evil  influence  of  half  a  pound  of  cheesy  matter,  or  less, 
in  a  hundred  pounds  of  butter  (p.  551). 

5°.  Though  the  curd  or  casein  appears  to  be  the  enemy  against  whose 
secret  machinations  the  dairy  farmer  has  chiefly  to  guard,  yet  tlie  oxygen 
of  the  atmosi)here  is  a  second  agent  by  which  the  fatty  matters  of  butter 
are  liable  to  be  brought  into  a  state  of  decomposition,  and  the  presence 
of  which,  therefore,  should  be  excluded  as  carefully  as  possible. 

We  liave  seen  that  by  the  action  of  oxygen  the  solid  margaric  acid  of 
butter  may  be  changed  into  the  oleic  or  liquid  acid  of  butter  (p.  560.) 

'  Mr.  Ballantyne  thus  describes  the  method  of  salting  butter  practised  at  his  dairy  farm  of 
30  cows,  near  Edinburgh  :— "  Ttie  butter  is  drawn  warm  from  tiie  churn,  and  it  is  an  invari- 
able rule  never  to  wash  it  or  dip  it  into  water,  when  intended  to  be  salted.  The  dairymaid 
puts  it  into  a  clean  tub,  which  in  previously  well  rinsed  with  cold  water,  and  then  works  it 
with  cool  hands  till  all  the  milk  is  thoroughly  squeezed  out.  Half  the  allowed  quantity  of 
salt  is  then  added,  and  well  mixed  up  with  the  butter,  and  in  this  state  it  is  allowed  to  stand 
till  next  morning,  when  it  is  asain  wrou-fht  up,  any  brine  squeezed  out,  and  the  remainder 
of  the  salt  added.  It  is  then  packed  into  kits,  which,  when  full,  should  be  well  covered  up, 
and  placed  in  a  cool  dry  store— a  small  quantity  of  salt  is  usually  sprinkled  on  the  surface. 
The  proportion  of  salt  used  at  this  dairy  is  half  a-pound  to  fourteen  pounds  of  butter. ■■'— 
Journal  of  Agriculture,  New  Series,  vol.  I.,  p.  26. 
24* 


566  EVIL   EFFECT    OF    THE    AIR   UPON    BUTTER. 

This  is  the  first  stage  in  the  decomposition,  which,  when  once  begun, 
generally  spreads  or  extends  with  increasing  rapidity.* 

Again,  I  have  also  stated  that  this  fluid  (oleic)  acid  of  butter  absorbs 
oxygen  with  great  rapidity  from  the  air  (p.  560),  and  changes  rapidly  into 
other  compounds.  This  is  the  second  stage,  and  is  succeeded  by  others, 
which  it  is  unnecessary  to  enumerate. 

To  this  action  of  the  air  is  partly  to  be  ascribed  that  peculiar  kind  of 
rancidity,  which,  without  penetrating  into  the  interior  of  well  packed 
butter,  is  yet  perceptible  on  its  external  surface,  wherever  the  air  has 
come  in  contact  with  it.  A  knowledge  of  this  action  of  the  atmosphere, 
therefore,  urges  strongly  the  necessity  of  closely  incorporating  and  knead- 
ing together  the  butter  in  the  cask  or  firkin — that  no  air  holes  or  openings 
for  air  be  left — that  the  cask  itself  be  not  only  water-tight  but  air-tight — 
and  that  it  should  never  be  finally  closed  till  the  butter  has  shrunk  in  as 
far  as  it  is  likely  to  do,  and  until  the  vacancies,  which  may  have 
arisen  between  the  butter  and  the  cask,  have  been  carefully  filled  up 
again. 

§  17.   Of  the  natural  and  artificial  curdling  of  milk. 

When  milk  is  left  to  itself  for  a  certain  length  of  time  it  becomes  sour 
and  curdles.  The  curd  and  whey,  however,  do  not  readily  separate  un- 
less a  gentle  heat  be  applied,  when  the  curd  contracts  in  bulk,  and  either 
squeezes  out  and  floats  upon  the  whey,  or,  when  cut  into  pieces  or  placed 
in  a  perforated  cheese-vat,  allows  the  whey  freely  to  flow  from  it.  If 
the  mixed  curd  and  whey  from  the  entire  milk  be  allowed  to  simmer  for 
a  length  of  time  at  a  slow  fire,  the  buttery  part  will  separate  from  the 
cheese,  and  will  float  on  the  top  in  the  form  of  a  fluid  oil. 

1°.  Natural  curdling, — The  natural  curdling  of  milk  is  produced  by 
the  lactic  acid,  which,  as  we  have  seen  (j).  544),  is  always  formed  from 
the  milk-sugar  when  milk  is  allowed  to  stand  for  any  length  of  time  iu 
the  air.  It  does  not  curdle  immediately  upon  becoming  sour,  for  a  reason 
which  I  shall  presently  explain.  « 

2°.  Artificial  curdling. — But  it  is  not  usual  in  the  manufacture  of 
cheese  to  allow  the  milk  to  sour  and  curdle  of  its  own  accord.  The  pro- 
cess is  generally  hastened  by  the  artificial  addition  of  acid,  or  of  some 
substance,  such  as  rennet,  by  which  the  natural  production  of  acid  is  ac- 
celerated. Almost  any  acid  substance  will  have  the  effect  of  curdling 
milk.  Muriatic  acid  (spirit  of  salt),  diluted  with  water,  is  said  to  be  ex- 
tensively, though  not  universally,  employed  in  Holland  for  this  pur- 
pose.    In  other  countries  vinegar, f  tartaric  acid,  lemon  juice,  cream  of 

*  I  do  not  know  whether  a  converse  change  is  ever  observed  in  butter  by  long  keeping  in 
contact  with  brine— whether  it  ever  becomes  very  sensibly  harder.  Tallow,  as  is  well 
known  to  candle-makers,  and  especially  to  the  manufacturers  of  stearin  candles,  becomes 
harder  by  keeping,  indeed  sometimes  is  unfit  for  use  until  it  is  a  year  old— candles  in  a  damp 

Klace  become  harder  by  keeping — and  in  tallow  that  has  lain  long  in  a  wet  mine  the  oily  part 
as  been  found  entirely  changed  into  the  solid  fat  of  tallow  (Beetz)  A  similar  change, 
therefore,  is  not  impossible  nor  inexplicable  in  butter  also— only  if  it  ever  do  take  place,  we 
should  expect  the  changed  butter  to  be  less  solid  and  dense  than  before. 

t  "  To  coagulate  a  cotyla  of  milk  we  add  a  cyathus  of  sweet  vinegar"  (Dioscorides).  Milk 
is  also  curdled  by  ardent  spirits,  by  the  juice  of  the  fig,  and  by  a  decoction  of  the  flowers  of 
the  artichoke,  of  the  white  and  yellow  bed-straw  (gcdium),  and  of  the  crowfoot  (ranunculus 
Jlammula  and  lingula).  The  Tuscan  ewe-cheese  is  curdled  with  the  juice  of  the  fresh,  or 
with  a  decoction  of  the  dried  flowers  of  the  wild  thistle,  or  with  the  flowers  of  the  artichoke, 
which  gives  a  cheese  of  finer  colour  and  less  pungent  taste. 


NATURAL   AND    ARTIFICIAL    CcRDLING    OF   MILK.  567 

tartar,  and  salt  cf  sorrel  have  been  occasionally  used,  and  in  Switzerland 
— especially  in  the  manufacture  of  the  schabzieger  cheese — it  is  cus- 
tomary to  add  merely  a  little  sour  milk  for  the  purpose  of  producing  the 
curd. 

3°.  Chemical  action  of  the  acid. — But  how  does  the  acid  act  in  causing 
the  milk  to  curdle,  and  why  is  it  necessary  to  allow  a  little  time  to 
elapse  and  to  apply  ^Blso  a  gentle  heat  before  the  curd  will  completely 
separate  ? 

In  regard  to  casein  or  the  cheesy  matter  of  milk,  we  have  seen  (p. 
561)— 

a.  That  though  nearly  insoluble  in  pure  water,  it  dissolves  readily  in 
water  containing  in  solution  a  small  quantity  of  potash  or  soda,  either  in 
the  caustic  or  carbonated  state.  In  other  words  the  casein,  which  is  an 
acid  substance,  unites  chemically  with  the  potash  or  the  soda,  and  forms 
a  compound  ivhich  is  soluble  in  water. 

h.  That  when  an  acid  is  added  to  this  solution,  it  takes  the  potash  or 
soda  from  the  casein  and  combines  with  it,  leaving  the  curd  again  in  its 
original  insoluble  state,  and  causing  it,  therefore,  to  separate  from  the 
water. 

Now  in  milk,  as  it  comes  from  the  cow,  the  casein  is  in  chemical 
combination  with  a  small  quantity  of  soda,  by  which  it  is  rendered  so- 
luble in  the  water  of  which  the  milk  chiefly  consists.  When  the  milk 
stands  for  a  time  in  the  air,  the  sugar  of  milk,  as  we  have  seen,  is  trans- 
formed into  lactic  acid — this  acid  takes  the  soda  from  the  casein,  and 
forms  lactate  of  soda,  and  the  cheesy  matter,  in  consequence,  being  itself 
insoluble  in  water,  separates  in  the  form  of  curd.  The  application  of  a 
gentle  heat  acts  in  two  ways.  It  aids  the  acid  in  more  completely  taking 
the  soda  from  the  casein,  and  causes  the  latter  at  the  same  time  to 
shrink  in,  to  become  less  bulky,  and  thus  to  separate  readily  from  the 
whey. 

If  we  add  an  acid  artificially  to  milk,  the  effect  is  exactly  the  same. 
Either  muriatic  acid,  or  tartaric  acid,  or  vinegar,  or  sour  milk,  will,  in  the 
same  way,  take  the  soda  from  the  casein,  and  render  it  insoluble.  And 
that  this  is  the  true  action  is  readily  proved  by  adding  a  little  soda  to 
curdled  milk,  when  the  curd  will  be  re-dissolved,  and  the  milk  will  be- 
come sweet.  Add  acid  to  it  now,  or  let  it  sour  naturally  a  second  time, 
and  the  curd  will  again  be  separated. 

The  action  of  rennet  is  in  some  degree  different,  though  no  less  simple 
and  beautiful.  Let  us  first,  however,  consider  what  rennet  is,  and  how 
\{.  is  prepared. 

§  18.   Of  the  preparation  of  rennet. 

Rennet  is  prepared  from  the  salted  stomach  or  intestines  of  the  suck- 
ling calf,  the  unweaned  lamb,  the  young  kid,  or  the  young  pig.*  In 
general,  however,  the  stomach  of  the  calf  is  preferred,  and  there  are 
various  ways  of  curing  and  preserving  it. 

1°.  Preparing  the  stomach. — The  stomach  of  the  newly  killed  animal 
contains  a  quantity  of  curd  derived  from  the  milk  on  which  it  has  been 
fed.     In  most  districts  (Switzerland,  Gloucester,  Cheshire)  it  «6  usual  to 

•  Dried  pig's  bladder  is  often  employed  instead  of  the  dried  kid'a  stomach  for  curdling  the 
goat's  milk  on  Mont  Dor. 


568  METHODS    OF    MAKING    THE    RENNET. 

remove  by  a  gentle  washing  the  curd  and  slimy  matters  which  are  pre- 
sent in  the  stomach,  as  they  are  supposed  to  impart  a  strong  taste  to  the 
cheese.  In  Cheshire  the  curd  is  frequently  salted  separately  for  imme- 
diate use.  In  Ayrshire  and  Limburg,  on  the  other  hand,  the  curd  is 
always  left  in  the  stomach  and  salted  along  with  it.  Some  even  give 
the  calf  a  copious  draught  of  milk  shortly  before  it  is  killed,  in  order  that 
the  stomach  may  contain  a  larger  quantity  of  the  vfHuable  curd. 

2°.  Salting  the  stomach. — In  the  mode  of  salting  the  stomach  similar 
differences  prevail.  Some  merely  put  a  few  handfuls  of  salt  into  and 
around  it,  then  roll  it  together,  and  hang  it  near  the  chimney  to  dry. 
Others  salt  it  in  a  pickle  for  a  few  days,  and  then  hang  it  up  to  dry 
(Gloucester),  while  others  again  (Cheshire)  pack  several  of  them  in 
layers  with  much  salt  both  within  and  without,  and  preserve  them  in  a 
cool  place  till  the  cheese-making  season  of  the  following  year.  They 
are  then  taken  out,  drained  from  the  brine,  spread  upon  a  table,  sprinkled 
with  salt  which  is  rolled  in  with  a  wooden  roller,  and  then  hung  up  to 
dry.  In  some  foreign  countries,  again,  the  recent  stomach  is  minced  very 
fine,  mixed  with  some  spoonfuls  of  salt  and  bread-crumb  into  a  paste, 
put  into  a  bladder,  and  then  dried.  In  Lombardy  the  stomach,  after 
being  salted  and  dried,  is  minced  and  mixed  up  with  salt,  pepper,  and  a 
little  whey  or  water  into  a  paste,  which  is  preserved  for  use.  [Cattaneo, 
II  latte  e  i  suoi  prodotti,  p.  204.] 

In  whatever  way  the  stomach  or  intestine  of  the  calf  is  prepared  and 
preserved,  the  almost  universal  opinion  seems  to  be,  that  it  should  be 
kept  for  10  or  12  months  before  it  is  capable  of  yielding  the  best  and 
strongest  rennet.  If  newer  than  12  months,  the  rennet  is  thought  in 
Gloucestershire  "  to  make  the  cheeses  heave  or  swell,  and  become  full 
of  eyes  or  holes."  [British  Husbandry,  ii.,  p.  420.] 

3°.  Making  the  rennet. — ^^In  making  the  rennet  different  customs  also 
prevail.  In  some  districts,  as  in  Cheshire,  a  bit  of  the  dried  stomach  is 
put  into  half  a  pint  of  lukewaim  water  with  as  much  salt  as  will  lie 
upon  a  shilling,  is  allowed  to  stand  over  night,  and  in  the  morning  the 
infusion  is  poured  into  [he  milk.  For  a  cheese  of  601bs.  weight,  a  piece 
of  the  size  of  half-a-crown  will  often  be  sufficient,  though  of  some  skins 
as  much  as  10  square  inches  are  required  to  produce  the  same  effect  [Dr. 
Holland.] 

It  is  perhaps  more  common,  however,  to  take  the  entire  stomach 
{dried-maws,  veils,  reeds,  or  yirning*  they  are  often  called),  and  to  pour 
upon  them  from  one  to  three  quarts  of  water  for  each  stomach,  and  to 
allow  them  to  infuse  for  several  days.  If  only  one  has  been  infused,  and 
the  rennet  is  intended  for  immediate  use,  the  infusion  requires  only  to  be 
skimmed  and  strained.  But  if  several  maw-skins  be  infused — or,  as  is 
the  custom  in  Cheshire,  as  many  as  have  been  provided  for  the  whole 
season — about  two  quarts  of  water  are  taken  for  each,  and,-  after  stand- 
ing not  more  than  two  days,  the  infusion  is  poured  off,  and  is  completely 
saturated  with  salt.  During  the  summer  it  is  constantly  skimmed,  and 
fresh  salt  added  from  time  to  time.     Or  a  strong  brine  may  at  once 

*  In  Northumberland  fhedrted  stomach  is  sometimes  called  the  kealap,  which  ie  evidently 
the  German  kdse-lab,  cheese-rennet.  Loppert  and  lajrpert^  applied  in  Northumberland  and 
the  West  of  Scotland  respectively  to  sour,  curdled  milk,  is  derived  from  the  same  German 
lab,  rennet,  or  laber,  to  coagulate. 


THEORY    OF    THE    ACTION    OF    RENxNET.  569 

be  poured  upon  the  skins,  and  the  infusion,  when  the  skins  are  taken 
out,  may  be  kept  for  a  length  of  time.  Some  even  recommend  that 
the  liquid  rennet  should  not  be  used  until  it  is  at  least  two  months  old. 
When  thus  kept,  however,  it  is  indispensable  that  the  water  should  be 
fully  saturated  with  salt. 

In  Ayrshire,  and  in  some  other  counties,  it  is  customary  to  cut  the 
dried  stomach  into  small  pieces,  and  to  put  it,  with  a  handful  or  two  of 
salt  and  one  or  two  quarts  of  water,  into  a  jar,  to  allow  it  to  stand  for  two 
or  three  days,  afterwards  to  pour  upon  it  another  pint  for  a  couple  of  days, 
to  mix  the  two  decoctions,  and,  when  strained,  to  bottle  the  whole  for 
future  use.     In  this  state  it  may  be  kept  for  many  months.* 

In  all  the  methods  above  described,  the  exhausted  skins  are  thrown 
away.  Where  they  are  cut  into  pieces,  as  in  Cheshire  and  Ayrshire, 
they  cannot  of  course  be  put  to  any  second  use,  but  where  they  are  steeped 
whole,  there  is  ever}'  reason  to  believe  that  they  might  be  used  with  al- 
most equal  advantage  a  second  or  even  a  third  time.  Accordingly,  it 
has  long  been  the  custom  in  the  north  of  England  to  re-salt  the  stomach 
after  it  has  been  once  steeped,  and  when  long  dried,  as  before,  to  use  it 
a  second  and  even  a  third  time  for  the  preparation  of  rennet.  When  we 
explain  the  mode  in  which  rennet  acts,  you  will  see  that  the  same  skin 
may,  with  good  reason,  be  expected  to  yield  a  good  rennet,  after  being 
salted  again  and  again  for  an  indefinite  number  of  times. 

In  making  rennet,  some  use  pure  water  only,  others  prefer  clear  whey, 
others  a  decoction  of  leaves — such  as  those  of  the  sweetbriar,  the  dog- 
rose,  and  the  bramble — or  of  aromatic  herbs  and  flowers,  while  others, 
again,  put  in  lemons,  cloves,  mace,  or  brandy.  These  various  practices 
are  adopted  for  tli^e  purpose  of  making  the  rennet  keep  better,  of  lessen- 
ing its  unpleasant  smell,  of  preventing  any  unpleasant  taste  it  might 
give  to  the  curd,  or  finally  of  directly  improving  the  flavour  of  the  cheese. 
The  acidity  of  the  lemon  will,  no  doubt,  increase  also  the  coagulating 
power  of  any  rennet  to  which  it  may  be  added. 

4°.  Hoiv  the  rennet  is  used. — The  rennet  thus  prepared  is  poured  into 
the  milk  previously  raised  to  the  temperature  of  90°  or  95°  F.,  and  is 
intimately  mixed  with  it.  The  quantity  which  it  is  necessary  to  add 
varies  with  the  quality  of  the  rennet — from  a  table-spoonful  to  half  a 
pint  for  .30  or  40  gallons  of  milk.  The  time  necessary  for  the  complete 
fixing  of  the  curd  varies  also  from  15  minutes  to  an  hour  or  even  an  hour 
and  a  half.  The  chief  causes  of  this  variation  are  the  temperature  of  the 
milk,  and  the  quality  and  quantity  of  the  rennet  employed. 

But  how  does  the  rennet  act  in  causing  this  coagulation?  Before 
we  can  answer  this  question  it  is  necessary  to  encjuire  what  rennet 
really  is. 

§  19.   Theory  of  the  action  of  rennet. 

It  has  been  stated,  and  hitherto  almost  generally  received,  that  the  only 
effective  substance  contained  in. rennet  is  the  gastric  juice  derived  from 
the  stomach  of  the  calf.     To  this  persuasion  is,  no  doubt,  -to  be  ascribed 

• 

*  A  table-spoonful  of  this  rennet,  according  to  Mr.  Aiton,  will  coagulate  30  gallons  of  milk, 
nod  will  curdle  it  in  five  or  ten  minutes,  whereas  the  English  rennet  requires  from  one  to 
three  hours.  This  superiority  he  ascribes  to  the  custom  of  leaving  the  curdled  milk  in  the 
stomach.    He  denies  also  that  this  milk  gives  nay  harsh  taste  to  the  cheese. 


570  THE  SUBSTANCE  OF  THE  STOMACH  CHANGES 

the  custom  both  of  preserving  the  natural  contents  of  the  stomach — and 
of  generally  throwing  away  the  bag  after  being  once  salted,  dried,  and 
extracted.  The  gastric  juice  which  exudes  from  the  interior  surface  of 
the  stomachs  of  all  animals  is  known  to  curdle  milk  readily,  and,  there- 
fore, it  was  natural  to  ascribe  the  action  of  rennet  to  the  presence  of  this 
substance,  and  to  infer  that,  oeing  once  extracted,  it  was  in  vain  to  ex- 
pect much  advantage  from  salting  and  infusing  the  membrane  a  second 
time.     But  the  three  facts — 

a.  That  in  most  places  it  is  customary  to  wash  the  interior  of  the 
stomach  before  salting  it,  and  thus  to  remove  the  greater  part  of  the  gas- 
tric juice  it  may  contain  ; 

6.  That  besides,  in  many  places,  the  lags  are  laid  up  in  brine  for 
weeks  and  months,  and  are  then  drained  out  of  this  brine  before  they  are 
dried — by  which  any  gastric  juice  remaining  must  be  almost  entirely  re- 
moved,— and 

c.  That  after  being  (hied  and  steeped  once  for  the  preparation  of  ren- 
net, experience  has  proved  that  they  may  again  be  salted  and  used  over 
again  ; 

— these  three  facts,  I  think,  shew  that  the  efficacy  of  rennet  does  not  de- 
pend upon  any  thing  originally  contained  in  the  stomach,  hut  upon 
something  derived  from  the  substance  of  the  stomach  itself 

Now  when  considering  the  properties  of  milk-sugar  and-of  lactic  acid, 
1  have  stated  that  if  a  piece  of  the  fresli  membrane  of  the  stomach  or  in- 
testine, or  even  of  the  bladder  of  an  animal,  be  exposed  to  the  air  for  a 
few  days,  and  be  then  immersed  into  a  solution  of  milk-sugar,  it  will 
gradually  transform  the  sugar  into  lactic  acid.  In  milk  this  membrane 
would  produce  a  similar  eftect,  aiding  and  hastening  the  natural  souring 
and  curdling  effect  of  the  casein.  By  exposure  to  the  air,  the  surface  of 
the  membrane  has  undergone  such  a  degree  of  change  or  decomposition, 
as  enables  it  to  induce  the  elements  of  the  sugar  to  alter  their  mutual 
arrangement,  and  to  unite  together  in  such  a  way  as  to  form  lactic  acid. 

If  the  moist  membrane  be  exposed  for  a  longer  time  to  the  air  this 
change  of  its  surface  will  penetrate  deeper,  and  it  will  become  more  ef- 
fective in  inducing  the  transformation  of  the  sugar  into  lactic  acid.  But, 
at  the  same  time,  a  portion  of  its  surface  may  run  into  a  state  of  putre- 
faction, and  besides  accpiiring  a  disagreeable  odour  may  become  capable 
also  of  bringing  on  fermentation  and  putrefactive  decay  in  the  solutions 
upon  which  it  may  be  made  to  act.  It  is  not  expedient,  therefore,  to  at- 
tempt to  heighten  the  transforming  effect  of  animal  membranes  by 
exposing  them  for  a  greater  length  of  !.me  to  the  air  in  a  moist  and  fresh 
state. 

But  if  the  membrane  be  salted,  au.l  thus  preserved  from  the  rapid 
action  of  the  air,  it  will  be  protected  from  putrefaction  in  a  great  degree, 
while,  at  the  same  time,  it  will  undergo  that  gradual  change  upon  its 
surface  to  which  its  power  of  transforming  solutions  of  sugar  is  ascribed. 
And  this  change  will  be  materially  hastened  and  increased  and  made  to 
penetrate  deeper,  if  the  salted  membrane  be  subsequently  dried  slowly 
in  the  air  by  a  gentle  heat,  and  be^afterwards  kept  for  a  length  of  time 
where  the  air  has  more  or  less  ready  access  to  it.  Such  is  the  mode  of 
treatment  to  whicli  the  calf's  stomach  is  subjected  for  the  preparation  of 
rennet,  and  it  is  an  important  practical  observation  that  the  membrane 


WHEN    EXPOSED    A    SHORT    TIME    TO    THE    AIR  571 

should  be  kept  at  least  12  months,  if  it  is  to  acquire  very  powerful 
coagulating  properties. 

It  is  necessary  further  to  remind  you  that  when  malt  is  steeped  in 
water  for  a  few  minutes,  a  substance,  named  diastase,  is  extracted  from 
it,  which  possesses  the  remarkable  property  of  clianging  starch  into 
sugar  in  a  very  short  time,  and  in  large  quantity  (p.  119).  Now  if  this 
diastase  be  exposed  to  the  air  for  a  length  of  time,  it  undergoes  a  change 
similar  to  that  experienced  by  the  surface  of  animal  membranes,  and 
acquires  the  property  of  transforming  sugar  into  lactic  acid.  After  un- 
dergoing this  change  it  still  disscjives  readily  in  water,  and  if  a  solution 
of  it  be  poured  into  one  of  sui»ar,  the  transformation  of  the  latter  into  lactic 
acid  gradually  proceeds.  There  exist,  therefore,  substances  soluble  in 
water,  which  possess  the  same  power  as  slightly  decayed  but  insoluble 
animal  membrane,  of  converting  sugar  into  lactic  acid. 

During  the  protracted  drying  and  decay  of  the  salted  stomach,  the 
change  undergone  at  length  by  the  surface  of  the  membrane  is  such  as  to 
produce  a  ([uantity  of  matter  capable  of  dissolving  in  water,  and  which 
also  possesses  the  property  of  quickly  converting  the  sugar  into  the  acid 
of  milk.  This  matter,  water  extracts  from  the  dried  skin,  and  it  forms 
the  active  ingredient  in  rennet. 

I  need  not  further  explain  to  you  upon  what  this  activity  depends — 
since  as  you  already  know  any  thing  which  will  rapidly  change  sugar 
into  lactic  acid,  will  also,  if  gently  warmed,  rapidly  curdle  milk  (p. 
567). 

Thus  the  action  of  rennet  resolves  itself  simply  into  a  curdling  of  milk 
by  the  action  of  its  own  acid.  It  is  the  same  thing  as  when  sour  milk 
in  Switzerland  is  at  once  mixed  with  that  from  which  the  cheese  is  to  be 
made ;  or  it  is  only  a  more  speedy  way  of  bringing  about  the  curdhng 
that  takes  place  when  milk  sours  naturally  and  is  then  gently  warmed 
till  the  curd  separates. 

But  how,  it  may  be  asked,  is  the  coagulation  effected  so  much  more 
rapidly  by  the  action  of  rennet  than  when  the  milk  is  left  to  sour  of  its 
own  accord  ?  It  is  because  the  whole  of  the  animal  matter  in  the  rennet 
is  already  in  the  state  in  which  it  easily  transforms  the  sugar  into  acid, 
and  being  intimately  mixed  with  the  whole  milk  in  a  warm  state,  it  pro- 
duces acid  near  every  particle  of  the  cheesy  matter.  From  this 
cheesy  matter  the  acid  formed  takes  away  the  soda  that  holds  it  in  solu- 
tion, and  thus  renders  it  insoluble  or  curdles  the  milk.  In  milk,  on  the 
other  hand,  which  is  left  to  sour  and  curdle  of  itself,  the  casein  must  first 
be  changed  by  the  action  of  the  air  before  it  can  transform  the  sugar  and 
produce  acid.  This  change  takes  place  more  or  less  slowly,  and  chiefly 
at  the  surface  of  the  milk  where  it  is  in  contact  with  the  air.  The  sour- 
ing, therefore,  must  also  proceed  slowly,  and  the  curdling  of  which  it  is 
the  cause. 

It  is  no  objection  to  this  explanation  of  the  action  of  rennet,  that  neither 
the  milk  nor  the  whey  become  sensibly  sour  during  the  separation  of  the 
curd.  The  acid,  as  it  is  produced,  combines  directly  with  the  soda  pre- 
viously united  to  the  curd,  and  renders  the  latter  insoluble — while,  if 
any  excess  of  acid  do  happen  to  be  formed,  it  is  in  great  part  taken  up 
and  retained  mechanically  by  the  curd,  and  thus  is  not  afterwards  sen- 
sibly perceived  in  the  whey. 


572  USE    OF    THE    CURD    FOUND    IN    THE    CALF's    S\   JMACE 

Using  the  same  skin  a  second  lime. — If  this  then  be  a  true  explanation 
of  the  action  of  rennet — if  the  coajijulating  ingredient  in  it  be  merely  a 
portion  of  the  changed  niembianoof  the  stomach  itself — it  is  obvious  that 
the  bag,  after  being  once  used,  may  be  again  salted  and  dried  with  ad- 
vantage. The  slow  decay  may,  after  a  second  salting,  become  still 
slower,  and  thus  it  may  require  to  be  longer  kept  after  the  second  than 
after  the  first  salting,  before  it  will  give  a  rennet  as  poweriul  as  that 
which  was  first  extracted  from  it.  But  txuless  it  be  merely  the  inner 
membrane  of  the  stomach  and  intestines  which  is  capable  of  undergoing 
that,  kind  of  change  upon  which  the  coagulating  power  depends,  there  is 
no  apparent  reason,  as  I  have  already  sta*ed  to  you,  why  the  same 
maiv-  skin  may  not  be  salted,  dried,  and  steeped  many  times  over. 

Use  of  whey. — Again,  in  the  making  of  rennet  there  seems  some  pro- 
priety ui  the  use  of  whey  rather  than  of  water.  The  whey  may  contain 
a  portion  of  the  rennet  which  had  been  adJed  to  the  milk  from  which 
it  was  extracted,  and  may  thus  be  able  of  itself  to  curdle  milk.  It  is 
sure  also  to  contain  some  milli-sugar,  which,  being  changed  into  acid 
when  the  whey  is  poured  upon  the  dried  stomach,  will  add  to  the  coag- 
ulating power  of  the  rennet  obtained. 

Use  of  the  curdled  milk  contained  in  the  stomach. — Docs  the  view  we 
have  taken  of  the  action  of  rennet  throw  any  light  upon  the  use  of  the 
curdled  milk  fijund  in  the  stomach  ?  Is  it  of  any  service,  or  ought  it  to 
be  rejected? 

We  are  certain  that  it  must  be  of  service  m  coagulating  milk,  since  in 
Cheshire,  according  to  Dr.  Holland,  it  is  frequently  taken  out  and  salted 
by  itself  for  immediate  use.  But  a  slight  consideration  of  the  properties 
of  casein,  as  I  have  already  stated  them  to  you  (p.  562),  will  explain 
why  this  curdy  matter  should  be  serviceable  for  such  a  purpose. 

You  will  recollect  that  casein,  after  being  exposed  to  the  air  for  a  short 
time,  acquires,  like  animal  membranes,  the  property  of  converting  sugar 
into  lactic  acid  (p.  562),  and  of  curdling  milk.  Now  the  curdy  matter 
taken  from  the  stomach  of  the  calf,  after  being  exposed  to  the  air,  ac- 
quires this  property  as  completely  as  a  more  pure  curd  will  do.  If  salted 
and  kept,  it  will  be  changed  still  further,  and  will  acquire  this  property 
in  a  greater  degree.  In  short,  keeping  will  affect  the  curd  precisely  in 
the  same  way  as  it  does  the  membrane  of  the  stomach  itself,  and  will 
render  it  alike  fit  to  be  employed  in  the  preparation  of  rennet.  Nor  is 
it  unlikely  that  fresh  well-s(pieezed  curd,  if  mixed  with  much  salt  and 
kept  in  slightly  covered  jars  for  10  or  12  months,  might  yield  a  rennet 
possessed  of  good  coagulating  properties. 

It  thus  appears  that,  so  far  as  economy  is  concerned,  the  curdy  matter 
contained  in  the  calfs  stomach  ought  to  be  preserved  and  salted  for  use. 
If  in  any  district  this  curd  be  suspected  to  impart  an  unpleasant  flavour 
to  the  cheese,  this  bad  effect  may  probably  be  remedied  by  taking  it  out 
of  the  stomach,  washing  it  well  with  water — as  is  done  in  some  dairy 
districts — mixing  it  with  salt,  and  then  returning  it  into  the  stomach 
again. 

Another  practical  conclusion  may  also  be  drawn  from  this  explanation 
of  the  action  of  the  stomach.  Since  it  is  the  membrane  alone  that  acts, 
there  can  no  loss  accrue  by  carefully  washing  the  stomach  as  well  as 
the  curd  it  contains.     On  the  contrary,  by  so  doing  we  may  remov« 


CHEESE   OP   DIFFERENT    QUALITIES — HOW    OBTAINED.  573 

from  its  inner  surface  some  substances  which,  if  allowed  to  remain,  might 
afterwards  act  injuriously  upon  the  flavour  or  upon  tlie  other  qualities  of 
the  cheese. 

§  20.  Of  the  ^circumstances  by  which  the  quality  of  cheese  is  affected. 

All  cheese  consists  essentially  of  the  curd  mixed  with  a  certain  por- 
tion of  the  fatty  matter  and  of  the  sugar  of  milk.  But  differences  in  the 
quality  of  the  milk,  in  the  proportions  in  which  the  several  constituents 
of  milk  are  mixed  together,  or  in  the  general  mode  of  dairy  manage- 
ment, give  rise  to  varieties  of  cheese  almost  without  number.  Nearly 
every  dairy  district  produces  one  or  more  qualities  of  cheese  peculiar  to 
itself.  It  will  not  be  without  interest  to  attend  briefly  to  some  of  these 
causes  of  diversity. 

1°.  Natural  differences  in  the  milk. — It  is  obvious  that  whatever  gives 
rise  to  natural  differences  in  the  quality  of  the  milk  must  affect  also  that 
of  the  cheese  prepared  from  it.  If  the  milk  be  poor  in  butter,  so  must 
the  cheese  be.  If  the  pasture  be  such  as  to  give  a  milk  rich  in  cream, 
the  cheese  will  partake  of  the  same  quality.  If  the  herbage  or  other  food 
affect  the  taste  of  the  milk  or  cream,  it  will  also  modify  the  flavour  of  the 
cheese. 

2°.  Milk  of  different  animals. — So  the  milk  of  different  animals 
will  give  cheese  of  unlike  qualities.  The  ewe-milk  cheeses  of  Tuscany, 
Naples,  and  Languedoc,  and  those  of  goat's  milk  made  on  Mont  Dor 
and  elsewhere,  are  celebrated  for  qualities  which  are  not  possessed  by 
cheeses  prepared  from  cow's  milk  in  a  similar  way.  Buffalo  milk  also 
gives  a  cheese  of  peculiar  qualities,  which  is  manufactured  in  some  parts 
of  the  Neapolitan  territory. 

Other  kinds  of  cheese  agam  are  made  from  mixtures  of  the  milk  of  dif- 
f&ren*  animals.  Thus  the  strong  tasted  cheese  of  Lecca  and  the  cele- 
brated Roquefort  cheese  are  prepared  from  mixtures  of  goat  with  ewe- 
milk,  aiid  the  cheese  of  Mont  Cenis*  from  both  of  these  mixed  with  the 
milk  of  the  cow.f 

3°.  Creamed  or  uncreamed  milk. — Still  further  differences  are  pro- 
duced according  to  the  proportion  of  cream  which  is  left  in  or  is  added  to 
the  milk.  Thus  if  cream  only  be  employed,  we  liave  the  rich  cream- 
cheese  which  must  be  eaten  in  a  comparatively  recent  state.  Or,  if  the 
cream  of  the  previous  night's  milking  be  added  to  the  new  milk  of  the 
morning,  we  may  have  such  cheese  as  the  Stilton  of  England,  or  the 
small,  soft,  and  rich  Brie  cheeses,  so  much  esteemed  in  France.  If  the 
entire  milk  only  be  used,  we  have  such  cheeses  as  the  Cheshire,  the 
Double  Gloucester,  the  Cheddar,  the  Wiltshire,  and  the  Dunlop  cheeses 
of  Britain,  the  Kinnegad  cheese,  I  believe,  of  Ireland,  and  the  Goudaand 
Edam  cheeses  of  Holland.  Even  here,  however,  it  makes  a  difference 
whether  the  warm  milk  from  the  cow  is  curdled  alone,  as  at  Gouda  and 
Edam,  or  whether  it  is  mixed  with  the  milk  of  the  evening  before,  as  is 
generally  done  in  Cheshire  and  Ayrshire.  Many  persons  are  of  opin- 
ion that  cream,  which  has  once  been  separated,  can  never  be  so  well 
'• 
*  Lecca  U  a  province  in  the  Eastern  pail  of  the  Neapolitan  territory  ;  Roquefort,  a  town 
in  the  pastoral  department  of  Aveiron,  in  the  South  of  France,  famed  for  its  sheep;  and 
Mont  Cenis,  a  mountain  in  Savoy, 
t  The  milk  of  2  goats  is  mixed  with  that  of  20  sheep  and  5  cows. 


574  BUTTER-MILK,    WHET,     iND    VEGETABLE    CHEESES. 

mixed  again  with  the  milk,  that  a  portion  of  the  fatty  matter  shall  not 
flow  out  with  the  whey  and  render  the  cheese  less  rich. 

If,  again,  the  cream  of  the  evening's  milk  be  removed,  and  the  skim- 
med milk  added  to  the  new  milk  of  the  next  morning,  such  cheeses  as 
the  Si7igle  Gloucester  are  obtained.  If  the  cream  be  taken  once  from 
all  the  milk,  the  better  kinds  of  skimmed-milk  cheese,  such  as  the  Dutch 
cheese  of  Leyden,  are  prepared — while  if  tlie  milk  be  twice  skimmed, 
we  have  the  p(X)rer  cheeses  of  Friesland  aiid  Groningen.  If  skimmed 
for  three  or  four  days  in  succession,  we  get  the  hard  and  horny  cheeses 
of  Essex  and  Sussex,  which  often  require  the  axe  to  break  them  up. 

4°.  Butter-tuilk  cheese. — But  poor  or  butterless  cheese  will  also  differ 
in  quality  according  to  the  state  of  the  milk  from  which  it  is  extracted. 
If  the  new  milk  be  allowed  to  stand  to  throw  up  its  cream,  and  this  be 
then  removed  in  the  usual  way,  the  ordinary  skimmed-milk  cheese  will 
be  obtained  by  adding  rennet  to  die  milk.  But  if,  instead  of  skimming, 
we  allow  the  milk  to  stand  till  it  begins  to  sour,  and  then  remove  the 
butter  by  churning  the  whole,  we  obtain  the  milk  in  a  sour  state  {butter- 
milk). From  this  milk  tlie  curd  separates  naturally  by  gentle  heating. 
But  being  thus  prepared  from  sour  milk  and  without  the  use  of  rennet, 
butter-milk  cheese  differs  more  or  less  in  quality  from  that  which  is  made 
from  sweet  skimmed  milk. 

The  acid  in  the  butter-milk,  especially  after  it  has  stood  a  day  or  two, 
is  capable  of  coagulating  new  milk  also,  and  thus,  by  mixing  more  or 
less  sweet  milk  with  the  butter-milk  before  it  is  warmed,  several  other 
qualities  of  mixed  butter  and  sweet  ndlk  cheese  may  readily  be  manu- 
factured. 

If,  as  is  stated  by  Mr.  Ballantyne,  the  churning  of  the  whole  milk 
gives  butter  in  larger  quantity,  of  better  quality,  and  more  uniformly 
throughout  the  whole  year  (j).  553),  the  manufacture  of  these  butter-milk 
cheeses  is  deserving  of  the  attention  of  dairy  farmers,  especially  in  those 
districts  where  butter  is  considered  as  the  most  important  produce. 

5°.  Whey-cheese. — The  whey  which  separates  from  the  curd,  and 
especially  the  white  whey,  which  is  pressed  out  towards  the  last,  contains 
a  portion  of  curd,  and  not  unfrequently  a  considerable  quantity  of  butter 
also.  When  the  whey  is  heated,  the  curd  and  butter  rise  to  the  surface, 
and  are  readily  skimmed  off.  This  curd  alone  will  often  yield  a  clieese 
oC  excellent  quality,  and  so  rich  in  butter,  that  a  very  good  imitation  of 
Stilton  cheeee  may  sometimes  be.  made  with  alternate  layers  of  new 
milk-ciml  and  this  curd  of  whey. 

6°.  Mixtures  of  vegetable  substances  with  the  milk. — New  varieties 
of  cheese  are  formed  by  mixing  vegetable  substances  with  the  curd.  A 
green  decoction  of  two  parts  of  sage-leaves,  one  of  marigold,  and  a  little 
parsley,  gi^es  its  colour  to  the  green  cheese  of  Wiltshire  ;  some  even  mix 
up  the  entire  leaves  with  the  curd.  The  celebrated  Schabzieger  cheese 
of  Switzerland  is  made  by  crushing  the  ski'm-milk  cheese  after  it  is  se- 
veral mondis  old  to  fine  powder  in  a  mill,  mixing  it  then  with  one-tenth 
of  its  weight  of  fine  salt  and  one-twentieth  of  the  powdered  leaves  of  the 
mellilot  trefoil  {trifoliwn  melilotvs  cerulea),  and  afterwards  with  oil  or 
butter — working  the  whole  into  a  paste,  which  is  pressed  and  carefully 
dried. 

Potato  cheeses,  as  they  ara  calloi,  are  made  in  various  ways.     One 


TEMPERATURE    AND    IIKATINQ    OE    THE    MILK.  575 

pound  of  sour  milk  is  mixed  with  five  pounds  of  boiled  potatoes  and  a 
little- salt,  and  the  whole  is  beat  into  a  pulj),  which,  after  standing  five  or 
six  days,  is  worked  up  again,  and  then  dried  in  the  usual  way.  Others 
mix  three  parts  of  drie.l  boiled  potatoes  with  two  of  fresh  curd,  or  equal 
weights,  or  more  curd  than  potato  according  to  the  quality  required. 
Such  cheeses  are  made  in  Thuringia,  in  Saxony,  and  in  other  parts  of 
Germany.  In  Savoy,  an  excellent  cheese  is  made  by  mixing  one  of  the 
pulp  of  potatoes  with  three  of  ewe  milk  curd,  and  in  Westphalia  a  po- 
tato cheese  is  made  with  skimmed  milk.  This  Weslphalian  cheese, 
while  in  the  pasty  state,  is  allowed  to  undergo  a  certain  extent  of  fer- 
mentation before  it  is  finally  worked  up  with  butter  and  salt,  made  into 
shapes  and  dried.  The  extent  to  vvhicli  thisferij^entation  is  permitted  to 
go  determines  tUe  flavour  of  the  cheese. 

§  21.   Circumstances  under  ivhich  cheese  of  different  quqlities  may  he 

obtained  from  the  same  milk. 
But  from  the  same  milk,  in  the  same  state,  dilTe rent  kinds  or  qualities 
of  clieese  may  be  prepared  according  to  tlie  way  in  which  the  milk  or 
the  curd  is  treated.     Let  us  consider  also  a  few  of  the  circumstances  by 
which  this  result  may  be  brought  about. 

1°.  Temperature  to  which  the  milk  is  heated. — The  temperature  of  new 
or  entire  milk,  when  the  rennet  is  added,  should  be  raised  to  about  95*^  F. 
— that  of  skimme.l  milk  need  not  be  quite  so  high.  If  the  milk  be 
warmer  the  curd  is  hard  and  tough,  if  colder,  it  is  soft  and  difficult  to  ob- 
tain free  from  the  whey.  When  the  former  happens  to  be  the  case,  a 
portion  of  the  first  whey  that  sepaiates  may  be  taken  out  into  another 
vessel,  allowed  to  cool,  and  then  poured  in  again.  If  it  prove  to  have 
been  too  cold,  hot  milk  or  water  may  be  added  to  it — or  a  vessel  contain- 
ing hot  water  may  be  put  into  it  before  the  curdling  commences — or 'the 
first  portion  of  whey  that  separates  may  be  heated  and  poured  again 
upon  the  curd.  The  quality  of  the  cheese,  however,  will  always  be 
more  or  less  affected  when  it  happens  to  be  necessary  to  adopt  any  of 
these  remedies.  To  make  the  best  cheese,  the  true  temperature  should 
always  be  attained  as  nearly  as  possible,  before  the  rennet  is  added. 

2".  Mode  in  which  the  milk  is  warmed. — If,  as  Is  the  case  in  some 
dairies,  the  milk  be  warmed  in  an  iron  pot  upon  the  naked  fire,  great  care 
must  be  taken  that  it  is  not  singed  or  jire-fanged.  A  very  slight  inat- 
tention may  cause  this  to  be  the  case,  and  the  taste  of  the  cheese  is  sure 
to  be  more  or  less  atfected  by  it.  In  Cheshire  the  milk  is  put  into  a  large 
tin  pail,  which  is  plunged  into  a  boiler  of  hot  water,  and  frequently  stir- 
red till  it  is  raised  to  the  proper  temperature.  In  large  dairy  establish- 
ments, however, the  safest  method  is  to  have  a  pot  with  a  double  bottom, 
consisting  of  one  pot  within  anodier-^after  the  manner  of  a  glue-pot — the 
space  between  the  two  being  filled  with  water.  The  fire  applied  be- 
neath thus  acts  only  upon  the  water,  and  can  never,  by  any  ordinary 
neglect,  do  injury  to  the  milk.  It  is  desirable  in  this  heating,  not  to  raise 
the  temperature  higher  than  is  necessary,  as  a  great  heat  is  apt  to  give 
an  oiliness  to  the  fatty  matter  of  the  milk. 

3*^.  The  time  during  which  the  curd  stands  is  also  of  importance.  It 
shot.  Id  be  broken  up  as  soon  as  the  milk  is  fully  coagulated.  The  longer 
it  stands  after  this  the  harder  and  tougher  it  w?    become. 


676  QUALITY    AND    QUANTITY    OF    TF «    RENNET. 

4°.  The  quality  of  the  rennet  is  of  much  importance  not  only  in  regEird 
to  tlie  certainty  ot"  the  coagulation,  but  also  to  the  flavour  of  the  cheese. 
In  some  parts  of  Cheshire,  as  we  have  seen,  it  is  usual  to  take  a  piece 
of  the  dried  membrane  and  steep  it  overnight  with  a  little  salt  for  the 
ensuing  morning's  milk.  It  is  thus  sure  to  be  fresh  and  sweet  if  the 
dried  maiu  be  in  good  preservation.  But  where  it  is  customary  to  steep 
several  skins  at  a  time,  and  to  bottle  the  rennet  for  after-use,  it  is  very 
necessary  to  saturate  the  solution  completely  with  salt  and  to  season  it 
with  spices,  in  order  that  it  may  be  preserved  in  a  sweet  and  wholesome 
state.  In  some  parts  of  Scotland  the  rennet  is  said  to  be  frequently  kept 
in  bottles  till  it  is  almost  putrid,  and  in  this  state  is  still  put  into  the  milk. 
Such  rennet  may  not  orjy  impart  a  bad  taste  to  the  cheese,  but  is  likely 
also  to  render  it  more  difficult  to  cure  and  to  bring  on  putrefaction  after- 
wards and  a  premature  decay. 

5°.  The  qu0ntiti/  of  rennet  added  ought  to  be  regulated  as  carefully 
as  the  temperature  of  the  milk.  Too  much  renders  the  curd  tough  ;  too 
little  causes  the  loss  of  much  time,  and  may  permit  a  larger  portion  of 
the  butter  to  separate  itself  from  the  curd.  It  is  to  be  expected  also  that 
when  rennet  is  used  in  great  excess,  a  portion  of  it  will  remain  in  the 
curd,  and  will  naturally  afifect  the  kind  and  rapidity  of  the  changes  it 
afterwards  undergoes.  Thus  it  is  said  to  cause  the  cheese  to  heave  or 
swell  out  from  fermentation.  It  is  probable  also  that  it  will  affect  the 
flavour  which  the  cheese  acquires  by  keeping.  Thus  it  may  be  that  the 
agreeable  or  unpleasant  taste  of  the  cheeses  of  certain  districts  or  dairies 
may  be  less  due  to  the  quality  of  the  pastures  or  of  the  milk  itself,  than 
to  the  quantity  of  rennet  with  which  it  has  there  been  customary  to  co- 
agulate the  milk. 

6°.  The  way  in  which  the  rennet  is  made,  no  less  than  its  state  of  pre- 
servation and  the  quantity  employed,  may  also  influence  the  flavour  or 
other  qualities  of  the  cheese.  For  instance,  ia  the  manufacture  of  a 
celebrated  French  cheese — that  of  Epoisse — the  rennet  is  prepared  as  fol- 
lows : — Four  fresh  calf-skins,  with  the  curd  they  contain,  are  well 
washed  in  water,  chopped  into  small  pieces,  and  digested  in  a  mixture 
of  5  quarts  of  brandy  with  15  of  water,  adtling  at  the  same  time  21  lbs. 
of  salt,  half  an  ounce  of  black  pepper,  and  a  quarter  of  an  ounce  each 
of  cloves  and  fennel  seeds.  At  the  end  of  six  weeks  the  liquor  is  filtered 
and  preserved  in  well  corked  bottles,  while  the  membrane  is  put  into  salt- 
water to  form  a  new  portion  of  renriet.  For  making  rich  cheeses,  the 
rennet  should  always  be  filtered  clear.   [II  latte  e  i  suoi  prodotti,  p.  274.] 

Again,  on  Mont  Dor,  the  rennet  is  made  with  white  wine  and  vinegar. 
An  ounce  of  common  salt  is  dissolved  in  a  mixture  of  half  a  pint  of 
vinegar  with  2j  pints  of  white  wine,  and  in  this  solution  a  prepared 
goat's  stomach  or  a  piece  of  dried  pig' s  bladder  is  steeped  for  a  length  of 
time.  A  single  spoonful  of  this  rennet  is  said  to  be  sufficient  for  45  or 
50  quarts  of  milk.  No  doubt  the  acid  of  the  vinegar  and  of  the  wine  aid 
the  coagulating  power  derived  from  the  membrane. 

Rennets  prepared  in  the  above  ways  must  affect  the  flavour  of  the 
cheese  differently  from  such  as  are  obtained  by  the  several  more  or  less 
careful  methods  usually  adopted  in  this  country. 

7°.  Wlien  acids  are  used  alone — as  vinegar,  tartaric  acid,  and  muria- 
tic acid  sometimes  arc — for  coagulating  tlie  milk,  the  flavour  of  the 


now    THE   WHEY    IS    SEPARATED.  677 

cheese  can  scarcely  fail  to  be  in  some  measure  different  from  that  which 
is  prepared  with  ordinary  rennet. 

8°.  The  way  in  which  the  curd  is  treated. — It  is  usual  in  our  best 
cheese  districts  carefully  and  slowly  to  separate  the  curd  from  the  whey — 
not  to  hasten  the  separation,  lest  a  larger  portion  of  the  fatty  matter  should 
be  squeezed  out  of  the  curd  and  the  cheese  should  thus  be  rendered  poorer 
than  usual.  But  in  some  places  the  practice  prevails  of  washing  the 
curd  with  hot  water  after  the  whey  has  been  partially  separated  from  it. 

Thus  at  Gouda  in  Holland,  after  the  greater  part  of  the  whey  has  been 
gradually  removed,  a  quantity  of  hot  water  is  added,  and  allowed  to  re- 
main upon  it  for  at  least  a  quarter  of  an  hour.  The  heat  makes  the 
cheese  more  solid  and  causes  it  to  keep  better. 

In  Italy,  again,  the  so-called  pear-shaped  cacdo-cavallo  cheeses  and 
the  round  palloni  cheeses  of  Gravina,  in  the  Neapolitan  territory,  are 
made  from  curd,  which,  after  being  scalded  with  boiling  whey,  is  cut  into 
slices,  kneaded  in  boiling  water,  worked  with  the  hand  till  it  is  perfectly 
tenacious  and  elastic,  and  then  made  into  shapes.  The  water  in  which 
the  curd  is  washed,  after  standing  24  hours,  throws  up  much  oily  mat- 
ter, which  is  skimmed  off'  and  made  into  butter. 

The  varieties  of  cheese  prepared  by  these  methods  no  doubt  derive  the 
peculiar  characters  upon  which  their  reputation  depends  from  the  treat- 
ment to  which  the  curd  is  subjected — but  it  is  obvious  that  none  of  them 
can  be  so  rich  as  a  cheese  from  the  same  milk  would  be,  if  manufactured 
in  a  Cheshire,  a  Wiltshire,  or  an  Ayrshire  dairy. 

9°.  The  separation  of  the  whey  is  a  part  of  the  process  upon  which  the 
quality  of  the  cheese  in  a  considerable  degree  depends.  In  Cheshire 
more  time  and  attention  is  devoted  to  the  perfect  extraction  of  the  whey 
than  in  almost  any  other  district.  Indeed,  when  it  is  considered  that  the 
whey  contains  sugar  and  lactic  acid,  which  may  undergo  decomposition, 
and  a  quantity  of  rennet  which  may  bring  on  fermentation — by  both  of 
which  processes  the  flavour  of  the  cheeses  must  be  considerably  affected 
— it  will  appear  of  great  importance  that  the  whey  should  be  as  com- 
pletely removed  from  the  curd  as  it  can  possibly  be.  To  aid  in  effecting 
this  a  curd-mill,  for  chopping  it  fine  after  the  whey  is  strained  off",  is  in 
use  in  many  of  the  large  English  dairies,  and  a  very  ingenious,  and  I 
believe  effectual,  pneumatic  cheese-press  for  sucking  out  the  whey  was 
invented  by  the  late  Sir  John  Robinson,  of  Edinburgh.  [Transactions 
and  Prize  Essays  of  the  Highland  Society,  vol.  x.,  p.  204.] 

But  the  way  in  which  the  whey  is  separated  is  not  a  matter  of  indif- 
ference, and  has  much  influence  upon  the  quality  of  the  cheese.  Thus 
in  Norfolk,  according  to  Marshall,  when  the  curd  is  fairly  set,  the  dairy- 
maid bares  her  arm,  plunges  it  into  the  curd,  and  with  the  help  of  her 
wooden  ladle  breaks  up  minutely  "and  intimately  mixes  the  curd  with  the 
whey.  This  she  does  for  10  or  15  minutes,  after  which  the  curd  is  al- 
lowed to  subside,  and  the  whey  is  drawn  off".  By '  this  agitation 
the  whey  must  carry  off"  more  of  the  butter  and  the  cheese  must  be 
poorer. 

In  Cheshire  and  Ayrshire,  again,  the  curd  is  cut  with  a  knife,  but  1%: 
gently  used  and  slowly  pressed  till  it  is  dry  enough  to  be  chopped  fine,  an:', 
thus  more  of  the  oily  matter  is  retained.  On  the  same  principle,  in  making 
the  Stilton  cheese,  the  curd  is  not  cut  or  broken  at  all,  but  is  pressed 


578  RIND    OF    SALT,    AND    HOW    IT    IS    APPLIED. 

gently  and  with  care  till  the  whey  gradually  drains  out.  Tlius  the  butter 
and  the  curd  remain  intermixed,  and  the  rich  cheese  of  Siiltori  is  the  result. 

Thus  you  will  see  that  while  ii  is  of  importance  that  all  the  whey 
should  be  extracted  from  the  curd,  yet  that  the  (juickest  way  may  not  be 
the  best.  More  time  and  care  must  be  bestowed  in  order  to  effect  this 
object,  the  richer  the  cheese  we  wish  to  obtain.  You  will  see,  also,  how 
the  quality  of  the  milk  or  of  the  pastures  may  often  be  blamed  for  de- 
ficiencies in  the  richness  or  other  qualities  of  our  cheese,  which  are 
in  reality  due  to  slight  but  material  differences  in  our  mode  of  manufac- 
turing it. 

10°.  The  kind  of  salt  used  is  considered  by  many  to  have  some  effect 
upon  the  taste  of  the  cheese.  Thus  the  cheese  of  Gerome,  in  the  Vos- 
ges,  is  supposed  to  derive  a  peculiar  taste  from  the  Lorena  salt  with 
which  it  is  cured.  In  Holland,  also,  the  efficacy  of  one  kind  of  salt 
over  another  for  the  curing  of  cheese  is  generally  acknowledged,  [British 
Husbandry,  ii.,  p.  424.]  It  is  indeed  not  unlikely  that  the  more  or  less 
impure  salts  of  different  localities  may  affect  the  flavour  of  the  cheese, 
but  wherever  the  salt  may  be  manufactured,  it  is  easy  to  obtain  it  in  a 
uniform  and  tolerably  pure  state,  by  the  simple  process  of  purification, 
which  I  have  already  described  to  you  (p.  565.) 

11°.  The  mode  in  which  the  salt  is  applied. — In  making  the  large 
Cheshire  cheeses  the  dried  curd,  for  a  single  cheese  of  60  lbs.,  is  broken 
down  fine  and  divided  into  three  equal  portions.  One  of  these  is 
mingled  with  double  the  quantity  of  salt  added  to  the  others,  and  this 
is  so  put  into  the  cheese-vat  as  to  form  the  central  part  of  the  cheese. 
By  this  precaution  the  after-salting  on  the  surface  is  sure  to  penetrate 
deep  enough  to  cure  effectually  the  less  salted  parts.  In  the  counties  of 
Gloucester  and  Somerset  the  curd  is  pressed  without  salt,  and  the  cheese, 
when  formed,  is  made  to  absorb  the  whole  of  the  salt  afterwards  through 
its  surface.  This  is  found  to  answer  well  with  the  small  and  thin 
cheeses  made  in  these  counties,  but  were  it  adopted  for  the  large  cheeses 
of  Cheshire  and  Dunlop,  or  even  for  the  pine-apple  cheeses  of  Wiltshire, 
there  can  be  no  doubt  that  their  quality  would  frequently  be  injured.  It 
may  not  be  impossible  to  cause  salt  to  penetrate  into  the  very  heart  of  a 
large  cheese,  but  it  cannot  be  easy  in  this  way  to  salt  the  whole  cheese 
equally,  while  the  care  and  attention  re(}uired  must  be  greatly  increased. 

12°.  Addition  of  cream  or  butter  to  the  curd. — Another  mode  of  im- 
proving the  quality  of  cheese  is  by  the  addition  of  cream  or  butter  to  the 
dried  and  crumbled  curd.  Much  diligence,  however,  is  required  fully 
to  incorporate  these,  so  that  the  cheese  may  be  uniform  throughout.  Still 
this  practice  gives  a  peculiar  character  to  the  cheeses  of  certain  districts. 
In  Italy  they  make  a  cheese  after  the  manner  of  the  English.,  [II  latte  e  i 
suoi  prodotti,  p.  277],  into  which  a  considerable  quantity  of  butter  is 
worked;  and  the  Reckem  cheese  of  Belgium  is  made  by  ad.  ing  half  an 
ounce  of  butter  and  the  yoke  of  an  egg  to  every  pound  of  pressed  curd. 

13°.  The  colouring  matter  added  to  the  cheese  is  thought  by  many  to 
affect  its  quality.  In  foreign  countries  saffron  is  very  generally  used  to 
give  a  colour  to  the  milk  before  it  is  coagulated.  In  Holland  and  in 
Cheshire  annatto  is  most  commonly  employed,  while  in  other  dis- 
tricts the  marigold  or  the  carrot,  boiled  in  milk,  a??  the  usual  colouring 
matters. 


MODE    OF    CURING    THE    CHEESE.  679 

The  quantity  of  annatto  employed  is  comparatively  small — less  tlian 
naif  an  ounce  to  a  cheese  of  60  lbs. — but  even  this  quantity  is  considered 
by  many  to  be  an  injurious  admixture.  Hence  a  native  of  Cheshire 
prefers  the  uncoloured  cheese,  the  annatto  being  added  to  such  only  as 
are  intended  for  the  London  or  other  distant  markets. 

14°.  Size  of  the  cheese. — From  the  same  milk  it  is  obvious  that  cheeses 
of  different  sizes,  if  treated  in  the  same  way,  will  at  the  end  of  a  given 
number  of  months  possess  qualities  in  a  considerable  degree  different*. 
Hence,  without  supposing  any  inferiority,  either  in  the  milk  or  in  the  ge- 
neral mode  of  treatment,  the  size  usually  adopted  for  the  cheeses  of  a 
particular  district  or  dairy,  may  be  the  cause  of  a  recognized  inferiority 
in  some  quality  which  it  is  desirable  that  they  should  pn«;sess  in  a  high 
degree. 

15°.  The  method  of  curing  has  very  much  influence  upon  the  after- 
qualities  of  the  cheese.  The  care  with  which  they  are  salted — the 
warmth  of  the  place  in  which  they  are  kept  during  the  first  two  or  three 
weeks — the  temperature  and  closeness  of  the  cheese-room  in  which  they 
are  afterwards  preserved — the  frequency  of  turning,  of  cleaning  from 
mould,  and  of  rubbing  with  butter — all  these  circumstances  exercise  a 
remarkable  influence  upon  the  after-f|ualities  of  the  cheese.  Indeed,  in 
very  many  instances  the  high  reputation  of"  a  particular  dairy  district  or 
dairy  farm  is  derived  from  some  special  attention  to  one  or  other  or  to  all 
of  the  appajrently  minor  points  to  which  I  have  just  adverted. 

In  Tuscany,  the  cheeses,  after  being  hung  up  for  some  time  at  a  proper 
distance  from  the  fire,  are  put  to  ripen  in  an  underground  cool  and  damp 
cellar;  and  the  celebrated  French  cheeses  of  Roquefort  are  supposed  to 
owe  much  of  the  peculiar  estimation  in  which  they  are  held,  to  the  cool 
and  uniform  temperature  of  the  subterranean  caverns  in  which  the 
inhabitants  of  the  village  have  long  been  accustome;!  to  preserve  them. 

In  Ros^hire  it  is  said  to  be  the  custom  with  some  proprietors  to  bury 
their  cheeses  under  the  sea  sand  at  low  water,  and  that  the  action  of 
the  sea- water  in  this  situation  renders  them  more  juicy  and  of  an  exquisite 
flavour. 

16°.  Ammoniacal  cheese. — The  influence  of  the  mode  of  curing  upon 
the  ([uality  is  shown  very  strikingly  in  the  small  ammoniacal  cheeses  of 
Brie,  which  are  very  much  esteemed  in  Paris.  They  are  soft  unpressed 
cheeses,  which  are  allowed  to  ripen  in  a  room  the  temperature  of  which 
is  kept  between  60°  and  70°  F.  till  they  begin  to  undergo  the  putrefac- 
tive fermentation  and  emit  an  ammoniacal  odour.  They  are  ge- 
nerally unctuous,  and  sometimes  so  small  as  not  to  weigh  more  than  an 
ounce. 

A  little  consideration,  indeed,  will  satisfy  you,  that  by  varying  the 
mode  of  curing,  and  especially  the  temperature  .at  which  they  are  kept, 
you  may  produce  an  almost  endless  diversity  in  the  quality  of  the  cheeses 
you  bring  into  the  market. 

17°.  Inoculating  cheese. — It  is  said  that  a  cheese,  possessed  of  no 
very  striking  taste  of  its  own,  may  be  inoculated  with  any  flavour  we 
approve  of,  by  putting  into  it  with  a  scoop  a  small  portion  of  the  cheese 
which  we  are  desirous  that  it  should  be  made  to  resemble.  Of  course 
this  can  apply  ouly  to  cheeses  otherwise  of  equal  richness,  for  we  could 
scarcely  expect  to  give  a  single  Gloucester  the  flavour  of  a  Stilton, 


6^  AVERAGE    QUANTITY    OF   ClIEl.r;.    YIELDED. 

by  merely  putting  into  it  a  small  portion  of  a  rich  and  esteemed  Stilton 

cheese. 

§  22.   Of  the  average  quantity  of  cheese  yielded  by  different  varieties  of 
milk,  and  of  the  produce  of  a  single  cow. 
There  appear  to  be  very  great  differences  in  the  proportions  of  cheese 
yielded  by  milk  at  different  seasons  and  in  different  localities. 
.     In  milk,  of  an  average  quality,  there  are  contained  from  4  to  5  percent, 
of  casein  or  dry  cheesy  matter  (p.  534), which,  if  all  extracted,  would  give — 
6  lbs.  to  7  lbs.  of  skimmed  milk  cheese,  or  )  from  100  lbs.  of 
9  lbs.  to  10  lbs.  of  entire  milk  cheese,  ^  milk. 

This  is  very  nearly  the  proportion  actually  obtained  in  some  of  the 
best  dairy  districts  in  the  summer  season.     Thus — 

In  Ayrshire — 10  lbs.  of  milk,  or   )  gave  1  lb.  of  whole  milk 
1  im])erial  gallon,  ^  cheese  ; 

or  136  wine  quarts  gave  127 j^  lbs.  of  cheese  three  months  old.* 

In  Gloucester — 7  lbs.  of  milk,  or  )  gave  1  lb.  of  double 
3^  wine  quarts,      ^  Gloucester  ; 

this  is  a  much  larger  proportion,  and  is  probably  much  above  the  average 
of  the  county. 

In  Holstein,  it  is  said  that  100  lbs.  of  milk  will  give  about — 

New  skimmed  milk  cheese 6  lbs. 

Butter        3|  " 

Butter-milk 14    *' 

Whey 76^  " 


100  lbs. 

But  this  statement  is  so  far  indefinite  that  it  affords  us  no  means  of 
judging  how  much  curd  is  left  in  the  butter-milk,  nor  how  much  water 
was  present  in  the  new  cheese.  Indeed,  most  of  the  statements  on  record 
are  deficient  in  this  respect,  that  the  dryness  of  the  cheese  is  not  accu- 
rately expressed. 

In   Cheshire,  the  average  produce  of  a  cow  is  reckoned  at  360  lbs.  of 
whole  milk  cheese,  or  about  1  lb.  per  day  for  the  whole  year.     Taking 
8  wine  quarts  of  milk  as  the  average  daily  yield  of  a  cow  in  that  county, 
we  have  as  the  average  produce  of  the  milk  the  whole  year  through-— 
1  lb.  of  cheese  from  8  wine  quarts,  or  16  lbs.  of  milk. 

It  is  indeed  undoubted,  that  the  proportion  of  cheese  varies  very 
much  with  the  season  of  the  year  and  with  the  dryness  of  the  weather. 
Though,  therefore,  in  summer  7  or  8  lbs.  of  milk  may  sometimes  yield 
a  pound  of  cheese,  it  is  possible  that  as  much  as  20  lbs.  of  milk  may  at 
other  seasons  be  required  to  give  the  same  quantity.     Thus  in — 

South  Holland,  the  summer  produce  of  a  cow  is  reckoned  at  about  200 
lbs.  of  skimmed  milk  cheese,  and  80  lbs.  of  butter ;  or  in  a  week  10  lbs. 
of  skiiumed  milk  cheese,  and  4  to  7  lbs.  of  butter.  Of  whole  milk 
cheese  some  expect  as  much  as  3  or  4  Ihs.  a  day. 

*  Mr.  Alexander,  of  Southbar,  informs  me  that,  the  result  of  his  experience  with  a  dairy 
of  40  cows  in  the  higher  part  of  Ayrshire,  near  Muirkirk,  is,  that— 

90  imperial  quarts  of  sweet  milk  ijive  an  Ayrshire  stone  of  24  lbs.  of  full  milk  cheese, 
while  the  same  quantity  of  skim  milk  gives  oniy  16  lbs.  of  skimmed  milk  cheese.  That  is 
very  nearly— 

9  lbs.  of  new  milk  give  1  lb.  of  full  milk  cheese. 

14  lbs.  of  skim-milk  give  1  lb.  of  skim- milk  cheese  (see  p.  585). 


MlIiK   SPIRIT    AND    MILK    VINEGAR.  681 

In  Switzerland,  generally,  a  cow,  giving  12  quarts  of  millt  a  day  will, 
during  the  summer,  yield  a  daily  produce  of  1^  lbs.  of  whole  or  full  milk 
cheese — or  10|  quarts  of  milk,  about  21  lbs.,  will  give  a  pound  of  cheese. 

In  the  high  pastures  of  Snaria,  again,  in  the  same  country,  one  cow 
will  give  for  the  90  days  of  summer  about  60  lbs.  of  skiuimed-milk 
cheese  and  40  lbs.  of  batter — or  11  ounces  of  cheese  per  day. 

It  appears,  therefore,  as  we  should  otherwise  expect,  that  the  average 
produce  of  cheese  is  affected  by  many  circumstances — but  that  in  this 
country  8  to  10  lbs.  of  good  milk,  in  the  summer  season,  will  yield' ow« 
pound  of  ivhole  milk  cheese. 

§  23.   Of  the  fermented  liqiurr  from  milk,  and  of  milk  vinegar. 

Milk  is  capable  of  undergoing  what  is  called  the  vinous  fermentation, 
and  of  yielding  an  intoxicating  liquor.  The  Tartars  prepare  such  a 
liquor  from  mare's  milk,  to  which  the  name  of  kou7niss  is  given.  When 
made  from  cow's  milk  it  is  called  airen,  and  is  less  esteemed  because 
generally  of  a  weaker  quality.  The  Arabians  and  Turks  prepare  a  si- 
milar liquor,  which  the  former  call  leban,  and  the  latter  yaourt.  In  the 
Orkney  Islands,  and  in  some  parts  of  the  north  of  Scotland  and  Ireland, 
butter-milk  is  sometimes  kept  till  it  undergoes  the  vinous  fermentation, 
and  acquires  intoxicating  qualities. 

It  is  the  sugar  contained  in  milk  which,  by  the  fermentation,  is  changed 
into  alcohol.  As  mare's  milk,  like  that  of  the  ass,  contains  more  sugar 
(p.  534)  than  that  of  the  cow,  it  gives  a  stronger  liquor,  and  is  therefore 
naturally  preferred  by  the  Tartars.  By  distillation  ardent  spirits  are  ob- 
tained from  koumiss,  and  when  carefully  made  in  close  vessels,  a  pint  of 
the  liquor  will  yield  half  an  ounce  of  spirit.  The  koumiss  is  prepared  in 
the  following  manner : 

To  the  new  milk,  diluted  with  a  sixth  of  its  bulk  of  water,  a  quantity 
of  rennet,  or  what  is  better,  of  sour  koumiss,  is  added,  and  the  whole  is 
covered  up  in  a  warm  place  for  24  hours.  It  is  then  stirred  or  churned 
together  till  the  curd  and  whey  are  intimately  mixed,  and  is  again  left 
at  rest  for  24  hours.  At  the  end  of  this  time  it  is  put  into  a  tall  vessel, 
and  agitated  till  it  becomes  perfectly  homogeneous.  It  has  now  an  agree- 
able sourish  taste,  and  in  a  cool  place  may  be  preserved  for  several 
months  in  close  vessels.  It  is  always  shaken  up  before  it  is  drunk.  This 
liquor,  from  the  cheese  and  butter  it  contains,  is  a  nourishing  as  well  as 
an  exhilarating  drink,  and  is  not  followed  by  the  usual  bad  effects  of  in- 
toxicating liquors.  It  is  even  recommended  as  a  wholesome  article  of 
diet  in  cases  of  dyspepsia  or  of  general  debility. 

Milk  vinegar. — If  the  koumiss  be  kept  in  a  warm  place  the  spirit  dis- 
appears and  vinegar  is  formed.  In  some  parts  of  Italy  a  milk  vinegar 
of  pleasant  quality  is  prepared  by  adding  honey,  sugar,  spirit,  and  a  lit- 
tle yeast  to  the  boiled  whey,  and  setting  the  mixture  aside  to  ferment  in 
a  warm  place.     [II  latte  e  i  suoi  prodotti,  pp.  415  and  450.] 

§  24.   Of  the  composition  of  the  saline  constituents  of  milk 

"When  milk  is  boiled  down  to  dryness,  and  the  dry  residue  burned,  a 

small  quantity  of  ash   remains  behind.       The  proportion  which  the 

weight  of  this  ash  bears  to  that  of  the  whole  milk  is  variable — as  the 

qualities  of  the  milk  itself  are — so  that  1000  lbs.  will  leave  sometimes 

25 


582  USE  or  milk  in  the  animal  economy. 

only  2  lbs.,  at  others  as  much  as  7  lbs.  of  ash.-  This  ash  consists  of  a 
mixture  of  common  salt  and  chloride  of  potassium  (p.  188),  with  the 
phosphates  of  lime,  magnesia,  and  iron.  The  relative  proportions  of 
these  several  substances  yielded  by  1000  lbs.  of  the  railk  of  two  dif- 
ferent cows,  were  as  follows  [Haidlen,  Annal.  der  Chem.  und  Phar., 
xiv.,  p.  273]  : 

I.  II. 

Phosphate  of  lime 2-31  lbs.  3-44  lbs. 

Phosphate  oi"  magnesia     .     .     .     0-42     "  0-64     " 

Phosphate  of  peroxide  of  iron      .     0-07     "  0'07     ♦' 

Chloride  of  potassium  ....     1-44     "  1-83     " 

Chloride  of  sodium 0-24     "  0-34     '* 

Free  soda 0-42     "  0-45     " 

4-90     "  6-77     " 

It  is  probable  that  the  phosphates  and  chlorides  existed  as  such  in  the 
milk  as  it  came  from  the  cow,  the  free  soda  is  believed  to  have  been  in 
combination  with  the  casein,  and  to  have  held  it  iti  solution  in  the  milk. 
You  will  recollect  that  the  explanation  I  have  given  of  the  curdling  of 
milk  is,  that  the  acid  produced  in,  or  added  to,  the  milk,  takes  this  soda 
from  the  casein,  and  renders  it  insoluble  in  water,  and  that  in  conse- 
quence it  separates  in  the  form  of  curd  (see  p.  566). 

§  25.  Purposes  served  by  milk  in  the  animal  economy. 

Milk  is  the  food  provided  for  the  young  animal,  at  a  period  when  it  is 
unable  to  seek  food  for  itself.     It  consists,  as  we  have  seen,  of — 

1°.  The  casein  or  curd. — This  being  almost  identical  in  constitution 
with  the  lean  part  or  fibrin  of  the  muscles  serves  to  promote  the  growth 
of  the  flesh  of  the  animal. 

2°.  The  fat  or  butter^  which  is  mainly  expended  in  supplying  fat  to 
those  parts  of  the  body  in  which  fat  is  usually  deposited. 

3°.  The  sugar,  which  is  probably  consumed  by  the  lungs  during  re- 
spiration. 

4°.  The  saline  matter,  from  which  come  the  salts  contained  in  the 
blood,  and  the  earthy  part  of  the  bones  of  young  and  growing  animals 
fed  upon  milk. 

These  several  purposes  served  iH  milk  will  come  again  under  our 
consideration  in  the  following  lecture. 


NOTES. 
1°.  On  the  churning  of  butter  in  the  French  chum. 
Mr.  Burnett,  of  Gadgirth,  has  favoured  me  with  the  following  infor- 
mation regarding  the  merits  of  the  French  churn  mentioned  in  page 
555:— 

"  I  see  you  make  mention,  in  page  555  of  your  Lectures,  of  a  chum 
lately  introduced  by  Mr.  Blacker  from  France.  I  got  one  of  these  from 
Mr.  Blacker  about  two  years  ago,  and  have  proved  its  merits  to  be  very 
great.     I  use  none  else,  and  have  been  the  means  of  distributing  it  over 


CUURNINtt    IN    THE    FRENCH    CHURN.  583 

different  parts  of  England  and  Scotland.  It  is  made  of  tin,  of  a  barrel 
shape,  and  is  placed  in  a  trough  of  water,  heated  or  otherwise,  to  convey 
the  proper  temperature  to  the  cream.  I  have  tried  many  experi- 
ments to  ascertain  the  proper  temperature  for  churning  cream  in 
this  churn,  and  have  found  that  58°  F.  produces  the  best  quality  of  but- 
ter in  the  shortest  time — the  time  occupied  being  from  ten  to  twenty 
minutes.  At  60°  it  was  often  done  in  five  to  seven  minutes,  and  although 
a  little  soft  at  first,  produced  butter  of  a  good  colour  and  quality — on  no 
occasion  was  it  ever  white.  I  also  tried  56°  F.  It  took  generally  one 
hour,  was  harder,  but  no  better  in  quality  than  that  of  58°. 

"  With  regard  to  the  quantity  of  butter  from  a  given  quantity  of  cream, 
I  found  that  in  July,  when  the  cows  were  on  good  pasture,  and  occasion- 
ally house-fed  on  clover — 

16  quarts  of  cream  prod»uced     .     12  lbs.    8  oz. 

24       do.         do.  do.  .     16  lbs,  12  oz. 

30       do.         do.  do.  .     20  lbs.    8  oz. 


Or,  70  quarts  produced 49  lbs.  12  oz. 

When  fed  on  cabbage — 

50  quarts  of  cream  produced  .     .     32  lbs. 
Again — 

50  quarts  of  cream  produced  .     .     32  lbs.  4  oz. 
60     do.         do.  do.         .     .     40  lbs. 

Or  the  whole  six  quarts  of  cream  in  July  gave  4  lbs.  of  butter. 

"  On  churning  the  whole  milk  in  this  churn,  100  quarts  of  milk  at  60° 
produced  8  lbs.  of  butter  of  excellent  quality  in  one  hour  and  a  half — 8 
quarts  of  hot  water  were  put  into  the  churn  according  to  the  old  system. 

"  100  quarts  of  milk  from  the  same  cows  at  64°  produced  only  7  lbs. 
of  butter  of  a  soft  and  inferior  quality,  and  took  two  hours  to  churn,  16 
quarts  of  hot  water  being  put  into  the  churn  on  this  occasion. 

"  The  whole  milk  was  sometimes  churned  in  less  than  one  hour,  but 
from  that  to  one  hour  and  a  half  was  the  general  time  occupied,  whereas 
three  to  four  hours  is  the  time  occupied  in  churning  in  the  common  chum. 

"  To  ascertain  whether  the  whole  milk  or  the  cream  produced  the 
greatest  quantity  of  butter  in  this  churn,  I  took  the  milk  of  five  cows 
(Ayrshire  breed)  for  one  week  in  July  last,  amounting  to  508  quarts — 
the  yield  of  butter  was  36  lbs.  11  oz.  I  then  took  the  same  quantity  of 
milk  from  the  same  cows  for  the  same  period  of  time,  and  let  it  stand  for 
cream — the  butter  produced  was  37  lbs.  4  oz.  The  food  and  other  cir- 
cumstances were  quite  the  same. 

"  To  test  the  quality  of  my  butter,  I  sent  it  last  summer  to  a  show  at 
Ayr,  and  obtained  the  second  premium  both  for  fresh  and  salt ;  the  heat 
at  which  it  was  churned  was  58°,  and  the  time  not  exceeding  half  an 
hour." 

On  these  observations  of  Mr.  Burnett,  I  must  in  fairness  remark,  that 
several  other  persons  who  have  used  this  churn,  have  not  reported  by  any 
means  so  favourably  of  its  merits.  Perhaps  they  have  not  known  how 
to  manage  it  so  skilfully. 

2°.  Quantity  of  milk  and  butter  yielded  by  Ayrshire  cows. 
Mr.  Alexander,  of  Southbar,  has  furnished  me  with  the  following  pro- 


584  COMPARATIVK    PROFIT    OF 

portions  of  cream  and  butter  yielded  ly  his  dairy  of  38  cows,  at  Well- 
wood,  in  the  higher  part  of  Ayrshire,  near  Muirkirk,  during  six  several 
iays.  in  November  and  December,  1843  : — 

Cream  Butter 

Date.  in  imp.  galls.  in  pounds. 

November     1  ......  16  43^ 

7 19|  47^ 

14 18|  43 

21 21}  '47 

29 18  39 

December      7 19  43^ 

In  all 112^  galls,  gave.      263^ 

or,  seven  quarts  of  cream  in  November  gave  four  pounds  of  butter. 

The  cream  appears  from  the  table  to  have  become  gradually  less  rich, 
though  the  whole  quantity  did  not  diminish. 

Mr.  Alexander  remarks,  that  "  the  proportion  of  cream  varies  in  his 
dairy  from  |th  to  y\jth  of  the  bulk  of  the  milk,  and  that  the  Guernsey  or 
Highland,  or  any  black  or  black-marked  cow,  gives  more  cream  from  the 
same  quantity  of  milk."     That  is,  they  give  a  richer  milk. 

This  is  a  curious  physiological  fact,  and  is  probably  related  to  an  ob- 
servation made  in  the  fattening  of  these  races,  that  the  same  quantity  of 
food  goes  further  in  fattening  a  black  or  black-marked  than  a  dun  or  white 
beast.  I  do  not  suppose  that  any  thing  of  this  kind  has  been  observed  in  the 
Durham  breed — as  white  animals,  of  pure  blood,  are  often  great  favour- 
ites with  the  breeders  of  Tees-Water  stock. 

3°.  Profit  of  making  butter  and  cheese  compared  with  that  of 
selling  the  milk. 
For  the  following  particulars  I  am  also  indebted  to  Mr.  Alexander. 
The  produce  of  cheese  and  butter  is  the  average  of  his  experience  at 
Well  wood,  in  Ayrshire. 

There  are  three  ways  in  which  the  milk  is  usually  disposed  of.  It  is 
sold  in  the  state  of  new  milk,  or  it  is  made  into  full  milk  cheese,  and  the 
whey  given  to  pigs — or  it  is  made  into  butter,  and  the  skim-milk  sold,  or 
made  into  cheese,  or  given  to  pigs.  The  profit  of  each  of  these  three 
methods,  at  the  Ayrshire  prices,  is  as  follows  approximately  : — 

s.  d. 
a. — 90  quarts  of  new  milk,  at  2d.  a  quart,  are  sold  for  .  15  0 
b. — 90  quarts  of  new  milk  give  24  lbs.  of  full  milk  cheese, 

which,  at  4^d.,  per  lb.  are  sold  for         .         .         .         .90 
The  whey  is  worth,  at  least 0     6 

9  6 
c. — 90  quarts  of  milk,  churned  altogether,  give  9  lbs.  of  butter, 

at9d. 6     9 

90  quarts  of  butter-milk,  at  Id.  per  quart  .         .         .         .39 

10     6 
In  the  country,  where  the  butter-milk  cannot  be  sold,  it  is  given  to  the 
pigs,  and  does  not  yield  so  large  a  return. 


MAKIIVG    BUTTER  AND    CHEESE.  585 

S.    d. 
d.     90  quarts  of  new  milk  give  18  quarts  of  cream,  yielding 

9  lbs.  of  butter  at  9d.,  as  before 6     9 

18  quarts  of  butter-milk,  at  ^d 0     9 

70  quarts  of  skim-milk,  at  ^d. 2  11 

10  5 

When  the  skim-milk  cannot  be  sold,  it  may  be  given  to  the  pigs,  or 
it  may  be  made  into  skim-niilk  cheese.  In  the  latter  case  the  profit  is 
as  follows : — 

s.  d. 

e. — Butter  and  butter-milk,  as  before 7     6 

70  quarts  of  skim-milk  give  16  lbs.  of  cheese,  which,  at  3d. 

per  lb 4     0 

11  6 
Thus  we  have  90  quarts  of  milk — 

s.  d. 
a — sold  as  new  milk,  worth  .  .  .  .  15  0 
6 — made  into  full-milk  cheese     ....  96 

c — made  into  butter  and  butter-milk,  where  the  latter 

can  be  sold 10     6 

d — made  into  butter  and  skim-milk,  where  the  latter 

can  be  sold 10     5 

e — made  into  butter  and  skim-milk  cheese  .  .  11  .  6 
In  the  country,  therefore,  according  to  these  calculations,  the  most  pro- 
fitable way  is  to  make  butter  and  skim-milk  cheese^  The  farmer  is  thus 
in  a  great  measure  independent  of  an  adjoining  population.  The  small 
quantity  of  bulter-milk  he  thus  obtains  he  will  easily  be  able  to  dispose 
of,  or  otherwise  to  employ  to  advantage. 

According  to  Mr.  Ayton,  it  is  still  more  profitable  to  feed  calves  with 
the  milk,  but  I  find  many  people  differ  from  him  on  this  point.  At  all 
events,  a  good  and  ready  market  is  required  for  the  veal. 


LECTURE  XXI. 

Of  the  feeding  of  animals,  and  the  purposes  served  by  their  food.-~Substances  of  which  the 
parts  of  animal  bodies  consist. — Whence  do  the  animals  derive  these  substances— are 
they  all  present  in  the  food? — Use  of  the  starch,  gum.  and  sugar  contained  in  vegetable 
food.— Functions  of  a  full-grown  animal. — Of  the  respiration  of  animals. — General  origin 
and  purposes  served  by  the  fat  in  carnivorous  an  1  herbivorous  animals.— Of  the  digestive 
process  in  animals. — Purposes  served  by  food  and  digestion. — The  food  sustains  the  full- 
grown  animal. — Necessity  of  a  mixed  food. — It  sustains  and  increases  the  fattening  ani- 
mal.— Relative  fattening  powers  of  different  kinds  of  fooii.— How  circumstances  affect  this 
fattening  property.— Purposes  served  by  food  in  the  pregnant — in  the  yonng  and  growing 
animals,  such  as  the  calf— and  in  the  milk  cow. — Effect  of  different  kinds  of  food  on  the 
quality  of  the  milk. — Fattening  of  the  cow  as  the  milk  lessens  in  quantity — Experimental, 
economical,  and  theoretical  value  of  different  kinds  of  food  for  these  several  purposes. — 
Circumstances  which  affect  these  values. — Soil,  manure,  form  in  which  the  food  is  given, 
ventilation,  light,  warmth,  exeicise,  activity,  salt  and  other  condiments. 

Having  in  the  preceding  lectures  considered  tlie  composition  of  the 
direct  products  of  the  soil — grains,  roots,  ana  grasses — and  of  the  most 
important  indirect  products — milk,  butter,  and  cheese — the  only  part  of 
our  .subject  which  now  remains  to  be  discussed  is  the  relative  values  of 
these  several  products  in  the  feeding  of  animals. 

Under  this  head  it  will  be  necessary  to  enquire  how  far  these  values 
are  affected  by  the  age,  the  growth,  the  constitution,  and  race  of  the  ani- 
mal— by  the  purposes  for  which  it  is  fed — and  by  the  circumstances 
under  which  it  is  placed  while  the  food  is  administered  to  it. 

§  1.   O/*  the  substance  of  which  the  parts  of  animals  consist. 

The  bodies  of  animals  consist  of  solid  and  fluid  parts. 
1°.  The  solid  parts  are  chiefly  made  up  of  the  muscles,  the  fat,  and 
the  bones. 

a.  The  muscles^  in  their  natural  state,  as  I  have  already  had  occasion 
to  mention  (p.  444),  consist  in  100  parts  of  about — 

Dry  matter 23 

Water 77 

100 
so  that,  to  add  100  lbs.  to  the  weight  of  an  animal  in  the  form  of  muscle, 
only  23  lbs.  of  solid  matter  require  to  be  incorporated  with  its  system. 

When  the  muscular  or  lean  part  of  beef,  mutton,  &c.,  is  wa.shed 
in  a  current  of  water  for  a  length  of  time — the  blood,  to  which  the  red 
colour  is  owing,  and  all  the  soluble  substances,  gradually  disappear,  and 
the  muscle  becomes  perfectly  white.  In  this  state,  with  the  exception 
of  some  fatty  and  other  matters  which  still  remain  intermixed  with  it,  the 
white  mass  forms  what  is  known  to  chemists  by  the  name  of  fibrin. 
This  name  is  given  to  it  because  it  forms  the  fibres  which  run  along  the 
muscles  and  constitute  the  greater  portion  of  their  substance. 

The  following  table  exhibits  the  relative  proportions  of  muscular  fibre 
and  other  substances  contained  in  the  flesh  of  several  different  animals  in 
its  natural  .state,  [Schlossberger,  Annalen  der  Pharmacie,  December, 
1842,  p.  344]  :— 


'''''■         o    I.  1    t    i 


COMPOSITION    or    RECENT    MUSCLE.  687 

Calf. 

O        1°.     2°.        S        PS         a.        O        O 

Muscular  fibre,  vessels.nerres 

and  cellular  substance  .     .  17'5    150  162   16-8   18-0    ITO    16-5    120    11-1 

Soluble  albumen  and  colour-. 

ins.  matter  of  blood  (hema-  ^^ 

tosin) 2-2     3-2    26     24     23     45     3-0     52     4^4 

Alcoholic extractjcontaining  J   ^.^     ^.^     ^.^     ^.^  .         r^.Q     ^.4     ^.q"    1-6 
saline  matter S  > 24  ) 

Watery  extract,  containing  j   J. 3      ^.q    ^.q     q.q  (         i  1-5     1.2     1-7     0-2 
saline  matter ) 

Phosphate  of  lime,  with  a  lit- 
tle albumen* trace     01  trace  trace    0*4     —      0*6     —      22 

Water  and  loss 775   797  782  783  769   76-0  77-3   80-1   805 

100    100   100    100    100    100    100    100    100 

The  proportions  in  the  above  table  are  not  to  be  regarded  as  constant ; 
they  seem,  however,  to  shew  what  we  should  otherwise  expect,  that  the 
muscular  part  of  fishes  contains  a  less  proportion  of  fibrin  than  that  of 
land  animals  in  general. 

When  dried  beef  is  burned  it  leaves  about  4|  per  cent,  of  incombus- 
tible ash — or  100  lbs.  of  the  muscle  of  a  living  animal  in  its  natural 
state  contain  about  one  pound  of  saline  or  inorganic  matter. 

Of  this  inorganic  matter,  it  is  of  importance  to  know  that  about  two- 
thirds  consist  of  phosphate  of  Lime.  Thus  to  add  100  lbs.  to  the  muscular 
part  of  a  full  grown  animal,  there  must  be  incorporated  with  its  substance 
about — 

Water 77  lbs. 

Fibrin,  with  a  little  fat      .         .         22     " 


Phosphate  of  lime     . 
Other  saline  matters 


100 

6.  The  fat  of  animals  consists,  like  the  fat  of  butter,  of  a  solid  and 
fluid  portion.  The  fluid  fat  is  in  great  part  squeezed  out  when  the  whole 
is  submitted  to  powerful  pressure. 

The  fluid  portion  of  the  fat,  called  by  chemists  oleine,  so  far  as  it  has 
yet  been  examined,  appears  to  be  identical  in  all  animals.  It  is  also  the 
same  thing  exactly  as  the  fluid  part  of  olive  oil,  of  the  oil  of  almonds, 
and  of  the  oils  of  many  other  fruits.  It  exists  in  larger  quantity  in  the 
fat  of  the  pig  than  in  that  of  the  sheep,  and  hence  pork  fat  is  softer  than 
beef  or  mutton  suet.  From  lard  it  is  now  expressed  on  a  great  scale  in 
the  United  States  of  America,  for  burning  in  lamps  and  for  other  uses. 
The  manufacturers  of  stearine  candles  express  it  from  beef  and  mutton 
fat,  but  chiefly  for  the  purpose  of  obtaining  the  solid  part  in  a  harder 
state,  that  it  may  make  a  more  beautiful  and  less  fusible  candle.  The 
fluid  oil  of  animal  fats,  however,  is  known  to  differ  from  the  liquid  part 
of  butter  {butter-oil)  described  in  the  preceding  Lecture  (p.  559),  and 
from  the  fluid  part  of  linseed  and  other  similar  oils  which  dry,  and  form 

'  This  phosphate  of  lime  is  over  and  above  that  wrhich  exists  naturally  in,  and  is  insepar. 
able  from,  the  musculur  fibre  itself  a^d  from  the  albumen. 


588  OF    FAT,    AND    OF    WHAT    BONES    CONSIST. 

a  kind  of  varnish  when  exposed  to  the  air.  Tliese  latter  facts  are  not 
without  their  importance,  as  we  shall  hereafter  see. 

The  solid  part  of  the  fat  of  animals  is  known  to  vary  to  a  certain  ex- 
tent among  different  races.  Thus  the  solid  fat  of  man  is  the  same  with 
that  of  the  goose,  and  with  that  which  exists  in  olive  oil  and  in  butter. 
To  this  the  name  of  margarine  is  given.  But  the  solid  fat  of  the  cow, 
tffe  sheep,  the  horse,  and  the  pig,  differs  from  that  of  man,  and  is 
known  by  the  name  of  stearine. 

The  solid  and  fluid  parts  are  mixed  together  in  different  proportions  in 
the  fat,  not  only  of  different  animals,  but  of  the  same  animal  at  differ- 
ent periods,  and  in  different  parts  of  its  body.  Hence  the  greater  hard- 
ness observed  in  the  suet  than  in  other  portions  of  the  fat  of  beef  and  mut- 
ton, and  hence  also  the  different  quality  and  appearance  of  the  fat  of  an 
ox  according  to  the  kind  of  food  upon  which  it  has  been  fed  or  fattened. 

c.  T'he  hones,  Uke  the  muscles,  consist  of  a  combustible  and  an  incom- 
bustible portion,  but  in  the  bones  the  inorganic  or  incombustible  part  is 
by  much  the  greater.  To  the  organic  matter  of  bones  the  name  of  gel- 
atine or  glue  is  given,  and  it  can  be  partly  extracted  from  them  by  boil- 
ing. The  proportion  of  gelatine  which  exists  in  bones  varies  with  the 
kind  of  animal — widi  ihe  part  of  the  body  from  which  the  bone  is  taken 
— and  very  often  with  the  age  and  state  of  health  of  the  animal,  and  with 
the  way  in  which  it  has  been  accustomed  to  be  fed.  It  is  greater  in  spongy 
bones,  in  the  bones  of  young  animals,  and  probably  also  in  the  bones  of 
such  as  are  in  high  condition.  In  perfectly  dry  bone  it  rarely  exceeds 
from  35  to  40  per  cent,  of  the  whole  weight. 

The  incombustible  portion  consists  for  the  most  part  of  phosphate  and 
carbonate  of  lime.     The  relative  proportions  of  these  two  earthy  com- 
pounds also  vary  with  the  kind  of  animal,  with  its  age,  its  condition,  its 
food,  and  its  state  of  health.     To  form  100  lbs.  of  bone  the  animal  will 
usually  require  to  incorporate  with  its  own  substance  about — 
35  pounds  of  gelatine, 
55  pounds  of  phosphate  of  lime, 
4  pounds  of  carbonate  of  lime, 
3  pounds  of  phosphate  of  magnesia, 
3  pounds  of  soda,  potash,  and  common  salt. 

100 

d.  Hair,  horn,  and  wool,  are  distinguished  from  the  muscular  parts  of 
the  animal  body  by  the  large  proportion — about  five  per  cent. — of  sul- 
phur which  they  contain.  They  consist  of  a  substance  which  in  other 
respects  closely  resembles  gluten  and  gelatine  in  its  chemical  composi- 
tion (page  445).  When  burned,  they  leave  from  one  to  two  per  cent,  of 
ash,  which  in  the  case  of  a  variety  of  human  hair,  which  left  1-1  per  cent, 
of  ash,  was  fimnd  by  Van  Laer  to  consist  of — 

Per  cent. 

Soluble  chlorides  and  sulphates 0-51 

Oxide  of  iron 0-39 

Phosphate  and  sulphate  of  lime,  phosphate  of  magnesia  and  silica  .  0-20 

1-10 
The  inorganic  matter  contained  in  l.air  is  therefore,  generally  speak- 


OF   HAIR,    HORN,    AND    WOOL,    AND    OF   BLOOD.  589 

ing,  the  same  in  kind  as  that  which  exists  in  the  muscular  fibre  and  in 
the  bone.  It  contains  the  same  phosphate  of  lime  and  magnesia — the 
same  sulphates  and  the  same  chlorides,  among  which  latter  common  salt 
is  the  most  abundant.  The  absolute  quantity  of  ash  or  inorganic  matter 
varies,  as  well  as  the  relative  proportions  in  which  the  several  substances 
are  mixed  together  in  the  ditferent  solid  parts  of  die  body,  but  the  sub- 
stances themselves  of  which  the  inorganic  matter  is  composed  are  nearly 
the  same,  whether  they  be  obtained  from  the  bones,  from  the  muscles,  or 
from  the  hair. 

2°.  Of  the  jiaid parts  of  the  body,  the  blood  is  the  most  important, 
and  by  far  the  most  abuifdant.  The  body  of  a  full  grown  man,  of  mo- 
derate dimensions,  contains  about  12  lbs.  of  blood,  [Lehniaim,  Physi- 
ologische  Chemie,  I.,  pp.  113  and  338,]  that  of  a  full  grown  ox,  six 
times  as  heavy,  cannot  contain  less  than  70  or  80  lbs.  Blood  consists  of 
about — 

Per  cent. 

Water 80 

Organic  matter 19 

Saline  matter 1 

100 
The  organic  matter  consists  chiefly  o^  Jibrin,  which,  when  the  blood 
coagulates,  forms  the  greater  part  of  the  clot — and  of^  albumen,  which  re- 
mains dissolved  in  the  serum  or  fluid  part  of  clotted  blood,  but  which, 
like  the  white  of  egg,  runs  together  into  insoluble  clots  when  the  serum 
is  heated. 

The  saline  matter  remains  dissolved  in  the  serum  after  the  albumen 
has  been  separated  by  heating,  and  consists  chiefly  of  phosphates,  sul- 
phates, and  chlorides — nearly  the  same  compounds  as  exist  in  the  soluble 
part  of  the  ash  left  Ijy  the  solid  parts  of  the  body. 

Besides  this  soluble  saline  matter  which  remains  in  tlie  serum,  a  por- 
tion of  phosphate  of  lime  and  a  small  quantity  of  phosphate  of  magnesia 
exist  also  in  the  fibrin  and  in  the  albumen  of  the  blood.     Thus  in  the  dry 
state  these  substances  contain  respectively  of  the  mixed  phosphates- 
Albumen  of  ox  blood     .     .     .     .     1*8  per  cent.  }  /jy        i-      \ 
Fibrin  of  human  blood  ....     0-7  per  cent.  ^  V^erzeims.) 

Thus  the  same  saline  and  earthy  compounds,  which  form  so  large  a 
portion  of  the  bones,  are  distributed  every  where  in  sensible  proportions 
throughout  all  the  more  important  solids  and  fluids  of  the  body 

§  2.   Whence  does  the  body  obtain  these  substances  1    Are  they  contained 
in  the  food  ? 

Whence  does  the  body  derive  all  the  substances  of  which  its  several 
parts  consist  ? 

The  answer  to  this  question  appears  at  first  sight  to  be  easy.  They 
must  be  obtained  from  the  food.  But  when  the  enquiry  is  further  con- 
sidered, a  reply  to  it  is  not  so  readily  given. 

It  is  true,  indeed,  that  the  organic  part  of  the  food  contains  carbon, 
hydrogen,  oxygen,  and  nitrogen — the  elements  of  which  the  organic  parts 
of  tlie  body  are  composed.  The  in-organic  "flatter  also  which  exists  in 
25* 


690  WHENCE    THE    TAT   AND    BONES    OF   ANIMALS. 

the  food  contains  the  lime,  the  magnesia,  the  potash,  the  soda,  the  sul- 
phur, the  phosphorus,  and  the  iron,  which  exist  in  the  inorganic  parts  of 
the  animal  body — so  that  the  (question  seems  already  resolved.  The 
body  obtains  from  the  food  all  the  elements  of  which  it  consists,  and 
if  these  be  not  present  in  the  food,  the  body  of  the  animal  cannot  be 
properly  built  up  and  supported. 

But  to  the  chemist  and  physiologist  the  more  important  part  of  the 
question  still  remains.  In  what  slate  do  these  elements  enter  into  the 
body  ?  Are  the  substances  of  which  the  food  consists  decomposed  after 
they  are  taken  into  the  stomach  ?  Are  their  parts  first  torn  asunder,  and 
then  re-united  in  a  different  way,  so  as  to  form  the  chemical  compounds 
of  which  the  muscles,  bones,  and  blood  consist  ?  Are  the  vital  powers 
bound  to  labour,  as  it  were,  for  the  existence  and  support  of  the  body  ? 
Do  they  compound  or  build  up  out  of  their  ultimate  elements  the  various 
substances  of  which  the  body  is  composed — or  do  they  obtain  these  sub- 
stances ready  prepared  from  the  vegetable  food  on  which  animals,  in 
general,  are  fed  ?  The  answer  which  recent  chemical  researches  give  to 
this  second  question  forms  one  of  the  most  beautiful  contributions  which 
have  been  made  to  animal  physiology  in  our  time. 

1°.  We  have  seen  that  the  flour  of  wheat  and  of  our  other  cultivated 
grains  consists  in  part  of  gluten,  of  albumen,  or  of  casein.  These  sub- 
stances all  contain  nitrogen,  and  are  identical  in  constitution  with  each 
other,  and  with  the  fibrin  of  which  the  muscles  of  animals  chiefly  con- 
sist.* The  substance  of  the  muscles  exists  ready  formed,  therefore,  in  the 
food  which  the  animal  eats.  The  labour  of  the  stomach  is  in  conse- 
quence restricted  to  that  of  merely  selecting  these  substances  from  the 
food  and  dispatching  them  to  the  several  parts  of  the  body,  where  they 
are  required.  The  plant  compounds  and  prepares  the  materials  of  the 
muscles — the  stomach  only  picks  out  the  bricks,  as  it  were,  from  the  other 
building  materials,  and  sends  them  forward  to  be  placed  where  they 
happen  to  be  wanted. 

2°.  Again,  we  have  seen  that  in  all  our  crops,  so  far  as  they  have 
been  examined,  there  exists  a  sensible  proportion  of  fatty  or  oily  maru'r 
more  or  less  analogous  to  the  several  kinds  of  fat  which  exist  in  the  holies 
of  animals.  In  regard  to  this  portion,  therefore,  of  the  body,  the  vege- 
table performs  also  the  larger  part  of  the  labour.  It  builds  up  fatty  sub- 
stances out  of  their  elements — carbon,  hydrogen,  and  nitrogen.  These 
substances  the  stomach  extracts  from  the  food,  and  the  body  appropriates 
them,  after  they  have  been  more  or  less  slightly  changed,  in  order  to 
adapt  them  to  their  several  purposes.  There  may  possibly  be  othi^r 
sources  of  fat,  as  we  shall  hereafter  see,  but  the  simplest,  the  most  na- 
tural— and  probably,  where  a  sufficient  supply  exists,  the  only  one  had 
recourse  to  by  the  healthy  animal — is  the  fat  which  is  found,  re  idy 
formed,  in  the  vegetable  food  it  eats. 

3°.  Further,  the  bones,  the  muscles,  and  the  blood,  contain  phosphate 

"  The  chemical  reader,  who  is  aware  of  the  exact  state  of  our  knowledge  upon  this  sub- 
ject, will  perceive  that  I  speak  here  of  the  identity  of  these  substances  only  in  so  far  as  the 
proportions  of  carbon,  hydrogen,  oxygen,  and  nitrogen  are  concerned  Ii  is  unnecessa-y  to 
allude  in  this  place  to  the  different  proportions  of  sulphur  and  phosphonjs  they  are  known 
to  contain— as  the  more  popular  nature  of  this  work  will  not  permit  me  to  discuss  the  re- 
fined, though  singularly  beautiful,  physiological  questions  with  which  these  differences  arc 
connected. 


THE    FUNCTION    OF    RESPIRATION.  591 

of  lime,  phosphate  of  magnesia,  common  salt,  and  other  saline  com- 
pounds. These  same  compounds  exist,  ready  formed,  in  the  vegetable 
food,  associated  generally  with  the  gluten,  the  albumen,  or  the  casein, 
it  contains.  The  materials  of  the  harder  parts  of  the  body,  therefore — 
(the  phosphates)  as  well  as  the  inorganic  saline  substances  which  are 
found  in  the  blood,  and  in  the  other  fluids  of  the  body — are  all  formed  in 
or  by  the  plant,  or  are  by  it  extracted  fiOm  the  soil  and  incorporated  with 
the  food  on  which  the  animal  is  to  live. 

Not  only,  therefore,  do  the  mere  elements  of  which  the  parts  of  the 
bodies  of  animals  are  formed,  exist  in  the  food — but  they  occur  in  it,  put 
together  and  combined,  nearly  in  the  state  in  which  they  are  wanted,  in 
order  to  form  the  several  solids  and  fluids  of  the  body.  The  plant,  in 
short,  is  the  compounder  of  the  raw  materials  of  living  bodies.  The  ani- 
mal uses  up  these  raw  materials— cutting  them  into  shape  when  neces- 
sary, and  fitting  them  to  the  several  places  into  which  they  are  intended 
to  be  built. 

This  is  a  very  simple,  and  yet  a  very  beautiful  view  of  one  of  the 
many  forms  of  chemical  connection  which  exist  between  the  processes 
and  purposes  of  animal  and  vegetable  life.  Nature  seems  to  divide  the 
burden  of  building  up  living  bodies  between  the  vegetable  and  the  animal 
kingdoms — the  lower  appearing  to  exist  and  to  labour  only  for  the  good 
of  the  higher  race  of  beings. 

§  3.  Of  the  respiration  of  animals,  and  of  the  purposes  served  hy  the  starchy 
guirij  and  sugar,  contained  in  vegetable  food. 

But,  besides  the  gluten  of  plants  and  seeds,  which  supplies  the  mate- 
rials from  which  the  muscular  parts  of  animals  are  formed,  the  oil  which 
is  converted  into  the  fat  of  animals,  and  the  saline  and  earthy  matters 
of  plants  which  supply  the  salts  of  the  blood  and  the  earth  of  the  bones — 
vegetable  food  in  general  contains  a  large  proportion  of  starch,  sugar, 
gum,  and  other  substances  which  consist  of  carbon  and  the  elements  of 
water  only  (p.  111).  What  purpose  is  served  by  this  part  of  the  food? 
Is  it  merely  taken  into  the  stomach  and  again  rejected,  or  is  it  decom- 
posed and  made  to  serve  some  vital  purpose  in  the  economy  of  the 
living  animal  ?  From  the  fact  that  so  large  a  part  of  all  vegetable  food 
consists  of  these  substances,  we  might  infer  that  they  were  destined  to 
.serve  some  important  purpose  in  the  animal  economy.  To  the  herbiv- 
orous animal  they  are,  in  fact,  almost  necessary  for  the  support  of  a 
healthy  life. 

In  order  to  understand  this  fact,  it  will  be  necessary  briefly  to  advert  to 
the  respiration  of  animals — the  chemical  changes  produced  by  it,  and 
the  purposes  it  is  su])posed  to  serve  in  the  animal  economy. 

1°.  Of  the  function  of  respiration. — All  animg.ls  possessed  of  lungs  al- 
ternately inhale  and  exhale  the  atmospheric  air.  They  breathe,  that  is, 
or  respire.  The  air  they  draw  into  their  lungs,  supposing  it  to  be  dry, 
consisfjs  by  volume  (pp.  32  aoi  148)  very  nearly  of — 

Nitrogen  79-16 

Oxygen 20-80 

Carbonic  acK-.  0-04 

100 


592  FAT    SUPPORTS    RESPlllATIOJN    IN    SOMli, 

— the  proportion  of  carbonic  acid  being  very  small.     But  as  it  is  breathed 

out  again  it  consists  of  about-— 

Nitrogen 79-16 

Oxygen 16-84  to  12 

Carbonic  acid 4-00  to    8 


100 
— the  proportion  of  oxygen  being  considerably  less,  that  of  carbonic  acid 
very  piuch  greater,  than  before.     On  an  average  the  natural  proportion 
of  carbonic  acid  in  the  air  is  found  to  be  increased  100  times  after  it  is 
expelled  by  breathing  from  the  lungs. 

Now  carbonic  acid  consists,  as  we  have  previously  seen,  of  carbon  and 
oxygen.  In  breathing,  therefore,  the  animal  throws  off'  into  the  air  a 
quantity  of  carbon — in  the  form  of  carbonic  acid — which  varies  at  dif- 
ferent times,  in  different  species  of  animals,  and  in  different  individuals  of 
the  same  species.  By  a  heahhy  man  the  quantity  of  carbon  thus 
thrown  off*  varies  from  5  to  13  ounces,  and  by  a  cow  or  a  horse  from  3  to 
5  pounds,  in  24  hours.  All  this  carbon  must  be  derived  from  the  food. 
The  animal  eats,  therefore,  not  merely  to  support  or  to  add  weight  to  its 
body,  but  to  supply  the  carbon  also  which  is  wasted  by  respiration. 

2°.  How  the  respiration  is  fed. — What  part  of  the  ibod  supplies  the 
waste  caused  by  respiration  ?     How  is  the  respiration  fed  ? 

In  animals  which  live  upon  flesh — carnivorous  animals — it  is  the  fat 
of  their  food  from  which  the  carbon  given  off"  by  their  lungs  is  derived. 
It  is  only  when  the  fat  fails  in  quantity  that  the  lean  or  muscular  part 
of  the  flesh  they  eat  is  decomposed  for  the  purpose  of  supplying  carbon 
to  their  lungs. 

In  an  animal  to  which  no  food  is  given  for  a  time,  the  lungs  are  fed, 
so  to  speak,  from  fat  also.  But  in  this  case  it  is  the  living  fat  of  the 
animal's  own  body.  When  digestion  is  fully  performed  and  hunger  is 
keenly  experienced,  the  body  begins  to  feed  upon  itself— the  lungs  still 
play,  respiration  continues  for  many  days  after  food  has  ceased  to  be  ad- 
ministered, but  the  carbon  given  otfis  derived  from  the  substance  of  the 
body  itself.  The  fat  first  disappears — escapes  with  the  breath — and  af- 
terwards the  muscular  part  is  attacked.  Hence  the  emaciation  which 
follows  a  prolonged  abstinence  from  food. 

In  animals  which  live  upon  vegetable  food  again — herbivorous  ani- 
mals— it  is  the  starch,  gum,  and  sugar,  of  the  food  which  supply  th") 
carbon  for  respiration.  It  is  only  when  the  food  does  not  contain  a  suf 
ficient  supply  of  these  compounds  that  the  oil  first,  and  then  the  gluten, 
are  decomposed,  and  made  to  yield  their  carbon  to  the  lungs. 

In  man,  who  lives  on  both  kinds  of  food,  and  in  the  domestic  dog,  and 
the  pig,  which  also  eat  indifferently  both  animal  and  vegetable  food,  the 
carbon  of  respiration  may  be  derived  in  part  from  the  fat,  and  in  part 
from  the  starch  and  sugar  which  they  eat — according  as  they  are  chiefly 
supported  by  the  one  or  by  the  other  kind  of  food. 

It  may  be  asked  how  we  know  that  such  are  the  parts  of  the  food,  to 
which  the  duty  of  supplying  the  demands  of  the  lungs  is  especially  com- 
mitted. There  are  several  considerations  which  lend  force  to  this  opin- 
ion.    Of  these  I  willtlraw  your  attention  to  one  or  two. 

a.  Why  is  the  fa",  rather  than  the  lean  part  of  the  food  of  carnivorous 


STARCH    AND    SUGAR    IN    OTHEil    RACES.  693 

animals  devoted  to  the  service  of  the  lungs,  and  why  do  starving  ani- 
mals lose  their  fat  first  ?  Because  the  chemical  decomposition  by  which 
carbon  can  be  derived  from  the  tat  is  simpler  and  more  easily  etfected 
than  thai  by  which  it  can  be  ob  a-ned  from  muscular  fibre.  By  combi- 
nation with  oxygen,  fat  can  be  converted  into  carbonic  acid  and  water 
only,  of  which  the  former  will  pass  oIFby  the  lungs  and  the  latter  in  the 
urine.  The  muscular  fibre,  on  the  other  hand,  contains  much  nitrogen 
(p.  444),  and,  if  deprived  of  its  carbon  for  the  uses  of  respiration,  must 
undergo  very  complicated  decompositions,  and  form  a  series  of  com- 
pounds, the  use  of  which,  in  the  animal  economy,  it  is  not  easy  to  perceive. 

Besides,  in  producing  the  carbonic  acid  of  the  luairs  from  the  fat  of  the 
animal  food  or  of  the  living  body,  there  is  less  waste  of  material.  Fat 
consists  wholly  of  the  three  elements,  carbon,  hydrogen,  and  oxygen. 
These  all  disappear  entirely  in  the  form  of  carbonic  acid  and  water — both 
of  which  are  used  up.  Muscle,  on  the  other  hand,  besides  nitrogen,  con- 
tains a  constant  proportion  of  sulphur  and  phosphorus.  If  the  muscle, 
then,  be  decomposed  for  tlie  purpose  of  supplying  carbon  to  the  lungs, 
not  only  the  large  quantity  of  nitrogen,  but  the  sulphate  and  phosphorus 
also,  would  go  to  waste,  and  would  pass  off  in  the  urine.  In  nature, 
however,  such  waste  is  rarely  seen  to  take  place  ;  and,  therefore,  as  a 
general  rule,  the  resj^iration  will  be  supported  by  the  muscular  fibre  only 
when  other  kinds  of  food  are  deficient. 

b.  But  in  the  stomachs  of^ herbivorous  animals,  why  are  the  starch  and 
sugar  especially  appropriated  to  the  use  of  the  lungs  ?  The  food  of  ani- 
mals which  live  upon  vegetable  substances  contains  fat  as  well  as  starch 
— why  then  is  the  starch  in  this  case  dissipated  by  the  process  of  respira- 
tion, while  the  fat  is  applied  as  it  is  supposed  to  another  use  ?  The 
answer  to  this  question  is  both  beautiful  and  satisfactory. 

Starch,  gum,  and  sugar,  consist  of  carbon  and  water  only,  and  we  can 
conceive  them  in  their  passage  through  the  body  to  be  actually  separated 
into  these  two  substances — in  which  case  the  carbon  has  only  to  combine 
with  oxygen  and  form  carbonic  acid,  to  be  ready  to  pass  off  by  the  lungs. 
Here,  therefore,  only  one  chemical  combination  is  required — the  union 
of  carbon  with  oxygen.  It  is  the  simplest  way  in  which  we  can  con- 
ceive carbon  to  be  supplied  for  the  use,  or  for  the  purposes  of  the  lungs.* 

But  it  is  otherwise  with  fat.  Though  nearly  all  kinds  of  fat  consist  en- 
tirely of  carbon,  hydrogen,  and  oxygen—yet  they  cannot  be  supposed  to 
consist  only  of  carbon  and  water.  They  contain  much  more  hydrogen  than 
is  necessary  to  form  water  with  the  oxygen  which  is  present  in  them.  If, 
'hen,  the  carbon  of  these  fats  be  separated,  this  excess  of  hydrogen  will 
ilso  be  set  free,  and  if  the  f()rmer  be  made  to  combine  with  oxygen  to 
form  carbonic  acid,  the  latter  must  also  combine  with  hydrogen  to  form 
water.  Thus  two  chemical  changes  must  go  on  simultaneously,  for 
which  more  oxygen  will  be  required,  and  which  involve  more  labour  in 
the  system  than  when  the  carbon  alone  is  to  be  combined  with  oxygen. 
It  is  natural,  therefore,  that  where  both  starch  and  oil  are  present  to- 
gether, the  former  should  be  first  converted  to  the  uses  of  the  lungs,  the 
latter  only  when  the  supply  of  starch  or  sugar  has  been  exhausted. 

'The  chemical  reader  will  understand  that  I  am  here  only  giving  a  popular  view  of  the 
final  result  of  the  several  changes  through  which  the  carbon  no  doubt  passes  before  it 
escapes  in  the  form  of  carbonic  acid. 


594  PURPOSES    SERVED    BY    RESPIRATION. 

There  appears,  therefore,  to  he  a  beauliful  adaptation  to  the  wants  and 
convenience  of  animals  in  the  large  proportion  of  starch,  gum,  and  sugar, 
which  the  more  abundant  varieties  of  vegetable  food  contains.  In  obtaining 
carbon  from  these,  the  least  possible  labour,  so  to  speak,  is  imposed  upon 
the  digestive  organs  of  the  herbivorous  races.  The  starch  and  sugar 
abound  because  much  carbon  is  required,  while  fatty  matter  or  oil  is 
present  in  smaller  quantity,  because  comparatively  little  of  this  is  neces- 
sary to  the  performance  of  the  usual  healthy  functions  of  the  animal 
body.  And  it  is  another  adaptfition  of  the  living  body  to  the  circum- 
stances in  which  it  may  be  pla  ,'3d,  that  when  starch  or  sugar  cannot  be 
obtained,  the  oil  of  the  food  is  consumed  for  the  supply  of  carbon  to  the 
lungs — and  failing  this  also,  the  gluten  and  albumen  of  the  vegetable  food 
or  the  muscular  fibre  of  the  animal  food,  or  even  of  the  living  animal  it- 
self. 

3°.  Purposes  served  by  res}dratioii. — But  for  what  purpose  essential  to 
life  do  animals  respire  ?  If  the  starch  and  sugar  be  so  necessary  to  feed 
the  respiration — the  breathing  itself  must  be  of  vital  importance  to  the 
living  animal. 

Some  doubts  still  exist  upon  this  point.  It  is  generally  believed, 
however,  that  carbon  is  consumed  or  given  off  from  the  lungs  for  the  pur- 
pose of  sustaining  the  heat  of  the  living  body.  When  starch,  or  sugar, 
or  gum,  are  burned  in  the  open  air,  they  are  changed  into  carbonic  acid 
and  water,  and  at  the  same  time  produce  much  heat.  It  is  supposed  that 
in  the  body  the  same  change — the  conversion  of  starch  and  sugar  into 
carbonic  acid  and  water — taking  place,  heat  must  in  like  manner  be  pro- 
duced. A.  slow  combustion,  in  short,  is  su[)posed  to  be  going  on  in  the 
interior  of  the  animal — the  heal  of  the  body  being  greater,  in  proportion 
to  the  quantity  of  carbonic  acid  given  off  from  the  lungs.  In  favour  of 
this  view  many  strong  reasons  have  been  advanced,  but  there  are  also 
objections  against  it  of  considerable  weight,  which  cannot  as  yet  be  satis- 
factorily removed. 

Were  we  to  adopt  this  opinion  in  regard  to  tlie  main  purpose  served  by 
respiration  as  the  true  one,  it  would  afford  a  very  distinct  reason  for  the 
large  amount  of  starch  existing  in  all  our  cultivated  crops.  Respiration, 
according  to  this  view,  is  necessary  to  supply  heat  to  the  animal,  and 
this  respiration  is  most  simy)ly  and  easily  fed  by  the  starch  contained  in 
the  vegetable  food.  The  life  and  labours  of  the  plant  again  minister  to 
the  life  and  labours  of  the  animal. 

§  4.   Of  the  origin  and  the  purposes  served  by  the  fat  of  animals. 

1°.  The  immediate  origin  or  source  of  the  fat  of  animals  depends  upon 
the  kind  of  food  with  which  the  animal  is  fed.  Carnivorous  animals 
obtain  or  extract  it  ready  formed  from  the  flesh  they  eat — herbivorous 
animals  from  the  vegetable  food  on  which  they  live. 

It  has  only  been  lately  shown  that  the  corn,  hay,  roots,  and  herbage, 
on  which  cattle  are  fed,  contain  a  sufficient  quantity  of  oily  matter  ready 
formed  to  supply  all  the  fat  which  accumulates  in  their  bodies — or  which, 
by  the  milk  cow,  is  yielded  in  the  form  of  butter.  Before  t lie  different 
kinds  of  food  had  been  analyzed,  with  the  view  of  determining  the  quan- 
tity of  oil  and  fat  they  severally  contain,  it  was  supposed  that  the  fat  of 
animals  was  derivefi  almost  solcty  from  the  starch  and  sugar  or  gum,  of 


ORIGir        F    THE    FAT    OF    ANIMALS.  595 

which  so  large  a  proportion  of  vegetable  food  consists.  This  opinion, 
however,  has  given  way  before  the  advance  of  analytical  research. 
Animals  fatten  quickest  upon  Indian  corn,  or  oil  cake,  or  oil  mixed  with 
chopped  straw,  or  upon  oily  seeds  and  nuts — or,  as  in  the  case  of  poultry, 
on  a  mixture  of  meal  or  suet — because  these  kinds  of  food  contain  a  large 
proportion  of  fatty  matter  ready  formed  which  the  animal  can  easily  ex- 
tract, and  after  a  slight  chemical  change  can  convert  into  a  portion  of  its 
own  substance. 

The  conversion  of  starch  or  sugar  into  fat  in  the  animal  body  implies 
a  chemical  change  of  a  less  simple  nature — one  which  seems  to  impose 
upon  the  vital  principle  a  greater  amount  of  labour  than  is  implied  in  the 
simple  appropriation  of  the  fat  which  exists  ready  fornjcd  in  the  food.  If, 
then,  there  be  in  the  food  as  mucli  fat  as  is  necessary  to  supply  all  that 
the  animal  appropriates  to  itself,  and  if  it  is  observed  to  lay  on  or  appro- 
priate more  when  the  food  is  richer  in  fatty  oils,  we  are  led  to  believe 
that  the  natural  purpose  served  by  the  oil  in  the  vegetable  food  is  to  supply 
the  fat  of  the  animal  body.  In  other  words,  the  vegetable  ministers  to  the 
animal  and  lessens  its  labour  by  preparing  beforehand  the  materials  out 
of  which  the  animal  is  to  build  up  the  fatty  parts  of  its  body. 

But  thf)Ugh  this  is  the  general  source  of  the  fat  of  animals,  circum- 
stances may  occur  in  which  the  only  vegetable  food  which  the  animal  can 
procure  does  not  contain  a  sufficient  proportion  of  fat  to  supply  all  the 
wants  of  its  body — or  to  enable  it  to  perform  the  several  natural  functions 
it  is  destined  to  fulfil.  Thus  wax  is  a  kind  of  fat,  and  it  has  been  shown 
(Milne  Edwards)  that,  when  fed  upon  pure  sugar,  the  bee  is  capable  of 
forming  wax  from  its  food.  When  fed  upon  such  sugar,  it  not  only  lays 
up  a  store  of  honey,  but  it  continues  to  build  its  cells  of  wax.  Now  the 
starch  of  the  food  is  readily  changed  into  sugar.  It  may  be  so  changed 
in  the  stomach  of  man  and  of  otlier  animals.  That  power  which  the  bee 
possesses  they  also  may  in  cases  of  emergency  be  able  to  exercise. 
Where  a  sufficient  supply  of  oil  for  the  necessary  uses  of  the  animal  is 
not  contained  in  the  food  it  eats,  it  may  form  an  additional  portion  from 
the  starch  or  sugar  in  which  its  food  abounds. 

According  to  the  present  state  of  our  knowledge,  therefore,  the  most 
probable  opinion  in  regard  to  the  origin  of  the  fat  of  animals  seems  to  be 
expressed  in  these  two  proposition. 

a.  That  the  fat  of  animals  is  contained  ready  formed,  and  is  usually 
derived  from  the  vegetable  or  other  food  on  which  they  live — and  that 
when  the  food  abounds  largely  in  fat,  the  animal  lays  it  more  quickly 
and  abundantly  upon  its  own  body. 

h.  That  when  the  food  does  not  contain  a  sufficient  proportion  of  fat  to 
enable  the  animal  comfortably  to  perform  the  various  functions  of  its 
body,  it  has  the  power  to  form  an  additional  quantity  from  the  starch  or 
sugar  it  eats — but  that  it  will  not  readily  fatten  or  lay  on  large  additions 
of  fat  upon  its  body  when  fed  upon  farinaceous,  saccharine,  or  other  foo^ 
in  which  oil  is  not  naturally  contained.* 

*  For  tlie  sake  of  the  chemical  reader  I  may  be  permitled  here  to  show  by  what  kind  of 
chemical  changes— 1°,  the  fat  of  animals  in  general  may  be  derived  from  the  starch  or  sugar 
of  their  food  ;  and  2°,  how  the  peculiar  kinds  of  fat  contained  in  the  body  of  any  given  ani- 
mal maybe  formed  from  the  peculiar  kinds  of  fat  contained  in  its  food. 

1°.  How  fat  may  be  formed  from  starch  or  tugar  .—'These  two  substances,  as  we  have 
already  seen,  may  be  represented  by  carbon  ard  water  only— 


CHAMQES    OF    OX    FAT    INTO   HUMAN    FAT.  596 

2°.  The  purposes  served  by  the  fat. — In  all  healthy  animals  which 
»ake  a  sufficient  quantity  of  exercise  to  maintain  tliem  in  a  healthy  con- 

Cirhon.       Water. 

Starch, consisting;  of  12    +     10,  represented  by  Ci2  Hio  Oio 

Caiie  sugar,  consistini;  of  12    +    lli  represented  by  Cia  Ilu  Oil 
Paf,  again,  margarine  for  example,  the  solid  fat  of  the  humiu  body,  is  represented  (p. 
559,  note,)  by  Cj7  HiO  O5     Compare  this  with  4  of  starch,  and  we  have— 
4  of  starch  =  C4S  II40  Oio 

1  of  margarine =  Ci?  H35  O5. 

Difference =    Cii  H4  O33 

This  dUTorence  is  equal  to,  or  may  be  represented  by, 

U  of  carbonic  acid  +  4  of  water  +  9  of  oxygen 

11  coi  +4110        +      90 

So  that  by  the  separation  of  carbonic  acid,  which  may  be  given  off  from  the  lunga — of 
water,  which  may  or  may  not  remain  in  the  system, — and  of  a  portion  of  oxygen,  which 
may  be  used  up  in  various  ways  in  the  blood,  the  starch  or  sugar  of  the  food  may  be  con- 
verted into  fat. 

That  in  some  such  way  these  substances  may  be  changed  into  the  fat  of  animals  was  first 
insisted  upon  and  explained  by  L^ebig ;  and  it  is  probable,  as  I  have  said  in  the  text,  that  in 
case-i  of  emergency  fat  is  really  formed  in  the  animal  body  from  such  kinds  of  food.  But 
when  Liebig  put  forth  his  views  on  this  subject,  it  was  not  known  that  vegetable  substances 
naturally  contained  so  large  a  proportion  of  fat  as  has  since  been  found  in  them.  The  ne- 
cessity for  the  constant  production  or  formation  of  fat  in  the  body  itself,  therefore,  is  not  now 
eo  apparent,  and  the  soundest  opinion,  according  to  our  present  knowledge,  seems  to  be 
that,  while  the  vegetable  food  usuaily  supplies  all  the  fat  ready  formed  which  the  animal  re- 
quires, yet  that  a  conversion  of  a  certain  part  of  the  starch,  ^um,  sugar,  and  even  of  the  cel- 
lular fibre  of  the  food,  into  fat,  may  take  place,  when  all  the  wants  of  the  body  are  not  sup- 
plied by  the  fat  which  the  food  naturally  contains.  Of  course  this  opinion  applies  only  to 
animals  in  perfect  health.  In  certain  diseased  states  of  the  body  a  larger  and  more  con- 
stant production  of  fat  from  the  food  may  Lnke  place,  as  appears  to  be  the  case  in  animals 
which  no  diminution  of  food  seems  to  prevent  from  kyinif  on  fat. 

2^.  IIoiD  the  peculiar  kinda  of  fat  in  the  body  tnay  be  difrivedfrom  the  peculiar  kinds  of  fat 
in  the  food. 

a.  We  have  already  seen  (p.  55S)that  the  solid  part  of  butler,  of  olive  oil,  and  of  the  goose, 
is  identical  with  the  so.'id  fat  of  the  human  body.  When  eaten  by  man,  therefore,  these  se- 
veral kinds  of  fat  may  be  at  once  conveyed,  without  change,  from  the  stomach  to  the  several 
parts  of  the  body  whei-e  they  are  required.  From  this  circumstanoe  these  kinds  of  fat  seem 
remarkably  fitted  for  tlie  foo  i  of  man. 

b.  The  solid  fat  of  the  ox  and  the  sheep  is  called  stoarine.  TIpon  this  man  hves  much 
and  converts  it  into  the  solid  fat  (margarine)  of  his  own  body.  This  may  take  place  after 
the  following  maimer  :— 

2  of  margarine =  C?!  II72  Oio 

1  of  stearine =  C74  Hg9  O7 

Diff3rence =  Ca    H3    O3 

If  we  double  this  difference,  we  have  Cg  Hi  Os  ;  which  is  the  formula  for  lactic  acid. 
Recent  researches,  however,  have  failed  in  detecting  this  acid  in  the  blood — if  it  be  formed 
at  all,  therefore,  it  must  exist  only  in  a  transition  state,  and  mu.st  be  sneeiiily  converted  into 
other  compounds.  The  final  result  may  pos.sibly  be  the  evolution  of  the  3  of  carbon  (Us  ) 
by  tlie  lungs  in  the  form  of  carbonic  acid. 

c.  That  the  body  or  its  parts  pos-<es:i  the  power  of  easily  transforming  these  different  kinds 
of  fat  one  into  the  other,  we  know,  also,  from  other  facta.  Thus  the  calf  lives  upon  milk, 
and  from  the  two  kinds  of  fat  contained  in  the  crea-in  of  the  milk,  it  forms  the  solid  and  liquid 
fats  of  its  own  body.  The  stearine  of  the  animal  in  this  case  may  be  formed  from  the  mar- 
garine of  the  butter,  hein-i  exactly  the  converse  of  the  previous  case,  while  the  butter  oil  may 
be  changed  into  the  Uquid  fat  of  the  tallow. 

This  latter  is  more  difficult  »o  explain,  since  the  composition  of  elainc — the  liquid  fat  of 
the  ox,  calf,  and  .sheep— compared  with  that  of  butter  oil,  presents  a  considerable  difference. 
Thus— 

Elaine =  €47  \Ui  Os 

Butter  oil =  C37  IIo3  Os 

Diff.jrence  .     .     .     ,    z=Cio  II9 
What  becomes  of  thi.«t  difference,  Cio  119,  we  are  unable  as  yet  precisely  to  explain.    By 
tlie  intervention  of  a  little  oxygen  it  misht  readily  give  rise  to  a  little  more  fat. 

d.  The  cow  and  ciilf  to.'^ethcr,  however,  illustrate  very  clearly  tlie  existence  of  this  trans- 
forming power  of  the  animal  body.  We  are  unacquiinted,  as  yet.  with  the  composition  of 
the  several  kinds  of  fat  which  occur  in  vegetables — but  we  know  that  out  of  these  the  cow 
can  form  the  two  kinils  of  fat — the  stearine  and  the  elaitie — which  exist  in  its  own  tallow, 
and  at  the  same  time  the  two  kirejs  of  fat — margarine  and  butter-oil — which  are  found  in  ita 
milk.    The  calf,  again,  can  change  these  two  latter  fats  into  these  which  ita  own  body,  as 


PURPOSES    SERVED    BY    THE    FAT.  597 

dition,  the  principal  purposes  served  by  the  fat  are  simple  and  the  same. 
It  lubricates  the  joints — covers  and  protects  the  internal  viscera — keeps 
the  muscles  separate,  and  enables  them  to  play  freely  among  each  otiier 
— makes  the  hair  and  skin  soft  and  flexible, — and,  by  filling  up  1  ml  lows, 
contributes  to  the  roundness  and  plumpness  of  the  parts,  and  defends  the 
extremities  of  the  bones  from  external  injury.  When  exercise  is  taken, 
a  portion  of  the  fat  of  the  body  appears  to  be  more  or  less  changed  and 
removed,  and  is  afterwards  found  in  the  perspiration,  or  in  the  dung.  It 
is  to  make  up  for  this  natural  waste  that  all  animak,  even  when  the  fat 
of  their  body  undergoes  no  increase,  require  a  certain  supply  to  be  daily 
given  to  them  in  their  food. 

The  accumulation  of  fat  in  animals  seems  to  be  an  effort  of  nature  to 
lay  in  a  store  of  food  in  time  of  plenty,  which  may  be  made  available  in 
the  performance  of  the  usual  functions  of  the  animal  when  a  time  of 
scarcity  comes.  If  the  food  contain  too  little  oil  to  lubricate  the  joints 
and  lo  supply  the  natural  waste  of  this  kind  of  matter,  then  the  store  of 
fat  which  has  been  accumulated  in  tjj^ie  of  plenty  is  drawn  upon,  a  por- 
tion of  it  is  worked  up,  so  to  speak,  and  the  fat  of  the  body  diminishes  in 
quantity.  We  have  seen  also  that  the  --espiration  of  carnivorous  animals 
is  supported  at  the  expense  of  the  fat  Avhich  they  eat — and  that  the  lean- 
ness which  attends  upon  starvation  is  owing  to  the  fat  of  the  living  body 
beingconsumed  in  supplying thecarbon given  o(f  from  the  lungs.  Another 
purpose,  therefore,  for  which  animals  seem  to  be  invested  with  the  power 
of  laying  on  fat,  is,  that  a  store  of  food  for  the  purposes  of  respiration 
may  be  carried  about  in  the  body  itself,  to  meet  any  unusual  demand 
which  the  food  may  not  be  able  wholly  to  supply. 

§  5.  Of  the  natural  waste  of  the  parts  of  the  body  in  a  fall  grown  animal. 
We  have  seen  that,  if  the  food  of  the  animal  be  unable  to  supply  the 
carbon  given  off  from  the  lungs,  and  the  fat  which  the  movements  of  the 
limbs  require,  the  parts  of  the  body  themselves  are  laid  under  contribu 
tion  in  order  to  supply  these  substances.  Thus,  when  the  food  is  stinted, 
the  body  necessarily  undergoes  a  waste  from  this  cause. 

But  this  is  not  a  constant  waste.  It  is  prevented  by  the  use  of  a  larger 
quantity  of  food.  The  }:)arts  of  the  body,  however,  do  undergo  a  con- 
stant and  natural  waste,  to  make  up  for  which  is  one  of  the  main  pur- 
poses served  by  the  food. 

It  has  been  ascertained  by  physiologists,  that  all  the  parts  of  the  body 
undergo  a  slow  and  insensible  process  of  renewal.  The  hair  and  the  nails 
we  can  see  to  be  constantly  renewed.  They  grow,  or  are  thrust  out- 
wards. But  the  muscles  and  even  the  bones  are  by  little  and  little  re- 
well  as  that  of  its  mother,  requires.  And,  lastly,  man  by  eating  the  fat  of  the  calf  can  re 
convert  it  into  margarine  and  those  other  fatty  substances  which  are  found  in  the  various 
parts  of  Ins  borly.  Substances  which  can  thus  so  frequently  and  so  readily  be  changed,  the 
one  into  the  other,  must  be  very  cloeely  connected,  and  the  mode  in  which  their  mutual 
transformations  are  effected  will,  no  doubt,  prove  to  be  simple  when  these  are  rightly  im- 
derstood. 

The  chemical  reader  will  understand  that  it  is  for  the  sake  of  simplicity  only  that  I  have 
in  this  note  compared  together  the  entire  fats  stearine,  margarine,  &c.,  instead  of  the  fatty 
acids  only  which  they  are  known  to  contain. 

The  reader  will  consult  with  much  advantage  and  satisfaction  upon  this  subject,  a  work 
upon  ChcmicfU  Physiology,  by  Professor  MuMer,  of  Utrecht,  (Procve  eener  Algemeene  Phy- 
siulo  f^sche  Scheikunde,  p.  2(50,  el  acq.)  of  which  I  am  happy  to  say  that  a  translation  from 
the  Dutch  is  now  in  progresis  by  my  assistant,  Mr.  Fromberg,  and  will  speedily  be  published 
by  the  Messrs.  Blackwood. 


598  FOOD    REQUISITE    FOR    THE    NATURAL    WASTE. 

moved  inwardly  and  rejected  in  the  excretions — the  place  of  that  which 
18  removed  being  supplied  by  new  portions  of  matter  derived  from  the 
food. 

This  removal,  tliough  imfelt  by  us,  goes  on  so  rapidly  that  in  a  space 
of  time,  which  varies  from  one  to  five  years,  the  whole  body  of  the  ani- 
mal is  renewed.  There  does  not  remain,  it  is  said,  in  any  of  our  bodies, 
a  single  particle  of  the  same  matter  which  formed  their  substance  three 
or  five  years  ago.  It  is  just  as  if  we  were  to  take  a  single  old  brick  every 
day  out  ofthe  corneuof  a  house,  and  put  in  a  new  one — the  form  and 
dimensions  ofthe  house  would  remain  unaltered,  and  yet  in  the  course 
of  a  few  years  its  walls  would  be  entirely  renewed. 

In  full  grown  animals,  some  parts  of  the  body  are  renewed  more  ra- 
pidly than  others — the  muscles,  for  example, more  frequently  and  rapidly 
than  the  bones  and  the  brain.  In  young  animals,  again,  the  whole  body 
is  oftener  renewed  than  in  such  as  are  advanced  in  years,  but  all  the 
parts  of  all  animals  are  believed  to  be  more  or  less  quickly  removed  and 
replaced.  ^ 

The  new  materials  which  are  conveyed  to  the  different  parts  of  the 
body  are  derived  directly  from  the  food.  The  fibrin  of  the  muscles  is 
replaced  from  the  gluten  which  the  food  contains — the  fat  from  its  oil — 
and  the  earthy  matter  of  the  bones  and  the  salts  of  the  l)lood,  fiora  the 
phosphates  and  saline  substances  which  are  naturally  present  in  it.  On 
the  other  hand,  those  parts  which  are  extracted  from  the  muscles  and 
bones,  and  carried  off  in  the  excretions,  are  decomposed  during  their  re- 
moval. New  chemical  compounds  are  produced  from  them,  which  are 
found  in  the  urine  and  dung  of  the  animal,  and  which  give  to  these  ex- 
cretions their  richness  and  value  in  the  manuring  ofthe  soil. 

§  6,  Ofthe  kind  and  quantity  of  food  necessary  to  make  ujjfor  the  natural 
■waste  in  the  body  of  a  full  grown  animal. 

The  substances  which  constantly  disappear  from  the  body  in  conse- 
quence of  the  natural  waste  above  describf^d,  are  of  three  kinds — the  fbrin 
and  other  analogous  organic  compounds,  whicli  form  the  muscles  and  the 
cartilage  of  the  bones — the  earthy  phosphates  (of  lime  and  magnesia), 
which  form  so  large  a  proportion  of  the  bones,  and  exist  in  small  quan- 
tity in  the  muscles  also — and  the  soluble  saline  substances,  which  abound 
in  the  blood  and  in  the  other  fluids  of  the  livmg  animal.  In  the  solid  and 
liquid  excretions,  a  larger  quantity  of  each  of  these  three  classes  of  com- 
pounds is  carried  out  ofthe  body.  How  much  of  each  must  be  contained 
in  the  daily  food  of  a  full-grown  animal  in  order  that  it  may  be  kept  in 
its  actual  condition? 

1°.  Quantity  of  fibrin  or  other  analogoiis  compounds  {albumen  or 
casein)  which  the  daily  food  must  contain. — The  most  accurate  experi- 
ments that  have  yet  been  made  upon  this  subject  (Lecanu)  appear  to 
show  that  a  full  grown  man  rejects  in  his  urine  alone  about  half  an  ounce 
of  nitrogen  (230  grs.)  every  24  hours.  This  quantity  of  nitrogen  is  con- 
tained in  about  three  ounces  of  dry  muscular  fibre,  which  must,  therefore, 
every  day  be  decomposed  or  removed  in  order  to  yield  it. 

But  if  the  body  is  kept  in  condition,  this  quantity  of  fibrin  must  be 
daily  restored  again  by  the  food.  Now,  to  supply  three  ounces  of  dry 
fibrin,  there  must  be  eaten  about — 


IN    THE    BODY    OF    A    FDLL-GROWN    ANIMAL.  509 

30  ounces  of  wheaten  flour  ;  or 

45       "       of  wheaten  brend  ;  or 

14       "       of  fresh  beef  or  mutton  ;  or 

12  "  of  pease  or  bean  meal ;  or 
4  "  of  cheese  ;* 
Or,  if  we  live  wholly  upon  potatoes  or  rnilk,  we  must  eat  no  less  than 
six  cr  seven  pounds  of  the  former  daily,  or  drink  three  or  four  imperial 
pints  of  the  latter — if  we  would  restore  to  the  body  as  much  of  the  sub- 
stance of  its  muscles  and  cartilage  as  is  daily  removed  from  it  by  the 
urine. 

But  the  urine  is  not  the  only  channel  through  which  nitrogen  is  given 
ofT  from  the  animal  body.  A  considerable,  though,  of  course,  a  variable 
proportion  is  found  in  the  solid  excretions  or  dung,  which  has  also  been 
derived  from  the  substance  of  the  body  itself.  A  small  quantity  of  ni- 
trogen is  believed  to  be  given  otf  from  the  lungs  also  in  breathing,  and 
from  the  skin  in  the  perspiration,  which  nitrogen  must  have  been  either 
directly  or  indirectly  derived  from  the  food.  And,  lastly,  of  the  fibrin  or 
other  food  containing  nitrogen  which  may  be  introduced  into  the  stomach, 
a  portion  must  pass  the  mouths  of  the  absorbent  vessels  as  it  descends 
through  the  intestines  and  thus  escape  with  the  dung,  without  having 
performed  its  part  in  the  ordinary  nourishment  of  the  body. 

It  is  impossible  to  maice  any  correct  estimate  of  the  amount  of  nitrogen 
which  escapes  from  the  animal  in  the  several  ways  just  noticed — in  the 
solid  excretions  from  the  lungs  and  from  the  skin — or  of  the  quantity  of 
food  which  is  necessary  to  supply  its  jjlace.  If  we  suppose  the  loss 
through  all  these  sources  taken  togetlier  to  be  equal  to  one-half  or  two- 
thirds  of  that  which  is  found  in  the  urine,  then  the  whole  quantity  of  dry 
fibrin  which  the  f(X)d  ought  to  contain  would  amount  to  four  and  a  half  or 
five  ounces  in  the  day.  To  supply  this,  we  must  eat  of  bread,  beef, 
cheese,  potatoes,  or  milk,  one  half  more  than  the  quantities  already 
specified. 

No  experiments  have  hitherto  oeen  published  from  which  we  can  de- 
termine the  average  quantity  of  nitrogen  rejected  in  the  excretions  of  the 
horse,  the  cow,  or  the  sheep,  and,  consequently,  the  amount  of  waste 
which  takes  place  in  ordinary  circumstances  in  the  muscles  and  cartilage 
of  these  animals.  If  we  suppose  that  in  the  horse  or  cow  it  is  in  direct 
proportion  to  their  weights,  compared  with  that  of  a  full  grown  man — or 
five  times  greater  than  in  a  man — then  the  loss  of  dry  fibrin  would 
amount  to  20  or  25  ounces  in  the  24  hours.  To  supply  this,  the  animal 
must  eat  the  following  quantities  of  one  or  other  of  tlie  kinds  of  food  here 
mentioned : — 

120  lbs.  of  turnips.  17  lbs.  of  clover  hay. 

115     ♦'     of  wheat  straw.  12     "     of  pea  straw. 

75     •'     of  carrots.  12     "     of  barley. 

67     "     of  potatoes.  10     "     of  oats. 

20     "     of  meadow  hay.  5     "     of  beans,  f 

Or  instead  of  the  whole  quantity  of  any  one  of  these,  a  half  or  quarter  or 
any  other  proportion  of  each  may  be  taken,  and  the  animal  will  pro- 

*  8upposine  the  wheaten  flour  to  contain  10  per  cent,  of  gluten,  and  the  cheese  one  half 
ks  weight  of  dry  curd  (see  also  pp.  506  and  531.) 
T  These  numbers  are  calculated  from  the  table  givec  in  p.  531. 


600  A    MIXED    FOOD    NECKS3ARY    TO   ANIMALS. 

bably  be  found  to  thrive  better  on  the  mixture  than  if  fed  upon  any  one 
of  these  kinds  of  food  alone. 

2°.  Quantity  of  fixed  saline  matter  and  of  earthy  phosphates  which 
the  food  ought  to  contain. — A  fidl  growi]  animal  rejects  in  its  dung,  its 
urine,  and  its  perspiration,  as  much  saline  and  eaithy  matter  as  its 
food  contains.  If  its  body  is  merely  maintained  in  its  existing  condition, 
only  that  which  is  removed  from  it  by  the  daily  waste  is  restored  to  it  by 
the  daily  food.  Thus  whatever  quantity  of  saline  and  earthy  matter  is 
present  in  the  food,  an  equal  quantity  is  found  in  the  excretions  of  the 
living  animal. 

But  how  much  of  that  which  is  found  in  the  excretions  has  actually 
formed  part  of  the  living  body,  and  been  removed  from  it  in  consequence 
of  the  natural  waste  ?  This  we  have  no  means  as  yet  of  determining. 
It  must  be  considerable,  but  it  varies  with  many  circumstances,  and  the 
experiments  which  have  hitherto ^been  made  and  published  do  not  enable 
us  to  say  how  much  the  average  waste  really  is,  and  how  much  of  the 
several  more  common  kinds  of  food  ought  to  be  consumed  by  a  full 
grown  animal,  in  order  to  supply  it  w4th  the  necessary  daily  proportion 
of  sahne  and  eartliy  substances. 

The  benefits  so  often  derived  from  the  use  of  salt  in  the  feeding  of 
stock  show  liow  a  judicious  admixture  of  saline  matter  with  the  food 
may  render  its  other  constituents  more  available  than  they  would  other- 
wise be,  to  the  support  and  increase  of  the  animal  body. 

§  7.    The  health  of  the  animal  can  he  sustained  only  hy  a  mixed  food. 

From  what  I  have  already  stated,  you  see  that  the  vegetable  food  eaten 
by  a  full  grown  animal  for  the  purpose  of  keeping  up  its  condition  should 
contain — 

1°.  Starch  or  sugar,  to  supply  the  carbon  given  off'  in  respiration. 

2*^.  Fat  or  fatty  oil,  to  supply  the  fatty  matter  which  exists  more  or 
less  abundantly  in  the  bodies  of  all  animals. 

3°.  Gluten  or  fibrin,  to  make  up  for  the  natural  waste  of  the  muscles 
and  cartilage. 

4°.  Earthy  phosphates,  to  supply  what  is  removed  from  the  bones  of 
the  full  grown  animal  by  the  daily  waste  ;    and — 

5°.  Saline  substances — sulphates  and  chlorides — to  replace  what  is 
daily  rejected  in  the  excretions. 

Hence  the  food  upon  which  any  animal  can  be  fed  with  the  hope  of 
maintaining  it  in  a  healthy  state  7nust  be  a  mixed  food.  Starch,  or  sugar 
alone,  or  pure  fibrin  or  gelatine  alone,  will  not  sustain  tlie  animal  body, 
because  these  substances  do  not  contain  what  is  necessary  to  build  up  all 
its  parts,  or  to  supply  what  is  daily  given  off'  during  respiration  and  in 
the  excretions.  The  skilful  feeder,  therefore,  will  not  attempt  to  main- 
tain his  stock  on  any  kind  of  food  which  does  not  contain  a  sufficient 
supply  of  every  one  of  the  kinds  of  matter  which  the  body  requires. 

Two  other  points  he  will  also  attend  to.  First,  he  will  occasionally 
change  the  kind  of  food,  or  will  vary  the  proportions  in  which  he  gives 
the  ditferent  kinds  of  fodder  to  his  feeding  stock.  This  practice  is  founded 
on  the  fact  that,  although  every  crop  he  raises  contains  a  certain  propor- 
tion of  all  the  substances  v  lich  the  animal  requires,  yet  some  contain 
one  of  these  in  larger  qua  itity  than  others  do,  and  by  an  occasional 


ADDITIONAL    FOOD    Rr^fJIRED    FOR    FATTENING.  601 

change  or  variation  he  may  hope  more  fully  to  supply  to  the  animal  the 
necessary  quantity  of  each. 

Second,  he  will  adapt  the  kind  and  quantity  of  food  to  the  age  of  the 
animal,  and  to  the  other  purposes  for  which  it  is  fed.  This  rule  depends 
partly  upon  the  same  fact,  that  different  vegetables  contain  the  several 
kinds  of  necessary  food  in  different  proportions,  but  in  a  great  degree  also 
upon  the  further  fact,  that  the  animal  requires  these  substances  in  differ- 
ent proportions,  according  to  its  age  and  to  the  special  purpose  for  which 
it  is  fed.  Let  me  direct  your  attention  to  this  latter  fact  a  littler  more 
at  length. 

§  8.   O/"  the  kind  and  quantity  of  additional  food  required  by  the 
fattening  animal. 

In  the  animal  which  is  increasing  in  size  or  in  weight,  the  food  has  a 
double  function  to  perform.  It  must  sustain  and  it  must  increase  the 
body.  To  increase  the  body,  an  additional  quantity  of  food  must  be  con- 
sumed, but  the  kind  or  nature  of  this  additional  food  will  depend  upon 
the  kind  of  increase  which  the  animal  is  making  or  is  intended  to  make. 

One  of  the  important  objects  of  the  stock  farmer  is  to  make  his  full 
grown  animals  lay  on  fat,  so  that  they  may  as  quickly  as  possible,  and 
at  the  least  cost,  be  made  ready  for  the  butcher.  To  effect  this  object, 
he  adjusts  the  kind  and  quantity  oi  the  food  he  gives,  to  the  practical  ob- 
ject he  wishes  to  attain. 

We  have  already  seen  reason  to  believe,  that  the  natural  and  imme- 
diate source  of  the  fat  of  animals  is  in  the  oily  matter  which  the  food 
contains.  If  we  wish  only,  or  chiefly,  to  lay  on  fat,  therefore,  we 
ought  to  give  some  kind  of  food  which  contains  a  larger  proportion  of 
fatty  matter  than  that  upon  which  the  animal  has  been  accustomed  to 
live.  .This  is  what  the  practical  man  has  actually  learned  to  do.  To 
his  sheep  and  oxen  he  gives  oil-cake  or  linseed  oil  mixed  with  chopped 
straw,  to  his  dogs  cracklings,*  to  his  geese  and  turkeys  Indian  corn, 
which  contains  much  oil,  and  to  liis  poultn,''  beef  or  mutton  suet. 

Many  experiments  are  yet  wanting  to  determine  with  accuracy  the 
proportion  of  fat  contained  in  all  the  different  kinds  of  food  usually  con- 
sumed by  animals.  Nearly  all  we  yet  know  upon  this  subject  is  ex- 
hibited in  the  tabular  view  of  their  composition  to  which  I  have  already 
directed  your  attention  (p.  531.) 

One  thing,  however,  of  considerable  practical  value  has  been  recently 
ascertained — that  the  oily  matter  of  seeds  exists  chiefly  near  their  outer 
surface, — in  or  immediately  under  the  skin  or  husk.  This  fact  is  shown 
in  the  case  of  wheat,  by  the  following  results  of  the  examination  of  two 
varieties  of  this  grain,  one  grown  near  Durham,  the  other  in  France. 
The  result  as  to  the  French  grain  is  given  by  Dumas  : — 

PER   CENTAdE  OF  FATTY   OIL. 

English.  French. 

Fine  flour     ...     1-5  1-4 

Pollard    ....     2-4  4-8 

Boxings  ....     3-6  — 

Bran 3-3  5-2 

*  Cracklings  are  the  skinny  parts  of  the  suet  from  which  the  tallow  has  been  for  the  most 
part  squeezed  out  by  the  tallow  chandlers.  Mipht  cattle  not  be  fattened  upon  cracklings 
crushed  and  mixed  with  their  otlier  food  1  Might  not  some  cheap  varieties  of  oil  also  be 
mixed  with  their  food  for  the  purpose  of  fattening. 


602  FATTY    MATTER    IN    THE    l  •.  8RS    OF    SEEDS. 

This  fact  of  the  existence  of  more  fut  in  tlie  husk  than  in  the  inner 
part  of  the  grain,  explains  what  often  seems  inexplicable  to  the  practical 
man — why  bran,  namely,  which  appears  to  contain  little  or  no  nourish- 
ing substance,  should  yet  fatten  pigs  and  other  full  grown  animais,  when 
given  to  them  in  sufficient  quantity  along  with  their  other  food.  It  also 
explains  why  ricz  dust  should  be  found  to  fatten  stock,*  though  the 
cleaned  and  prepared  rice  contains  but  little  oil,  and  is  believed,  there- 
fore, to  be  unfitted  for  laying  on  fat  upon  animals  with  any  degree  of 
rapidity.  No  doubt  ihe  dust  from  pearl-barley  and  from  oats,  as  well  as 
the  husk  of  these  grains,  might  be  economically  employed  by  the  stock 
feeder  where  they  can  readily  be  obtained. 

§  9.  Kind  and  quantity  of  additional  food  required  hy  a  growing 
animal. 

The  young  and  growing  animal  requires  also  that  its  food  should  be 
adjusted  to  its  peculiar  wants.  In  infancy  the  muscles  and  bones  in- 
crease rapidly  in  size  when  the  food  is  of  a  proper  kind.  This  food, 
therefore,  should  contain  a  large  supply  of  the  phosphates,  from  which 
bone  is  formed,  and  of  gluten  or  fibrin,  by  which  the  muscles  are  en- 
larged. Some  kinds  of  fodder  contain  a  larger  proportion  of  these  phos- 
phates. Such  are  corn  seeds  in  general,  and  the  red  clover  among  grass- 
es. Some  again  contain  more  of  the  materials  of  muscles.  Such  are 
beans  and  peas  among  our  usually  cultivated  seeds,  and  tares  and  other 
leguminous  plants  among  our  green  crops. 

Hence  the  skilful  feeder  or  rearer  of  stock  can  often  select  with  judg- 
ment that  kind  of  food  which  will  specially  supply  that  which  the  ani- 
mal, on  account  of  its  age  or  rapid  growth,  specially  requires — or  which, 
with  a  viewto  some  special  object,  he  wishes  his  animal  specially  to  lay 
on.  Does  he  admire  the  fine  bone  of  the  Ayrshire  breed? — he  will  try 
to  stint  it  while  young  of  that  kind  of  food  in  which  the  phosphates 
abound.  Does  he  wish  to  strengthen  his  stock,  and  to  enlarge  their 
bones  ? — he  will  supply  the  phosphates  liberally  while  the  animal  is 
rapidly  growing. 

An  interesting  application  of  these  principles  is  seen  in  the  mode  of 
feeding  calves  adopted  in  different  districts.  Where  they  are  to  be  reared 
for  fattening  stock,  to  be  sold  to  the  butcher  at  two  or  three  years  old, 
they  are  well  fed  with  good  and  abundant  food  from  the  first,  that  they 
may  grow  rapidly,  attain  a  great  size,  and  carry  much  flesh.  If  starved 
and  stunted  while  young,  they  often  fatten  rapidly  when  put  at  last  upon 
a  generous  diet,  but  they  never  attain  to  their  full  natural  size  and  weight. 

When  they  are  reared  for  breeding  stock  or  for  milkers,  similar  care  is 
taken  of  them  in  the  best  dairy  countries  from  the  first,  though  in  some 
the  allowance  of  milk  is  stinted,  and  substitutes  for  milk  are  early  given 
to  the  young  animals. 

But  it  is  in  rearing  calves  for  the  butcher  that  the  greatest  skill  in 
feeding  is  displayed,  where  long  practice  has  made  the  farmers  expert  in 
this  branch  of  husbandry.  To  the  man  who  has  a  calf  and  a  milk  cow, 
the  principal  question  is,  how  can  I,  in  the  locality  in  which  I  am  placed, 
make  the  most  money  of  my  calf  and  my  milk  ?  Had  I  better  give 
ray  calf  a  little  of  the  milk,  and  sell  the  remainder  in  the  form  of  new 

*  Rice  dust  is  very  good  food  for  fattening  pigs,  makes  excellent  pork,  and  1b  TOiy  profit* 
aUe  when  given  along  witb  whey. 


TEEDING    OF    YOU>'G    CALVES  603 

milk — or  had  I  better  make  butter  and  g:  •  e  the  skimmed  milk  to  my 
calves — or  will  the  veal,  if  I  give  my  calf  all  the  milk,  pay  me  a  bet- 
ter price  in  the  end  ?  The  result  of  many  trials  has  shown,  that  in  some 
districts  the  high  price  obtained  for  well  fed  veal  gives  a  greater  profit 
than  can  be  derived  from  the  milk  in  any  other  way. 

While  the  calf  is  very  young — during  tlie  first  two  or  three  weeks — 
Its  bones  and  muscles  chiefly  grow.  It  requires  the  materials  of  these, 
therefore,  more  than  fat,  and  hence  half  the  milk  it  gets,  at  first,  may  be 
skimmed,  and  a  little  bean  meal  may  be  mixed  with  it  to  add  more  of 
the  casein  or  curd  out  of  which  the  muscles  are  to  be  formed.  The  cos- 
tive effect  of  the  bean  meal  must  be  guarded  against  by  occasional  me- 
dicine, if  required. 

In  the  next  stage,  more  fat  is  necessary,  and  in  the  third  week  at 
latest,  full  milk,  with  all  its  cream,  should  be  given,  and  more  milk  than 
the  mother  supplies  if  the  calf  requires  it.  Or,  instead  of  the  cream,  a 
less  costly  kind  of  fat  may  be  used.  Oil-cake,  finely  crushed,  or  lin- 
seed meal,  may  supply  at  a  cheap  rate  the  fat  which,  in  the  form  of 
cream,  sells  for  much  money.  And,  instead  of  the  additional  milk,  bean 
meal  in  larger  quantity  may  be  tried,  and  if  cautiously  and  skilfully  used, 
the  best  effects  on  the  size  of  the  calf  and  thfe  firmness  of  the  veal  may 
be  anticipated. 

In  the  third  or  fattening  stage,  the  custom  is,  with  the  same  quantity 
of  milk,  to  give  double  its  natural  quantity  of  cream — that  is,  to  supply 
in  this  way  the  fat  which  the  animal  is  wished  chiefly  to  lay  on.  This 
cream  may  either  be  mixed  directly  with  the  mother's  milk,  or,  what  is 
better,  the  afterings  of  several  cows  may  be  given  to  the  calf  along 
with  its  food.  For  the  "expensive  cream  there  might  no  doubt  be  sub- 
stituted many  cheaper  kinds  of  fat  which  the  young  animal  might  be 
expected  to  appropriate  as  readily  as  it  does  the  fat  of  the  milk.  Lin- 
seed meal  is  given  with  economy.  Might  not  vegetable  oils  and  even 
animal  fats  be  made  up  into  emulsions  which  the  calf  would  readily 
swallow,  and  which  would  increase  his  weight  at  an  equally  low  cost  ? 
A  fat  pease-soup  has  been  found  to  keep  a  cow  long  in  milk  ;  might  it 
uot  be  made  profitable  also  to  a  fattening  calf? 

The  selection  of  articles  of  food  which  will  specially  increase  the  size 
of  the  bones  in  the  growing  animal,  by  supplying  a  large  quantity 
of  the  phosphates,  is  at  present  limited  in  a  considerable  degree.  The 
grain  of  wheat,  barley,  and  oats  is  the  source  from  which  these  phos- 
phates are  most  certainly  and  most  abundantly  supplied  to  the  animals 
that  feed  upon  them.  But  in  many  cases  corn  is  too  expensive  a  food, 
and  those  kinds  of  corn  which  contain  the  largest  proportion  of  the  phos- 
phates supply  only  a  comparatively  small  quantity  in  a  given  time  to  the 
growing  animal.  Why  should  not  bone-dust  or  bone-meal  be  introduced 
as  an  article  of  general  food  for  growing  animals  ?  There  is  no  reason 
to  believe  tliat  animals  would  dislike  it — none  that  they  would  be  unable 
to  digest  it.  With  this  kind  of  food  at  our  command,  we  might  hope  to 
minister  directly  to  the  weak  limbs  of  our  growing  stock,  and  at  pleasure 
to  provide  the  spare-boned  animal  with  the  materials  out  of  which  a 
limb  of  great  strength  might  be  built  up. 

Chemical  analysis  comes  further  to  our  aid  in  pointing  out  the  kind 
of  food  we  ought  to  give  for  the  purpose  of  increasing  this  or  that  part 


(W)4  FOOD  REQUIRED  DURING  PREGNANCY. 

of  tne  animal  body.  Thus  in  regard  to  the  same  growth  of  bone,  it  ap- 
pears that,  while  linseed  and  other  oil  cakes  are  mainly  used  with  the 
view  of  adding  to  the  fat,  some  varieties  are  more  fitted  at  the  same  time 
to  minister  to  the  growth  of  bone  than  others  are.  Thus,  four  varieties 
of  oil-cake  examined  in  my  laborato'-y,  contained  respectively  of  earthy 
phosphates  and  of  other  inorganic  matter  in  100  lbs.  the  following  quan- 
tities : — 

PER  CENTAGE   OP 

Earthy  phosphates.  Other  inorganic  matter. 

British  linseed  cake     .     .     2-86  2-86 

Dutch         do.  .     .     2-70  2-54 

Poppy  cake       ....     5-22  1*24 

Dodder  cake      ....     6-67  3-37 

The  numbers  in  the  first  column,  opposite  to  poppy  and  dodder  cake, 
show  that  these  varieties  of  oil-cake  contained  a  much  larger  proportion 
of  the  phosphates  thaa  the  others  did,  and  consequently  that  an  equal 
weight  of  them  would  yield  to  growing  stock  more  of  those  substances 
which  are  specially  required  to  build  up  their  increasing  bones. 

§  10.  Kind  and  quantity  of  additional  food  required  by  a 
pregnant  animal. 

The  food  of  the  pregnant  animal  must  sustain  the  full-grown  mother, 
and  must  add  at  the  same  time  to  the  substance  of  her  unborn  young. 
The  quantity  of  food  which  is  necessary  to  sustain  the  mother — if  herself 
full-grown,  which  is  often  far  from  being  the  case — varies  with  many 
circumstances. 

It  is  said  that  in  the  stall  an  ox  or  a  cow  will  eat  one-fifth  of  its  weight 
of  turnips  in  a  day,  or  one-fiftieth  of  dry  food,  such  as  hay  and  straw. 
With  this  allowance  of  food  the  animal  would  probably  increase  in 
weight  in  some  degree, — but  according  to  Riedesel  one-sixtieth  of  its 
weight  of  dry  hay  is  necessary  merely  to  sustain  it.  From  what  we 
have  already  seen  of  the  composition  of  the  different  grasses,  it  is  obvi- 
ous that  the  quantity  required  will  be  much  affected  by  the  kind  of  hay 
with  which  the  animal  is  fed. 

To  nourish  the  young  calf  in  the  womb  of  its  mother,  an  additional 
quantity  of  food  must  be  given,  and  this  quantity  must  be  increased  as 
the  state  of  pregnancy  advances.  And  though  the  kind  of  additional 
food  which  is  given  must  readily  supply  the  materials  of  the  growing 
oones  and  muscles  of  the  foetus,  yet  it  must  contain  also  a  larger  quan- 
tity of  starch  or  sugar  also  than  the  mother  in  her  ordinary  slate  would 
require.  This  is  owing  to  the  circumstance  that  the  mother  must  now 
breathe  for  two  animals,  for  herself  and  her  young.  The  quantity  of 
blood  is  increased,  more  oxygen  is  taken  in  by  the  lungs,  and  more  carbon 
is  given  oif  in  the  form  of  carbonic  acid.  To  supply  this  carbon,  more 
of  farinaceous  or  saccharine  food  must  be  eaten  from  the  time  when 
pregnancy  takes  place,  and  it  must  increase  as  the  young  animal  en- 
larges in  size. 

Except  in  the  way  of  feeding  the  mother,  in  all  respects  well,  I  am 
not  aware  that  any  experiments  have  been  made  with  the  view  of  spe- 
cially affecting  the  condition  of  the  future  calf  by  the  kind  of  food  given 
to  the  mother.     A  certain  proportion  of  bone  and  muscle  no  doubt  must 


FOOD    REQUIRED    BY    A    COW    IN    MILK.  605 

be  supplied  to  the  young  animal  by  the  food  given  to  the  mother,  or  tho 
bones  and  muscles  of  the  mother  herself  will  be  laid  under  contribution  to 
supj)ly  it — but  it  does  not  appear  impossible  to  affect  the  size  of  the  bone 
by  the  quantity  of  phosphates  which  are  given  in  the  food,  or  the  growth 
and  development  of  the  muscles  by  that  of  the  gluten,  fibrin,  or  casein 
with  which  the  mother  is  fed.  Might  not  an  addition  of  bone-meal  to  the 
food  of  the  pregnant  cow  give  a  calf  of  larger  bone  ?  Would  not  bean- 
meal  or  skim-milk  add  to  the  size  of  its  muscles  ? 

§  11.    Kind  and  quantity  of  additional  food  required  by  a 
milking  animal. 

After  the  young  animal  is  born,  the  mother  has  still  to  feed  it  with  her 
milk.  And  as  the  calf  grows  rapidly,  the  food  it  requires  increases  daily 
with  its  bulk,  and  the  demands  upon  the  mother  therefore  every  day  be- 
come greater.  At  this  period,  therefore,  the  cow  must  obtain  larger  sup- 
plies of  food  to  sustain  herself  and  to  produce  a  sufficient  quantity  of 
milk  for  her  calf  than  at  any  other  period.  If  these  adequate  supplies 
are  not  given,  a  portion  is  daily  taken  from  her  own  substance — her  body 
becomes  leaner,  and  her  limbs  more  feeble,  while  her  young  also  is 
stinted  and  puny  in  its  growth. 

By-and-bye,  however,  the  calf  begins  to  pick  up  food  for  itself.  It 
begins  to  live  partly  upon  vegetables.  The  mother  is  in  consequence 
relieved  of  a  part  of  her  burden — her  udders  are  less  drawn  upon — the 
quantity  of  milk  secreted  becomes  less — she  begins  again  to  lay  muscle 
and  fat  upon  herself — her  udders  at  length  become  dry,  and  she  slowly 
recovers  her  original  plump  condition.  She  has,  indeed,  at  this  period  a 
tendency  to  fatten  if  the  same  supply  of  food  is  continued  to  her,  and 
in  many  districts  it  is  customary  to  feed  her  off  at  this  time  for  the 
butcher. 

What  I  have  already  said  of  the  artifices  by  which  the  food  given  to 
the  cow  may  possibly  be  made  to  affect  the  bodily  character  of  the  future 
calf,  applies  equally  to  the  means  of  more  or  less  effectually  promoting 
the  growth  of  the  young  ariimul  while  it  is  fed  solely  upon  milk.  The 
land  of  food  given  to  the  mother  may  make  the  milk  richer  in  curd, 
which  will  promote  the  growth  of  muscle— or  richer  in  phosphates,  by 
which  the  enlargement  of  the  bones  of  the  calf  will  be  assisted.  Scarcely 
any  two  samples  of  milk,  indeed,  are  found,  upon  analysis,  to  contain 
the  same  proportion  of  phosphates  and  of  other  saline  substances,  and 
there  is  little  reason  to  doubt  that  if  an  unusual  quantity  of  these  be  given 
in  the  food  of  the  mother,  an  unusual  quantity  will  be  found  also  in  the 
milk  she  produces. 

For  the  production  of  milk  the  mother  requires  an  adequate  additional 
supply  of  all  the  substances  which  we  have  seen  to  be  necessary  to  the 
support  of  the  unborn  foetus — of  the  starch  as  well  as  of  the  gluten  and 
saline  substances  of  the  food.  But  it  is  interesting  to  mark  the  very  dif- 
ferent purposes  to  which  the  additional  supply  of  starch  in  her  food  is 
now  applied. 

The  pregnant  mother  requires  this  starch  to  supply  the  carbon  given 
off  more  abundantly  during  her  increased  lespiration.     She  breathes,  as 
I  have  already  said,  for  her  young  and  for  herself,  and  therefore  gives 
off  more  carbon  from  her  lungs. 
26 


606  USES    OF    MILK    IN    THE    ECONOirlV     )F    NATURE. 

But  when  the  young  animal  is  b(5rn  it  breathes  for  itself.  It  must, 
therefore,  be  supplied  with  that  kind  of  food  which  seems  specially  in-, 
tended  to  meet  the  wants  of  respiration. 

The  additional  starch  eaten  by  the  mother,  therefore,  instead  of  being 
breathed  away  in  her  own  lungs,  is  conveyed  in  the  form  of  sugar  into 
the  food  of  the  young  animal.  It  is  changed  into  the  sugar  of  the  milk, 
and  the  natural  function  of  this  sugar  is  to  supply  the  carbon  which  the 
young  animal  gives  off  wHen  it  begins  to  breathe  for  itself. 

It  is  not  difficult  to  understand  the  kind  of  process  by  which  the 
starch  of  the  mother's  food  is  converted  into  the  sugar  of  her  milk.     If  to 

2  of  starch  =  24C  +   20H  +  20O, 
we  add  4  of  water  =  4H  +     40, 


we  have  54C  +  24H  +  240,  which  is  the  formula  for 

milk  sugar.  In  passing  through  the  digestive  organs  of  the  cow,  there- 
fore, the  elements  of  the  2  of  starch  require  only  to  be  combined  with 
those  of  4  of  water  to  be  converted  into  the  sugar  of  milk. 

But  though  it  is  not  difficult  to  understand  in  what  way  this  change 
may  be  effected,  yet  it  is  exceedingly  interesting  to  lind  that  such  a 
chemical  change  as  this  should  be  made  to  commence  at  a  certain  special 
epoch  with  a  view  to  a  certain  special  end. 

Milk  is  a  perfect  food  for  a  growing  animal,  containing  the  curd  which 
is  to  form  the  muscles,  the  butter  which  is  to  supply  the  fat,  the  phos- 
phates which  are  to  build  up  the  bones,  and  the  sugar  which  is  to  leed 
the  respiration.  Nothing  is  wanting  in  it.  The  mother  selects  all  the 
ingredients  of  this  perfect  food  from  among  the  useless  substances  which 
are  mingled  in  her  own  stomach  with  the  food  she  eats — she  changes 
these  ingredients  chemically  in  such  a  degree  as  to  present  them  to  the 
young  animal  in  a  state  in  which  it  can  most  easily  and  with  least  laboui 
employ  them  for  sustaining  its  body — and  all  this  she  begins  lo  do  at  a 
given  and  appointed  moment  of  time.  How  beautiful,  how  wonderful, 
how  kindly  provident  is  all  this  ! 


But  apart  from  its  natural  use  in  the  economy  of  nature,  milk  may  be 
regarded  as  an  article  of  manufacture — an  important  article  of  agricul- 
tural husbandry.  As  a  mere  producer  of  milk  for  other  purposes  than 
the  feeding  of  calves,  the  cow  will  be  differently  fed  according  to  the  pur- 
pose for  which  her  milk  is  intended  ta  be  employed,  or  the  form  in  which 
it  is  to  be  carried  to  market. 

a.  The  town  dairyman,  who  sells  his  new  milk  to  daily  customers, 
requires  quantity  rather  than  quality.  He  gives  his  cattle,  therefore, 
succulent  food  in  which  water  abounds — green  grass — forced  rapidly  for- 
ward by  irrigation  or  otherwise — green  clover,  young  rye,  brewers* 
grains,  or  hay  tea.*  In  this  way,  without  the  actual  addition  of  water, 
he  can  make  his  milk  thin,  and  increase  its  bulk. 

b.  Those,  again,  who  desire  much  rich  cream,  or  who  grow  milk  for 

*  A  mixed  hay  tea  and  pease  soup,  which  is  excellent  for  making  cows  give  milk,  is  pre- 
pared by  putting  hay  into  a  pot  in  alternate  layers,  sprinkling  between  each  a  handful  of 
pease-meal,  adding  water  and  bringing  to  a  boil. 


TO  PRODUCE  MILK  FOR  CHEESE  OR  BUTTER.         f07 

the  manufacture  of  butter,  pay  less  attention  to  the  bulk  of  the  milk 
itself  than  to  that  of  the  cream  they  can  collect  from  its  surface.  The 
proportion  of  butter  is  increased  by  the  use  of  food  which  contains  much 
fatty  matter — of  any  of  those  kinds  of  food,  indeed,  by  which  an  ox  can 
be  made  rapidly  to  lay  on  fat.  Oil-cake  has  by  some  been  objected  to 
as  likely  to  give  a  taste  to  the  milk,  but  it  may  be  safely  used  in  small 
quantity,  and  gives  an  abundant  and  good  flavoured  cream. 

c.  In  cheese  countries,  again,  it  is  the  curd  that  is  chiefly  in  request. 
No  doubt  the  value  of  a  cheese  depends  much  upon  the  proportion  of 
butter  it  contains  diffused  throughout  its  substance,  but  the  weight  of 
cheese  produced  upon  a  farm  depends  mainly  upon  the  quantity  of  curd 
which  the  milk  of  the  dairy  yields.  Where  skim-milk  cheese  is  made, 
the  weight  of  produce  obtained  depends  almost  solely  upon  the  richness 
of  the  milk  in  curdy  matter.  Clovers,  vetches,  and  pea  straw  abound  in 
casein  or  vegetable  curd,  and  thus  give  a  rich  and  productive  milk  to  the 
cheese  maker,  while  bean-meal  and  pease-meal,  in  so  far  as  they  can  be 
given  to  the  cow  with  safety,  may  with  advantage  be  employed  to  pro- 
duce the  same  effect.  As  every  thing  which  t«nds  to  lay  on  fat  on  the 
animal  is  likely  also  to  increase  the  proportion  of  butter  in  its  milk,  sc 
every  thing  which  promotes  the  growth  of  muscle  will  also  add  to  the 
richness  of  the  milk  in  curd  or  cheese. 

§  12.  Influence  of  size,  condition,  warmth,  exercise,  and  light,  on  the 
quantity  of  food  necessary  to  make  up  for  the  natural  waste. 

But  the  quantity  of  food  of  any  kind  which  an  animal  will  require  is 
affected  by  many  circumstances.     Thus — 

1°.  The  size  and  condition  of  tlie  animal  will  regulate  very  much  the 
quantity  of  food  which  is  necessary  to  sustain  it.  The  larger  the  mus- 
cles and  bones  the  greater  will  be  the  daily  waste,  and  the  greater  the 
quantity,  therefore,  of  the  food  necessary  to  replace  it.  If  an  animal  re- 
quire a  50th  or  a  60th  of  its  weight  of  dry  food  daily,  of  course  his  size 
and  weight  will  regulate  almost  entirely  the  quantity  of  food  he  ought  to 
eat. 

A  knowledge  of  this  circumstance  is  occasionally  of  economical  value 
to  the  stock  feeder  or  dairy  farmer,  and  will  modify  very  much  the  line 
of  conduct  he  may  be  inclined  to  adopt  as  the  most  profitable. 

A  large  animal  requires  more  food  to  keep  it  in  its  actual  condition — 
to  make  up,  that  is,  for  the  natural  waste.  If  you  wish  to  convert  much 
produce  into  much  rich  dung,  therefore,  keep  large  animals.  They  will 
convert  a  large  quantity  of  vegetable  matter  into  manure  without  adding 
any  thing  to  their  own  substance.  If  one-fiftieth  of  its  weight  of  dry 
food  be  necessary  to  sustain  it,  then  an  animal  of  100  stones  weight  will 
convert  two  stones  of  hay  dailj/-  into  dung.  Whatever  it  eats  beyond  the 
two  stones,  will  go  to  the  increase  of  its  weight. 

But  a  small  animal,  of  50  stones,  requires  only  one  stone  a  day  to  sus- 
tain its  body,  or  converts  one  stone  wholly  into  dung.  Whatever  it  eats 
beyond  this  quantity,  therefore,  will  go  to  the  production  of  increased 
beef  and  bone.  Hence,  if  I  have  a  given  quantity  of  vegetable  produce, 
[  ought  to  be  able  to  manufacture  more  beef  from  it  by  the  use  of  small 
cattle  than  of  large,  provided  my  large  and  small  stock  are  equally  pur» 
in  breed,  are  equally  quiet,  and  tie  as  kindly  feeders. 


608  INFLUENCE   OF   EXERCISE   AND   WARMTH. 

The  same  reasoning  applies  to  dairy  cows  of  different  breeds.  If  I 
give  two  stones  of  hay  to  a  smad  Shetland  cow,  she  may  not  convert 
more  than  one  of  them  into  dung,  the  other  she  may  consume  for  the 
production  of  milk.  But  if  I  give  the  same  quantity  to  a  cow  of  double 
the  size,  nearly  the  whole  two  stones  may  be  converted  into  dung — may 
be  employed  in  sustaining  the  animal — and  if  she  yield  any  milk  at  all, 
it  will  be  poor  and  thin. 

This  reasoning  accounts  for  the  fact  which  has  been  long  observed, 
that  small  breeds  of  cattle  give  the  richest  milk,  and  that  such  as  the 
small  Orkney  breed  yield  the  largest  produce  of  butter  and  cheese  from 
the  same  quantity  of  food.  They  waste  less  of  their  food  in  sustaining 
their  own  bodies.  Lean,  spare  cows  also  require  less  to  sustain  them  ; 
and  hence  the  skin-and-bone  appearance  of  the  best  milkers  among  the 
Ayrshire  and  Alderney  breeds. 

2°.  The  quantity  of  exercise  which  an  animal  takes,  or  of  fatigue  it 
is  made  to  undergo,  requires  a  proportionate  adjustment  in  the  quantity 
of  food.  The  more  it  is  exercised  the  more  frequently  it  breathes,  the 
more  carbon  it  throws  off'  from  its  lungs,  the  more  starch  or  sugar  con- 
sequently its  food  must  contain.  If  more  is  not  given  to  it,  the  fat  or 
other  parts  of  the  body  will  be  drawn  upon,  and  the  animal  will  become 
leaner. 

Again,  the  natural  waste  of  the  muscles  and  bones  is  said  to  be  caused 
by,  or  at  least  to  be  in  proportion  to,  the  degree  of  motion  to  which  the 
several  parts  of  the  body  are  subjected.  Take  more  exercise,  therefore, 
move  one  or  more  limbs  oftener  than  usual,  and  a  larger  part  of  the  sub- 
stance of  these  limbs  will  be  decomposed,  removed,  and  rejected  in  the 
excretions.  Hence  the  reason  why  hard  work  recjuires  good  food,  and 
why  the  strength  of  all  animals  is  diminished,  if  they  be  subjected  to 
great  fatigue  and  are  not  in  an  equal  degree  supplied  with  nourishing 
food,  by  which  the  wasting  parts  of  the  body  may  be  again  built  up. 

3°.  The  degree  of  warmth  in  whicli  the  animal  is  kept,  or  the  tem- 
perature of  the  atmosphere  in  which  it  lives,  affects  also  the  quantity  of 
food  which  the  animal  requires  to  eat.  The  heat  of  the  animal  is  inse- 
parably connected  with  its  respiration.  The  more  frequently  it  breathes, 
the  warmer  it  becomes,  and  the  more  carbon  it  throws  off"  from  its  lungs. 
It  is  believed,  indeed,  by  many,  that  the  main  purpose  of  respiration  is  to 
keep  up  the  heat  of  the  body,  and  that  this  heat  is  produced  very  much 
in  the  same  way  as  in  a  common  fire,  by  a  slow  combustion  of  that  car- 
bon which  escapes  in  the  form  of  carbonic  acid  from  the  lungs.  Place  a 
man  in  a  cold  situation,  and  he  will  either  starve  or  he  will  adopt  some 
means  of  warming  himself.  He  will  probably  take  exercise,  and  by  this 
means  cause  himself  to  breathe  quicker.  But  to  do  this  for  a  length  of 
time,  he  must  be  supplied  with  more  fopd.  For  not  only  does  he  give 
off"  more  carbon  from  his  lungs,  but  the  exercise  he  takes  causes  a  greater 
natural  waste  also  of  the  substance  of  his  body. 

So  it  is  with  all  animals.  The  greater  the  difference  between  the  tem- 
perature of  the  body  and  that  of  the  atmosphere  in  which  they  live,  the 
more  food  they  require  to  "  feed  the  lamp  of  life" — to  keep  them  warm, 
that  is,  and  to  supply  the  natural  waste.  Hence  tlie  importance  of  plan- 
tations as  a  shelter  from  cold  winds  to  grazing  stock — of  open  sheds  to 
protect  fattening  stock  from  tlie  nightly  dews  and  colds — and  even  of 


EFFECT    OF   ABSENCE    OF   LIGHT.  609 

closer  covering  to  quiet  and  gentle  breeds  of  cattle  or  sheep,  which  feed 
without  restlessness  and  ([uickly  fatten. 

A  proper  attention  to  the  warmth  of  his  cattle  or  sheep,  therefore,  is  of 
great  practical  consequence  to  the  feeder  of  stock.  By  keeping  them 
warm  he  diminishes  the  quantity  of  food  which  is  necessary  to  sustain 
them,  and  leaves  a  larger  proportion  for  the  production  of  beef  or 
mutton. 

Various  experiments  have  been  lately  published,  which  confirm  the 
opinions  above  deduced  from  theoretical  considerations.  Of  these  I  shall 
only  mention  one  by  Mr.  Childers,  in  which  20  sheep  were  folded  in 
the  open  field,  and  20  of  nearly  equal  weight  were  placed  under  a  shed 
in  a  yard.  Both  lots  were  fed  for  three  months — January,  February, 
and  March — upon  turnips,  as  many  as  they  chose  to  eat,  half  a  pound 
of  linseed  cake,  and  half  a  pint  of  barley  each  sheep  per  day,  with  a 
little  hay  and  salt.  The  sheep  in  the  field  consumed  the  same  quantity 
of  food,  all  the  barley  and  oil-cake,  and  about  19  lbs.  of  turnips  per  day, 
from  first  to  last,  and  increased  on  the  whole  36  stones  8  lbs.  Those 
under  the  shed  consumed  at  first  as  much  food  as  the  others,  but  after 
the  third  week  they  eat  2  lbs.  of  turnips  each  less  in  the  day,  and  in  the 
ninth  week,  again  2  lbs.  less,  or  only  15  lbs.  a  day.  Of  the  linseed-cake 
they  also  eat  about  one-third  less  than  the  other  lot,  and  yet  they  in- 
creased in  weight  56  stones  6  lbs.,  or  20  stones  more  than  the  others. 

Thus  the  cold  and  exercise  in  the  field  caused  the  one  lot  to  convert 
more  of  their  food  into  dung,  the  other  more  of  it  into  mutton. 

But  why  did  the  sheltered  sheep  also  consume  less  food  ?  Why  did 
they  not  eat  the  rest  of  the  food  offered  them,  and  convert  it  also  into 
mutton  ?  Because  the  stomach  of  an  animal  will  not  do  more  than  a 
certain  limited  amount  of  work  in  the  way  of  digesting,  after  the  wants 
of  the  body  are  fully  supplied.  When  circumstances  cause  the  sustain- 
ing quantity  of  food  to  increase,  the  digestive  powers  are  stimulated  into 
unusual  activity,  and  though  plenty  of  food  be  placed  before  the  animal 
it  may  be  unable  to  consume  and  digest  more  than  is  barely  sufficient  to 
keep  it  in  condition.  If  the  sustaining  portion  be  lessened,  by  placing 
the  animal  in  new  circumstances,  more  food  maybe  digested  than  is  ab- 
solutely necessary  to  supply  the  daily  waste — that  is  to  say,  the  animal 
may  increase  in  weight.  But  the  unusual  stimulus  being  removed,  it 
may  not  now  be  inclined,  perhaps  not  be  able,  to  digest  so  large  a  quan- 
tity as  it  did  before  when  that  large  quantity  was  necessary  to  sustain  its 
body — that  is  to  say,  that  while  it  increases  in  weight  it  will  also  con- 
sume less  food. 

4°.  The  absence  of  light  has  also  a  material  influence  upon  the  effects 
of  food  in  increasing  the  size  of  animals.  Whatever  excites  attention  in 
an  animal,  awakens,  disturbs,  or  makes  it  restless,  appears  to  increase 
the  natural  waste,  and  to  diminish  the  effect  of  food  in  rapidly  enlarging 
the  body.  The  rapidity  with  which  fowls  are  fattened  in  the  dark  is 
well  known  to  rearers  of  poultry.*  In  India,  the  habit  prevails  of  sew- 
ing up  the  eyelids  of  the  wild  hog-deer,  the  spotted  deer,  and  other  wild 

•  It  is  astonishing  with  what  rapidity  fowls  (dorklngs)  increase  when  well  fed,  kept  in  con- 
fined cribs,  and  in  a  darkened  room.  Fed  on  a  mixture  of  4  lbs.  of  oatmeal,  1  lb.  of  suet, 
and  J  lb.  of  sugar,  with  milk  for  drink  five  or  six'limes  a  day  in  summer,  a  dorking  will  add 
to  its  weight  2  lbs.  in  a  week,  sometimes  IJ  lbs.  in  four  days.  A  young  turkey  will  lay  on  3 
.Ds.  a  week,  under  the  same  treatmenL 


610 


VENTILATION    AND    CLEANLINESS. 


animals  when  netted  in  the  jungles,  with  the  view  of  taming  and  speedily 
fattening  them.  The  ahsence  of  light  indeed,  ho>vever  produced,  seems 
to  soothe  and  quiet  all  animals,  to  dispose  ihem  to  rest,  to  make  less  food 
necessary,  and  to  induce  them  to  store  up  more  of  what  they  eat  in  the 
form  of  fat  and  muscle. 

An  experiment  made  by  Mr.  Morton,  on  the  feeding  of  sheep,  shows 
the  effect  at  once  of  shelter,  of  (juiet,  and  of  the  absence  of  light  upon 
the  quantity  of  food  eaten  and  of  mutton  produced  from  it. 

Five  sheep,  of  nearly  equal  weights,  were  fed  each  with  a  pound  of 
oats  a-day  and  as  much  turnips  as  they  chose  to  eat.  One  was  fed  in 
the  open  air,  two  in  an  o[)en  shed — one  of  them  being  confined  in  a  crib — 
two  more  were  fed  in  a  close  shed  in  the  dark — and  one  of  these  also  was 
confined  in  a  crib,  so  as  to  lessen  as  much  as  possible  the  quantity  of  ex- 
ercise it  should  take.  The  increase  of  live  weight  in  each  of  the  five, 
and  the  quantity  of  turnips  they  respectively  consumed,  appear  in  the 
following  table  : — 


Increase 

LIVB    WBIOHT. 

for  each 

.  Increase. 

Turnipa 

100  lbs.  of 

Nov.  18. 

March  9. 

eaten. 

turnips. 

lbs. 

lbs. 

lbs. 

lbs. 

lbs. 

Unsheltered 

108 

131-7 

23-7 

1912 

1-2 

In  open  sheds     .... 

-  102 

129-8 

27-8 

1394 

2-0 

Do.,  but  confined  in  cribs 

108 

130-2 

22-2 

1238 

1-8 

In  a  close  shed  in  the  dark 

104 

132-4 

28-4 

886 

31 

Do.,  but  confined  in  cribs 

111 

131-3 

20-3 

886 

2-4 

From  this  table  it  appears,  as  we  should  have  expected — 
a.  That  much  less — one-third  less — turnips  was  eaten  by  the  animal 
■which  was  sheltered  by  the  open  shed,  than  by  that  which  was  without 
shelter,  while  in  live  weight  it  gained  four  pounds  more. 

h.  That  in  the  dark  the  quantity  of  turnips  eaten  was  one-half  less, 
and  the  increase  of  weight  a  little  greater  still. 

c.  But  that  when  confined  in  cribs — though  the  food  eaten  might  be  a 
little  less — the  increase  in  weight  was  not  so  great.  The  animal,  in 
fact,  was  fretful  and  restless  in  confinement,  and  whatever  produces  this 
effect  upon  an  animal  prevents  or  retards  its  fattening. 

d.  That  the  most  profitable  return  of  mutton  from  the  food  consumed, 
is  when  the  animal  is  kept  under  shelter  an<]  in  the  dark. 

Such  a  mode  of  keeping  animals,  however,  must  not  be  entered  upon 
hastily  or  without  due  consideration.  The  habits  of  the  breed  must  be 
taken  into  account,  the  effect  of  the  confinement  upon  their  health  must 
be  frequently  attended  to,  and,  above  all,  the  ready  admission  of  fresh  air 
and  a  good  ventilation  -must  not  be  forgotten.  By  a  neglect  of  the  pro- 
per precautions,  unfortunate  results  have  frequently  been  obtained  and  a 
sound  practice  brought  into  disrepute. 

5°.  Ventilation  and  cleanliness  indeed  are  important  helps  to  economy 
in  the  feeding  of  all  animals.  Shelter  and  warmth  will  do  harm,  if  free 
and  pure  air  is  not  admitted  to  the  fattening  stock.  The  same  is  true  of 
cleanliness,  so  favourable  to  the  health  of  all  animals.  The  cleaner 
their  houses  and  skins  are  kept,  the  more  they  thrive  under  any  given 
form  of  treatment  in  other  respects. 


EFFECT    OF    THE   SOURING    OF    FOOD.  6ll 

§  13.  Influence  of  the  form  or  state  in  which  the  food  is  given  on  the 
quantity  required  by  an  animal. 
The  state  in  which  the  food  is  given  to  his  stock  has  often  an  important 
influence  upon  the  profits  of  the  teeder.     Thus — 

1°.  The  souring  of  the  food,  in  some  cases,  makes  its  use  more  econo- 
mical. Arthur  Young  details  several  series  of  experiments  on  the  fat- 
tening of  pigs,  in  which  bean  meal  was  given  mixed  with  water  in  the 
sweet  state,  and  after  it  had  been  allowed  to  stand  several  days  to  sour. 
In  every  case  in  which  it  was  given  sour,  the  pork  obtained  gave  a  profit 
upon  the  price  of  the  meal,  while  in  every  case  in  which  the  same  meal 
was  given'sweet  and  in  equal  quantity,  the  price  obtained  for  the  pork 
was  less  than  that  which  was  paid  for  the  meal. 

Upon  sour  food,  indeed,  pigs  are  universally  observed  to  fatten  best. 
In  Holstein,  it  is  customary  to  collect  waste  gre'en  herbage  of  every  kind, 
and  to  let  it  sour  in  water.  It  then  fattens  pigs  which  would  scarcely 
thrive  on  it  before.  During  this  souring  of  vegetable  matter  in  water,  it 
is  lactic  acid — the  acid  of  milk — which  is  chiefly  produced.  This  acid, 
therefore,  would  appear  to  favour  the  increase  of  size  in  the  pig,  and  to 
this  cause  may  be  owing  the  profitable  use  of  sour  whey  in  feeding  this 
kind  of  stock  in  cheese-making  districts. 

I  have  been  told  by  some  cow-feeders  who  use  brewers'  grains,  that 
the  dry  cows,  when  fattening  off',  relish  the  grains  most  when  slightly 
sour,  and  fatten  most  quickly  upon  them.  From  others,  however,  I 
have  obtained  a  contrary  opinion,  and  have  been  assured  that  fattening 
stock  of  all  kinds  like  the  grains  best,,  and  thrive  best  upon  them,  when 
perfectly  sweet  and  fresh.  It  is  a  matter  of  doubt,  therefore,  whether  or 
not  the  souring  of  food  generally,  of  all  kinds  and  for  all  kinds  of  stock, 
can  be  safely  tried  or  recommended. 

2°.  The  boiling  or  steaming  of  dry  food,  and  even  of  potatoes  and  tur- 
nips, is  recommended  by  many  as  an  economical  practice.  I  believe 
that  the  general  result  of  tlie  numerous  experiments  which  have  been 
made  upon  this  subject  in  various  parts  of  the  country  is  in  favour  of 
this  opinion  in  so  far  as  regards  fattening  and  growing  stock.  It  seems  a 
more  doubtful  practice  in  the  case  of  horses  which  are  intended  for  heavy 
and  especially  for  fast  work — though  even  for  these  animals  the  use  of 
steamed  food  is  beginning  to  be  adopted  by  some  of  the  most  extensive 
coach  contractors.     [Stephens'  Book  of  the  Farm.] 

3°.  It  is  a  curious  fact  not  less  worthy  of  the  attention  of  the  chemist 
than  it  is  of  the  practical  man,  that  the  age  of  the  food  singularly  affects 
its  value  in  the  nourishment  of  animals.  Thus  new  oats  are  not  con- 
sidered fit  for  hunters  before  the  months  of  February  or  March.  They 
affect  the  heels  and  limbs  with  something  like  grease,  and  make  the 
horse  unfit  for  fast  work.  Nor  is  it  merely  water  which  the  grain  loses 
by  the  five  or  six  months'  keeping — for  if  it  be  dried  in  the  kiln  it  is  still 
unfit  for  use,  from  its  stimulating  in  an  extraordinary  degree  the  action 
of  the  kidneys.  Some  chemical  change  takes  place  in  the  interior  of  the 
oat  which  has  not  yet  been  investigated. 

The  potato,  on  the  other  hand,  by  keeping,  loses  much  of  its  nutritive 
value,  even  before  it  has  begun  to  sprout — and  every  feeder  knows  tha* 
turnips  which  have  shot  into  flower,  add  much  less  than  before  to  the 
weight  of  his  fattening  stock. 


612  INFLUENCE   OF   SOIL   AND    CULTURE   ON    THE 

§  14.  Influence  of  sail  and  culture  on  the  nutritive  value  of  agricultural 

produce. 

I  have  on  several  former  occasions,  (pages  500  to  528),  directed  your 
attention  to  the  remarkable  influence  which  soil,  culture,  and  climate 
have  upon  the  chemical  composition  of  the  different  corn  and  green  crops 
usually  raised  for  food.  Every  such  change  of  composition  alters  also 
the  nutritive  value  of  any  given  crop.  If  the  wheat  or  barley  be  richer 
in  gluten,  it  will  build  up  more  muscle — if  it  abound  more  in  starch,  a 
smaller  weight  of  it  will  supply  the  carbon  of  respiration — if  it  be  richer 
in  fatty  matter,  it  will  round  off' the  edges  of  the  bones,  and  fill, up  the  in- 
equalities in  an  animal's  body  more  quickly  with  fat.  Such  differences 
as  these  I  have  already  shown  you  do  really  exist  among  samples  of  the 
same  kind  of  grain  grown  upon  soils  either  of  different  quality,  or  of  tke 
same  quality  when  differ^tly  cultivated  or  manured. 

But  this  different  culture  or  manuring  affects  the  relative  proportions 
of  the  several  kinds  of  inorganic  matter  also— the  phosphates  and  other 
saline  substances— which  are  known  to  exist  necessarily  in  all  vegetable 
productions.  In  illustration  of  this,  I  would  direct  your  attention  to  the 
following  analyses — made  in  my  laboratory  by  Mr.  Fromberg — of  the 
ash  of  two  samples  of  the  same  kind  of  turnip  (red  topped  yellow) 
raised  by  Lord  Blantyre,  on  the  same  field,  the  one  with  guano  alone, 
the  other  with  farm-yard  dung  alone.  The  quantity  of  ash  left  by  the 
two  varieties  of  turnip  was  0*68  and  0-7  per  cent,  respectively,  and  this 
ash  was  composed  as  follows : — 

Composition  of  the  ash  of  turnips  raised  loith  guano ^  and  with  farm-yard  dung. 


GUANO.  DtJNG. 


Chloride  of  Potassium 
Sulphate  of  Potash 
Carbonate  of  Potash   . 
Phosphate  of  Potash  . 

Lime    . 

Magnesia 

Alumina 

Carbonate  of  Lime 

Alumina 

Oxide  of  Manganese  . 
SiUca 


Interior. 

Eiterior. 

Interior. 

Exterior. 

556 

503 

540 

10-71 

3085 

37  04 

3120 

35-47 

11-38 

903 

36-74 

17-63 

20-93 

1017 

551 

3-65 

4-55 

449 

1-58 

202 

034 

1-62 

2-63 

313 

4-87 

9.94 

0-92 

2-76 

9-52 

9-72 

11-56 

14-82 

509 

2-79 

0-94 

0-46 

321 

590 

2-60 

5.33 

1-65 

343 

— 

3-04 

97-95  99-16  9908  99*02 

The  most  striking  difference  between  the  two  varieties  of  ash  is  in  the 
proportion  of  phosphates  they  respectively  contain.  The  ash  of  the 
guano  turnips  contained  from  25  to  30  per  cent,  of  phosphates,  that  of 
the  dung  turnips  only  from  9  to  11  per  cent.  This  could  not  fail  to 
make  an  important  difference  in  their  relative  values  for  the  feeding  of 
stock  whose  bones  are  growing,  and  which  require,  therefore,  a  larger 
supply  of  phosphates  in  their  food. 

The  phosphates  of  lime  and  magnesia  form,  as  we  know,  one  of  the 
valuable  constituents  of  guano,  but  we  could  scarcely  have  inferred  that 
this  manure  would  have  caused  so  much  larger  a  proportion  of  these 
phosphates  to  enter  into  the  constituents  of  the  turnips  raised  with  them. 


NUTRITIVE   VALUE    OF   AGRICULTURAL   PRODUCE.  613 

It  is  not  unlikely  that  turnips,  raised  from  bones,  will  also  abound  more 
largely  in  phosphates  than  turnips  raised  from  dung  or  rape  dust,  and 
may  therefore  be  better  fitted  for  growing  stock. 

§  15.  Can  we  correctly  estimate  the  relative  feeding  properties  of  different 
kinds  of  produce  under  all  circumstances. 

Since  the  several  nutritive  effects  of  different  kinds  of  food  are  de- 
pendent upon  so  many  circumstances — upon  the  state  of  the  animal 
itself — the  purpose  for  which  it  is  fed — the  mode  in  which  it  is  housed 
and  protected — the  form  and  period  at  which  it  is  given— can  it  be  pos- 
sible to  classify  them  in  an  order  which  will  indicate  their  relative  feed- 
ing values  in  all  cases  and  for  all  purposes  ?  This  is  obviously  impos- 
sible. We  may  easily  arrange  them  in  the  order  of  their  relative  values 
in  reference  to  some  one  of  the  several  purposes  for  which  food  is  given. 
We  may  shew  in  as  many  different  tables  the  order  of  their  relative 
values  in  laying  on  fat — in  increasing  the  muscles — or  in  promoting  the 
growth  of  bone ;  but  we  cannot  arrange  theoretically,  nor  can  experi- 
ment ever  practically  classify,  all  our  common  vegetable  productions  in 
one  invariable  order  which  shall  truly  represent  their  relative  values  in 
reference  to  each  of  these  three  different  points  : — 

1°.  Experimental  values. — This,  however,  practical  writers  have  often 
attempted  to  do.  Making  their  experiments  in  different  circumstances, 
with  different  varieties  of  the  same  produce,  upon  different  kinds  of 
stock,  or  upon  animals  fed  for  different  purposes,  they  have  obtained  re- 
sults of  the  most  diversified  kind,  and  have  classified  the  several  kinds  of 
fodder  in  the  most  unlike  order.  I  se'ect  a  few  of  these  results  for  the  sake 
of  illustration..  Taking  10  lbs.  of  meadow  hay  as  a  standard, — then,  to 
produce  an  equal  nutritive  effect,  the  different  quantities  of  each  of  the 
other  kinds  of  fodder  represented  by  the  numbers  in  the  following  table 
ought  to  be  used — according  to  the  several  authors  whose  names  are 
given. 

Experimental  quantities  of  fodder  which  must  he  used  to  produce  an 
equal  nutritive  effect^  according  to — 


Schwertz. 

Block. 

Petri. 

Thaer. 

PabsL 

Meyer. 

Middleton. 

Meadow  hay    .     . 

10 

10 

10 

10 

10 

10 

10 

Aftermath  hay      . 

11 

— 

10 

— 

— 

— 

-» 

Clover  hay  .     .     . 

10 

10 

9 

9 

10 



_». 

Green  clover  in  flow- 

er and  lucerne  . 

— 

43 

— 

45 

42 

— 

_„ 

Lucerne  hay    .     . 

9 

— 

9 

9 

10 

— 

— 

Wheat  straw    .     . 

— 

20 

36 

45 

30 

15 

_ 

Barley  straw     .     . 

40 

19 

18 

40 

20 

15 



Oat  straw     .     .     . 

40 

20 

20 

40 

20 

15 

_ 

Pea  straw    .     .     . 



16 

20 

13 

15 

15 

.^ 

Potatoes       .     .     . 

20 

22 

20 

20 

20 

15 

__ 

Old  potatoes    .    . 

— 

40 

— 

— 

— 

— 

Carrots    .... 

27 

37 

25 

30 

25 

23 

34 

Turnips  .... 

45 

53 

60 

52 

45 

29 

80 

Wheat     .... 

4 

3 

6 

6 

— 

— 

~^ 

Barley     .... 

3 

6 

5 

5 

Oats 

— 

4 

7 

— 

6 

— 

-— 

F^om  an  inspection  of  this  table,  we  should  naturally  conclude  eituer 
26* 


614  THEORETICAL    NUTRITIVE    VALUES. 

that  the  different  kinds  of  fodder  vary  very  much  in  quality,  or  that  those 
who  determined  their  relative  values  by  experiment  must  have  tried 
their  effects  upon  very  different  kinds  of  sto(;k,  fed  probably  also  for  dif- 
ferent purposes.  Both  of  these  conclusions  are  no  doubt  true.  We 
know  that  the  same  kind  of  produce  does  vary  very  much  in  chemical 
constitution,  but  it  is  not  likely  that  different  samples  of  the  same  kind  of 
turnip  are  so  unlike  each  other  that  29  lbs.  of  the  one  will  go  as  far  in 
feeding  the  same  animal  as  80  lbs.  of  another.  These  great  differences 
in  the  table,  therefore,  seem  to  show  that  different  kinds  or  varieties  of 
fodder  have  been  used,  or  under  different  circumstances,  or  results  so  dis- 
cordant could  scarcely  have  been  obtained. 

A  certain  value,  it  is  true,  attaches  to  the  numbers  in  the  table  when 
those  given  by  the  different  authors  nearly  agree.  Thus,  about  20  of 
potatoes  and  30  of  carrots  appear  to  be  equal  in  nutritive  value  to  10  of 
hay.  It  must  be  confessed,  however,  that  this  subject  of  the  experimental 
value  of  different  kinds  of  farm  produce  in  feeding  stock  of  the  same 
Tcindfor  the  same  purposes  is  still  almost  wholly  uninvestigated.  "Will 
none  of  the  skilful  stock  feeders,  of  whom  so  many  are  now  springing 
up,  turn  their  attention  to  tliis  interesting  field  of  experimental  inquiry  ? 

2°.  Theoretical  values. — But  the  theoretical  values  of  different  kinds 
of  food  in  reference  to  a  particular  object,  can  be  determined  by  analyti- 
cal investigations  made  in  the  laboratory.  This  has  been  done  in  a 
very  able  manner  by  Boussingault,  in  reference  to  the  value  of  different 
Jcinds  of  fodder  in  the  production  of  muscle.  These  values,  according  tc 
his  analyses,  are  as  follow,  10  of  hay  being  again  taken  as  a  standard  : — 
Theoretical  quantities  of  different  Mnds  of  vegetable  produce  which  ivill 
produce  equal  effects  in  the  growth  of  muscle  {Boussingault): — 


Hay 10 

Clover  hay,  cut  in  flower  .     .  8 

Lucerne  do 8 

Aftermath  do 8 

Green  clover,  in  flower  ...  34 

Green  lucerne 35 

"Wheat  straw 52 

Rye  straw 61 

Barley  sIb^w  ......  52 

Oat  straw 55 

Pea  straw 6 

Vetch  straw 7 

Potato  leaves 36 

Carrot  leaves 13 

Oak  leaves 13 

T^is  table  possesses  much  value. 


Potatoes 28 

Old  potatoes 41 

Carrots 35 

Turnips 61 

"White  cabbage    .....  37 

V'etches 2 

Peas 3 

Indian  corn 6 

Wheat 5 

Rye 5 

Barley 6 

Oats 5 

Bran 9 

Oil-cake 2 

It  cannot,  however,  be  relied  upon 


as  a  safe  guide  in  all  cases  by  the  feeder,  because  of  the  differences  in 
the  composition  of  our  crops,  which  arise  from  the  mode  of  culture  an^d 
the  kind  of  manure  employed.  It  possesses,  however,  a  higher  value 
from  this  circumstance — that  as  muscle  in  most  animals  for,ras  the  larger 
portion  of  their  bulk,  the  order  in  which  different  kinds  of  vegetable  food 
promote  the  growth  of  this  part  of  the  body,  may  in  most  cases  be  adopted 
as  the  order  also  of  their  relative  v^ilues  in  sustaining  animals  and  keep- 
ing them  in  ordinary  condition.     The  same  remark,  however,  will  not 


ErrECT  or  mode  of  feeding  on  the  manure.  616 

apply  to  animal  food,  since  we  may  have  a  kind  of  animal  food,  such  as 
gelt^ine,  which  would  greatly  promote  tlie  growth  of  muscle,  but  which, 
from  its  composition,  is  capable  of  ministering  so  little  to  the  wants  of 
the  other  parts  of  the  body'that  it  wUl  not  even  support  life  for  any  length 
of  time. 

§  16.  Effect  of  different  modes  of  feeding  on  the  manure  and  on  the  soil. 

There  remains  still  one  practical  point  in  connection  with  the  feeding 
of  stock,  to  which  I  think  you  will  feel  some  interest  in  attending. 

The  production  of  manure  is  an  object  with  the  European  farmer  of 
almost  equal  importance  with  the  production  of  milk  or  the  fattening  of 
stock.  What  influence  has  the  mode  of  feeding  or  the  purpose  for 
which  the  animal  is  fed,  upon  the  quantity  and  quality  of  the  manure 
obtained  ? 

1°.  The  quantity  of  the  manure  depends  upon  the  quantity  of  food 
which  is  necessary  to  sustain  the  animal.  With  the  exception  of  the 
carbon,  which  escapes  from  the  lungs  in  the  form  of  carbonic  acid,  and 
a  comparatively  small  quantity  of  matter  which  forms  the  perspiration, 
the  whole  of  the  food  which  sustains  the  body  is  rejected  again  in  the 
form  of  dung. 

Now  the  sustaining  food  increases  with  the  size  of  the  animal,  with 
the  coldness  of  the  teriiperature  in  which  it  is  kept,  and  with  the  quantity 
of  exen^ise  it  is  compelled  to  take.  Large,  hardly  worked,  much  driven, 
and  coldly  housed  animals,  therefore,  if  ample  food  is  given  them,  will 
produce  the  largest  Quantity  of  manure.  It  might  be  possible,  indeed,  tc 
keep  large  animals  for  no  other  purpose  but  to  manufacture  manure — by 
giving  them  an  unlimited  supply  of  food,  using  means  to  persuade  them 
to  eat  it,  and  causing  them  at  the  same  time  to  take  so  much  exercise  as 
to  prevent  them  from  ever  increasing  in  weight. 

2°.  Quality  of  the  manure. — The  quality  of  the  manure  depends  al- 
most entirely  upon  the  kind  of  food  given  to  an  animal,  and  upon  the 
purpose  for  which  it  is  fed. 

a.  ^he  full- grown  animal,  which  does  not  increase  in  weight,  returns 
in  its  excretions  all  that  it  eats.  The  manure  that  it  forms  is  richer  in 
saline  matter  and  in  nitrogen  than  the  food,  because,  as  I  have  already 
explained  to  you  in  detail  (p.  472),  a  portion  of  the  carbon  of  the  latter 
is  sifted  out  as  it  were  by  the  lungs,  and  diffused  through  the  air  during 
respiration.  In  other  respects,  whatever  be  the  nature  of  the  food — the 
quantity  of  saline  matter  or  of  gluten  it  contains — the  dung  will  contain 
nearly  the  same  quantities  of  both  or  of  their  elements. 

h.  The  case  of  the  fattening  animal  again  is  different.  Besides  the 
sustaining  food,  there  is  given  to  the  animal  some  other  fodder  which 
will  supply  an  additional  quantity  of  fat  If  this  additional  food  be  only 
oil,  then  the  dung  will  be  little  afiected  by  it.  It  will  be  little  richer  than 
the  dung  of  the  full-grown  animal  to  which  the  same  sustaining  food  is 
given. 

But  if  the  additional  food  contain  other  substances  besides  fat — saline 
substances,  namely,  and  gluten — then  these  will  all  pass  into  the  dung 
and  make  it  richer  in  precise  proportion  to  the  quantity  of  this  addition^ 
food  which  is  given.  Thus  if  oil-cake  be  given  for  the  purpose  of  laying 
on  fat — the  usual  sustaining  food  at  the  same'time  being  supplied — the 


616  WHY    OLD    PASTURES    CONTINUE    RICH. 

dung  will  be  enriched  by  all  those  other  fertilizing  constituents  present  in 
the  oil-cake  which  are  not  required  or  worked  up  by  the  fattening  aniipal. 

Hence  it  is  that  the  dung  of  fattening  stock  is  usually  richer  than  that 
of  stock  of  other  kinds.  Oil-cake  would  be  a  rich  manure  were  it  put 
into  the  soil  at  once;  it  is  not  surprising,  therefore,  that  after  it  has 
parted  with  a  portion  of  its  oil  it  should  still  add  much  to  the  richness  of 
common  dung. 

A  knowledge  of  the  kind  of  material,  so  to  speak,  which  the  animal 
requires  to  fatten  it,  explains  in  a  considerable  degree  another  practical 
fact  of  some  consequence  through  which  it  is  not  easy  at  first  sight  to  see 
one's  way.  There  are  in  various  parts  of  the  island  certain  old  pastures 
which,  from  time  immemorial,  have  been  celebrated  for  their  fattening 
qualities.  Full-grown  stock  are  turned  upon  them  year  after  year  in  the 
lean  state,  and  after  a  few  months  are  driven  off  again  fat  and  plump  and 
fit  for  the  butcher.  This,  T  have  been  told  when  on  the  spot,  has  gone 
on  time  out  of  mind,  and  yet  the  land,  though  no  manure  is  artificially 
added,  never  becomes  less -valuable  or  the  pasture  less  rich.  Hence  the 
practical  man  concludes  that  the  addition  of  manure  to  the  soil  is  un- 
necessary, if  the  produce  be  eaten  off  by  stock — that  the  droppings  of 
the  animals  which  are  fed  upon  the  land  are  alone  sufficient  to  maintain 
its  fertility. 

But  the  reason  of  this  continued  richness  of  such  old  pastures  is 
chiefly  this — that  the  cattle,  when  put  upon  them,  are  usually  full-grown 
—they  have  already  obtained  their  full  supply  of  bone  and  nearly  as 
much  muscle  as  they  require.  While  on  the  fields  they  chiefly  select 
fat  from  the  grasses  they  eat,  returning  to  the  soil  the  phosphates,  saline 
substances,  and  most  of  the  nitrogen  which  the  grasses  contain.  Their 
bodies  are  no  doubt  constantly  fed  or  renewed  by  new  portions  of  these 
substances  extracted  from  the  food  they  eat,  but  they  return  to  the  soil  an 
equal  quantity  from  the  daily  waste  of  their  own  bodies — and  thus  are 
indebted  to,  and  carry  off  the  land,  little  more  than  the  fat  in  which 
they  are  observed  daily  to  increase. 

But  as  the  materials  of  the  fat  may  be,  and  no  doubt  originally  are, 
derived  wholly — perhaps  indirectly,  yet  wholly — from  the  atmosphere, 
the  land  is  robbed  of  nothing  in  order  to  supply  it,  and  thus  may  con- 
tinue for  many  generations  to  exhibit  an  equal  degree  of  fertility. 

I  give  this  only  as  a  general  explanation,  by  which  the  difficulty 
m.ay  be  solved,  where  no  other  more  likely  explanation  can  be  found 
in  the  local  circumstances  of  the  spot,  or  of  the  district  in  which  such 
rich  old  pastures  exist. 

c.  The  growing  animaU  again,  does  not  return  to  the  soil  all  it  re- 
ceives. It  not  only  discharges  carbon  from  its  lungs,  but  it  also  extracts 
phosphates  from  its  food  to  increase  the  size  of  its  bones,  gluten  to  swell 
out  its  muscles,  and  saline  substances  to  mingle  with  the  growing  bulk 
of  its  blood.  The  dung  of  the  growing  animal,  therefore,  will  not  be  so 
rich  as  that  of  the  full-grown  animal  fed  upon  the  same  kind  and  quan- 
tity of  food.  Hence  from  the  fold-yard,  where  young  stock  are  reared, 
the  manure  will  not  be  so  fertilizing,  weight  for  weight,  as  from  a  yard 
in  which  full-grown  or  fattening  animals  only  are  fed. 

d.  The  milk  cow  exhausts  still  further  the  food  it  eats.     In  the  lean 


THE   GROWING    ANIMAL   AND    THE   MIliK   COW.  617 

milk  cow,  which  has  little  muscle  or  fat  to  waste  away,  and,  therefore, 
little  to  repair,  the  sustaining  food  is  reduced  to  the  smallest  possible 
quantity.  This  small  portion  of  food  is  all  that  is  returned  to  the  hus- 
bandman in  her  dung.  The  phosphates,  salts  and  gluten,  and  even  the 
starch,  of  the  remainder  of  the  food  she  eats,  are  transformed  in  her 
system,  and  appear  again  in  the  form  of  milk.  The  dung  of  the  milk 
cow  must  be  very  much  poorer,  and  less  valuable,  compared  with  the 
food  she  eats,  than  that  of  any  other  kind  of  stock. 

It  is  true  that  the  bulk  of  her  dung  may  not  be  v«ry  much  less  than 
that  of  a  full-grown  animal  which  is  yielding  no  milk,  but  this  bulk  is 
made  up  chiefly  of  the  indigestible  woody  fibre  and  other  comparatively 
useless  substances  which  her  bulky  food  contains.  The  ingredients  of 
the  milk  have  been  separated  from  these  other  substances  as  the  food 
passed  through  her  body,  and  hence,  though  bulky,  the  dung  of  the  milk 
cow  is  colder  and  less  to  be  esteemed  than  that  of  the  dry  cow  or  of  the 
full-grown  ox. 

Nothing  can  more  strikingly  illustrate  the  difference  between  the  effect 
of  the  digestive  organs  of  the  fattening  ox  and  those  of  the  milk  cow 
upon  the  food  they  consume,  than  the  well-known  and  remarkable  dif- 
ference in  quality  which  exists  between  distillery  dung,  obtained  from 
fattening  cattle  fed  upon  the  refuse  of  the  distilleries,  and  cow-feeders' 
dung,  voided  by  milk  cows  fed  upon  nearly  the  same  kind  of  food — 
namely,  the  refuse  of  the  breweries. 

§  17.  Summary  of  the  views  illustrated  in  the  present  Lecture. 

The  topics  discussed  in  this  Lecture  are  of  so  interesting  a  kind,  and  so 
beautifully  connected  together,  that  you  will  permit  me,  I  am  sure, 
briefly  to  draw  your  attention  again  to  the  most  important  and  leading 
points. 

1°.  It  appears  that  all  vegetables  contain  ready  formed — that  is, 
form  during  their  growth  from  the  food  on  which  they  live — those  sub- 
stances of  which  the  parts  of  animals  are  composed. 

2°.  That  from  the  vegetable  food  it  eats,  the  animal  draws  directly 
and  ready-formed  the  materials  of  its  own  body — phosphates  to  form  the 
bones — gluten,  &c.,  to  build  up  its  muscles — and  oil  to  lay  on  in  the 
form  of  fat. 

3°.  That  during  the  process  of  respiration  a  full  grown  man  throws 
off*  from  his  lungs  about  8  oz. — a  cow  or  horse  five  times  as  much — of 
carbon  every  24  hours ;  and  that  the  main  office  of  the  starch,  gum,  and 
sugar  of  vegetable  food  is  to  supply  this  carbon.  In  carnivorous  animals 
it  is  supplied  by  the  fat  of  their  food — in  starving  animals,  by  the  fat  of 
their  own  bodies — and  in  young  animals,  which  live  upon  milk,  by  the 
milk  sugar  it  contains. 

4°.  That  muscles,  bone,  skin,  and  hair  undergo  a  certain  necessary 
daily  waste  of  substance — a  portion  of  each  being  removed  every  day 
and  carried  out  of  the  body  in  the  excretions.  The  main  function  of  the 
gluten,  the  phosphates,  and  the  saline  substances  in  the  food  of  the  full 
grown  animal,  is  to  replace  the  portions  of  the  body  which  are  thus  re- 
moved, and  to  sustain  its  original  condition.  Exercise  increases  this  na- 
tural waste  and  accelerates  the  breathing  also,  so  as  to  render  necessary 


618  SUMMARY    OF    THE   VIEWS     LLUSTRATED. 

a  larger  sustaining  supply  of  food — a  larger  daily  quantity  to  keep  the 
animal  in  condition. 

5°.  That  the  fat  of  the  body  is  generally  derived  from  the  fat  of  the 
vegetable  food — which  fat  undergoes  during  digestion  a  change  or  trans- 
formation by  which  it  is  converted  into  the  pecuhar  kinds  of  fat  which 
are  specially  fitted  to  the  body  of  the  animal  that  eats  it.  In  carnivor- 
ous animals,  the  fat  is  also  derived  directly  from  the  fat  of  their  food — 
which  is,  in  like  manner,  changed  in  order  to  adapt  it  to  the  constitution 
of  their  own  bodies.  In  cases  of  emergency,  it  is  probable  that  fat  may 
be  formed  in  the  animal  from  the  starch  or  sugar  of  the  food. 

6°.  In  the  growing  animal,  the  food  has  a  double  function  to  perform, 
it  must  sustain  and  it  must  increase  the  body.  Hence,  if  tlie  animal  be 
merely  increasing  in  fat,  the  food,  besides  what  is  necessary  to  make  up 
for  the  daily  waste  of  various  kinds,  must  also  supply  an  additional  pro- 
portion of  oil  or  fat.  To  the  growing  animal,  on  the  other  hand,  it  must 
.supply  also  an  additional  quantity  of  gluten  for  the  muscles,  and  of  phos- 
phates for  the  bones.  If  to  each  of  a  number  of  animals,  equal  quantities 
of  the  same  kind  of  food  be  given,  then  those  which  require  the  smallest 
quantity  of  food  to  sustain  them  will  have  the  largest  proportion  to  con 
vert  into  parts  of  their  own  substance.  Hence,  whatever  tends  to  in- 
crease the  sustaining  quantity — and  cold,  exercise,  and  uneasiness  do  so 
— will  tend,  in  an  equal  degree,  to  lessen  the  value  of  a  given  weight  of 
food,  in  adding  to  the  weight  of  the  animal's  body.  To  the  pregnam 
and  to  the  milk  cow  the  same  remarks  apply.  The  food  is  partly  ap- 
pended in  the  production  of  milk,  and  the  smaller  and  leaner  the  cow  is, 
less  food  being  required  to  sustain  the  body,  the  more  will  remain  for  the 
production  of  milk. 

7°.  Lastly,  that  the  quantity  and  quality  of  the  dung — while  they  de- 
pend in  part  upon  the  kind  of  f(K)d  with  which  the  animal  is  fed — yet 
even  when  the  same  kind  of  food  is  given,  are  materially  affected  bj--  the 
purpose  for  which  the  animal  is  fed.  If  it  be  full-grown  and  merely 
kept  in  condition,  the  dung  contains  all  that  was  present  in  the  food,  ex- 
cept the  carbon  that  has  escaped  from  the  lungs.  If  it  be  a  growing 
animal,  then  a  portion  of  the  phosphates  and  gluten  of  the  food  are  re- 
tained to  add  to  its  bones  and  muscles,  and  hence  the  dung  is  something 
less  in  quantity  and  considerably  inferior  in  quality  to  that  of  the  full- 
grown  animal. 

So  it  is  in  the  case  of  the  milk  cow,  which  consumes  comparatively 
little  in  sustaining  her  own  body,  but  exhausts  all  the  food  that  passes 
through  her  digestive  organs,  for  the  production  of  the  milk  which  is  to 
feed  her  young. 

The  reverse  takes  place  with  the  fattening  ox.  He  takes  little  else 
from  the  rich  additional  food  he  eats  but  the  oil  with  which  it  is  intended 
that  he  should  invest  his  own  body.  Its  other  constituents  are  for  the  most 
part  rejected  in  his  excretions,  and  hence  the  richness  and  high  price  of 
his  dung. 


Such  are  the  main  points  I  have  endeavoured  to  illustrate  to  you  in 
this  Lecture — they  involve  so  many  interesting  considerations,  both  <rfa 


CO^'CLUDING    SECTION.  61«3 

theoretical  and  of  a  practical  kind,  that  bad  my  limits  peniiii.ted  1  could 
have  wished  to  dwell  upon  them  at  still  greater  length. 

§  18.   Concluding  Section. 

I  have  now  brought  the  subject  of  these  Lectures  to  a  close.  I  have 
gone  over  the  whole  ground  which  in  the  outset  I  proposed  to  tread.  It 
is  the  first  time,  I  believe,  that  much  of  it  has  been  trodden  by  scientific 
men,  and  I  have  endeavoured  in  every  part  of  our  journey  to  lay  before 
you,  as  clearly  as  I  could,  everything  we  knew  of  the  country  we  passed 
over,  in  so  far  as  it  had  a  practical  bearing  or  was  likely  to  be  suscepti- 
ble hereafter  of  a  practical  application. 

In  the  first  Part,  I  directed  your  attention  to  the  organic  portion  of 
plants — showed  you  of  what  substances  it  consisted — on  what  kind  of 
organic  food  plants  live — and  by  what  chemical  changes  the  peculiar 
organic  compounds  of  which  they  consist  are  formed  out  of  the  organic 
food  on  which  they  live. 

In  the  second  Part,  I  explained  in  a  similar  way  the  nature,  composi- 
tion, and  origin  of  the  inorganic  portion  of  plants.  I  dwelt,  also,  upon 
the  nature,  origin,  and  natural  differences  which  exist  among  the  soils  on 
which  our  crops  are  grown,  and  from  which  the  inorganic  constituents  of 
plants  are  altogether  derived.  This  led  me  to  explain  the  connection 
which  exists  between  Agriculture  and  Geology, ,  and  the  kind  of  light 
which  this  interesting  science  is  fitted  to  throw  upon  the  means  of  prac- 
tically improving  the  soil. 

In  the  third  Part,  I  dwelt  upon  the  various  means  which  may  be 
adopted  for  increasing  the  general  productiveness  of  the  land — whether  > 
these  means  be  of  a  mechanical  or  chemical  nature.     The  >|j^le  doc- 
trine of  manures  was  here  discussed  and  many  suggestions  offered  to 
your  notice,  which  have  already  led  to  interesting  practical  results. 

In  the  fourth  Part,  I  have  explained  the  chemical  composition  of  the 
several  kinds  of  vegetable  produce  which  are  usu'ally  raised  for  food — 
showed  upon  what  constituents  their  nutritive  values  depend — and  how 
soil,  climate,  and  manure  affect  their  composition  and  their  value  as 
food.  The  nature  and  composition  of  milk  and  of  its  products — butter 
and  cheese — the  theory  of  their  manufacture,  and  the  circumstances  upon 
which  their  respective  (juantities  and  (jualities  depend — and,  lastly,  the 
way  in  which  food  acts  upon  and  supports  the  animal  body,  and  how  the 
value  of  the  manures  they  make  is  dependent  upon  the  purpose  for 
which  the  animal  is  fed — these  subjects  have  also  been  considered  and 
discussed  in  this  fourth  Part. 

In  discussing  new  topics  I  have  had  occasion  to  bring  before  you  many 
new  views.  This,  however,  I  have  not  done  lightly  or  without  consi- 
deration, and  I  feel  it  to  have  been  one  of  the  greatest  advantages  which 
have  attended  the  periodical  form  in  which  these  Lectures  have  been 
brought  before  the  public,  that  it  has  allowed  me  leisure  to  think,  to  in- 
quire, and  to  make  experiments  in  regard  to  points  upon  which  it  was 
difficult  at  first  to  throw  any  satisfactory  light.  It  is  gratifying  to  me  to 
know  that  the  general  difflision  which  these  Lectures  have  obtained,  has 
already  done  some  service  to  the  agriculture  of  the  country. 


APPENDIX: 


CONTAINING 


SUGGESTIONS  FOR  EXPERIMENTS  IN  PRACTICAL  AGRI- 

CULTURE,  WITH  RESULTS  OF  EXPERIMENTS 

MADE  IN  1841,  1842.  AND  1843. 


APPENDIX. 


No.  I. 

SUGGESTIONS  FOR  EXPERIMENTS»IN  PRACTICAL  AGRICULTURE 
DURING   THE   ENSUING    SPRING   AND    SUMMER. 

One  of  the  most  important  objects  which  chemistry  is  at  present  desirous  of 
attaining  for  the  improvement  of  practical  agriculture,  is  the  discovery  and  ap- 
plication of  specific  or  special  manures. 

We  know  that  certain  substances,  such  as  fold-yard  manure,  are  capable  of 
fertilizing  to  a  considerable  extent  almost  any  land,  and  of  causing  it  to  yield 
a  better  return  of  almost  any  crop.  But  we  know  also  that  manures  or  fertili- 
zers of  nearly  every  kind  are  more  efficacious  on  one  soil  than  on  another,  and 
that  some  answer  better  also  for  one  species  of  crop  than  for  another.  The 
case  of  gypsum  will  serve  to  illustrate  both  these  positions. 

The  effects  of  gypsum  in  the  United  States,  in  Prussia,  and  other  parts  of 
Germany,  and  in  some  districts  of  England,  arc  said  to  be  absolutely  astonish- 
ing ;  while  in  many  other  parts  of  our  Island,  of  Germany,  and  even  of  the 
United  States,  the  benefit  derived  from  it  has  not  repaid  the  trouble  and  expense 
incurred  in  applying  it.  Gypsum,  therefore,  is  espedal.li/  adapted  for  use  in  cer- 
tain soils  only. 

Again,  the  remarkable  effects  of  gypsum  have  been  observed  most  distinctly 
on  clover*  and  certain  kinds  of  grass.  The  same  benefits  have  not  followed, 
to  any  thing  like  an  equal  extent,  from  its  use  on  barley,  oats,  wheat,  or  other 
kind  of  grain.  Therefore,  while  specially  adapted  to  certain  soils,  it  is  also 
specially  adapted  to  certain  crops.  It  is  a  kind  of  specific  manure  for  clover 
and  some  of  the  grasses. 

Now,  neither  of  these  subjects  which  it  is  so  important  to  investigate, — 
neither  that  of  the  manures  which  are  especially  fitted  for  each  soil,  nor  of  those 
which  are  specially  fitted  for  each  crop,— can  be  determined  either  from  theory 
or  from  experiments  devised  and  executed  in  the  laboratory  of  a  chemist.  The 
aid  of  the  practical  falrmer,  of  many  practical  farmers,  must  be  called  in.  Nu- 
merous experiments,  or  trials,  must  be  made  in  various  localities,  and  by  differ- 
ent individualsjf— all,  however,  according  to  the  same  rigorous  and  ticcurate 
method, — in  oi'der  that,  from  th^omparison  of  many  results,  something  like  a 
general  principle  may  be  deduced. 

It  is  partly  with  a  view  to  determine  the  mode  of  action  of  certain  fertilizers, 
and  partly  in  the  hope  of  obtaining  some  "additional  light  on  the  subject  of 
manures  specifically  adapted  to  particular  crops,  that  I  venture  to  suggest  to  you 
the  propriety  of  making  one  or  more  of  the  following  sets  of  experiments, 
during  the  spring  and  summer  of  the  present  year.    I  could  have  much  enlarged 

*  In  regard  to  its  use  in  Germany,  Lampadius  says,—"  It  may  with  certainty,  be  stated, 
that  by  the  use  of  gypsum  the  produce  of  clover  and  the  consequent  amount  of  Jive  stock 
have  been  increased  at  least  one- third."— DiK  Lehre  von  den  Mineralischen  Dunomit* 
rsLN,  p.  34.    ■ 


3  OP  GRASS  AND  CLOVER.  [Appendix, 

the  list  of  suggestions,  but  I  neither  wish  to  fatigue  yoAx  attention,  nor  to  place 
before  you  more  work  of  the  kind  than  can  be  readily  accomplished,  with  little 
expense  of  time,  labour,  or  money.  Another  season  will,  I  hope,  afford  us  an 
opportunity  of  interrogating  nature  by  further,  and  perhaps  more  refined,  modes 
of  Experimenting. 

1.    OF    GRASS    AND    CLOVBR. 

1°.  It  is  beyond  dispute,  that  on  certain  soils,  gypsum  causes  a  largely  in- 
creased growth  of  grass  and  clover,  but  experiment  alone  appears  capable  of 
determining  on  what  soils  it  is  likely  to  be  thus  beneficial.  Such  experiments, 
therefore,  ought  to  be  made  on  every  farm,  on  a  small  scale  at  first,  and  at  little 
cost,*  but  made  with  care  and  accuracy,  and  with  a  minute  attention  to  weights 
and  measures. 

2°.  The  action  of  gypsum  appears  to  be  entirely  chemical,  but  the  only  ex- 
planation of  this  action  yet  attempted  is  far  from  being  satisfactory.  It  is  desi- 
rable therefore,  that  experiments  witlf  other  substances  should  be  made,  which 
are  likely  to  throw  light  on  the  theory.  Important  practical  results  may  at  the 
same  time  be  obtained — they  are  sure,  indeed,  to  follow  from  a  right  under- 
standing of  the  theory. 

In  the  neighbourhood  of  Lyons,  it  has  been  found  that  very  dilute  sulphuric 
acidt  (oil  of  vitrol)  exliibits  the  same  beneficial  effect  upon  clover,  that  has  else- 
where attended  the  use  of  gypsum.  It  is  desira.ble,  therefore,  that  a  compara- 
tive experiment  should  be  made  with  this  acid  on  a  portion  of  the  same  field  to 
which  the  gypsum  is  applied.     Where  the  one  fails  the  other  may  act. 

3'^.  It  was  observed  by  Dr.  Home,  of  Edinburgh,  so  early  as  the  year  1756, 
that  sulphate  of  sodat  had  a  remarkable  effect  in  promoting  the  growth  of  plants 
— its  action  bein^  nearly  equal  to  that  of  saltpetre  or  nitrate  of  soda.  This  fact, 
though  mentioned  by  Lord  Dundonald,  has  been  lost  sight  of  by  practical  men, 
the  sulphate  of  soda  being  generally  represented  as  too  high  in  price  to  be  avail- 
able as  a  fertilizer.!  The  use  of  saltpetre,  however,  and  of  nitrate  of  soda,  both 
of  which  are  more  than  double  the  price  of  sulpliate  of  soda,  show  that  the  cost 
of  this  latter  article  should  not  stand  in  the  way  of  an  accurate  trial  of  its  value 
as  a  fertilizer  on  various  crops.  Dry  sulphate  of  soda  can  be  readily  obtained 
from  any  of  the  alkali  works  on  the  Tyne,ll  and  being  an  article  of  domestic 
manufacture,  it  is  proper  that  its  merits  should  be  ascertained,  and,  if  it  can  be 
available,  that  its  use  should  be  encouraged. 

From  the  circumstance  of  its  containing  sulphuric  acid,  therefore,  I  would 
recommend  that  it  should  be  tried  on  clover  and  grass,  in  comparison  with 
gypsum  and  sulphuric  acid,  and  on  a  portion  of  the  same  field.  It  may  suc- 
ceed where  the  others  fail. 

4°.  Nitrate  of  soda  also,  as  a  top-dressing  on  grass  land,  has  been  often  used 
with  great  benefit.  I  have  seen  grassland  in  Dumfriesshire,  which,  after  being 
long  let  for  pasture  at  30s.  an  acre,  had  been  sprinkled  with  an  annual  top- 
dressing  of  nitrate  of  soda  at  the  rate  of  20s.  an  acre,  and  had  since  readily  let 
at  je4  an  acre,  yielding  thus  an  annual  profit  of  30s.  an  acre  to  the  landlord. 

In  other  districts,  again,  it  has  been  found  to  answer  better  for  corn.  Thus, 
after  a  discussion  on  this  subject  in  the  Gloucester  Farmers'  Club,  it  was  agreed, 
that  nitrate  of  soda  "  was  a  very  valuaMe  mSiure  for  white  straw  crops,  but 

*  The  price  of  gypsum  in  London  is  about  2)*  6d.  per  cwt. ;  in  Newcastle,  3s. 

t  Gypsum  consists  of  sulphuric  acid  and  lime. 

X  Olauber  salts — consisting  of  sulphuric  acid  and  soda. 

§  Lord  Dundonald  says—"  From  experiments  it  has  been  proved  to  promote  vegetation  in 
a  very  high  degree.  The  high  price  at  present  of  this  article  precludes  the  use  of  it,  but 
could  it-be  made  and  sold  at  a  cheap  rate,  it  would  pi-ove  a  most  valuable  acquisition  to  agri- 
culture."'*'Since  the  time  of  Lord  Dundonald  some  trials  made  in  Germany  have  shown  it 
to  have  a  beneficial  action  on  rye,  potatoes,  and  fruit  trees. 

I  Messrs.  Aj^an  &  Co.,  of  the  Heworth  Alkali  Works,  deliver  it  in  Newcastle  and  the  neigh 
bouring  townsj'at  9s.  or  10s.  per  cwt. 


No,   7.j  OP   GRASS   AND   CLOVER.  S 

when  applied  to  green  crops  the  benefit  was  not  sufficiently  great  to  counter-bal- 
ance the  expense."  In  Northumberland,  where  it  has  been  tried  in  a  skilful 
manner  by  Mr.  Gray,  of  Dilston,  it  was  found  to  yield  a  most  profitable  return 
on  both  hay  and  barley. 

These  results  show  the  necessity  of  further  trials,  not  only  for  the  purposfe  of 
illustrating  the  cause  of  the  beneficial  action  of  this  saline  substance,  but  also 
with  the  view  of  arriving  at  some  general  rule  by  which  the  practical  man  may 
be  guided  in  determining  on  what  fields,  and  for  what  crops  07i  those  fields^  the 
nitrate  of  soda  may  be  beneficially  applied 

This  experiment,  like  the  others  above-mentioned,  will  be  much  more  valua- 
ble, if  ma*B  in  such  a  way  that  the  result  can  be  compared  with  that  obtained 
by  the  use  of  other  chemical  agents.  I  would,  therefore,  propose  that  in  the 
same  field  of  grass  or  clover,  a  portion  should  be  measured  off,  to  be  top- 
dressed  with  nitrate  of  soda,  that  thus  not  only  the  absolute,  but  also  the  com- 
farative,  weight  of  the  produce  may  at  the  same  time  be  ascertained. 

5*^.  There  are  other  trials  also,  from  which  this  general  subject  is  capable  of 
receiving  illustration.  The  fertilizing  power  of  gypsum  has  been  explained  by 
its  supposed  action  on  the  ammonia  which  is  presumed  to  exist  in  the  atmos- 
phere. If  this  be  the  true  explanation,  a  substance  containing  ammonia  should 
act  at  least  as  energetically.  At  all  events,  the  action  of  fold-yard  manure  and 
of  putrid  urine  is  supposed  to  depend  chiefly  on  the  ammonia  they  contain  or 
give  off.  Now,  among  the  substances  containing  ammonia  in  large  quantity, 
which  in  most  towns  are  allowed  to  run  to  waste,  the  ammoniacal  liquor  of 
the  gas  works  is  one  which  can  easily  be  obtained,  and  can  be  applied  in  a  li- 
quid state  at  very  little  cost.  It  must  be  previously  diluted  with  water  till  its 
taste  and  smell  become  scarcely  perceptible. 

I  would  propose,  therefore,  as  a  further  experiment,  that  along  with  one  or 
more  of  the  substances  above-mentioned,  the  ammoniacal  liquor  of  the  gas 
works  should  be  also  tried,  on  a  measured  portion  of  ground,  and,  if  possible, 
in  the  same  field. 

G°.  Soot,  as  a  manure,  is  supposed  to  act  partly,  if  not  chiefly,  in  conse- 
quence of  the  ammonia  it  contains.  In  Gloucestershire  it  is  applied  to  pota- 
toes and  to  wheat,  chiefly  to  the  latter,  and  with  great  success.  In  the  Wolds 
of  Yorkshire  it  is  also  applied  largely  to  the  wheat  crop,  at  the  rate  of  about  24 
bushels  to  the  acre.*  In  this  county  it  is  frequently  used  on  grass  land,  to  the 
amount  of  20  bushels  an  acre,  and  though  I  am  not  aware  that  it  is  extensively 
employed  upon  clover,  I  am  inclined  to  anticipate  that  the  sulphur  it  contains,t 
in  addition  to  the  ammonia,  would  render  it  useful  to  this  plant.  At  all  events, 
comparative  experiments  in  the  same  field  with  the  gypsum  and  the  ammonia- 
cal liquor,  are  likely  to  lead  to  interesting  results. 

7°.  Common  salt,  highly  recommended  as  a  manure  by  some,  has  been  as 
much  depreciated  by  others,  and  hence,  when  directly  applied,  is  considered  as 
a  doubtful  fertilizer  by  almost  all.  The  obscurity  in  regai'd  to  its  use,  however, 
rests  chiefly  on  the  quantity  which  ought  to  be  employed.  The  result  of  com- 
parative experiments  made  in  Germany,  showed  that  a  very  few  pounds  per 
acre  were  sufficient  to  produce  a  largely  increased  return  of  grass — while  in 
England  it  has  been  beneficially  applied  within  the  wide  limits  of  from  five  to 
twenty  bushels  per  acre,  and,  when  used  for  cleaning  the  land  for  autumn,  of 
thirty  bushels  an  acre. 

Among  the  comparative  experiments  upon  grass  and  clover  here  suggested, 
the  eflfect  of  salt  might  also  be  tried  with  the  prospect  of  practical  benefit.  It 
would  give  an  additional  interest  to  the  experiments  and  supply  an  additional 
term  of  comparison, 

'  The  price  is  from  6d.  to  Is.  a  bushel.  In  this  county  the  soot  is  said  to  be  often  of  an 
inferior  quality,  and  brings  therefore  a  less  price. 

t  The  gypaum,  I  might  also  say,  for  much  of  our  soot  contains  gypsum,  the  lime  being 
derived  chiefly  from  the  sides  of  the  flue. 


4  OF  GRASS  AND  CLOVER.  [Appendvtf 

The  cr^tire  scries  of  experiments,  therefore,  which  I  would  recommend,  would 
occupy  eight  patches  on  a  clover  or  grass  field,  one  of  which  would  be  left  ntu- 
dressed  for  the  purpose  of  comparison.     Thus,  each  plot  being  half  an  acre  • 


Gypsum. 

Sulphate  of 
Soda.  • 

Ammoniacal 
Liquor. 

Sulphuric 
Acid. 

Ni'rafe  of 
Soda. 

Common 
Salt. 

Soot. 

The  ammoniacal  liquor  and  the  soot  are  placed  as  far  as  possible  from  the 
gypsum  and  sulphuric  acid,  that  they  may  not  interfere  with  each  other's  action. 
In  a  large  field  they  might  be  placed  still  farther  apart,  and  other  trials  might  be 
made  in  one  or  two  of  the  vacant  places. 

The  appearance  of  each  patch  should  be  entered,  with  the  date,  in  an  experi- 
ment book,  at  weekly  intervals,  and  the  final  produce  both  of  hay  and  of  after- 
math carefully  noted,  both  as  to  weigJit  and  quality. 

Nor  will  the  experiment  be  completed  when  the  crop  for  the  year  is  gathered 
in;  but,  where  it  is  possible,  two  further  points  should  be  ascertained, — 

1°.  The  relative  feeding  or  nourishing  properties  of  the  produce.  To  those 
who  rear  and  fatten  cattle,  this  is  a  matter  of  great  importance,  and  it  is  one 
which  they  could  easily  determine,  at  least  very  approximately. 

2°.  What  has  been  the  permanent  effect  of  tlie  several  substances  on  the  soil, 
as  indicated  by  the  comparative  quantity  and  quality  of  the  crop  obtained  from 
each  half  acre,  on  the  siucceed/mg  or  during  the  two  following  years.  The  result  of 
these  further  observations  may  materially  modify  the  conclusion  we  should  draw 
from  the  comparative  weight  and  quality  of  the  produce  of  the  first  year. 

I  shall  only  observe,  in  conclusion,  on  this  head,  that  the  result  of  a  simulta- 
neous trial  of  all  these  substances  in  the  same  field  would  not  only  thx'ow  much 
light  on  the  specific  action  of  each  on  the  grass  or  clover  in  general,  but  would 
be  of  permanent  utility  to  that  farm  or  locality  in  which  the  experiments  were 
made.  It  would  indicate  the  kind  of  fertilizer  which  was  best  adapted  to  the 
farm  or  neighbourhood,  in  the  existing  condition  of  its  general  culture.  It  would 
form'  a  local  record,  useful  not  only  to  the  tenant  who  made  the  experiment  (if 
well  made)  and  by  whom  the  farm  at  the  time  was  tenanted,  but  more  useful 
by  far,  and  more  permanently  so,  to  the  owner  of  the  land,  whose  interest  in  it 
is  supposed  to  be  not  only  greater,  but  much  moi-e  lasting. 

In  regard  to  the  quantities  of  the  several  substances  above-mentioned,  which 
are  to  be  applied  to  each  acre,  they  may  probably  be  varied  according  to  cir- 
cumstances, but  the  following  may  be  recommended  in  the  comparative  experi- 
ments : 

1°.  Gypsum  2  to  3  cwt.  per  acre. 

2°.  Sulphate  of  Soda  1  cwt.  per  acre. 

3°.  Nitrate  of  Soda  1  cwt.  per  acre. 

4°.  Soot  20  bushels  per  acre — this  in  different  districts  may  be  varied  accord- 
ing to  the  known  quality  of  the  soot. 

5°.  Of  Sulphuric  Acid  from  30  to  40  lbs.  per  acre,  applied  at  three  or  four 
several  intervals — and  diluted  with  at  least  200  times  its  weight  of  water.  Or 
so  much  water  may  be  added  as  to  make  it  perfectly  tasteless,  or  so  weak  as 
not  sensibly  to  injure  the  texture  of  a  plant  left  in  it  during  the  previous  night.* 

6°.  Of  Ammoniacal  Liquor  100  to  200  gallons  per  acre,  according  to  its 
strength,  for  this  is  constantly  varying.  It  must  also  be  diluted  with  so  large  a 
quantity  of  water  as  will  render  it  perfectly  tasteless,  and  is  likely  to  prove  most 
beneficial  if  laid  on  at  several  successive  periods. 

*  The  quantity  above-mentioned  amounts  to  about  two  gallons  of  the  acid  of  the  shops,  and 
k  dl^ould  be  diluted  with  three  or  four  hundred  gallons  of  water. 


No.  I.}  OP  WHEAT,  BARLEY,  AND  OATS.  6 

7°.  Of  common  salt  it  will  be  safer  to  apply  not  more  than  four  to  six  bushels 
an  acre ;  though,  where  time  and  circumstances  permit,  comparative  trials  might 
also  be  made  on  the  efficacy  of  salt  when  applied  in  different  proportions,  to  the 
same  land  on  which  the  other  experiments  are  made. 

As  to  the  time  when  these  several  dressings  ought  to  be  applied,  some  varia- 
tion may  be  made  according  to  the  state  of  the  young  crop.  They  need  not,  in 
general,  be  used  before  the  lOth  of  April,  and  they  should  rarely  be  later 
than  the  middle  of  May. 

It  will  be  desirable  that  in  the  detail  of  every  set  of  experiments,  the  kind  and 
quality  of  the  soil  (and  subsoil)  should  be  stated — with  its  di-aina^e  and  expo- 
sure— and  the  kind  of  grass  or  clover  which  had  been  sown  upon  it. 

11..    OP   WHEAT,   BARLEY,    AND   OATS. 

It  is  known  that  saltpetre  and  nitrate  of  soda  produce  highly  beneficial  effects 
on  all  these  varieties  of  grain.  There  remains  much  to  be  done,  however,  be- 
fore the  principle  of  their  operation,  or  the  circumstances  on  which  their  most 
useful  application  depends,  can  be  clearly  understood.  Their  relative  effects  on 
the  same  kind  of  grain  must  be  made  the  subject  of  more  frequent,  more  precise, 
and  more  carefully  conducted  experiments — and  these  effects  must  be  compared 
with  those  of  other  fertilizing  substances,  in  order  that  we  may  arrive  ultimate- 
ly at  some  comparative  estimate  of  the  practical  value  of  each,  in  increasing  the 
growth  and  produce  of  those  crops  which  are  the  staples  of  animal  food. 

A.— Of  meat. 

It  is  confidently  stated  by  some,  as  a  general  rule,  that  saltpetre  is  more  ad- 
vantageous than  nitrate  of  soda,  when  applied  to  wheat.  On  the  other  hand,  it 
is  beyond  question  that  the  apphcation  of  nitrate  of  soda  to  wheat  has  been 
found  productive  of  remarkable  benefit. 

Is  saltpetre  especially  adapted  for  wheat  of  all  varieties,  on  all  soils,  and  under 
every  variety  of  management,  and  is  nitrate  of  soda,  in  like  manner,  especially 
fitted  for  barley  and  oats  1 

These  are  questions  to  which  the  experiments  hitherto  made  do  not  enable  us 
to  give  a  reply.  New  data  must  be  obtained  before  we  can  have  the  means  of 
reasoning  usefully  in  regard  to  any  of  them.     I  would  propose,  therefore, — 

1°.  That  where  two  varieties  of  wheat  are  sown  on  the  same  field,  or  on  dif- 
ferent fields  of  precisely  the  same  kind  of  land  and  in  the  same  condition,  that 
two  half  acres  of  each  variety  should  be  measured  off,  and  that  one  half  acre  of 
each  should  be  dressed  with  saltpetre,  and  the  other  with  nitrate  of  soda,  at  the 
rate  of  1  cwt.  per  acre.  If  three  varieties  could  be  so  treated,  the  experiment 
would  be  the  more  valuable. 

It  would  thus  be  determined  how  far  the  effect  of  each  of  these  nitrates  was 
dependent  upon  the  variety  of  wheat  sown — and  what  was  the  relative  action  of 
each  nitrate  upon  any  of  the  varieties. 

2°.  That  when  the  same  varieties  of  wheat  are  sown  upon  two  or  more  dif- 
ferent soils — in  different  parts  of  a  farm — that  one  portion  of  the  wheat  on  every 
different  soil  should  be  dressed  with  nitrate  of  soda,  and  another  with  nitrate  ot 
potash  (saltpetre).  By  this  experiment,  it  would  be  shown  how  far  the  effect 
of  these  substances  is  dependent  on  the  nature  of  the  soil,  and  how  far  the  action 
of  the  one,  compared  with  that  of  the  other,  is  modified  by  diversity  of  soil. 

In  these  different  experiments,  the  management  is  presumed  to  be  the  same. 
If  the  experiments  be  repeated  by  several  persons  in  different  parts  of  the  coun- 
try, the  effects  of  difference  of  management  will,  in  a  great  measure,  be  shown 
in  the  diversity  of  the  results. 

3°.  With  the  view  of  ascertaining  the  comparative  effect  of  the  sulphate  of 
soda  on  this  crop,  I  would  suggest  Siat  in  each  case  above  specified,  an  equal 
area  should  be  set  aside  to  be  dressed  with  this  salt,  in  the  proportion  of  1  cwt. 
per  acre. 

Of  each  variety  of  wheat,  therefore,  and  on  each  variety  of  soil,  four  patches 


OF  WHEAT,  BARLEY,  AND  OATS. 


l^AppendiXf 


Nitrate  of 
Soda. 

Saltpetre. 

Sulphate  of 
Soda. 

of  equal  area,  say  half  an  acre,  should  be  measured  off— one  of  which  should  be 
undressed  for  the  purpose  of  comparison :  thus — 

As  before,  the  nature  of  the  soil  and  the  kind  of 
grain  must  be  recorded — the  appearance  of  each  patch 
noted  week  by  week — with  the  time  of  ripening  and 
reaping — and  the  respective  qualities  and  weights  of 
the  grain  and  straw  collected  from  each  half  acre. 

The  quantity  of  gluten  contained  in  the  wheat 
should  also  be  determined,  or  a  sample  of  the  flour 
transmitted  for  the  purpose  to  the  writer  of  these  sug- 
gestions, accompanied  by  a  detail  of  the  experiments  they  eu-e  intended  to 
illustrate. 

B. — Of  Barley  and  Oats. 
To  barley  and  oats  the  above  remarks  all  apply,  with  this  difference,  that  to 
these  crops  saltpetre  is  said  to  be  less  beneficial  than  the  nitrate  of  soda.     In 
connection  with  these  crops,  however,  I  would  make  the  following  additional 
observation. 

According  to  any  theory  of  the  action  of  the  nitrates  of  potash  and  soda 
which  readily  presents  itself,  their  effect  on  any  crop  which  they  are  equally 
capable  of  benefitting  ought  to  be  nearly  equal,  weight  for  weight.  The  nitrate 
of  soda  ought  to  have  a  decidedly  more  powerful  action,  were  it  not  that  the 
state  of  moisture  in  which  it  is  generally  sold,  increases  its  weight  so  much  as 
in  a  great  measure  to  deprive  it,  in  equal  weights,  of  this  superiority. 

But  while  1  cwt.  of  saltpetre  (nitrate  of  potash)  is  recommended  as  a  suffi- 
cient dressing  for  an  acre,  1|  to  1^  cwt.  of  nitrate  of  soda  is  recommended  for 
an  equal  area.  It  would,  therefore,  be  desirable  where  nitrate  of  soda  is  applied 
to  any  large  extent  of  land,  either  with  oats  or  barley,  to  make  a  comparative 
trial  on  three  equal  portions  of  the  same  field,  with  1,  li,  and  IJ  cwt.  per  acre, 
respectively. 

In  addition,  therefore,  to  the  experiments  suggested  in  regard  to  wheat,  with 
the  view  of  determining — 

1°.  The  absolute  and  relative  efficacy  of  saltpetre  and  nitrate  of  soda  on  dif- 
ferent varieties  of  the  grain ; 

2°.  The  same  on  different  varieties  of  soil ; 

3°.  And  under  diversities  of  management, — as  in  tlie  previous  treatment  of 
the  land,  &c. ; 

There  may  be  added,  in  regard  to  oats  and  barley,  another  series  of  trial  to 
determine — 

4°.  Tha  relative  effects  of  the  different  proportions  of  the  nitrate  of  soda, 
which  is  at  present  supposed  to  be  specially  beneficial  to  these  kinds  of  grain. 
If  any  one  be  desirous  of  uniting  this  latter  series  with  the  fonner,  it  may  be 
done  thus — 

The  vacant  half-acre  being  as  before  left 
for  the  purpose  of  comparison.  Such  an 
entire  series  might  be  made  at  the  same 
time  on  a  field  of  Tartary  and  of  potatoe 
oats,  and  on  two  or  more  varieties  of  bar- 
ley. 

These  top-dressings  may  all  be  sown 
broad-cast — on  the  wheat  most  convenient- 
ly when  the  seeds  are  sown  in  April  or  May,  and  on  the  barley  and  oats  when 
the  fields  have  become  distinctly  green. 

I  may  be  permitted  to  add,  as  inducements  to  practical  men,  to  try  one  or 
more  of  these  experiments  in  the  accurate  manner  above  described: 

1°.  That  the  result  will  be  directly  available  and  of  immediate  practical  vedue 
on  his  own  farm,  to  the  person  by  whom  they  are  carefully  made.    That  they 


Sulphate  of 
Soda. 

Nitrate  of 

Soda,  Icwt. 

per  acre. 

Saltpetre. 

Nitrate  of 
Soda, 
H  cwt. 

Nitrate  of 
Soda, 
li  cwt. 

No.  I.]  or  TURNIPS.  7 

will  be  permanently  useful  to  his  landlord  (if  carefully  recorded),  ought  to  be 
an  inducement  to  the  latter  to  give  every  facility  and  encouragement  to  his  ten- 
ant in  making  them. 

2°.  That,  mstead  of  involving  expense  and  outlay,  which  in  many  instances 
may  ill  be  spared,  they  are  sure  in  almost  eveiy  case  to  do  more  than  repay  tkecost 
of  tnaking  them,  by  the  increased  quantity  or  value  of  the  produce  obtained. 
Any  of  the  series  of  experiments,  on  the  scale  suggested,  may  be  made  for  five 
pounds,  so  that  were  the  outlay  all  to  be  lost,  the  accurate  knowledge  obtained 
m  reference  to  the  general  tillage  of  his  lemd,  would  be  wortla  more  money  to 
the  holder  of  a  farm  of  a  Jmndred  acres. 

3°.  I  need  scarcely  add,  as  a  further  inducement,  the  additional  interest  which 
such  experiments  give  to  the  practice  of  farming — and  the  means  they  afford 
of  calUng  forth  tlie  intelligence  of  the  agricultural  population.  The  moment  a 
man  begins  to  make  experiments  under  the  guidance  of  an  understood  principle, 
from  that  moment  he  begins  to  think.  To  obtain  materials  for  thought  he  will 
have  recourse  to  books — and  thus  every  new  experiment  he  makes,  will  further 
stimulate  and  awaken  his  intellect,  and  lead  him  to  the  acquisition  of  further 
knowledge.  Does  it  require  anything  more  than  this  general  awakening  of  the 
minds  of  the  agricultural  class,  to  advance  the  science  of  agriculture  as  surely 
and  asf  rflpidly  as  any  of  the  other  sciences,  the  practical  application  of  which 
have  led  to  those  extraordinary  developments  of  natural  resources  which  are 
the  characteristic  and  the  pride  of  our  time  1 

III,       OF  TURNIPS. 

The  raising  of  turnips  is  of  such  vast  importance  in  the  prevailiti|;  system 
of  husbandry,  that  any  improvement  in  the  mode  of  culture  must  be  of  exten- 
sive and  immediate  benefit.  Experiments  so  numerous  and  so  varied  have  been 
made  with  this  view,  that  it  may  almost  seem  superfluous  in  ^^^e  now  to  make 
any  further  suggestions  on  the  subject.  But  when  experiments  have  been 
made  witli  a  view  to  one  subject  only,  it  often  happens  in  all  departments  of  na- 
'tural  science,  that  as  new  views  are  advanced  or  more  precise  methods  pointed 
out,  it  becomes  necessary  to  repeat  all  our  former  experiments, — either  for  the 
purpose  of  testing  the  results  they  gave  us,  or  of  observing  new  phenomena  to 
which  our  attention  had  not  previously  been  directed. 

I.  Numerous  experiments,  for  example,  have  been  made  upon  the  use  of  bones 
in  the  raising  of  turnips,  but  they  have  been  chiefly  directed  to  economiced  ends, 
and  so  far  with  the  most  satisfactory  results.  But  among  fifty  intelligent  and 
thinking  practical  men,  and  who  all  agree  in  regard  to  the  profit  to  be  derived 
from  the  use  of  bones  with  the  turnip  crop,  how  many  will  agree  in  regard  to 
the  mode  in  which  they  act — how  few  will  be  able  to  give  a  satisfactory  reason 
for  the'opinion  they  entertain !  The  same  is  true  of  theoretical  chemists,  some 
attributing  their  effect  more  especially  to  the  earthy  matter,  others  to  the  gelatine 
they  contain.  Dry  bonss  contain  about  two-thirds  of  their  weight  of  earthy 
matter,  the  other  third  consisting  chiefly  of  animal  matter  resembling  glue.  Of 
the  earthy  matter  five-sixths  consist  of  phosphate  of  lime  and  magnesia,  and 
the  rest  chiefly  of  carbonate  of  lime.     Thus  a  ton  of  bone  dust  will  contain- 

Animal  matter 746  lbs. 

Phospate  of  lime,  (tec 1245 

Carbonate  of  lime,  &c 249 


2240 

On  which  of  these  constituents  does  the  efficacy  of  bones  chiefly  depend  1 
Does  it  depend  upon  the  animal  matter  1  This  opinion  is  in  accordance  with  the 
following  facts  : — 

1°,  That  in  the  Doncaster  report  it  is  said  to  be  most  effectual  on  calcareou* 
soils, — for  in  the  presence  of  lime  all  organic  matter  more  rapidly  decomposea. 

27 


8  OF  TURNIPS.  [Api)endix~ 

2**.  That  horn  shavings  are  a  more  powerful  manure  than  bones, — since 
horn  contains  only  one  or  two  per  cent,  of  earthy  matter.* 

3°.  That  before  the  introduction  of  crushed  bones,  the  ashes  of  burned  bones 
had  been  long  employed  to  a  small  extent  in  agriculture,  but  have  since  fallen 
almost  entirely  into  disuse. 

4°.  That  old  sheep  skins  cut  up  and  laid  in  the  drills,  have  been  found  to 
yield  as  good  a  crop  of  turnips  and  after-crop  of  corn,  as  the  remainder  of  the 
field  which  was  manured  with  bones. 

5°.  That  "40  lbs.  of  bone  dust  are  sufficient  to  supply  three  crops  of  wheat, 
clover,  potatoes,  turnips,  &c.,  with  phosphates,"t  while  one  to  two-thirds  of  a 
ton  of  bones,  containing  from  400  to  800  lbs.  of  phosphates,  is  the  quantity  usu- 
ally applied  to  the  land. 

On  the  other  hand,  the  quantity  of  animal  matter  present  in  a  ton  of  bonea 
(746  lbs.)  is  so  small,  and  its  decomposition  so  rapid  during  the  growth  of  thd 
turnips — while  at  the  same  time  the  effects  of  the  bones  are  so  lasting  and  so 
beneficial  to  the  after-crop  of  corn — that  many  persons  hesitate  in  considering 
the  great  excess  of  phosphates  applied  to  the  land,  as  really  without  any  share 
of  influence  in  the  production  of  the  crops. 

Thus  Sprengel,  an  authority  of  the  very  highest  character,  both  in  theoretical 
and  practical  agriculture,  is  persuaded  that  the  phosphates  are  the  soleTerlilizing 
ingredients  in  bones,  and  he  explains  the  want  of  success  from  the  use  of  crush- 
ed bones  in  Mechlenburg  and  North  Germany,  on  the  supposition  that  the 
soils  in  those  countries  already  contain  a  sufficient  supply  of  phosphates,  while 
in  England  generally  they  are  deficient  in  these  compounds. 

Further,  if  the  animal  matter  be  the  fertilizing  agent  in  bones,  why  are  not 
they  of  equal  efficacy  on  grass  land  as  upon  turnips '? 

With  the  view,  therefore,  of  leading  to  some  rational  explanation  of  the  rela- 
tive effects  of  the  several  constituents  of  bones,  it  would  be  desirable  to  insthute 
comparative  experiments  of  the  following  kind — 

1°.  With  half  a  ton  of  bones  per  acre. 

2°.  With  three  or  four  cwt.  of  horn  shavings  or  glite  per  acre. 

3°.  With  two  cwt.  of  burned  bones  per  acre. 

4°.  With  six  or  seven  cwt.  of  burned  bones  per  acre. 

The  quantity  of  burned  bones  in  No.  4  is  that  which  is  yielded  by  a  ton  of 
fresh  bones ;  that  in  No.  3  is  upwards  of  five  times  what  should  be  taken  up  by 
the  crops — as  great  part  of  what  is  added  must  be  supposed  to  remain  in  the 
soil,  while  some  must  be  dissolved  and  carried  off  by  the  rains. 

The  result  of  such  experiments  as  these,  if  made  accurately  on  different  soils, 
will  lead  us  sooner  to  the  truth  than  whole  volumes  of  theoretical  discussion. 

II.  Nitrate  of  soda  has  also  been  applied  with  great  benefit  in  the  culture  of 
turnips.  Some  experiments,  exceedingly  favourable  in  an  economical  j^oint  of 
view,  have  been  made  by  Mr.  Barclay,  of  Eastwick  Park,  Surrey,|  who  found 
that  one  cwt.  per  acre,  drilled  in  with  the  seed,  gave  as  great  a  return  of  Swedes 
as  15  bushels  of  bones  with  15  of  wood  ashes  per  acre,  and  when  the  nitrate  of 
soda  was  sown  broadcast,  from  20  to  25  per  cent.  more.  In  every  part  of  the 
country,  therefore,  this  substance  ought  to  be  tried.  And  as  this  nitrate  is  very 
soluble  in  water,  and  may  therefore  be  readily  earned  off  by  the  rain,  and  as 
that  only  which  is  within  reach  of  the  plant  is  of  any  avail,  I  would  suggest 
that  not  more  than  one-fourth  of  the  whole  should  be  drilled  in  with  the  seed, 
for  the  purpose  oi bringing  away  the  plant;  and  that  after  the  thinning  by  the 
hoe,  the  rest  should  be  strewed  along  the  r  ows  by  the  hand  or  by  the  drill.     In 

*  This,  I  believe,  is  rather  a  matter  of  opinion  than  the  result  of  a  sufficient  number  of  ac- 
tual trials.  Some  trials  made  by  Mr.  Hawden  (British  Husbandry,  I.  p.  395)  gave  result* 
very  unfavourable  to  horn  shavings. 

t  Liebig,  p.  84.  The  acre  here  spoken  of  is  the  Hessian,  about  three-fifths  of  the  English 
acre.    The  English,  therefore,  will  require  66  lbs. 

t  ffournal  of  the  English  Agricultural  Society,  I.  p.  428. 


Atf.  /.]  OF  TURNIPS.  9 

this  way  the  whole  energy  of  the  salt  being  expended  where  it  is  required,  the 
greatest  possible  effect  will  be  produced. 

III.  I  have  already  stated  the  reasons  which  lead  me  to  anticipate  highly  be- 
neficial effects  to  vegetation  from  the  use  of  sulphate  of  soda  ;  I  would  suggest, 
therefore,  a  trial  of  this  salt  on  the  turnips  also,  at  the  same  rate  of  1  cwt.  per 
acre,  and  applied  in  the  way  above  recommended  for  the  nitrate  of  soda.  Of 
course  the  intelligent  farmer  will  vary  the  proportions  and  mode  of  application 
of  these  substances,  as  his  leisure  or  convenience  permit,  or  as  his  better  judg- 
ment may  suggest  to  him. 

The  entire  series  of  experiments  on  turnips,  above  suggested,  may  be  repre- 
sented as  follows,  adding  two  plots  for  different  proportions  of  the  nitrate  and 
sulphate  of  soda : 


Burned  Bones, 
2  cwt.  per  acre. 

Nitrate  of  Soda, 
IJ  cwt.  per  acre. 

Bone  Dust,  or 
Crushed  Bones, 
1  ton  per  acre. 

Burned  Bones, 

6  or  7  cwt.  per 

acre. 

Sulphate  of 
'  Soda, 
1  cwt.  per  acre. 

Horn  Shavings, 
or  Glue,  7  or  8 
cwt.  per  acre. 

Unmanured. 

Sulphate  of 

Soda, 

l^  cwt.  per  acre. 

Nitrate  of 

Soda, 

1  cwt.  per  acre. 

Some  of  these  experiments  most  of  you  may  easily  try.  Those  with  the 
burned  bones  and  horn  shavings,  which  in  this  part  of  the  country  are  less  easy 
to  be  obtained,  it  is  not  to  be  expected  that  inany  of  you  will  think  of  undertak- 
ing. I  hope,  however,  that  they  will  not  be  lost  sight  of  by  those  who  possess  fa- 
cilities for  obtaining  them  in  sufficient  quantity  to  make  a  satisfactory  experiment. 

In  many  parts  of  the  United  States,  gypsum  is  the  universal  fertilizer  for 
every  crop,  and  among  the  rest  it  is  said  to  l3enefit  turnips.  The  same  opinion 
is  entertained  in  Germany.  I  am  not  aware  how  far,  in  what  way,  or  with 
what  results,  it  has  been  applied  to  the  turnip  crop  in  this  country.  A  simple 
mode  of  testing  its  efficacy,  however,  would  be  to  strew  it  over  the  plants  when 
in  the  rough  leaf,  on  part  of  a  field,  the  whole  of  which  had  been  already  ma- 
nured in  the  ordinary  way  with  fold-yard  manure.  The  difference  of  produce 
would  thus  show  its  efficacy,  in  the  given  circumstances  ;  and  the  experiment 
could  be  made  effectually  at  the  cost  of  a  single  cwt.  of  gypsum. 

I  have  not  included  rape  dust  among  the  trials  above  suggested,  though  it  is 
undoubtedly,  under  certain  modes  of  management,  a  beneficial  manure  both  to 
corn  and  turnip  crops.  There  is  also  a  diversity  of  opinion  as  to  the  cause  of 
its  fertilizing  action,  as  well  as  a  manifest  difference  in  the  effect  of  different 
samples  of  the  dust  on  the  same  soil.  Though,  therefore,  certain  experiments 
which  I  may  on  a  future  occasion  suggest,  would  undoubtedly  throw  light  on 
the  cause  of  the  good  qualities  of  this  manure,  yet  as  its  action  (taking  different 
samples)  is  not  constant  on  the  same  soil,  results  obtained  with  it  cannot  pos- 
sess the  same  importance,  either  theoretical  or  practical,  as  those  which  are  ob- 
served to  follow  from  the  use  of  bones  and  of  saline  substances,  the  composi- 
tion of  which  is  nearly  invariable. 

Many  farmers,  however,  are  in  the  habit  of  constantly  using  rape  dust.  If 
any  of  these  could  conveniently  make  experiments  on  the  effect  of  different  sam- 
ples of  the  cake,  from  different  kinds  of  seed,  and  from  different  oil  mills,  and 
would  accurately  note  the  results,  they  would  perform  an  important  service  in 
preparing  the  way  for  that  clear  explanation  of  the  cause  of  its  fertilizing  action, 
which  is  at  present  wanted,*  and  which  experiment  alone  can  discover  to  us. 

*  Its  good  effects  are  generally  attributed  to  the  oil  which  is  left  in  the  seed,  and  its  vary, 
ing  action  to  the  ditferent  quantities  of  oil  left  in  it  by  different  crushers.  I  doubt,  however, 
if  the  oil  ought  to  be  considered  as  more  than  a  secondary  cause  of  its  beneficial  action. 


10  OF  POTATOES.  [Appetidta:, 

IV.      OF  POTATOES. 

1°.  Nitrate  of  soda  has  been  applied  with  great  benefit  to  potatoes  also.  Af- 
ter the  potatoes  have  been  hari'owed  down  and  (hand)  hoed,  and  the  plants  are 
four  to  six  inches  above  the  ground,  it  is  applied  by  tne  hand  round  the  stem 
of  the  plants,  and  the  earth  then  set  up  by  the  plough.  Mr.  Turnbull,  in  Dum- 
bartonshire, last  year  used  it  in  this  way  at  the  rate  of  U  to  2  cwt.  per  Scotch 
acre,  (1^  English  acres,)  and  the  produce  exceeded  that  of  the  land  to  which  no 
nitrate  was  applied,  by  20  Scotch  bolls  to  the  Scotch  acre. 

2°.  Applied  in  the  same  way  there  is  every  reason  to  believe  that  the  sul- 
phate of  soda  would  have  a  highly  beneficial  effect  also  I  repeat  my  recom- 
mendation that  this  substance  should  be  fairly  tried  with  every  crop,  because  it 
is  a  product  of  our  own  manufactories,  which  can  be  supplied  in  unlimited 
quantity,  and  without  the  chance  of  any  material  increase  of  cost:  while  the 
nitrate  of  soda  is  already  in  the  hands  of  speculators,  and  within  a  short  period 
has  risen  in  the  market  to  the  extent  of  nearly  one-third  of  its  former  price. 

In  plastering  their  potatoes,  the  Americans  generally  put  in  a  spoonful  of 
gypsum  with  every  cutting — a  similar  method,  if  preferred,  might  be  adopted 
with  the  nitrate  and  sulphate  of  soda,  though  the  chance  of  loss  by  percolation 
through  the  soil,  would,  by  this  method,  be  in  some  degree  increased.  In  Flan- 
ders, wood  ashes  and  rape  dust  are  frequently  thrown  in  by  the  hand,  when  each 
cutting  is  introduced. 

3°.  I  shall  have  occasion  hereafter  to  recommend  to  the  attention  of  the  prac- 
tical farmer,  many  waste  materials  of  various  kinds,  thrown  outfrom  our  manu- 
factories, the  application  of  which  to  useful  purposes  would  be  a  great  national 
benefit.  In  reference  to  the  culture  of  potatoes,  I  will  here  bring  under  your  no- 
tice the  chloride  of  calcium,  which  is  said  to  have  been  beneficially  applied  to 
various  crops,  but  to  potatoes  especially,  with  surprising  effect.  Under  the  in- 
fluence of  this  substance  the  sunflower  and  maize  have  grown  to  the  height  of 
14  to  18  feet,  and  potatoes  have  attained  the  weight  of  2  to  3  lbs.*  In  Germany, 
Sprengel  also  found  it  useful  to  potatoes. — {Chemu  fUr  Landwirthe,  I.  p.  635.) 

Thousands  of  tons  of  chloride  of  calcium  may  eveiy  year  be  prepared  from  the 
waste  materials  which  flow  into  the  river  Tyne,  from  the  alkali  works  upon  its 
banks.  Thousands  of  gallons  of  the  solution  of  this  substance  yearly  run  off 
from  the  works  o^  Messrs.  Allan  &  Co  at  Heworth,  and  might  be  procured  for 
little  more  than  the  expense  of  collecting.  It  is  also  contained  largely,  though 
mixed  with  other  substances,  in  the  mother  liquor  of  the  salt  pans;  and  from  the 
numerous  salt  works  on  the  coast  might  readily  be  obtained  for  trial.  Wlien 
prepared  in  the  dry  state,  this  substance  rapidly  deliquesces  and  runs  into  a  liquid. 
The  most  convenient  way  of  applying  it,  therefore,  would  be  in  the  state  of  so- 
lution— so  largely  diluted  as  to  have  only  a  slight  taste — and  by  means  of  a  wa- 
tering cart  so  contrived  as  to  allow  it  to  flow  on  the  tops  of  the  ridges  and  young 
plants,  by  which  unnecessary  waste  would  be  prevented. 

Without  knowing  the  strength  of  the  solution  likely  to  be  obtained  from  the 
works,  it  is  impossible  to  give  any  idea  of  the  quantity  of  the  chloride  of  calcium 
which  ought  to  be  employed;  but  500  gallons  per  acre  may  safely  be  used,  it 
the  solution  be  so  far  diluted  as  to  have  only  a  decided  taste  of  the  substance. 
The  experiments  here  suggested,  therefore,  require  four  patches,  as  follows: — 
These  experiments  are  supposed  to  be  made  in  ground 
already  prepared  for  the  potatoe  crop,  by  the  usual  quan- 
tity of  manure.     I  think  it  not  unlikely,  however,  that 
by  planting  the  potatoe  in  the  midst  of  nitrate  or  sul- 
phate (sprinkled  over  with  dry  soil)  at  the  rate  of  h  cwt. 
per  acre,  and  afterwards  applying  1  cwt.  per  acre,  when 
the  plants  are  hoed,  a  crop  might  be  obtained  without 
the  use  of  manure.     Of  course,  such  an  pxperiment  as 

*  The  Rohan,  a  French  variety  of  potatoe  lately  introduced  into  the  United  States— by  the 
ordinary  mode  of  culture — yields  tubers,  very  maxy  of  which  weigh  3  lbs.  and  many  attain  to 


Nitrate  of 
Soda.  1  to  I  >^ 
cwt.  pr  acre. 

Sulphate  of 
Soda,  1  to  1^ 
cwt.  pr  acre. 

Chloride  of 
Calcium,  500 
gals,  pr  acre. 

Manure 
only. 

No.  /.]  OF   MIXED   MANURES.  H 

this,  though  important  to  be  made,  should  be  tried  cautiously,  and  on  such  a 
scale  as  to  secure  the  experimenter  from  any  serious  loss. 

In  me  above  suggestions  I  have  introduced  nothing  in  regard  to  mixed  ma- 
nures— though  where  plants  require  for  the  supply  of  all  their  wants  nine  or 
teii  different  ingredients,  of  which  the  soil  they  gi-ow  in  can  perhaps  yield  in 
sufficient  quantity  only  three  or  four,  it  is  obvious  that  the  very  best  conse- 
quences may  follow  from  the  employment  of  mixed  manures.  To  this  class 
belong  common  night-soil,  urine,  animalised  carbon,  poudrette  (night-soil  mixed 
with  lime  and  gypsum),  the  poudre  vrgetaiif  (a  mixture  of  soot  and  saltpetre), 
the  urate  (now  manufactured  in  London),  and  many  others. 

The  mode  of  preparing,  and  the  special  uses  of  these  and  other  mixed  ma- 
nures, will  be  explained  in  the  third  part  of  these  lectures,  which  will  be  devoted 
to  the  consideration  of  the  nature  and  uses,  and  to  the  theory  of  the  action  of 
natural  and  artificial  fertilizers.  In  the  mean  time  it  is  desirable,  in  the  first 
place,  to  obtain  results  from  which  the  special  action  of  each,  when  used  alone, 
can  be  fairly  deduced. 

That  these  experiments  may  have  their  full  value,  it  is  indispensable  that  a 
measured  portion  of  each  field  should  be  left  without  manure  or  aressing  of  any 
kind,  in  order  that  a  true  idea  may  be  formed  of  the  exact  effect  of  each  sub- 
stance employed.  Experiments  are  valuable  to  the  practical  man  if  they  mere- 
ly show  the  superiority  of  one  species  of  manure  over  another,  but  they  are  in- 
sufficient to  show  how  much  each  of  them  tends  to  increase  the  produce — or  to 
enable  us  to  arrive  at  a  satisfactory  explanation  of  tlie  mode  in  which  they 
severally  act  in  promoting  vegetation. 

Among  other  important  experiments  lately  published,  to  which  the  above  ob- 
servation is  apphcable,  may  be  mentioned  those  of  Mr.  T.  Waite  of  Doncaster. 
The  effects  of  nitrate  of  soda  on  his  land  were  very  striking,  showing  a  remarkable 
increase  of  produce  over  bone  dust,  rape-dust,  or  rotten  fold-yard  manure — but 
he  does  not  seem  to  have  determined  the  produce  of  the  same  land  during  the 
same  season  and  vdLhmit  inanure.  We  have,  therefore,  no  term  of  comparison, 
by  means  of  which  we  can  ascertain  the  absolute  or  even  the  exact  comparative 
effect  of  the  different  substances  employed. 

It  has  been  well  observed  by  Sir  Elumphry  Davy,  "that  nothing  is  more 
wanting  in  agriculture  than  experiments  m  which  all  the  cir  cum  stances  are  mi- 
nutely and  scientifically  detailed,  and  that  this  art  will  advance  in  proportion  as 
it  becomes  exact  in  its  methods."*  The  above  suggestions  are  submitted  to 
practical  men  in  the  hope  that  they  may  assist  in  introducing  such  exact  meth- 
ods into  our  agricultural  operations,  and  at  the  same  time  promote  the  theoreti- 
cal advancement  of  the  most  important  art  of  life. 

Exact  methods  lead  to  theoretical  discoveries,  while  these  are  no  less  certain- 
ly followed  by  important  practical  improvements. 


No.  ir. 

{See  Lecture  II.,  p.  37.) 

In  illustration  of  the  effect  of  sudden  alternations  of  temperature  on  vegetable 
substances,  explained  in  a  note  subjoined  to  page  37,  I  quote  with  pleasure  the 

the  weight  of  5  lbs.    When  perfectly  ripe,  it  is  said  to  be  an  excellent  table  potatoe,  and  to  be 
best  in  Ihe  spring.— ^/6any  Cultivator,  for  March,  1841. 
*  Agricultural  Chemistry,  Lecture  L 


13  ON   SUDDEN   ALTERNATIONS    OF  TEMPERATURE.  [Appendix^ 

following  instructive  letter  from  an  ably  conducted  monthly  jo'irnal  published 
at  Albany,  in  the  State  of  JNew-York,  under  the  title  of  the  CiiUivator.  It  is 
extracted  from  the  Number  for  March  last : — 

"  In  regard  to  Irish  potatoes,  a  still  thinner  covering  of  earth  than  the  one 
just  mentioned  suffices  with  us  to  preserve  them  from  rotting.  Indeed,  it  would 
seem  as  if  they  could  freeze  and  thaw  several  times,  during  winter,  without 
being  destroyed,  provided  they  are  covered  with  earth  all  the  time ;  for  we  often 
find  them  near  the  surface  and  peifectly  souiad,  in  the  spring,  when  spading  up 
the  ground  in  which  the  crop  had  grown  during  the  previous  season.  There 
they  must  have  undergone  freezing  and  thawing  whenever  the  earth  was  in 
either  state,  as  it  often  is  to  a  much  greater  depth  than  the  potatoe  roots  ever 
extend.  Why  should  those  roots  always  be  destroyed  when  they  freeze  above 
ground,  and  not  suffer  equally  when  frozen  under  ground  ? 

"  The  reason  why  potatoes,  apples,  &c.  become  soft,  and  rot  when  frozen 
and  then  thawed  suddenly,  uncovered  and  in  open  air,  is  the  sudden  thawing. 
You  may  put  a  heap  of  apples  on  the  floor  of  a  room,  or  other  dry  place,  where 
they  will  freeze  perfectly  hard,  and  if  covered  close  with  any  thing  that  will  ex- 
clude the  air,  when  the  weather  becomes  warm  enough  to  thaw,  the  apples  will 
remain  sound  and  uninjured,  after  they  are  thus  closely  thawed.  The  cover 
may  be  of  the  coarse  tow  of  flax,  or  any  inicle  that  will  cover  them  close  and 
exclude  the  air.  So  apples  may  be  packet,  in  a  tight  barrel,  if  full  and  headed 
up  so  as  to  exclude  the  air.  They  may  be  suffered  to  remain  so  in  a  gaxret,  or 
any  dry  place  where  it  freezes  hard,  and  they  will  be  found  sound  and  free  from 
injury,  if  the  barrel  remains  tight  till  they  are  thoroughly  thawed.  It  is  the  sud- 
den thawing  that  causes  the  apples  or  other  vegetables  to  become  soft  and  rot, 

"  So  if  the  fingers  on  your  hand  be  frozen,  and  you  expose  them  to  sudden 
heat  by  warming  them  at  the  fire  and  they  suddenly  thaw,  the  flesh  will  morti- 
fy and  slough  off.  But,  if  you  freeze  your  fingers  or  other  limbs,  and  put  them 
in  snow,  and  rub  gently  till  they  thaw, — or  if  put  into  a  pail  of  water  just  drawn 
from  the  well,  which  will  be  less  cold  than  your  frozen  fingei-s, — they  will  thaw 
slowly,  and  suffer  but  little  injury. 

"  So  during  the  early  autunmal  frosts  in  September,  if  the  morning  after  the 
frost  is  cloudy,  the  frost  will  be  slowly  drawn  from  the  frozen  vegetables,  and 
they  will  be  uninjured  ;  but  if  they  receive  the  rays  of  the  early  and  clear  sun, 
they  thaw  so  suddenly,  that  they  will  hang  their  heads  and  perish.  If  wet  with 
water  from  the  well,  long  enough  to  extract  the  frost  before  the  sun  shines  on 
them,  they  do  not  suffer. 

"  Onions  are  a  difficult  root  to  keep  in  winter.  If  they  are  put  in  a  cellar 
warm  enough  to  save  them  from  frost,  they  will  vegetate  awd  be  deteriorated.  I 
put  them  in  the  warehouse,  where  they  freeze  as  hard  as  if  out  of  doors.  If  in 
a  heap,  I  cover  them  close  with  some  old  clothes,  or  any  thing  that  covers  close, 
to  exclude  the  air.  The  same  if  in  boxes  or  casks.  They  freeze  hard,  but  it 
does  not  appear  to  injure  them  for  present  use,  if  thawed  by  putting  them  into 
a  pail  of  fresh-drawn  water,  to  draw  out  the  frost  just  before  cooking  them. 
Onions,  thus  kept,  will  be  in  good  condition  in  the  spring,  after  thawing  under 
cover  from  the  air. 

"  I  put  parsneps,  carrots,  beets,  &c.,  in  boxes  or  casks,  and  then  cover  them 
with  potatoes,  wnich  preserves  them  from  drying." 

In  farther  illustration  of  this  subject  I  need  only  recall  to  the  recollection  of 
the  gardener  the  well  known  fact,  that,  when  the  winter  frosts  begin  to  set  in, 
and  his  finest  flowers  to  be  nipped,  those  continue  to  blow  the  longest,  on  which 
the  sun's  rays  fall  latest  in  the  day.  Dahlias  protected  in  this  way,  will  bloom 
occasionally  for  weeks,  after  those  which  regard  the  eastern  sky  are  completely 
withered. 

Professor  Lindley  has  published  a  series  of  valuable  observations  on  the  effects 
of  extreme  cold  upon  plants.  The  general  results  of  these  observations  are 
■tated  in  his  ^^  Theory  of  Horticulture,"  p.  88.     But  the  conclusions  at  which 


No.  IL]  ON    SUDDEN   ALTERNATIONS    OP  TEMPERATURE.  13 

he  has  arrived  are  deduced  from  the  appearance  presented  by  the  plant  after  it 
was  tkavjed.  He  found  the  tissue  more  or  less  lacerated,  the  contents  of  the  air 
and  sap  vessels  intermingled,  and  the  colouring  matter  and  other  secretions  de- 
composed. He  attributes  the  laceration  to  the  freezing  and  consequent  expan- 
sion of  the  juices,  but  this  cannot  be  the  necessary  consequence  of  that  freezing, 
since  it  does  not  appear,  if  the  whole  tuber  or  leaf  be  slowly  thawed,  I  wouH 
explain  the  phenomena  as  follows: — 

1°.  When  the  leaf,  fruit,  or  tuber  freezes,  the  fluid  portions  slightly  expand 
in  becoming  solid,  but  the  air  in  the  air  vessels  contracts  in  at  least  an  equal  de- 
gree, and  thus  allows  a  lateral  expansion  of  the  sap  vessels  sufficient  to  prevent 
lesion.  When  the  temperature  is  slighdy  raised,  the  air  expands  but  shghtly, 
and  ice  is  melted  long  before  the  gaseous  substances  reach  their  original  bulk. 

2°.  But  if  the  rays  of  the  sun  strike  suddenly  upon  the  leaf  or  fruit,  the  sur- 
face may  at  once  be  raised  in  temperature  30°  or  40°  F.  The  air  will  conse- 
quently'expand  suddenly,  and  before  the  s.ip  is  thawed  may  have  distended  and 
torn  the  vessels,  and  caused  sap  and  air  to  be  mutually  intermingled. 

3°.  But  the  moment  the  sun's  rays  strike  upon  the  green  leaf,  its  chemical 
functions  commence.  It  begins  to  absorb  and  decompose  carbonic  acid :  and 
as  in  the  frozen  part  of  ihe  leaf  the  circulation  is  not,  and  in  consequence  of  the 
lesion  cannot  be,  established,  the  chemical  action  of  the  sun's  rays  must  be  ex- 
pended upon  the  stagnant  sap  ;  and  hence  those  changes  not  only  in  the  sap 
Itself,  but  even  in  the  solid  parts,  which  are  seen  to  take  place  in  the  withered 
leaf 

4°.  Though  not  in  a  state  of  growth,  the  tuber  of  the  potatoe  contains  the 
living  principle,  and  there  must  be  such  a  circulation  going  on  in  its  interior  as 
to  mamtain  an  approximate  equilibrium  of  temperature  throughout  its  sub- 
stance. A  sudden  thawing  of  the  exterior,  will,  as  in  the  leaf,  expand  the  air 
before  the  circulation  can  be  established  throughout  the  frozen  mass.  The  solid, 
fluid,  and  aeriform  substances  which  nature  has  separated  and  set  apart  from 
each  other,  will  thus  all  be  intermingled,  and  from  their  mutual  action,  those 
chemical  changes  of  which  we  know  the  starch  of  the  potatoe  to  be  susceptible, 
will  speedily  ensue ; — in  other  words,  the  potatoe  will  rot. 

The  practical  applications  of  these  views  are  numerous.  If  a  sudden  frost 
come  on, — protect  your  delicate  flowers  in  the  early  morning  from  the  rays  ot 
the  approaching  sun,  and  cover  with  straw  or  earth  the  potatoes  which  have 


No.  III. 

RESULTS  OF  EXPERIMENTS    ON    PRACTICAL  AGRICULTURE    DURING 
THE    SPRING    AND    SUMMER    OF   1841. 

{See  Appendix,  No.  1.,  and  Lectures  VIII.  and  IX.) 

In  a  previous  article  inserted  in  this  Appendix,  and  which  was  published 
early  in  the  present  spring  (April,  1841,)  I  ventured  to  offer  to  the  practical  ag- 
riculturist some  suggestions  in  regard  to  the  experimental  use  of  certain  un- 
mixed manures.  From  the  results  of  these  experiments,  which  I  was  quite  sure 
some  of  the  many  zealous  agriculturists  of  the  day  would  be  induced  to  under- 
take after  the  manner,  and  with  the  precautions,  1  had  pointed  out,  I  anticipated 


14 


RESULTS  OF  EXPERIMENTS  ON  P51A0T1CAL  AGRICULTURE.         [AppendtXj 


a  two-fold  advantage.  In  the  first  place,  that  important  practical  benefits  to 
the  agriculture  of  certain  districts  would  be  derived  from  them,  and  secondly, 
that  interesting  and  important  light  would  be  thrown  by  them  on  many  parts 
of  agricultural  theory.  It  is  by  experiment  that  all  the  remarkable  results  - 
theoretical  as  well  as  practical — of  modern  chemistry  have  been  arrived  at ; 
but  by  experiments  cautiously  made,  frequently  repeated,  and  logically  reason- 
ed from.  The  proceedings  of  the  practical  farmer  are  a  continued  course  of  ex- 
perimental trials,  and  to  convert  him  into  an  experimental  philosopher,  and  to 
lead  him  to  philosophical  results,  it  is  necessaiy  only  that  his  experiments 
should  be  made  loit/i  a  constant  rcferemx  to  weight  and  ineasurc,  and  should  be 
repeated  nnder  varied  and  .:*arefully  noted  conditions — and  that  he  should  be 
taught  to  draw  from  then  no  conclusions  more  general  than  they  really 
justify. 

The  following  results  of  experiments  made  during  the  past  summer  confirm 
all  my  anticipations.  Though  necessarily  somewhat  limited,  and  local  in  their 
nature,  they,  nevertheless,  present  on  the  whole  a  beautiful  illustration  of  what 
we  have  yet  to  expect  from  a  continuation  of  such  experimental  researches,  con- 
ducted in  so  skilful  a  manner.  I  need  not  especially  commend  the  experiments 
of  Ml-.  Fleming  :  for  I  can  scarcely,  I  think,  render  a  better  service  to  practical 
agriculture  than  by  placing  alT  of  them  in  the  hands  of  practical  men,  and  ear- 
nestly commending  them  to  their  careful  consideration  and  imitation. 

I.  Experiments  made  near  Aske  Hall,  on  the  property  of  the  Earl  of  Zet- 
land, on  lots  of  half  an  acre  each. 


1.  Soot— put  on  May  24—10  biisMs  cost  Gs.  Gd. 
Weight  of  grass  when  mown,  3  tons  16  cwt. 
Weight  when  made  into  hay,  1    "     15     " 

s 

1 
1 

(0 

it 

r;0000?COO    1 

C          r-t   ,-1 

I--  OOOO    1 

hi 

SS^^^a^ 

2.  Salt— put  on  May  24—3  bushels  cost  6s.  Gd. 
Weight  of  grass  when  mown,  3  tons  19  cwt. 
'Weight  when  made  into  hay,  1    "     10     " 

3.  No  Manure. 

Weight  of  grass  when  mown,  3  tons  12  cwt. 

Weight  when  made  into  hay,  1     "    .  6    " 

S3 

4.  Nitrate  of  Soda— put  on  May  24 — 4  sto7ies 

cost  lis. 
Weight  of  grass  when  mown,  4  tons  10  cwt. 
Weight  when  made  into  hay,  1     "     12    " 

1 

MM^  1 

5.  Sulphate  of  Soda  (in  aystals)—put  on  May 

24—4  sto7ics  cost  10s. 
Weight  of  grass  when  mown,  3  tons  3  cwt. 
Weight  when  made  into  hay,  1    "     !)    " 

II 

Common  Salt  . 
Soot    .... 
Nitrate  of  Soda 
Sulphate  of  Soda 
Sulphuric  Acid 
No  Manure  .     . 

6.  Sulphuric  Acid—  ^  put  on  May  26,  ^  put  on 

June  7,  i  put  on  June  1 1 — \blhs.  cost  5s. 
Weight  of  grass  when  mown,  3  tons  4  cwt. 
Weight  when  made  into  hay,  1     "    6    " 

N.  B.  The  cost  of  the  manure  does  not  include 

Ihe 

expens< 

3  oflayingitott. 

No.   III.]      RESULTS    OP    EXPERIMENTS  ON    PRACTICAL   AGRICULTUKB.  15 

Mr.  Turner,  his  lordship's  agent,  thus  writes : — 

"  The  plan  I  followed  in  putting  on  the  different  manures,  and  the  quantities 
used,  accorded  as  nearly  as  1  could  manage  it,  with  the  directions  given  in  your 
published  lectures. 

"  The  field  on  which  the  experiments  were  tried  is  situate 'in  a  high,  blealt 
climate,  and  consists  of  a  thin  light  soil,  upon  a  bad  subsoil  of  barren  clay 
resting  upon  Hmestone.  It  had  been  completely  exhausted  by  a  succession  of 
white  crops,  and  was  full  of  weeds  and  quickens.  I  had  it  well  ploughed,  and 
took  a  crop  of  drilled  turnips  fairly,  but  not  extravagantly,  manured.  The  crop 
"was  a  poor  one.  I  ploughed  the  land  as  soon  as  the  turnips  could  be  got  off. 
Drained  it ;  and  in  the  spring  worked  it  very  fine.  The  following  August  I 
sowed  it  away  with  grass  seeds  without  a  crop.  The  seeds  came  up  beautiful- 
ly, and  were  the  admiration  of  all  who  saw  them,  keeping  a  deep  green  through 
the  winter,  and  beginning  to  grow  early  in  the  spring ;  and  it  was  on  this  crop 
that  the  experiment  was  tried  early  in  the  succeeding  summer. 

"  I  need  scarcely  remark,  that  the  crop  of  grass  for  such  land  was  enormous, 
and  has  fully  repaid  the  money  expended  upon  it,  with  the  exception  of  drain- 
ing, and  in  two  or  three  years  I  have  no  doubt  but  it  will  repay  this  also." 

Remarks. — On  comparing  the  effect  of  these  several  top-dressings  as  indi- 
cated by  the  results  above  stated,  the  reader  will  be  struck  with  the  extraordi- 
nary increase  caused  by  the  addition  of  common  salt.  I  have  in  the  text 
(Lecture  IX.,  p.  190,)  indicated  a  principle  which  may  serve  to  explain  in  sor.ie 
measure  both  the  localities  in  which  the  use  of  common  salt  may  be  expected 
to  be  beneficial,  and  the  reason  why  in  many  parts  of  our  island  the  employ- 
ment of  this  substance  has  not  been  attended  by  any  large  measure  of  success. 
The  position  of  the  land  experimented  upon  by  Mr.  Turner,  is  such  as  to  lead 
us  to  expect  it  to  be  improved  by  common  salt,  according  to  the  views  there 
stated. 

The  nitrate  of  soda  produced  less  effect  than  either  the  common  salt  or  the 
soot,  but  it  gave  an  increase  which  was  double  of  that  yielded  by  the  sulphate 
of  soda.  The  latter  salt,  however,  was  applied  in  the  state  of  crystals,  which 
contains')  per  cent,  of  water,  so  that  less  than  one  half  of  that  weight  of  drij 
salt  was  used,  which  was  recommended  in  the  suggestions  I  offered  for  the 
employment  of  this  substance  in  practical  agriculture.     At  the  same  time,  the 

Krice  paid  by  Mr.  Turner  for  this  salt  was  foiir  times  as  great  as«it  ought  to 
ave  been.  Any  quantity  of  the  dry  sulphate  of  soda  may  be  procured  at  lOs. 
a  cwt.,  at  which  price  it  is  forwarded  in  casks  to  all  parts  of  the  country  by 
Messrs.  Allan  &;  Co.,  Heworth  Alkali  Works,  Newcastle. 

The  most  valuable  practical  suggestion  to  be  derived  from  these  experiments 
is  certainly  this — that  a  liberal  use  of  common  salt  is  likely  to  increase  in  a  great 
degree  the  produce  of  grass  in  the  locality  where  they  were  made,  and  on  the 
same  kind  of  soil.  This  valuable  discovery  will  far  more  than  repay  the  ex- 
pense and  trouble  of  the  entire  series  of  experiments.  No  application  can  be 
so  cheap  as  this,  so  long  a^il  succeeds.  At  the  same  time  a  mixture  of  the  other 
substances — the  niH«te  and  the  sulphate,  which  were  partially  successful — might 
possibly  prove  still  more  efiicacious  on  the  grass,  and  might  be  expected  even 
to  ameliorate  the  condition  of  the  land  for  the  further  production  of  white  crops. 
In  a  future  part  of  this  Appendix  I  intend  to  offer  some  suggestions  in  regard  to 
the  kind  and  quantity  of  the  ingredients  which  may,  with  probable  advantage, 
enter  into  the  constitution  of  these  mixed  manures. 

I  have  calculated  and  introduced  into  Mr.  Turner's  table  an  additional  col- 
umn, exhibiting  the  weight  of  hay  yielded  by  100  lbs.  of  grass,  with  the  view 
of  showing  the  relative  succulence  of  the  several  crops  when  cut.  As  a  gen- 
eral rule,  the  weight  of  dry  hay  does  not  exceed  one-fourth  of  the  weight  of  the 
grass  when  cut.  In  the  experiments  of  Mr.  Turner,  however,  the  weight  of 
hay  in  every  case  was  mucli  beyond  this  quantity — the  most  succulent  crop, 
tl^at  to  w.'iich  no  dressing  was  applied,  yielding  36  per  cent,  of  hay.  This  gen- 
27* 


16  RESULTS   OP    EXPERIMENTS  ON   PRACTICAL    AGRICULTURE.       [Appendix. 

eral  result  may  have  been  partly  due  to  the  state  of  ripeness  in  which  all  the 
grasses  were  cut,  while  the  greater  produce  of  hay  from  the  dressed  portions 
may  indicate  the  relative  ripeness,  and  therefore  dryness,  of  each  when  cut  down. 
U  is  evident,  therefore,  that  the  relative  values  of  crops  of  grass  or  clover  are 
not  to  be  judged  of  by  the  several  weights  when  green,  but  by  the  weights  of 
the  diy  hay.  This  is  further  confirmed  by  the  results  of  an  experiment  with 
nitrate  of  soda,  communicated  to  me  by  Mr.  Carrutiiers,  of  Warmonbie,  near 
Annan,  in  which  the  relative  weights  of  hay  obtained  were  vitich  niore  in  favour 
of  the  use  of  the  nitrate  than  the  several  weights  of  grass  yielded  by  the  dressed 
and  undressed  portions  of  the  field.  On  the  contrary,  from  a  field  on  Oliver 
Farm,  near  Richmond,  Mr.  Sivers  informs  me,  that  the  weight  of  hay  wasvmc/i 
less  in  favour*  of  the  use  of  tlie  nitrate  of  soda  than  the  relative  weights  of 
grass.  In  all  cases,  therefore,  the  weight  of  the  dry  crops  obtained  by  different 
methods  should  be  compared  with  each  other,  as  the  safest  test  of  the  relative 
merits  of  the  several  modes  of  procedure  by  which  they  have  respectively  been 
raised. 

II.  Experiments  made  at  Erskine,  on  the  property  of  Lord  Blantyre. 
I  insert  the  clear  and  well-digested  statement  of  his  Lordship's  agent  without 
alteration:  — 

"  Freelomd,  Erskine,  by  Old  Kilpatrick,  Glasgoiv,  29/A  July,  1841. 
"  Sir — Agreeably  to  Lord  Blantyre's  instructions  I  send  you  a  copy  of  the  re- 
sults of  some  experiments  with  manures  on  young  grass  for  hay,  undertaken 
on  two  separate  pieces  of  land — the  one  a  very  good  light  soil  (subsoil  gravel)  ; 
the  other  stiff  clay  soil  with  a  clay  subsoil.  The  manures  were  applied  on  1st 
May,  the  hay  cut  on  the  1st  and  weighed  on  the  19th  July  current;  the  extent 
of  each  plot  one-twentieth  of  an  imperial  acre.  From  the  small  extent  of  each  plot 
it  will  be  evident  that  the  results  cannot  be  exactly  depended  on,  farther  than  as 
a  general  result ;  because  in  so  small  a  portion  of  land  the  least  variation  in  the 
soil  or  crop  naturally  will  affect  the  results  very  materially ;  still,  on  the  whole, 
I  am  of  opinion  that  the  experiment  gives  the  compai'ative  view  of  the  value  of 
the  different  manures  used  pretty  nearly. 

"  One  thing  has  astonished  us  with  regard  to  soda  (nitrate).  On  all  the  fields 
I  have  observed  it  sown  on,  the  part  dressed  has  a  much  greater  vigour  of  after- 
math than  where  no  nitrate  of  soda  was  given :  showing  that  this  manure  is  not 
so  evanescent  as  was  generally  supposed. 

"  I  am,  Sir,  your  most  obedient  servant, 

"  Jas.  Wilson." 
Experiments  with  Manures  as  «  top-dressing  for  Hay,  at  Erskine,  1841, 
Remarks, — It  will  be  observed  in  these  experiments,  that  the  saltpetre  and 
nitrate  of  soda  produced  nearly  an  equal  increase  on  both  kinds  of  soil,  the  ni- 
trate of  soda  having  the  greater  effect  on  the  light,  the  nitrate  of  potash  on  the 
heavy  soil.  Next  to  these  on  the  light  soil  are  the  common  salt  and  sulphate  of 
soda,  though  on  the  heavy  soil  the  common  salt  had  the  better  effect  of  the  two. 
It  is  to  be  observed,  however,  that  in  this  case  the  sulphate  was  used  in  crystals, 
and  therefore  only  in  half  the  quantity  recommended.  Had  twice  the  quantity 
been  employed  upon  the  light  soil  the  produce  might  have  equalled  that  from  the 
nitrates. 

It  is  a  singular  illustration,  however,  of  the  necessity  of  applying  different 
substances  to  different  soils — that  so  far  as  this  experiment  is  to  be  depended 
upon,  the  sulphate  of  soda  almost  entirely  failed  on  the  heavy  land. 

The  most  valuable  practical  deduction  from  these  experiments  also,  is,  that 
on  both  the  soils  in  question,  the  grass  land,  in  its  present  condition,  may  be  salted 
to  advantage.  At  the  same  time,  it  appears  probable  that  on  the  light  soil  the 
increased  produce  would  amply  repay  the  cost  of  applying  either  nitrate  or  sul- 

"  In  Mr.  Sivers'  experiments,  100  square  yards,  nitrated,  gave  68  stones  of  hay,  unnitrated 
62  stones,  but  when  dry  they  were  reduced  to  12  stones  each.  How  very  much  more  suc- 
culent these  grasses  were  than  those  of  Mr.  Turner ! 


No.  Ill] 


C-N    MANURE  AS  A  TOP-DRESSING    FOR  HAY. 


17 


phate  of  soda  at  the  rate  of  120  lbs.  per  acre — the  latter  being  in  its  dry  or  un- 
crystallized  state.  « 

The  effect,  generally,  of  all  the  dressings  is  strikingly  greater  on  the  light 
soil — a  fact  which  speaks  strongly  in  favour  of  the  adoption  of  any  of  those 
methods  by  which  the  openness  and  friability  of  the  land  has  been  found  to  be 
permanently  promoted.  On  the  stiff  soil,  even  the  ammonia,  by  some  deemed 
so  vitally  necessary  to  vegetation,  appeal's  to  have  produced  no  sensible  alter- 
ation. 


Manures  used,  and  quantities  applied,  to 
each  plot  of  l-20th  of  an  acre. 

1. 

l~ 

Total  produce 

Total  additional 

o 

•Sid 

o'oJ 

per 

weight  per 

PL, 

!^.S^ 

^^ 

Imperial  Acre. 

Imperial  Acre. 

1 

Exp.  I.  Good  light  soil,  subsoil  gravel. 

1  lb.  sulphuric  acid,  diluted  in  47  \ 

galls,  water          .         .         .      ) 

271 

44 

ts.  cwt.  qrs.  lbs. 
2    8     1  16 

ts.  cwt. 

-    7 

qrs.  lbs. 
3  12 

2 

Gibs,  saltpetre  (nitrate  of  potash) 

322 

95 

2  17 

2    0 

-  16 

3  24 

3 

G  lbs.  nitrate  of  soda  . 

339:112 

3    0 

2    4 

1    0 

0    0 

4 

6  lbs.  sulphate  of  soda  (in  crystals) 

292 

65 

2  12 

0  16 

-  11 

2  12 

5 

17  lbs.  gypsum  .... 

254 

27 

2    5 

1  12 

-    4 

3    8 

6 

1  bush,  wood  charcoal  (pounded) 

277 

50 

2    9 

1  24 

-    8 

3  20 

7 

i  bush,  common  salt,  25  galls,  water 

294 

67 

2  12 

2    0 

-  11 

3  24 

8 

1  gal.  ammoniacal  liquor,  47gls,water 

277 

50 

2    9 

1  24 

-    8 

3  20 

9 

No  application  .... 
Exp.  II.  Clay  sail,  subsoil  dmj. 

227 

2    0 

2    4 

~"    "" 

~"    ^ 

1 

lib.  sulphuric  acid,  diluted  in*47) 
galls,  water      .         .         .          \ 

25G 

26 

2    5 

2  24 

-    4 

2  16 

2 

Gibs,  saltpetre  (nitrate  of  potash) 

28(? 

56 

2  11 

0    8 

-10 

0    0 

3 

G  lbs.  nitrate  of  soda  . 

282 

52 

1  10 

1  12 

-    9 

1    4 

4 

6  lbs.  sulphate  of  soda  (in  crystals) 

232 

2 

2    1 

1  20 

-    0 

1  12 

5 

17  lbs.  gypsum  .... 

240 

10 

2    2 

3  12 

-    1 

3    4 

G 

I  bush,  wood  charcoal  (pounded) 

257 

27 

2    5 

3  16 

-    4 

3    8 

7 

i  bush,  common  salt,  25  galls,  water 

2G9 

39 

2    8 

0    4 

-    6 

3  24 

8 

1  gal.  ammoniacal  liquor,  47gls.water 

201 

— 

1  15 

3  16 

—    _ 

_    _ 

9 

No  application  .... 

230 

— 

2    1 

0    8 

-    -■ 

-    - 

The  Dressings  were  applied  1st  May,  the  Grass  cut  1st  July,  and  the  Hay 
weighed  19th  July. 


III.  Experiments  made  under  the  immediate  superintendence  of  W.  Fleming, 
Esq.,  of  Barochan,  near  Paisley,  and  on  his  own  property.  The  statement  is 
drawn  up  by  Mr.  Fleming  himself 

1. — Experiments  on  Hay  with  Nitrate  and  Sulphate  of  Soda  and  with  Cfypsum^ 


Description  of 

Rate  per 

Weight  per 

Weight 

No. 

Field. 

Dressing. 

imp.  Rooii 

Rood,  green. 

when  stack'd 

1 

Covenlea, 

Nothing, 



3361  lbs. 

1120  lbs. 

2 

Do. 

Nitrate  of  Soda. 

40  lbs. 

4907  " 

1636  " 

3 

Do. 

Sulphate  of  Soda. 

40  lbs. 

3966  " 

1322  " 

4 

Do. 

Gypsum. 

10  lbs. 

3831  " 

1277  " 

1 

Crook's  High 

«     Nothing. 



4436  " 

1478  " 

2 

Do. 

Nitrate  of  Soda. 

40  lbs. 

4999  " 

1666  " 

1 

Crook's  Low. 

Nothing. 

2185  '' 

728  " 

2 

Do. 

Nitrate  of  Soda. 

40  lbs. 

3764  " 

1364  " 

3 

Do. 

Gypsum. 

80  lbs. 

3110  « 

1036  " 

18 


BXPKRIMENTS  ON  WINTER  RYE. 


[Appendtte, 


Character  of  the  Soil — Nos.  1,  2,  3,  and  4  were  good  sharp  soil,  on  rotten 
rock,  (decayed  trap,)all^as  neaf  as  possible  the  same  description  of  land, 
drained,  and  lying  together.  Nos.  1  and  2,  Crook's  High,  stiff  clay,  drained; 
the  hay  was  after  wheat.  Nos.  1,  2,  and  3,  Crook's  Low,  light  clay-loam, 
drained ;  the  hay  was  after  barley. 

On  Covenlea  the  dressings  were  applied  on  the  22nd  of  April,  and  the  hay  cut 
on  the  2nd  of  July  ;  on  the  other  fields  the  nitrate  and  gypsum  were  applied  on 
the  12th  of  April,  and  the  hay  cut  on  the  9th  of  July. 

N.  B.  The  above  is  the  average  of  trials  in  three  parts  of  the  Covenlea  field; 
a  small  portion  of  moss  was  also  sown  with  nitrate  of  soda,  in  the  low  part  of 
the  same  field,  but  no  benefit  was  observable,  beyond  the  usual  dark  green 
colour  which  appeared  about  ten  (Jays  after  the  application.  The  sulphate  of 
soda,  although  evidently  beneficial,  does  not  produce  the  dark  green  colour.  In 
the  Crook's  fields  the  effect  of  nitrate  of  soda  in  producing  the  dark  green  colour 
was  as  remarkable  as  in  the  Covenlea  field.  The  gypsum  on  both  fields  seems 
to  have  had  a  good  effect,  particularly  on  the  aftermath  clover. 

Rkmarks. — In  these  experiments  also  the  sulphate  of  soda  was  used  in  only 
half  the  quantity  recommended.  By  referring  to  the  prices  paid  by  Mr.  Fleming, 
it  will  appear  that  the  use  of  sulphate  of  soda  gave  an  increase  of  200  lbs.  of 
hay  for  Is.  9d.  (or  500  lbs.  for  4s.  5d.),  while  the  nitrate  of  soda  gave  an  increase 
of  516  lbs.  for  7s.  lOd. ;  so  that,  though  the  actual  increase  of  hay  per  rood  was 
considerably  less  by  the  use  of  the  sulphate,  yet  that  increase  was  obtained  at 
little  more  than  half  the  cost  of  the  same  weight  of  increase  derived  from  the  ni- 
trate. A  similar  remark  applies  to  the  gypsum,  so  that  these  experiments  give 
ample  encouragement  for  the  application  of  both  these  substances  in  somewhat 
large  quantity  to  succeeding  crops,  on  the  same  land. 

2. — Experiments  on  Winter  Rye,  dressed  with  Nitrate  of  Soda,  Lime  vriih  Potash^ 
Sidfhate  of  Soda,  and  Muriate  of  Avrmonia,  {Sal  AmvioJiiac.') 


Rate  per 

Weight  of 

Weight  of 

Bushels 

No. 

Field. 

Description  of 

rood 

Grain. 

Straw 

per 

Dressing. 

imperial. 

per  rood. 

per  rood. 

rood. 

1 

Garden  Plot. 

Nothing. 

^ 

160  lbs. 

1024  lbs. 

3i 

2 

Do. 

Nitrate  of  Soda. 

40  lbs. 

336  " 

1664  " 

6i 

3 

Do. 

Lime  and  Potash. 

40  " 

272  " 

1344  " 

5i 

4 

Do. 

Sulphate  of  Soda. 

40  " 

224  " 

1152  " 

M 

b\ 

Do. 

Mur.  of  Ammonia 

5  " 

232  " 

1216  " 

41 

Character  of  the  Soil. — Tilly  clay,  which  had  been  trenched,  and  in  potatoes 
the  year  before.     The  Rye  was  sown  on  their  6eing  lifted  in  October,  1840. 

The  applications  were  made  on  the  14th  of  April,  the  grain  was  cut  on  the 
9th  of  August,  and  thrashed  on  the  25th. 

N.  B.  As  early  as  the  end  of  April  the  effects  of  the  nitrate  of  soda  were  very 
apparent  from  the  dark  green  colour  produced,  and  broad  leaves,  and  after  it  was 
ripe  the  heads  were  longer  than  any  of  the  others  ;  but  it  was  so  strong  that  it 
was  laid  a  month  before  it  was  cut ;  none  of  the  others  were  laid.     Every  ap- 

f)lication  seems  to  have  done  good, 'by  increasing  the  produce.  The  potash  and 
ime  was  made  by  slaking  quick-lime  and  sand  with  a  solution  of  potash,  and 
allowing  them  to  lie  together  for  a  month.  As  much  was  used  as  contained  1 
lb.  of  carbonate  of  potash  to  the  pole. 

Remarks. — From  these  experiments,  it  appears  that,  besides  the  proportionate 
increase  of  straw,  that  of  grain  was 

From  nitrate  of  soda,         12  bushels  for  31s.  Od.,  or  2s.  9d.  per  bush.; 
"      lime  and  potash,        7        "      for  33s.  6d.,  or  4s.  9d.       " 
"      sulphate  of  soda,      3        "for    7s.  Od.,  or  2s.  4d.       " 
**      sal-ammoniac,  5        "      for  10s.  9d.,  or  2s.  2d,      " 


No.  Ill] 


EXPERIMENTS  ON  WHEAT  FIELD. 


0 


Although,  therefore,  the  total  increase  by  the  employment  of  sulphate  of  soda 
and  muriate  of  ammonia,  in  the  proportions  actually  put  on,  was  not  so  great  as 
by  the  use  of  the  other  two  dressings,  yet  this  increase  was  obtained  at  a  con- 
siderably less  cost  per  bushel.  The  lime  and  potash,  though  producing  an  im- 
portant effect,  will  probably  not  yield  a  remunerating  return  with  this  crop  on 
this  soU,  while  the  results  hold  out  a  fair  inducement  for  the  trial  of  the  last  two 
dressings  in  larger  and  varied  proportions. 

The  five  samples  weighed  respectively,— 45  3-5,  513-4,  514-5,  52  3-5,  and 
48  4-5  lbs.  per  bushel,  so  that,  while  on  all  the  dressed  plots  the  grain  was 
heavier  than  on  the  undressed,  that  which  was  dressed  with  sulphate  of  soda 
was  considerably  the  heaviest. 

3. — Experiments  on  Wheat  field ^  Crook^s  {crop,  1841.) 


Weiaht  of 

Weight 

Weight  of  to*- 

Description 

Rate  per 

produce  of 

of 

tal  produce, 
when  cut,  of 

No. 

of  Top-dres.sing. 

Scotch  acre. 

Grain  of 

Grain 

>8'th  acre. 

pr.  bsiiL 

j^tli  an  acre. 

1 

Nitrate  of  Soda. 

160  lbs. 

209  lbs. 

63  lbs. 

9,500  lbs. 

2 

Potash 
and   Lime. 

160  lbs.     \ 
40  bush.  } 

210  " 

62  " 

8,930  " 

3 

Common  Salt. 

160  lbs. 

249  " 

62  " 

12,540  " 

4 

Mur.  Ammonia. 

20  lbs. 

208  " 

62  " 

8,360  " 

5 

Nitrate  of  Soda 
and  Gypsum. 

80  lbs.     > 
160  bush.  S 

214  " 

62  " 

8,620  " 

6 

Nitrate  of  Soda 
and  Rape-dust. 

80  lbs.     ) 
5  cwt.    ( 

240  " 

62i" 

11,970  " 

7 

Mur.  Ammonia 
and  Lime. 

20  lbs.    I 
40  bush,  f 

230  " 

63  " 

9,500  " 

8 

Common  Salt 
and  Lime. 

28  lbs.     \  ^r.  ,. 

sobush.  }r 

631" 

8,740  " 

9 

Nothing. 

-         190  " 

61  " 

8,050  " 

Character  of  the  Soil. — The  land  was  a  heavy  loam,  and  of  as  nearly  as  pos- 
sible the  same  quality.  It  had  been  in  potatoes,  and  the  wheat  was  sown  when 
they  wei-e  lifted  in  October,  1840.      • 

The  applications  were  all  made  on  the  13th  of  April,  and  the  crop  was  reaped 
on  the  2d  of  September. 

The  produce  of  Jth  of  a  Scotch  acre,  thrashed  and  weighed  and  well  cleaned, 
gave  an  a/verage  of  from  32  to  33  bushels  of  61  lbs.  each  per  Scotch  acre  of  grain. 

Rkmarks. — This  table  presents  us  with  two  remarkable  results, — that  ob- 
tained by  the  use  of  common  salt,  and  that  from  a  mixture  of  soda  and  rape- 
dust.     Thus,  exclusive  of  the  straw, — 

Nitrate  of  soda  alone  gave  152  lbs.  of  wheat  for  31s.,  or  12s.  2d.  per  bushel; 

Nitrate  with  rape-dust  gave  400  lbs.  of  wheat  for  43s.  6d.,  or  6s.  9d.  per  bushel ; 

Common  salt  gave  472"lbs.  of  wheat  for  3s.  6d.,  or  6d.  per  bushel. 

The  increased  produce,  by  the  use  of  common  salt,  is  by  far  the  most  valua- 
ble result  to  Mr.  Fleming  in  an  economical  point  of  view,  and  plainly  indicates 
the  kind  of  application  he  can  most  profitably  make — to  his  wheat  crops  at  least — 
on  land  similar  to  the  above,  and  in  the  district  where  he  resides. 

Neither  the  nitrate  of  soda  nor  the  mixture  of  this  salt  with  rape-dust,  gave 
such  an  increase  as  to  repay  their  own  cost,  unless  when  corn  is  very  high.  It 
is  interesting,  however,  to  observe  that  the  mixture  with  rape-dust  gave  so  large 
an  increase,  though  the  value  of  this  particular  experiment  is  lessened  by  the  ab- 
sence of  any  trial  with  rape-dust  alone,  by  which  the  effect  of  each  of  the  ingre- 
dients ought  to  be  judged  of  I  have  reckoned  the  rape-dust  at  £7  a  ton,  so  that 
5  cwt.  would  cost  28s.,  and  we  know  that  a  top-dressing  of  this  substance  alone, 
in  a  somewhat  larger  quantity,  gives  a  remunerating  return  in  many  of  our  wheat 
lands. 


90 


EXPERIMENTS    ON   EARLY   POTATOES, 


[Appendix^ 


Mr.  Outhwaite  of  Banesse,  in  the  North  Riding  of  Yorkshire,  a  skilful  and 
enterprising  practical  farmer,  who  has  for  some  years  been  using  rape-dust  over 
a  great  breadth  of  his  wheat  crop,  has  favoured  me  with  the  result  of  one  of  his 
more  accurate  trials  on  spring  wheat,  made  during  the  past  season.  The  wheat 
was  sown  after  turnips  taken  off  in  April,  and  part  of  the  field  was  dressed  with 
rape-dust  at  the  rate  of  5|  cwt,  (or  at  £l  a  ton,  of  40s.)  per  acre.  The  produce 
of  the  dusted  portion  was  39  bushels,  and  of  the  undusted  29  bushels  per  acre, 
and  the  increase  of  straw  was  one-fifth  of  the  whole.  Both  samples  were  of 
equal  weight,  and  sold  at  the  same  price, — 8s.  3d.  per  bushel.  In  this  experi- 
ment the  increased  10  bushels  cost  40s.,  or  4s.  per  bushel,  giving,  on  a  large 
breadth  of  land,  a  handsome  remuneration. 

These  results  will,  I  trust,  encourage  others  to  make  trials  similar  to  tliose  of 
Mr,  Fleming  and  Mr.  Outhwaite;  while  these  gentlemen  will,  doubtless,  be  in- 
duced each  to  try  that  applicaUon  which  has  succeeded  so  well  in  the  other's 
hands.  It  might  be  useful  as  well  as  interesting  to  compare  the  produce  of  four 
plots  arranged  and  dressed  as  follows  : — 


Common  Salt. 

Rape- dust. 

Common  Salt 
and  Rape-dust. 

Nothing. 

4. — Experiments  on  Early  Potatoes,  1841, 
All  were  dunged  in  the  usual  manner  with  farm-yard  manure,  at  the  rate  of 
about  30  cubic  yards  per  acre.     The  potatoes  were  all  planted  on  the  25th  of 
March,  on  the  same  heahy  black  soil.     The  several  dressings  were  applied  on 
the  20th  of  May,  and  the  potatoes  were  all  lifted  on  the  28th  of  September. 


Description 

Rate 

Produce 

Weight  of 

fi 

of 

per  imp. 

per  imp. 

Produce  of 

i 

Top-dressing. 

acre. 

acre. 

18  yards  drill. 

Notf The 

1 

Nothing. 



Of)  bolls. 

77  lbs. 

peck  is  35  lbs. 

2 

Nitrate  of  Soda. 

160  lbs. 

80    " 

93   " 

weight,  and  16 

3 

Sulphate  of  Soda.  |2(>0  " 

73     " 

86   " 

make    a    boll 

4iDo.&:Nitr.ofSoda200  " 

107    " 

124  " 

or  5  cwt. 

This  break  of  ground  consists  of  a  piece'of  poor  clay  mixed  with  moss,  about 
9  inches  deep ;  subsoil  a  very  stiff  blue  till.  The  dung  was  old  from  the  farm-yard, 
about  the  ordinary  quantity  (30  cubic  yards  per  acre)  spread  upon  the  land,  and 
dug  in.  The  potatoes  were  drilled  in  with  the  hoe;  as  the  ground  was  wet  the 
plants  came  up  but  weak.  The  nitrate  of  soda  was  sown  before  the  other  top- 
dressings,  and  had  remarkably  quick  effect,  as  it  showed  the  third  night  after 
being  sown.  The  sulphate  of  soda  does  not  occasion  the  dark  green  colour 
which  is  seen  upon  the  potatoes  after  the  dressing  of  the  nitrate,  but  there  is  not 
the  smallest  doubt  of  its  beneficial  effects,  although  not  in  so  great  a  degree  as 
the  nitrate.  The  mixture,  which  is  composed  of  gds  of  sulphate  of  soda  and  ^d 
of  nitrate,  has  a  wonderful  effect  in  strenothening  the  growth  (which  it  keeps 
longer  than  with  nitrate  alone),  and  the  mixture  has  the  same  effect  in  producing 
the  dark  green  colour  as  the  nitrate  alone. 

Remarks. — That  a  mixture  of  substances  is  likely  to  be  more  efficacious  as  a 
dressing,  than  the  application  of  one  substance  alone,  except  in  peculiar  circum- 
stances, is  consistent  not  only  with  long  practical  experience — for  how  many 
substances  are  mixed  together  in  farm-yard  manure  1 — but  also  with  the  theore- 
tical principles  laid  down  in  the  text.  [See  Lectures  IX.  and  X.]  These  experi- 
ments upon  potatoes  show  that  this  crop  upon  Mr.  Fleming's  land  was  benefitted 
by  both  nitrate  and  sulphate  of  soda,  but  in  a  vastly  greater  degree  by  a  mixture 
of  the  two.  And  I  might  consider  my  suggestion  in  regard  to  the  employment 
of  sulphate  of  soda  as  a  manure,  to  have  been  of  no  mean  use  in  practical  agri- 
culture, had  it  led  to  nothing  else  than  to  this  happy  mixture  of  Mr,  Fleming. 

I  have  received  also  from  Mr.  Fleming's  gardener  (Mr.  Alexander  Gardiner) 


No.  III.]  EXPERIMENTS   ON   EARLY    POTATOES.  21  • 

a  very  well  digested  and  well  drawn  up  paper,  detailing  numerous  experiments 
made  by  himself  during  the  past  summer.  Among  these  is  one  upon  the  use  of 
this  same  mixture  upon  thepotatoe  crop,  which  I  shall  quote  in  his  own  words: 

"  April  26th. — Planted  potatoes  of  the  red  Don  variety,  soil  a  mellow  loam, 
two  feet  deep,  subsoil  yellow  till.  Farm-yard  dung  was  trenched  in  some  days 
before  planting,  at  the  rate  of  40  cubic  yards  per  acre  ;  sets  drilled  in  with  the 
hoe.  Plants  came  up  very  regular,  and  were  top-dressed  with  a  mixture  of  | 
sulphate  and  J  nitrate  of  soda  on  June  2nd,  at  the  rate  of  2  cwt.  per  acre.  They 
grew  very  strong  after  this  application.  Stems  six  or  seven  feet  in  length,  dark 
green,  and  the  produce,  when  lifted  in  October,  was  16  Renfrewshire  pecks  of  35 
lbs.  each  per  Scotch  fall  of  potatoes  fit  for  market." 

This  produce  is  equal,  1  believe,  to  about  26  tons  per  Scotch,  or  21  tons  per 
imperial  acre,  about  equal  to  that  of  Mr.  Fleming  with  the  same  mixture.  And 
what  an  amazing  luxuriance  of  vegetation,  to  yield  at  once  stems  seven  feet  in 
length  and  upwards  of  20  tons  of  tubers  per  acre  ! 

Those  who  are  the  most  sceptical  in  regard  to  the  benefits  to  be  derived  from 
agricultural  experiments,  when  well  conducted,  will  scarcely  question  the  impor- 
tance of  this  result — the  most  backward  in  making  experiments  will  be  anxious 
to  repeat  this  upon  his  own  potatoes.  The  cost  of  the  mixture  to  be  applied  in 
the  quantity  used  by  Mr.  Fleming  is  as  follows : — 

S„,pha.eofSoda    |  ,g  ^s'.  St^'e^Js'l^arsr."  |     «     ^ 
Nitrate  of  Soda  .   .     75  lbs.  at  22s 14     9 


21     6 

The  return  for  this  21s,  6d.  was  in  each  of  the  above  cases  upwards  of  8  tons 
of  potatoes. 

I  may  here  mention  also  two  other  interesting  experiments  of  Mr.  Gardiner, 
in  which  he  tried  the  effect  of  sal-ammoniac  upon  his  potatoe  crop, — 

1°.  In  the  one  he  mixed  sal-ammoniac,  previously  dissolved  in  water,  in  the 
proportion  of  1  lb.  to  each  cubic  yard  of  a  compost  formed  from  the  refuse  of  the 
garden,  and  planted  early  potatoes  with  it  at  the  rate  of  35  cubic  yards  per  acre. 
The  produce  was  one-sixth  more  than  when  no  ammonia  was  used.  The  va- 
riety of  potatoe  was  Taylor's  forty-fold,  the  soil  moss  and  clay.  The  cost  of 
this  application  was  19s.  per  acre. 

2°.  Sal-ammoniac,  dissolved  in  water,  was  sprinkled  on  moss  or  peat  earth, 
at  the  rate  of  20  lbs.  to  a  ton  of  earth,  and,  after  strewing  a  little  lime  at  the  bot- 
tom of  the  drills,  this  mixture  was  put  in  at.  the  rate  of  2  tons  per  acre.  The  po- 
tatoes were  14  days  later  in  coming  through  the  ground  than  the  same  variety 
planted  with  farm-yard  manure.  They  were  strong  in  the  stem,  of  a  dark  green 
colour,  and  equal,  in  point  of  produce,  to  the  others.  The  variety  of  potatoe 
was  the  Irish  apple,  the  soil  a  very  light  brown  loam,  of  that  description  locally 
named  deaf 

I  may  observe  on  this  latter  experiment,  that  the  application  is  not  so  simple 
as  it  appears.  The  lime  would  decompose  the  sal-ammoniac,  and  form  chloride 
of  cakiiini,  while  ammonia  would  be  liberated.  The  effect,  therefore,  may  be 
partially  due  to  both.  It  will  be  recollected  that  in  a  previous  part  of  this  Ap- 
pendix I  suggested  the  trial  of  this  chloride  of  calcium  as  a  top-dressing  for  va- 
rious crops. 

5. — Experiments  on  Moss  Oats,  soion  about  \st  May,  1841,  top-dressed  Slhth  June. 
*'  These  top-dressings  were  applied  on  the  5th  of  June,  and  by  the  24th  there 
was  a  striking  improvement,  especially  on  No.  2  and  No.  7.  It  was  quite  visi- 
ble in  greater  strength  and  evenness  of  crop.  One  or  two  of  the  others  also 
showed  improvement,  but  not  so  visibly  as  to  merit  particular  notice.  I  exam- 
ined them  from  time  to  time,  and  at  different  dates :  the  appearances  much  the 
same  as  noticed  upon  June  24th.    I  again  examined  them  a  fev  days  before 


23  EXPERiMENxa  ON  OATS.  [Appcudix^ 

they  were  cut,  when  I  was  much  satisfied  with  No.  2 ;  the  straw  appeared  to  me 
as  stiff  and  shinmg,  and  the  ear  as  well  filled,  as  if  it  had  been  grown  upon  stiff 
loam,  and  1  consider  the  same  dressings  applied  to  grain  crops  upon  moss,  will  ith- 
sure  a  good  crop  of  loell-JiUed  oais.  No.  7  was  nearly  as  good,  but  the  want  of  the 
bones  being  dissolved  was  a  drawback.  However,  I  consider  the  two  merit 
the  expense  of  another  trial." 


No. 


Top-dressing  per  pole  (imperial). 


Nothing. 

Bones  dissolved  in  sulphuric  acid  and  nitrate  of  soda  |  lb, 

Sulphate  of  soda  ^  lb.,  bone  dust  \  peck. 

Potash  1  lb.,  lime  and  bone  dust  ^  peck. 

Chloride  of  calcium  1  lb.,  bones  J  peck. 

Lime,  potash,  and  chloride  of  calcium,  \  lb.  each. 

Potash  and  lime,  nitrate,  and  bones,  \  lb.  each. 


Character  of  the  Soil. — Moss  4  feet  to  clay.  No.  3  the  best  crop  and  heaviest 
grain  (not  thrashed).  Nos.  3,  4,  and  5  not  so  good  as  No.  2,  but  all  much 
better  than  Nos.  1  or  G.  No.  6  the  worst — not  better  than  No.  1.  No.  7  very 
good — next  to  No.  2. 

Remarks. — These  experiments  of  Mr.  Fleming  on  moss  oats  may  be  con- 
sidered as  affording  another  illustration  of  the  benefits  which  are  yet  to  accrue 
to  practical  agriculture  from  the  suggestions  of  natural  science.  It  is  well  known 
to  those  who  have  directed  their  attention  to  the  reclaiming  of  peat  lands,  that 
the  crops  of  oats  raised  on  such  land  yield  abundance  of  straw,  but  that  the  ear 
is  small  and  badly  filled.  It  is  also  well  known  that  claying  such  lands  is  an  al- 
most unfailing  remedy  for  this  defect  in  the  ear,  as  well  as  for  the  less  important 
one  which  is  also  observed  in  the  straw.  My  friend,  Mr.  Alexander,  of  South 
Bar,  a  neighbour  of  Mr.  Fleming,  and,  like  him,  extensively  engaged  in  the  im- 
provement of  peat  lands,  finding,  as  most  other  persons  have,  that  in  some  lo- 
calities the  claying  of  his  land  was  very  expensive,*  conceived  the  idea  that 
some  chemical  application  might  be  made  to  this  soil,  which  would  supply 
what  the  defective  oat  plants  required,  and  thus  supersede  the  necessity  of 
clmilng.  He  was  pleased  to  communicate  this  opinion  to  me — stating  the  de- 
fect in  the  crop,  and  asking  a  chemical  remedy.  Looking  chiefly  to  what  was 
evidently  requii-ed  by  the  ear,  I  suggested  a  trial  of  various  mixtures,  in  all  of 
which, — from  an  idea  that  phosphates,  among  other  substances,  might  be  ne- 
cessary to  complete  the  ear, — bone-dust  formed  a  necessary  part.  The  result  of 
these  suggestions  is  seen  in  the  above  experiments  of  Mr.  Fleming.  They  have 
been  varied  and  improved  upon,  as  Mr.  Fleming's  united  chemical  knowledge 
and  practical  skill  enabled  him  to  do,  and  as  first  results  on  a  new  field  of  re- 
search, Nos.  2  and  7  may  be  considered  as  highly  encouraging,  if  not,  indeed, 
eminently  successful.  -  Too  much  confidence,  however,  must  not  be  placed  on 
the  effects  observed  in  one  or  two  instances ;  yet  I  hope  those  above  stated  are 
such  as  will  induce  others  to  repeat  the  experiments  with  equal  care,  in  order 
that  another  year,  affording  us  more  numerous  results,  may  enable  us  to  base 
our  conclusions  upon  a  larger  experience. 

6. — Experiments  upon  Oats  top-dressed  with  Sulphate  arid  Nitrate  of  Soda  (Jmcer 
end  of  Barn  Park.) 
"  The  first  was  sown  on  the  1 1th  May,  viz.,  3  ridges  with  sulphate  of  soda, 
at  the  rate  of  1  ^  cwt.  per  acre.     This  was  examined  from  time  to  time,  but  there 

*  Mr.  Garden,  of  Glenae  House,  near  Dumfries,  a  gentleman  to  whom,  though  personally 
unknown,  I  am  indebted  for  many  valuable  communications,  informs  me  that,  In  improving 
his  porous  peat  lands,  he  has  found  it  necessary  to  lay  on  a  coaling  of  clay  six  inc'ics  thick, 
at  an  expense  of  £\b  an  acre.  A  coating  of  two  or  three  inches  on  tkeir  peat,  he  says,  sinks 
down,  and  in  a  few  years  descends  beyond  the  reach  of  the  plough,  and  hence  it^is  mora 
economical  to  lay  on  at  once  an  entire  soil  of  six  inches, 


No.  III.]  EFFRCTS    OF    SULPHATE    AND   NITRATE    OF    SODA.  23 

appeared  to  be  little,  if  any,  difference  from  the  general  crop  (it  has  not  yet  been 
thrashed.)  Next,  3  ridges  were  sown  with  nitrate  of  soda,  at  the  rate  of  SO  lbs. 
per  acre.  This  made  a  little  alteration  both  in  colour  and  strength,  but  it  was 
too  little  to  make  a  very  decided  difference.  Also,  alongside  of  the  last-men- 
tioned, a  piece  was  dressed  with  a  mixture  of  suiphate  and  nitrate  of  soda,  in  the 
f>roportion  of  frds  of  the  former  to  ^rd  of  the  latter.  This  immediately  took  the 
ead  of  the  others  both  in  colour  and  strength,  so  much  so,  that  by  iMay  27th  it 
could  be  seen  from  a  distance.  Many  examinations  were  made  of  them  all 
during  the  season,  and  this  always  appeared  the  best.  A  few  days  before  it  was 
cut,  it  sliowed  the  largest  and  best  filled  ear.  There  was  a  piece  of  yellow-col- 
oured earth  at  the  bottom  of  the  fi(.'l;l,  showing  t!ie  presence  of  iron,  upon  which 
was  sown  potash  and  lime.  The  plant  was  yellow  and  sickly-looking,  but  im- 
mediately after  the  application  it  acquired  a  dark  green  colour,  and  became  vi- 
gorous, and  yielded  a  crop  at  least  equal  to  any  in  the  field.  There  were  some 
other  dressings  put  on  other  ridges  of  this  field,  but  it  was  dry  weather  directly 
after  they  were  sown,  and  the  crop  was  too  far  forward  before  they  began  to  take 
effect  to  say  any  thing  decided  about  them.  By  mistake  t'lere  were  two  varie- 
ties of  oats  sown  upon  the  fielJ,  which  prevented  the  experiments  being  so  de- 
cided, as  the  dressings  were  put  on  indiscriminately  upon  the  land  before  it  was 
known." 

Rrmauks. — The  only  remark  I  need  make  upon  these  experiments  is.  to  sug- 
gest to  my  readers  that,  by  repeating  the  above  trials  upon  oats  with  Mr.  Flem- 
ing's mixtures,  they  may  not  only  benefit  their  own  crops,  but  may  also  aid 
materially  in  the. advancement  of  practical  agricultural  knowledge. 

7. — On  the  effect  of  Sulphate  of  Soda  applied  as  a  top-dressing  to  Beans  and  Peas. 

"  The  first  dressing  was  applied  the  4th  of  May,  on  .-^o.me  beans  on  a  border 
in  the  garden ;  the  drills  that  were  dressed  quickly  took  the  lead  of  the  others. 
There  was  no  alteration  of  colour,  but  greater  strength,  and  it  tillered  v:onder- 
fullij.  There  were  five  or  six  stems  from  every  seed  sown,  and  the  pods  were 
larger  and  more  numerous,  and  the  beans  in  the  pods  a  great  deal  larger  than 
the  same  variety  undressed.  It  was  also  put  upon  some  of  the  ridges  of  the 
beans  in  the  field,  and  with  the  same  effect,  and  gave  a  very  large  crop  (not  yet 
thrashed.) 

"  Upon  peas  in  the  garden  it  appeared  to  add  little,  if  any  thing,  to  the  strength 
of  straw,  but  those  that  were  dressed  had  a  far  greater  number  of  pods,  and  those 
better  filled,  and  the  peas  of  a  better  flavour,  and  it  seems  a  valuable  dressing  for 
all  Icgunmious  crops.  When  sown  in  the  drills  along  with  the  peas,  it  nearly 
killed  every  on&  of  them,  while  the  same  quantity,  put  on  as  a  top-dressing  to 
some  drills  next  to  them  (where  the  peas  were  tv/o  inches  high,)  did  no  injuiy. 

REMARKS. — The  testimony  of  Mr.  Fleming  to  the  value  of  sulphate  of  soda 
as  a  dressing  for  leguminous  crops,  is  very  valuable  and  satisfactory.  We  may- 
hope  that  next  year  will  furnish  us  with  experiments,  all  the  results  of  which 
shall  have  been  so  carefully  ascertained,  as  to  enable  us  to  decide  upon  the  eco- 
nomical value  of  this  sulphate  as  a  manure,  by  a  comparison  of  the  amount  of 
increase  in  the  crop,  with  the  cost  of  the  application. 

8. — On,  Nitrate  of  Soda  as  a  top -dressing  to  Gooseherrtj  and  Currant  flushes. 

"  It  was  applied  April  14th,  at  about  the  rate  of  ^  cwt.  per  acre,  or  \  lb.  per 
bush.  It  had  the  effect,  in  the  course  of  a  week,  of  producing  on  the  bushes  a 
dark  green  colour  and  broader  leaves,  and  the  fruit  set  better  and  more  plentiful-; 
ly,  especially  on  some  red  currants  that  had  borne  little  for  two  years.  These 
set  their  fruit  well,  and  yielded  double  their  former  produce.  The  dressed  bushes 
kept  the  lead  in  strength  and  vigour  all  the  season,  and  now,  when  the  undressed 
bushes  have  lost  their  leaves,  the  others  are  quite  green." 

9. — "  Many  experiments  were  tried  in  the  garden  on  turnips,  by  top-dressing 
with  nitrate  of  soda,  but  with  no  perceptible  effect.     However,  the  Swedish,  and 


24  ON  EXPERIMENTS  WITH  GUANO.  [Appendix 

red-top  yellow,  in  a  field  of  rather  stiff  soil,  were  benefitted,  the  former  yielding 
i  more  produce  in  weight,  and  the  latter  |  more  weight.  Wm,  Fleming. 

''Barochcm,  26th  October,  1841." 

Note.— The  price.s  paid  by  Mr.  Fleming  were  as  follow :— Bone  dust  (fine)  Is.  9d.  per  bushel ; 
sulphate  of  ammonia  (in  crystals)  28s.  per  cwt.  ;  potash  (very  impure)  24s.  per  cwt.  ;  sulphate 
of  soda  (in  crystals)  6s.  per  cwt.  ;  nitrate  of  soda  22s. ;  and  sal-ammoniac  60s.  per  cwt. 


No.  IV. 

SUGGESTIONS    FOR    COMPAHATIVE    J^XPERIMEXTS    WITH    GUANO 
AND    OTHER    MANURES. 

Guano  is  the  name  given  in  South  America  to  thedvmg  of  the  sea  fowl  which 
hover  in  countless  flocks  along  the  shores  of  the  Pcicific,  and  which,  from  time 
immemorial,  have  deposited  their  droppings' on  the  rocks  and  the  islands  which 
arc  met  with  along  the  coast  o.  Peru. 

Besides  the  fresh  white  guano  wliich  is  deposited  year  by  year  in  these  locali- 
ties, there  exist,  in  some  spots,  large  accumuhuionsmore  or  less  buried  beneath 
a  covering  of  drifted  sand,  which  have  been  thus  buried  and  partially  preserved 
from  an  unknown  antiquity.  This  ancient  guano  is  of  a  brown  colour,  more  or 
less  dark,  and  forms  layers  or  heri[)s  of  limited  extent,  but  which  are  said  some- 
times to  exceed  even  (50  feet  in  thickness. 

In  the  :ime  of  the  Incas  this  substance  was  known  and  highly  valued  as  a  ma- 
nure,— the  country  along  the  coast  for  a  length  of  200  leagues  was  entirely  ma- 
nured by  it, — the  islands  on  whtcli  it  was  formed  were  carefully  watched  and 
preserved, — and  it  was  declared  to  be  a  capital  of!ence  tokill  any  of  the  sea  fowl 
by  which  it  was  deposited.  Ever  since  that  time  it  has  been  more  or  less  em- 
ployed for  the  same  purpose,  and  much  of  the  culture  now  practised  on  this 
thinly-peopled  coast  is  entirely  dependent  for  its  success,  if  not  for  its  existence, 
on  the  stores  of  manure  which  the  sea  fowl  thus  place  within  reach  of  those  parts 
of  the  country  which  are  susceptible  of  cultivation. 

In  modern  times,  hov»-ever,  the  access  of  foreign  shipping,  and  the  want  of 
careful  protection,  have  driven  away  many  of  the  sea  fowl,  and  lessened  to  a  very 
great  degree  the  production  of  the  recent  guano.  Thus  tlie  country  is  more  de- 
pendent than  in  former  times  on  the  more  ancient  deposits,  which  are  now  assi- 
duously sought  for,  and  when  discovered  beneath  the  sand,  are  carefully  exca- 
vated and  transported  to  the  sea-ports  for  sale. 

The  dung  of  birds  of  all  kind-'^,  when  exposed  to  the  air,  gradually  undergoes 
decomposition,  gives  off  ammonia,  and  acquires  a  brown  colour.  As  this  am- 
monia is  one  of  the  most  fertilizing  substances  it  contains,  it  will  be  readily  un- 
derstood that  the  old  brown  guano  is  much  less  valuable  as  a  manure  than  that 
•which  is  recent  and  white  ;  hence  the  care  of  the  ancient  Peruvians  in  collect- 
ing the  fresh,  and  their  comparative  neglect  of  the  ancient  guano. ' 

When  the  brown  guano  is  put  into  water,  a  large  quantity  of  it — sometimes 
70  per  cent,  of  the  wliole — is  dissolved.  Hence,  it  is,  because  the  climate  of 
Peru  is  so  dry  and  arid  that  in  the  plains  rain  scarcely  ever  falls,  that  the  guano 
can  accumulate  as  it  is  found  to  do.  North  and  soudi  of  this  line  of  coast, 
where  rains  are  less  unfrequent,  such  accumulations  are  not  met  with,  though 
the  birds  appear  equally  plentifvd,  and  it  may  be  safely  stated  that,  had  the  cli- 
mate of  Peru  been  like  that  of  England,  the  rains  would  have  washed  the  guano 
from  the  rocks  almost  as  rapidly  as  it  was  deposited. 

Of  the  brown  guano  several  cargoes  have  lately  been  brought  to  England  by 


No.  iV.]  ON    EXPERIMENTS   WITH    GUANO.  SS 

an  enterprising  merchant  in  Liverpool,  and  it  has  been  deservedly  recommend- 
ed to  the  attention  of  British  agriculturists.  It  has  already  been  tried  upon  va- 
rious crops,  both  of  lny  and  corn,  upon  turnips  also,  and  upon  hops,  and  there 
can  be  no  doubt  whatever  that  in  our  climate,  as  well  as  in  that  of  Peru,  it  is 
fitted  to  promote  vegetation  to  a  very  reaiarkable  degree. 

This  brown  guano  varies  much  in  quality,  accordmg  probably  to  the  degree 
of  exposure  to  the  air  to  which  it  has  been  subjected,  or  to  its  position  in  the  de- 
posit from  which  it  has  been  dug.      Two  different  portions,   taken  at  random 
from  the  same  box,  gave  me  the  following  very  different  results  : — 
1°. — Water,  salts  of  ammonia,  and  organic  matter,  expelled 

by  a  red  heat, 235 per  ct. 

Sulphate  of  soda, ;  1-8      " 

Common  salt,  with  a  little  phosphate  of  soda,  .         .         303      " 
Phosphate  of  lime,  with  a  little  phosphate  of  magnesia 

and  carbonate  of  lime, 44-4      " 

100* 

2°.— Ammonia =    70    ] 

Uric  acid, =08     1 59.3  . 

Water,  carbonic  and  oxalic  acids,  &.c.,  expelled  j  ^ 

by  a  red  heat, =51-5    j 

Common  salt,  with  a  little  sulphate  &  phosphate  of  soda,  11-4     " 
Phosphate  of  lime,  &c 293     " 

100 

According  to  M.  Winterfeldt,  this  brown  guano  is  sold  at  the  ports  near 
which  it  is  obtained  at  about  3s.  a  cwt.  It  might,  therefore,  if  this  be  correct, 
oe  importeci  into  the  country,  and  sold  at  less  than  lOs.  per  cwt.  The  price  at 
present  asked,  however,  is  25s.  per  cwt.,  a  cost  at  which  it  is  doubtful  if  the 
English  agriculturist  can  afford  to  use  it. 

In  any  case  it  seems  improbable  that  the  guano  can  continue  to  be  imported 
into  this  country  for  any  length  of  time.  It  is  absolutely  necessary  to  the  cul- 
tivation of  the  land  in  Peru,— and  it  is  also  diminishing  in  quantity, — the  first 
settled  government,  therefore,  which  is  formed  in  that  country,  must  prohibit 
the  further  exportation  of  a  substance  so  important  to  the  national  interests.  It 
is  a  matter  not  unworthy  of  the  attention  of  chemists,  therefore,  to  consider 
whether  a  mixture  similar  to  the  guano,  and  of  equal  efficacy,  cannot  be  form- 
ed by  art — not  only  at  a  cost  so  reasonable  as  at  once  to  make  the  British 
farmer  independent  of  the  importer, — hut  also  in  such  abundance  as  at  the  same 
time  to  place  so  valuable  a  manure  within  the  reach  of  all. 

The  following  mixture  contains  the  several  ingredients  found  in  guano  in 
nearly  the  average  proportions  ;  and  I  believe  it  is  likely  to  be  at  least  as  effica- 
cious as  the  natural  guano,  for  all  the  crops  to  which  the  latter  has  hitherto  been 
applied  in  this  country: — 

315  lbs,  [7  bushels]  of  bone  dust  at  2s.  9d.  per  bushel 
100  lbs.  of  sulphate  of  ammonia,t  containing  35  lbs.  of  ammo- 
nia at  20s.  a  cwt 

5  lbs.  of  pearl-ash       .         .  .... 

100  lbs.  of  common  salt         .  

1 1  lbs.  of  dry  sulphate  of  soda  .... 

531  lbs.  of  artificial  guano  cost      .  .... 

*  The  first  contained  also  8  per  cent,  and  the  second  IJ  per  cent,  of  sand,  which  has  been 
left  out  of  the  true  composition  of  the  guano  considered  as  free  from  sand. 

t  Sulphate  of  ammonia  is  now  manufactured  largely  at  Glasgow,  and  may  be  had  for  less 
than  208.  a  cwt. 


26 


ON    EXPERIMENTS   WITH    GL'ANO, 


[Appendix, 


The  quantity  here  indicated  may  be  intimately  mixed  with  100  lbs.  of  chalk, 
and  will  be  fully  equal  in  efficacy,  I  believe,  to  4  cwt.  of  guano,  now  selling 
at  £5. 

At  the  same  time  it  is  desirable  that  the  i-elative  efficacy  both  of  this  mixture 
(artificial  guano),  and  of  the  American  guano,  should  be  tried  by  actual  experi- 
ment in  comparison  with  other  substances  of  known  value,  and  which  are 
supposed  to  act  in  a  way  somewhat  similar.  'I'hs  substances  with  which  I 
would  suggest  that  such  comparative  experiments  should,  in  the  first  place,  be 
made,  are  farm-yard  manure,  bone  dust,  and  rape  dust,  and  the  following 
scheme  exhibits  the  proportions  in  which  they  may  be  added  to  the  different 
plots  of  land  on  which  the  experiments  are  intended  to  be  made  : — 


20  tons  of 
farm-yard  manure. 

20buslielsof 

bones 
with  ashes. 

6  cwt.  of  guano, 

mixed  with 
clialk  or  gypsum. 

6  cwt.  of 
artificial  guano. 

10  fons  do. 

with  10  bushels  of 

bone  dust. 

20  cwt.  of 
rape  with  ashes. 

•  U)  Ions  of  farm- 
yard manure  with 
3  cwt.  of  guano. 

10  tons  of  farm-yard 
manure  with  3  cwt. 
of  artificial  guano. 

10  fons  do. 

with  10  cwt.  of 

rape  dust. 

10  cwt.  of 

rape  witii  3  cwt. 

of guano. 

10  tons  do.  with 
2  cwt.  of  guano. 

10  tons  do.  with  2 

cwt.  of  artificial 

guano. 

The  practical  farmer  need  not  be  deterred  by  the  formidable  array  of  experi- 
ments above  suggested.  He  may  try  any  two  or  three  of  them,  and  his  results 
will  be  valuable  in  proportion  to  the  accuracy  with  which  his  land  is  measured 
and  his  manures  and  crops  weighed.  I  have  taken  20  tons  of  farm-yard  manure 
as  a  standard,  though  in  many  highly  farmed  parts  of  the  country  lio  more  than 
15  tons  are  usually  applied.  Twenty  bushels  of  bones  are  recommended  by  the 
Doncaster  report,  and  I  have  lately  found  that  in  the  Lothians  1  cwt.  of  rape 
dust  is  considered  to  replace  1  ton  of  farm-yard  manure.  This  proportion  of 
course  will  vary  with  the  c[uality  of  the  latter  manure ;  but  whatever  quantity 
of  this  latter  we  take  as  the  standard  of  comparison,  it  is  easy  to  adjust  the 
proportions  of  the  other  substances  accordingly.  I  have  not  recommended  any 
trial -to  be  made  with  more  than  G  cwt.  of  guano,  because,  where  farm-yard 
manure  is  valued  only  at  6s.  or  7s.  per  ton,  5  cwt.  of  the  former  would  cost  as 
much  as  20  tons  of  the  latter. '^ 

The  above  experiments  are  intended  to  be  made  with  the  green  crop,  and  to 
be  continued  during  an  entire  rotation  :t  any  pair  of  them,  however,  may  be 
tried  on  single  crops,  whether  of  corn  or  of  turnips  and  potatoes.  In  this  way 
guano  ought  also  to  be  tried  against  nitrate  of  soda  and  against  bones,  upon 
seeds  and  upon  old  grass-lands.  The  mode  in  which  such  experiments  may 
be  made  will  speedily  suggest  themselves  to  the  intelligent  farmer.  J71  all 
cases  the  results  should  be  accurately  recorded,  and,  if  possible,  published. 

'  When  this  paragraph  was  written,  the  price  of  guano  was  25s.  a  cwt.  :  it  is  now  (May, 
1842>  reduced  to  15s.  )  .  &  ,  v      7, 

t  By  this  I  mean  that  the  effect  of  these  several  manures,  applied  once  for  all  to  the  green 
op  at  the  commencement  of  the  rotation,  should  be  traced  on  each  successive  cron  throuffh 


crop 

the  entire  course  of  cropping. 


the  rotation,  should  be  traced  on  each  successive  crop  through 


No,  V.\  OF   THK    PHYSICAL.   PRCr£RTIES   OP  THE   SOIL,  ^ 

No.   V. 

OF  THE   EXAMINATION  AND  ANALYSIS  OP  SOILS. 

l'^.  Silection  of  spe-Anieiis  of  soils. — In  the  same  field  different  varieties  of  soil 
often  occur,  and  some  r3commend  that  in  collecting  a  specimen  for  analysis, 
portions  should  be  taken  from  diiferent  parts  of  the  field  and  mixed  together, 
by  which  an  av3ragj3  quality  of  soil  would  be  obtained.  But  this  is  bad  advice, 
when  the  soils  in  difl'erent  parts  of  the  fieli  are  really  unlike.  Suppose  one 
part  of  a  field  to  be  clay,  and  another  sandy,  as  is  often  the  case  in  this  county, 
and  that  an  averao;e  mixture  of  then  is  subnitted  to  analysis,  the  result  you 
get  will  apply  neither  to  the  one  part  of  the  field  nor  to  the  other — that  is,  it 
will  be  of  little  or  no  value.  In  selecting  a  specimen  of  soil,  therefore,  one  or 
two  pounds  should  be  takm  from  each  of  four  or  five  parts  of  the  field  where 
the  soil  appears  nearly  alike,  those  should  be  well-mixed  together  and  dried  in 
the  open  air  or  before  the  fire.  Two  separate  pounds  should  then  be  taken 
from  the  whole  for  the  purpose  of  analysis,  or  if  it  is  to  be  sent  to  a  distance 
should  be  tied  up  in  clean  strong  paper,  or  what  is  much  better,  should  be  en- 
closed in  clean  well-corked  bottles. 

I. — OF    THE    PHYSICAL    PROPERTIES    OF    THE    SOIL. 

2\  Determination  of  th-;  densily  of  the  soil. — In  order  to  determine  the  den- 
sity of  the  soil,  a  portion  of  it  must  be  dried  at  the  temperature  of  boiling 
water  (212=),  till  it  ceases  to  lose  weight,  or  upon  a  piece  of  white  paper  in  an 
oven  at  a  heat  not  great  enough  to  render  the  paper  brown.  A  common  phial 
or  other  small  bottle  perfectly  clean  and  dry  may  then  be  taken  and  filled  up 
to  a  mark  made  with  a  file  on  the  neck,  with  distilled  or  pure  rain  water,  and 
then  carefully  weighed.  Part  of  the  water  may  then  be  poured  out  of  the 
bottle,  and  1000  grains  of  the  dry  soil  introduced  in  its  stead,  the  bottle  must 
then  b3  well  shaken  to  allow  the  air  to  escape  from  the  pores  of  the  soil,  filled 
up  again  with  water  to  the  mark  on  the  neck,  and  again  weighed.  The  weight 
of  the  soil,  divided  by  the  difference  between  the  weight  of  the  bottle  with  soil 
ani  water  ani  th3  sum  of  the  weights  of  the  soil  and  the  bottle  of  water  to- 
gether, gives  the  specific  gravity. 

Thus,  let  the  botde  with  water  weigh  2000  grains,  and  with  water  and  soil 
2000,  then- 
Grains. 

The  weight  of  the  bottle  with  water  alone  = 2000 

The  weight  of  the  dry  soil 1000 

Sum,  being  the  weight  which  the  bottle  with  the  soil  and  water  2 

wmili,  kave  had  co\\\(\.  \.\\G  scil  have  been  introduced  without  >     3000 
displacing  any  of  the  water } 

But  the  weight  of  the  bottle  with  soil  and  water  was      ....        2600 

Difference,  being  the  weight  of  water  taken  out  to  admit  1000  \        .r^r. 
grains  of  dry  soil \ 

Therefore^  1000  grains  of  soil  have  the  same  bulk  as  400  grains  of  water,  or 
the  soil  is  2 J  times  heavier  than  water,  since  1000 -r  100  =  2-5  its  specific 
gravity. 

3^.  Delerminalion  of  the  absolute  weight. — The  absolute  weight  of  a  cubic 
foot  of  solid  rock  is  obtained  in  pounds  by  multiplying  its  specific  gravity  by 
G3^— the  weight  in  pounds  of  a  cubic  foot  of  water.  But  soils  are  porous,  and 
contain  more  or  less  air  in  their  interstices  according  as  their  particles  are  more 
or  less  fine,  or  as  they  contain  more  or  less  sand  or  vegetable  matter.  Fine 
sands  are  heaviest,  clays  next  in  order,  and  peaty  soils  the  lightest.  The 
simplest  mode  of  determining  their  absolute  weight,  therefore,  is  to  weigh  an 
exact  imperial  half  pint  of  the  soil  in  any  state  of  dryness,  when  tliis  weight 


28  OP   THE    PHTS>'AL    PROPERTIES    OF   THE    SOIL.  [AppeudlV, 

multiplied  by  150,  will  give  very  r>early  the  weight  of  a  cubic  foot  of  the  soil  in 
that  state. 

4"^.  Dstcrminatian  of  the  relative  proportions  of  gravel,  sand,  and  day. — Five 
hundred  grains  of  the  dry  soil  may  be  boiled  in  a  flask  half  full  of  water  till  the 
particles  are  thoroughly  separated  from  each  other.  Being  allowed  to  stand 
for  a  couple  of  minutes,  the  water  with  the  fine  matter  floatinj^  in  it  may  be 
poured  off  into  another  vessel.  This  may  be  repeated  several  times  till  it  ap- 
pears that  nothing  but  sand  or  gravel  remains.  This  sand  and  gravel  is  then 
to  be  washed  completely  out  of  the  flask,  dried,  and  weighed.  Suppose  the 
weight  to  be  300  grains,  then  GO  per  cent.*  of  the  soil  is  sand  and  gravel.  The 
sand  and  gravel  are  now  to  be  sifted  through  a  gauze  sieve  more  or  less  fine, 
when  the  gravel  and  coarse  sand  are  separated,  and  may  be  weighed  and  their 
proportions  estimated. 

These  separate  portions  of  gravel  and  sand  should  now  be  moistened  with 
water  and  examined  carefully  with  the  aid  of  a  microscope,  with  the  view  of 
ascertaining  if  they  are  wholly  silicious,  or  if  they  contain  also  fragments  of 
different  kinds  of  rock — sand-stones,  slates,  granites,  traps,  lime-stones,  or  iron- 
stones. A  few  drops  of  strong  muriatic  acid  (spirit  of  salt)  should  also  be 
added — when  the  presence  of  lime-stone  is  shown  more  distinctly  by  an  effer- 
vescence, which  can  be  readily  perceived  by  the  aid  of  the  glass, — of  per-oxide 
of  iron  by  the  brown  colour  which  the  acid  speedily  assumes, — and  of  black 
oxide  of  manganese  by  a  distinct  smell  of  chlorine  which  is  easily  recognised. 
In  the  subsequent  description  of  the  soil,  these  points  should  be  carefully  noted. 

Suppose  the  sand  and  gravel  to  contain  half  its  weight  of  fine  sand,  then 
our  soil  would  consist  of  coarse  sand  and  small  stones  30  per  cent.,  fine  sand 
30  per  cmt.,  clay  and  other  lighter  matters  40  per  cent. 

5^.  Absorbing  power  of  the  soil. — A  thousand  grains  of  the  perfectly,  (^r?/  soil, 
crushed  to  powder,  should  be  spread  over  a  sheet  of  paper  and  exposed  to  the 
air  for  twelve  or  twenty-four  hours,  and  then  weighed.  The  increase  of  weight 
shows  its  power  of  absorbing  moisture  from  the  air.  If  it  amount  to  15  or  20 
grains,  it  is  so  far  an  indication  of  great  agricultural  capabilities. 

6^.  Its  power  of  hot  ling  writrr. — This  same  portion  of  soil  may  now  be  put 
into  a  funnel  upon  a  doubled  filter  and  cold  water  pourod  upon  it,  drop  by  drop, 
till  the  whole  is  wet  and  the  water  begins  to  trickle  down  the  neck  of  the  filter. 
It  may  now  be  covered  with  a  piece  of  glass  and  allowed  to  stand  for  a  few 
hours,  occasionally  adding  a  few  drops  of  water,  until  there  remains  no  doubt 
of  the  whole  soil  being  perfectly  soaked.  The  two  filters  and  the  soil  are  then 
to  be  removed  from  the  funnel,  the  filters  opened  and  spread  for  a  few  minutes 
upon  a  linen  cloth  to  remove  the  drops  of  water  which  adhere  to  the  paper. 
The  wet  soil  and  inner  filter  being  now  put  into  one  scale,  and  the  outer  filter 
in  the  other,  and  the  whole  carefully  balanced,  the  true  weight  of  the  wet  soil 
is  obtained.  Suppose  the  original  thousand  grains  now  to  weigh  1400,  then 
the  soil  is  capable  of  holding  40  per  cent,  of  water. J 

7°.  Rnpidiiy  with  which  the  soil  dries. — The  wet  soil  with  its  filter  may  now 
be  spread  out  upon  a  plate  and  exposed  to  the  air,  in  what  may  be  considered 
ordinary  circumstances  of  temperature  and  moisture,  for  4,  12,  or  24  hours,  and 
the  loss  of  weight  then  ascertained.  This  will  indicate  the  comparative  ra- 
]iidity  with  which  such  a  soil  would  dry,  and  the  consequent  urgent  demand 
for  draining,  or  the  contrary.  As  great  a  proportion  of  the  water  is  said  to 
evaporate  from  a  given  weight  of  sand  saturated  with  Avater,  in  4  hours,  as 
from  an  equal  weight  of  pure  clay  in  11,  and  of  peat  in  17  hours — when  placed 
in  the  same  circumstances. 

8°.  Power  of  absorbing  h.cat  from  the  sun. — In  the  '/receding  experiment  a  por- 
tion of  pure  quartz  sand  or  of  pipe  clay  may  be  employed  for  the  purpose  of 

•  As  500  :  300  ::  100  to  60  per  cent. 
t  That  is,  one  filter  within  another. 
X  1000  :  400,  the  increase  of  weight  as  100  :  40*  ■ 


No.    K]  OF   THE    PHYSICAL    rROPERTIES    01'   THE    SOIL.  29 

obtaining  a  comparative  result  as  to  the  rapidity  of  drying.  The  same  method 
may  be  adopted  in  regard  to  the  power  of  the  soil  to  become  warm  under  the 
influence  of  the  sun's  rays.  'I'wo  small  wooden  boxes,  containing  each  a 
layer  of  one  of  the  kinds  of  soil,  two  inches  in  depth,  may  be  exposed  to  the 
same  sunshine  for  the  same  length  of  time,  and  the  heat  they  severally  acquire 
determined  by  a  thermometer,  buried  about  a  (quarter  of  an  inch  beneath  the 
surface.  Soils  are  not  found  to  differ  so  much  m  the  actual  temperature  they 
are  capable  of  attaining  under  such  circumstances — most  soils  becoming  20° 
or  30°  warmer  than  the  surrounding  air  in  the  time  of  summer — as  in  the  re- 
lative iksree  of  rapidity  with  which  they  acquire  this  maximum  temperature — 
and  this,  as  stated  in  the  text,  appears  to  depend  cliieily  upon  the  darkness  of 
their  colour.  The  detennination  of  this  quality,  therefore,  except  as  a  matter 
of  curiosity,  may,. at  the  option  of  the  experimenter,  be  dispensed  with. 

n. OF    TIIK    ORGANIC    MATTER    PRESENT    IN    THE    SOIL. 

9^.  Deter ndnaiion  of  the  pcr-cevtoge  of  organic  viattcr. — The  soil  must  be 
thoroughly  dried  in  an  oven  or  otherwise,  at  a  temperature  not  higher  than  be- 
tween 250°  to  300°  F.  FTumic  and  ulmic  acids  will  bear  this  latter  tempera- 
ture without  change.  An  accurately  weighed  portion  (100  to  200  grains)  must 
then  be  burned  in  the  open  air,  till  all  the  blackness  disappears.  This  is  best 
done  in  a  small  platinvmi  capsule  over  an  argand  spirit  or  gas  lamp.  The  loss 
indicates  the  total  weight  of  organic  matter  present.  It  is  scarcely  ever  pos- 
sible, however,  to  render  soils  absolutely  dry  without  raising  them  to  a  tem- 
perature so  high  as  to  char  the  organic  matter  present,  and  hence  its  weight,  as 
above  determined,  will  always  somewhat  exceed  the  truth,  the  remaining  water 
being  driven  off  along  with  the  organic  matter  when  the  soil  is  heated  to  red- 
ness. This  excess,  also,  will  in  general  be  greater  in  proportion  to  the  quantity 
of  clay  in  the  soil,  since  this  is  the  ingredient  of  most  soils  from  which  the 
water  is  expelled  with  the  greatest  difficulty. 

10".  Deterndnatinn  of  tke  kuvdc  aid. — I'his  acid,  whether  merely  mixed  with 
the  soil,  or  combined  with  some  of  the  lime  and  alumina  it  contains,  is  extracted  by 
boiling  with  a  solution  of  the  common  soda  of  the  shops.  Into  about  two  ounces 
by  measure  of  a  saturated  solution  of  this  salt,  contained  in  a  flask,  200  or  300 
grains  of  soil,  previously  reduced  to  coarse  powder,  are  introduced,  an  equal 
bulk  of  water  added,  and  the  whole  boiled  or  digested  on  the  sand  bath  with 
occasional  shaking  for  an  hour.  The  flask  is  then  removed  from  the  fire,  filled  up 
with  water,  well  shaken,  and  the  particles  of  soil  afterwards  allowed  to  subside. 
The  clear  liquid  is  then  poured  off.  If  it  has  a  brown  colour  it  has  taken  up 
some  humic  acid.  ]n  this  case,  the  process  must  be  repeated  once  or  twice 
with  fresh  portions  of  the  soda  solution,  till  the  whole  of  the  soluble  organic 
matter  appears  by  the  pale  colour  of  the  solution  to  be  taken  up.  These  coloured 
solutions  are  then  to  be  mixed  and  filtered,  'i  he  filtering  generally  occupies 
considerable  time,  the  humic  and  ulmic  acids  clogging  up  the  pores  of  the  filter 
in  a  remarkable  manner,  and  permitting  the  liquid  to  pass  through  sometimes 
with  extreme  slowness. 

When  filtered,  muriatic  acid  is  to  be  slowly  added  to  the  coloured  liquid — 
which  should  be  kept  in  motion  by  a  glass  rod — till  effervescence  ceases,  and 
the  whole  has  become  dictinctly  sour.  On  being  set  aside  the  humic  acid  falls 
in  brown  flocks.  A  filter  is  now  to  be  dried  and  carefully  weighed,*  the  liquid 
filtered  through  it,  and  the  humic  acid  thus  collected.  It  must  be  washed  in  the 
filter  with  pure  water — rendered  slightly  sour  by  muriatic  acidt — till  all  the  soda  is 

*  This  is  best  effected  by  piitting  the  filter  into  a  covered  porcelain  crucible  of  knowa 
wei«ht,  and  heatinj;  it  for  ten  minuies  over  a  lamp  or  otherwise,  at  a  temperature  which 
just  does  not  discolour  the  paper,  allowing  then  the  crucible  to  cool  under  cover,  and  whien 
cold  weighing  it.  The  increase  above  the  known  weight  of  the  crucible  is  that  of  the  filter 
which,  besides  being  recorded  in  the  experiment  book,  should  also  be  marked  in  sevenu 
places  on  the  edge  of  the  filter  with  a  black  lead  pencil. 

t  This  is  to  prevent  in  some  measure  the  humic  acid  from  passing  through  the  filter, 
which  it  is  very  apt  to  do,  when  the  saline  matter  is  nearly  washed  out  of  it. 


30  OP   THK    ORGANIC    MATTER    PRESENT   IN   THE    SOIL.         [AppCTldlXf 

separated  from  it,*  when  it  is  to  be  dried  at  250°  F.,  till  it  ceases  to  lose  weight 
Tlie  final  weight,  minus  that  of  the  filter,  gives  the  quantity  of  humic  acid  con- 
tained in  the  portion  of  soil  submitted  to  examination.  As  it  is  rarely  possible  to 
wash  the  humic  acid  perfectly  upon  the  filter,  rigorous  accuracy  requires  that  the 
filter  and  acid  should  be  burned  after  being  weighe;!,  and  the  weight  of  ash  left, 
minus  the  known  weight  of  ash  left  by  the  filter,t  deducted  from  that  of  tlie 
acid  as  previously  determined.  It  is  to  be  observed  here  that  by  this,  which 
is  I'eally  the  only  available  method  we  possess  of  estimating;  the  humic  acid,  a 
certain  amount  of  loss  arises  from  its  no«.  being  wholly  insoluble,  the  acid 
liquid  which  passes  through  the  filter  being  always  more  or  less  of  a  brown 
colour.: 

11°.  Determination  of  the  insoluble  hunniis. — Many  soils  after  this  treatment 
with  carbonate  of  soda  ai-e  still  more  or  less  of  a  brown  colour,  evidently  due 
to  the  presence  of  other  organic  matter.  To  separate  this,  Sprengel  recom- 
mends to  boil  the  soil,  which  has  been  treated  with  carbonate  of  soda,  and 
which  we  suppose  still  to  remain  in  the  flask,  with  a  solution  of  caustic  potash, 
repeated,  if  necessary,  as  in  the  case  of  the  soda  solution.  By  this  boiling, 
the  vegetable  matter,  which  was  insoluble  in  the  carbonate  of  soda,  is  changed 
in  constitution  and  dissolves  in  the  caustic  potash,  giving  a  brown  solution, 
from  which  it  may  be  separated  in  brown  flocks  by  the  addition  of  muriatic 
acid,  and  then  collected  and  weighed  as  above  described. 

In  some  soils,  also,  distinct  portions  of  vegetable  fibre,  sucfi  as  portions  of 
roots,  &c.,  are  present,  and  may  be  separated,  mechanically  dried,  and  weighed. 

12'^.  Of  other  organk  sidstatices  present  in  the  soil. — The  sum  of  the  weights 
of  the  above  substances  deducted  from  the  whole  weight  of  organic  matter,  as 
determined  by  burning,  gives  that  of  othr.r  organic  substances  present  in  the 
soil.  The  quantity  of  these  is  in  general  comparatively  small,  and,  unless  they 
are  soluble  in  water,  there  is  no  easy  method  of  separating  them,  and  determin- 
ing their  weight.  The  following  two  methods,  however,  may  be  resorted  to: — 

1*^.  Half  a  pound  or  more  of  the  moist  soil  may  be  boiled  with  two  separate 
pints  of  distilled  water,  the  liquid  filtered  and  evaporated  to  a  small  bulk.  From 
clay  soils,  when  thus  boiled  with  water,  the  fine  particles  do  not  readily  subside. 
Sometimes,  after  standing  for  several  days,  the  water  is  still  muddy,  and  passes 
muddy  through  the  filter,  but,  after  being  evaporated,  as  above  recommended,  to 
a  small  bulk,  most  of  the  fine  clayey  matter  remains  on  the  paper  when  it  is 
again  filtered.  As  soon  as  it  has  thus  passed  through  clear,  the  liquid  may  be 
evaporated  to  perfect  dryness  at  2,50"  F.,  and  weighed.  Being  now  treated 
v.nth  water — a  portion  will  be  dissolved — this  must  be  poured  off,  and  the  inso- 
luble remainder  again  perfectly  dried  and  weighed.  If  this  remainder  be  now 
heated  to  redness  in  the  air,  any  organic  matter  it  contains  will  be  burned  off, 
and  its  weight  ascertained  by  the  loss  on  again  weighing.  I'his  loss  may  be 
considered  as  humic  acid  rendered  insoluble  by  drying.§  It  does  not  require  to 
be  added  to  the  weight  of  humic  acid  already  determined  (lO'^),  because  in 
that  experiment  a  portion  of  soil  was  employed  which  had  not  been  boded  in 
water.,  and  from  which  therefore  the  carbonate  of  soda  would  at  once  extract 
all  the  humic  acid.     The  present  experiment  need  only  be  made  when  it  is  de- 

*  This  is  ascertained  by  collecting  a  few  drops  of  what  is  passing  through  upon  a  piece  of 
clean  glass  or  platinum,  and  drying  them  over  the  lamp,  when,  if  a  perceptible  stain  or  spot  is 
left,  the  substance  is  not  sufficiently  washed. 

t  The  ash  left  by  the  paper  employed  for  filters  should  always  be  known.  This  is  ascer- 
tained, once  for  all,  by  drying  a  quantity  of  it  in  the  way  described  in  the  previous  note, 
weighing  it  in  this  dry  state,  burning  it,  and  again  weighing  the  ash  that  is  left.  In  good 
filtering  paper,  the  ash  ought  not  to  exceed  one  per  cent. 

X  The  portion  which  thus  remains  in  the  solution  may  be  precipitated  by  adding  a  small 
quantity  of  a  solution  of  alum,  and  afterwards  pouring  in  ammonia  in  excess.  The  alumina 
falls  coloured  by  the  organic  matter,  and  after  being  colleiited  on  a  filter,  washed,  and  dried, 
the  weight  of  organic  matter  in  the  precipitate  may  be  determined  approximately  as  des- 
cribed under  12°  (2°). 

§  See  Lecture  xiii.,  §  I. 


No.   v.]  OP  THE  ORGANIC  MATTKR  PRESENT  IN  THE  SOIL.  31 

s'rable  to  ascertain  how  much  humic  acid  a  soil  contains  in  a  state  in  which  it 
is  soluble  in  water.  Where  ammonia,  potash,  or  soda  is  present  in  the  soil, 
some  chemists  consider  this  quantity  to  be  very  considerable,  and  to  exercise 
an  important  influence  upon  vegetation. 

That  which  was  taken  up  by  water  from  the  dried  residuum  is  again  to  be 
evaporated  to  dryness,  dried  at  150°,  weighed,  and  burned  at  a  low  red  heat. 
The  loss  is  organic  matter,  and  may  have  been  crenic  or  apocrenic,  or  some 
other  of  the  organic  acids  formed  in  soils,  the  compounds  of  which,  with  lime, 
alumina,  and  prot-oxide  of  iron,  are  soluble  in  water.  If  any  little  sparkling  or 
burning  like  match-paper  be  observed  during  this  heating  to  redness,  it  maybe 
considered  as  an  indication  of  the  presence  of  nitric  acid — in  the  form  of  ni- 
trate of  potash,  soda,  or  lime.  In  this  case  the  loss  by  burning  will  slightly  ex- 
ceed the  true  amount  of  organic  matter  present,  owing  to  the  decomposition  and 
escape  of  the  nitric  acid  also.  The  mode  of  estimating  the  quantity  of  this  acid, 
when  it  is  present  in  any  sensible  proportion,  will  be  hereafter  described. 

2'^.  The  caustic  potash  employed  to  dissolve  the  insoluble  humus  (11")  takes 
up  also  any  alumma  which  may  have  been  in  combination  with  the  humic 
acid  or  may  still  remain  united  to  the  mudesous*  or  other  organic  acids.  When 
the  solution  is  filtered  and  the  humic  acid  separated  by  the  addition  of  muriatic 
acid  till  the  liquid  has  a  distinctly  sour  taste,  this  alumina,  and  the  acids  with 
which  it  is  in  combination,  still  remain  in  solution.  After  the  brown  flocks  of 
humic  acid,  however,  are  collected  on  the  filter,  the  alumina  may  be  thrown  down 
from  the  filtered  solution  by  adding  caustic  ammonia  to  the  sour  liquid,  until 
it  has  a  distinctly  ammoniacal  smell.  The  light  precipitate  which  falls  must 
be  collected  on  a  filter  and  washed  with  hot  water  till  the  potash  is  as  completely 
separated  as  possible.  It  is  then  to  be  dried  at  300'^  F.,  weighed  and  heated 
for  some  time  in  a  close  crucible  over  the  lamp,  at  a  temperature  which  begins 
to  discolour  it,  and  again  weighed.  Being  now  burned  in  the  air  till  it  is  quite 
white,  and  weighed,  the  last  loss  may  be  considered  as  mudesous  or  some  simi- 
lar acid. 

The  reason  why  this  second  method  of  drying  over  the  lamp  is  here  re- 
commended, is,  that  alumina  and  nearly  all  its  compounds  part  with  their 
water  with  great  difficulty,  and  even  with  the  precautions  above  indicated,  it  is 
not  unlikely  that  a  larger  per-centage  of  organic  matter  may  thus  be  indicated, 
than  in  reality  exists  in  the  soil.  The  check  which  the  accurate  experimenter  has 
upon  all  these  determinations  is  this,  that  the  sum  of  the  several  weights  of  the 
humic  acid,  the  insoluble  humus,  the  vegetable  fibre,  and  of  the  crenic  and  mu- 
desous acids,  if  present,  should  be  somewhat  less  than  tliat  of  the  whole  com- 
bustible organic  matter,  as  determined  by  burning  the  dry  soil  in  the  open  air 
(9").  This  quantity  we  have  seen  to  be  in  most  cases  greater  than  the  truth, 
b'^cause  any  remainmg  water  or  any  nitric  acid  the  soil  may  contain,  are  at  the 
same  time  driven  off*. 

I  may  further  remark  upon  this  subject  that  the  quantity  of  alumina  thus 
dissolved  by  the  caustic  potash  is  in  most  soils  very  small,  and  the  quantity  of 
organic  matter  by  which  it  is  accompanied  in  many  cases  so  minute,  that  the 
determination  of  it  may  be  considered  as  a  matter  of  curiosity,  rather  than  one 
of  practical  importance, 

HI. — OF    THE    SOLUBLE    SALINE    MATTER    IN   THE    SOIL. 

13*^.  With  a  view  to  determine  the  nakire  of  the  soluble  saline  matter  in  the 
soil,  a  preliminary  experiment  must  be  made.  An  unweighed  portion  must  be 
introduced  into  five  or  six  ounces  of  boiling  distilled  water  in  a  flask,  and  kept 
at  a  boiling  temperature,  with  occasional  shaking  for  a  quarter  of  an  hour.  It 
may  then  be  allowed  to  subside,  after  which  the  liquid  is  to  be  filtered  till  it 
passes  through  clear.     It  is  then  to  be  tested  in  the  following  manner.     Small 

■  Except  where  gyp.sum  is  present  in  the  insoluble  portion,  which  is  n^jnfrequently  the 
case,  when  the  loss  will  be  partly  water — since  gypsum,  after  being  driest  250°,  loses  still 
about  20  8  per  cent,  of  water  when  heated  to  redness. 

28 


32  OF    THE    SOLUBLE    SALINE    MATTER    IN    THE    SOIL.  [AppCndtX, 

separate  portions  are  to  be  put  into  so  many  clean  wine  glasses,  and  the  effect 
produced  upon  these  by  different  chemical  substances  carefully  noted. 
If  with  a  few  drops  of— 

a.  Nilrate  of  Baryta^  it  gives  a  white  powdery  precipitate,  which  does  not 
disappear  on  the  addition  of  nitric  or  muriatic  acid,  the  solution  contains  sulphu- 
ric acid.  If  the  precipitate  does  appear,  it  contains  carbonic  acid.  In  this  lat- 
ter case,  the  liquid  will  also  effervesce  on  the  addition  of  either  of  the  acids 
above  mentioned. 

b.  If  with  oxalate  of  ammonia,  it  gives,  either  immediately  or  after  a  time,  a 
white  cloud,  it  contains  lime,*  and  the  greater  the  milkiness,  the  larger  the 
quantity  of  lime  may  be  presumed  to  be. 

c.  If  with  nitrate  of  silver,  it  gives  a  white  curdy  precipitate,  insoluble  in  pure 
nitric  acid,  and  speedily  becoming  purple  in  tlie  sun,  it  may  be  presumed  to 
contain  chlorine. 

(l.  If  with  caustic  ammonia,  it  gives  a  pure  white  gelatinous  precipitate,  it 
contains  either  alumina,  or  magnesia,  or  both.  In  this  case,  muriatic  acid  must 
be  added  till  the  precipitate  disappears,  and  the  solution  is  distinctly  acid.  If 
on  the  addition  of  ammonia  in  excess,  the  precipitate  reappears  undiminished 
in  quantity,  it  contains  alumina  only.  If  it  be  distinctly  kss  in  quantity,  we 
may  infer  the  presence  of  both  magnesia  and  alumina ;  and  if  no  precipitate  now 
appears,  that  it  contains  magnesia  only.  If  a  large  quantity  of  magnesia  be  present, 
it  may  be  necessary  to  re-dissolve  and  acidify  the  solution  a  second  time  be- 
%re,  on  the  7-^-addition  of  ammonia,  the  precipitate  would  entirely  disappear. 

If  the  precipitate,  by  ammonia,  have  more  cr  less  of  a  brown  colour,  the  pre- 
sence of  iron,  and  perhaps  manganes?,  may  be  inferred.  If,  on  the  second 
addition  of  ammonia,  the  colour  of  the  precipitate  has  disappeared,  it  has  been 
due  to  the  manganese  only— if  it  still  continue  brown,  it  is  owing  chiefly  or 
altogether  to  the  presence  of  oxide  of  iron.  If  the  colour  of  the  precipitate,  by 
ammdnia,  be  very  dark,  it  consists  almost  entirely  of  oxide  of  iron,  and  may 
contain  little  or  no  alumina, — when  it  is  only  more  or  less  brown,  the  presence 
of  both  alumina  and  oxide  of  iron  may  with  certainty  be  infeired. 

e.  If,  after  the  first  addition  of  ammonia,  the  solution  be  filtered  to  separate 
the  alumina,  the  oxides  of  iron  and  manganess,  and  the  magnesia  that  may  be 
thrown  down — if  oxalate  of  ammonia  be  then  added  till  all  the  lime  falls,  and 
the  liquid  be  again  filtered,  evaporated  to  dryness,  and  then  heated  to  incipient 
redjiess  in  the  air,  till  the  excess  of  oxalate  of  ammonia  is  destroyed  and  driven 
off — and  if  a  soluble  residue  then  remain, t  it  is  probable  that  potash  or  soo'a,  or 
both,  are  present.  If,  on  dissolving  tliis  residue  in  a  little  water,  the  addition  of 
a  few  drops  of  a  solution  of  tartaric  acid  to  it  produce  a  deposite  of  small 
colourless  crystals  (of  cream  of  tartar),  or  if  a  drop  of  a  solution  of  bi-chlo- 
ride  of  platinum  produce  in  a  short  time  a  yellow  powdery  precipitate,  it  con- 
tains potash.  If  no  precipitate  is  produced  by  either  of  tliese — re-agents  as  they 
are  called — the  presence  of  soda  may  be  inferred.  If  the  yellow  precipitate, 
containing  potash  and  platinum,  be  separated  by  the  filter,  and  the  solution,  after 
being  treated  with  sulphuretted  hydrogen  and  filtered  to  separate  the  excess  of 
bi-chloride  of  platinum,  be  evaporated  to  dryness — if,  then,  a  soluble  saline 
residue  still  remain,  the  solution  contains  soda  as  well  as  potash. 

It  is  to  be  observed  that  some  magnesia,  if  present,  may  accompany  the  pot- 
ash and  soda  through  these  several  processes.  After  the  separation  of  the  potash, 
a  little  caustic  ammonia  will  detect  the  presence  of  magnesia,  but  it  will  rarely 
be  found  so  far  to  interfere  with  ih\s  preliminary  examination  as  to  prevent  the 
experimenter  from  arriving  at  correct  results  (see  p.  35,  /). 

*  Tlie  learned  reader  will  understand  why,  for  the  sake  of  simplicity,  I  take  no  notice  of 
substances  not  likely  to  be  present  in  the  soil— as,  for  example,  baryta,  which  would  here  be 
thrown  down  along  with  the  lime,  or  of  oxalic  acid,  which,  equally  with  the  sulphuric  or  car- 
bonic (a),  woulcyjive  a  white  precipitate  with  nitrate  of  baryta. 

t  Not  precipiwed  from  its  solution  by  ammonia,  for  if  precipitated  it  13  partly  at  least 
chloride  of  magnesium. 


No.    V.\  OP    THE    SOLUBL*^    SAL.1NK    MATTER    IN   THE    SOTL.  33 

/.  If  the  addition  of  bi-chloride  of  platinum  to  the  sohition  directly  filtered 
from  the  soil  give  a  yellow  precipitate,  it  contains  either  potash  or  aviraonia. 
If,  when  collected  on  the  filter,  dried,  and  heated  to  bright  redness  in  the  air, 
white  fumes  are  given  off  by  this  yellow  precipitate,  and  only  a  spongy  mass 
of  metallic  platinum  remains  behind,  the  solution  contains  aniiiionia  only.  If, 
with  the  platinum,  be  mixed  a  portion  of  a  soluWe  substance  having  a  taste 
like  that  of  common  salt,  and  giving  again  a  yellow  precipitate  with  bi-chloride 
of  platinum,  it  contains  j^oiaA'h — and  if  the  spongy  platinum  contained  in  the 
burned  mass,  after  prolonged  heating,  amount  to  more  than  57  per  cent,  of 
its  weight,  or  if  it  be  to  the  soluble  matter  in  a  higher  proportion  than  that  of 
4  to  3,  the  solution  contains  both  po'ask  and  amvioma. 

The  presence  oi  amvionia  in  the  saline  substance,  or  in  the  concentrated  solu- 
tion, is  more  readily  detected  by  adding  a  few  drops  of  a  solution  of  caustic 
potash,  when  the  smell  of  ammonia  becomes  perceptible,  or  if  in  too  small 
quantity  to  be  detected  by  the  smell,  it  will,  if  present,  restore  the  blue  colour 
to  reddened  litmus  paper.    This  experiment  is  best  made  in  a  small  tube. 

g.  If,  when  the  solvuion,  obtained  directly  from  the  soil,  is  evaporated  to  dry- 
ness, and  the  residue  heated  to  redness  in  the  air,  a  deflagration  or  burning  like 
match-paper  be  observed,  nitric  acid  is  present.  Or,  if  the  dry  mass,  when  put 
into  a  test  tube  with  a  litde  muinatic  acid,  evolves  distinct  red  fumes  on  being 
heated,  or  enables  the  muriatic  acid  to  dissolve  gold-dust,  and  form  a  yellow 
solution ;  or,  if  to  a  colourless  solution  of  green  vitiiol  (sulphate  of  iron), 
introduced  into  the  tube  along  with  the  muriatic  acid,  it  imparts  more  or  less  of  a 
brown  colour — in  any  of  these  cases  the  presence  of  nitric  acid  may  with  cer- 
tainty be  inferred.  It  will  be  only  on  rare  occasions,  however,  that  salts,  so 
soluble  as  the  nitrates,  will  be  found  in  sensible  quantity  in  the  small  portion 
of  a  soil  likely  to  be  employed  in  these  preliminary  experiments. 

Ji.  If  ammonia  throw  down  nothing  (see  under  r/)  from  the  solution,  and  if 
no  precipitate  appear  when  chloride  of  calcium  or  magnesium  is  afterwards 
added,  the  solution  contains  no  vhospkuric  add.  But  if  ammonia  cause  a  pre- 
cipitate, and  after  this  is  separated  by  the  filter,  nothing  further  falls  on  adding 
either  of  the  above  chlorides,  the  phosphoric  acid,  if  any  is  present,  will  be  con- 
tained in  the  precipitate  which  is  upon  the  filter.  Let  this,  after  being  well 
v/ashed  with  distilled  water,  be  dissolved  off  with  a  little  pure  nitric  acid 
diluted  with  water,  and  then  neutralized  as  exactly  as  possible  with  ammonia. 
If  a  solution  of  acetate  (sugar)  of  lead  now  throw  down  a  white  precipitate,  phos- 
phoric acid  is  present.  The  phosphate  of  lead — the  white  precipitate  which 
falls — melts  readily  before  the  blow-pipe,  and,  on  cooling,  crystallizes  into  a  bead 
with  beautiful  crystalline  facets. 

Or — if  the  precipitate  thrown  down  by  ammo)»ia  be  wholly  or  in  part  insolu- 
ble in  pure  acetic  acid  (vinegar),  that  which  is  undissolved  contains  phosphoric 
acid.  If  acetic  acid  dissolve  the  whole,  it  may  be  inferred  that  no  phosphoric 
acid  is  present  in  the  soil. 

But  if  no  precipitate  be  thrown  down  by  ammonia,  instead  of  the  chloride  of 
calcium  above  recommended,  a  few  drops  of  a  dilute  solution  of  alum  may  be 
mixed  vvith  the  solution,  after  adding  the  ammonia,  and  the  whole  well  shaken. 
If  the  white  pi-ecipitate,  which  now  falls,  dissolve  wholly  in  acetic  acid,  no  phos- 
phoric acid  is  present,  and  vice  versa. 

These  preliminary  trials  being  made,  notes  should  be  kept  of  all  the  appear- 
ances presented,  as  the  method  to  be  adopted  for  separating  and  determining 
the  weight  of  each  substance  will  depend  upon  the  number  and  nature  of  those 
which  are  actually  found  to  be  present. 

14"^.  Determination  of  the  quanlMies  of  the  several  conslitue7its  of  the  soluble 
saline  mailer. — The  quantity  of  soluble  saline  matter  extracted  from  a  mode- 
rate quantity  of  any  of  our  soils  is  rarely  so  great  as  to  admit  of  a  rigorous 
analysis,  and  the  preceding  determination  of  the  kind  of  substances  it  contains 
will  be  in  most  cases  sufficient.     Cases  may  occur,  however,  in  which  much 


34 


OF  THE  SOLUBLE  SALINE    MATTER  IN  THE  SOIL. 


[AppeTidix, 


saline  matter  may  be  obtained;*  it  will  be  proper,  therefore,  briefly  to  state 
the  methods  by  which  the  respective  quantities  of  each  constituent  may  be  ac- 
curately determined. 

a.  EsliinalLon  of  the  Salpkuric  Acid. — The  solution  being  gently  warmed,  a 
few  drops  of  nitric  acid  are  to  be  added  until  the  solution  is  slightly  acid,  and 
any  carbonic  acid  that  may  be  present  is  expelled,  after  which  nitrate  of  baryta 
is  to  be  added  to  the  solution  as  long  as  any  thing  falls.  The  white  precipi- 
tate (sulphate  of  baryta)  is  then  to  be  collected  on  a  weighed  filter,  well  washed 
with  distilled  water,  dried  over  boiling  water  as  long  as  it  loses  weight,  and 
then  weighed.  The  weight  of  the  filter  being  deducted,!  every  100  grains  of 
the  dry  powder  are  equal  to  3 137  grains  of  sulphuric  acid. 

b.  Estiviatioii  of  the  Chlorine. — The  solution  of  nitrate  of  silver  must  be  add- 
ed as  long  as  any  precipitate  falls,  the  precipitate  then  washed,  dried  at  212^^  F., 
and  weighed  as  before.  Every  100  grs.  of  chloride  of  silver  indicate  24-07  grs. 
of  chlorine,  or  40-88  grs.  of  common  salt. 

c.  Estimation  of  the  Lime. — A  little  diluted  muriatic  acid  being  added  to  throw 
down  the  excess  of  silver,  and  a  little  sulphuric  acid  to  separate  the  excess  of 
baryta,  added  in  the  former  operations,  and  the  precipitates  separated  by  fil- 
tration—caustic  ammonia  is  to  be  poured  in,  till  the  solution  is  distinctly  alcaline. 

'  This  is  the  case  with  the  rich  soils  of  India  and   Egypt,  and  of  other  warm  climates. 

This  will  appear  from  the  following  analyses  of  some  Indian  soils,  made  on  the  spot  by  Mr. 

Fleming,  of  Barochan,  during  the  hours  of  leisure  left  him  by  his  more  important  duties  :— 

Analysis  of  soils  in  North  and  South  Bchar^  Bengal  Presidency — (200  grains  of 

each  being  analysed.)  ' 


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REMARKS. 


1°.  Near  Gy  a,  South  Behar.— Of  a  dark  colour,  soapy 
to  the  touch  when  moist,  hard  and  cracks  when  dry  ; 
yields  a  crop  of  rice  and  one  of  wheat  every  year.  Ne- 
ver lies  fallow,  but  is  covered  with  water  during  part  of 
the  rainy  season,  and  is  productive — from  30  to  50 
bushels  of  wheat  per  acre. 

2°.  Soil  from  the  same  district. — Also  soapy  when 
moist  and  cracks  when  dry— rather  more  productive 
than  No.  1. 

3°.  From  the  same  district. — Heavy  red  clay  soil, 
producing  wheat,  pease,  cotton,  or  poppy  in  the  dry 
season,  and  Indian  corn  and  millet  in  the  wet  season  ; 
not  inundated  in  the  rains,  and  sometimes  manured 
with  ashes  of  wood  and  row  dung. 

4°.  Soil  from  North  Behar,  Tirlvoot. — A  deep  loam, 
yielding  two  crops  yearly;  not  inundated,  producing 
wheat,  barley,  Indian  corn,  indig;i,  poppy,  &c.  From 
25  to  35  bushels  of  wheat  per  acre ;  is  not  usually 
manured. 

5°.  Tirlioot. — Soil  light  coloured  ;  producing  nearly 
the  same  crops,  but  not  so  productive  as  No  4.  Saline 
efflorescence  in  patches. 

6°.  Tirlioot. — Not  so  productive  as  No.  5,  and  some 
patches  nearly  sterile  from  the  saline  efflorescence, 
except  in  the  rainy  season,  when  it  produces  good 
crops  of  Indifll  corn.     Soil  light  coloured. 


I  have  already  alluded  (Lecture  VIII.,  p.  159)  to  the  influence  which  this  large  proportion 
of  saline  matter  exercises  upon  the  luxuriance  of  the  vegetation. 

t  Or  the  whole  may  be  heated  to  redness  in  the  air,  and  the  filter  burned  away.  In  this 
case  the  weight  of  ash  left  by  the  paper  must  be  ascertained  by  previous  trials,  and  the  du« 
proportion  deducted  from  the  weight  of  the  sulphate. 


No.   v.]  OP   THE    SOLUBLE    SALINE    MATTER   IN  THE    SOIL.  35 

If  no  precipitate  fall,  oxalate  of  ammonia  is  to  be  added  as  long  as  any  white 
powder  appears  to  be  produced.  The  solution  must  then  be  left  to  stand  over 
night — that  the  whole  of  the  lime  may  separate,-  the  white  powder  afterwards 
collected  on  a  filter,  washed,  driel,  and  burned  with  the  filter,  at  a  low  red  heat. 
The  grey  powder  obtained  is  carbonate  of  lime,  every  100  grs.  of  which  con- 
tain 43'71  grs.  of  lime. 

d.  Esliniatinn  of  the  O.vi.ie  of  Iron  mid  of  the  Aluviina. — But  if  a  precipitate 
fall  on  the  addition  of  ammonia,  as  above  prescribed — the  solution  may  con- 
tain magnesia,  alumina,  and  the  oxides  of  iron,  and  manganese.  In  this  case 
the  precipitate  is  to  be  re-dissolved  by  the  addition  of  muriatic  acid  till  it  is  dis- 
tinctly acid,  and  ammonia  again  added  in  slight  excess.  If  any  precipitate  now 
fall,  it  will  consist  only  of  alumina  and  oxide  of  iron,  unless  magnesia  and 
oxide  of  manganese  be  present  in  large  proportion,  when  a  minute  quantity  of 
each  may  fall  at  the  same  time. 

The  precipitate  is  to  be  collected  on  the  filter  as  quickly  as  possible, — the  fun- 
nel being  at  the  same  time  covered  with  a  plate  of  glass  to  prevent  as  much  as 
possible  the  access  of  the  air, — washed  with  distilled  water,  and  then  re-dissolved 
in  muriatic  acid.  This  is  best  effected  by  spreading  out  the  filter  in  a  small 
porcelain  dish,  adding  dilute  acid  till  all  is  dissolved,  and  then  washing  the  pa- 
per well  with  distilled  water,  A  few  drops  of  nitric  acid  are  then  to  be  added, 
and  the  solution  heated,  to  peroxidize  the  iron.  A  solution  of  caustic  potash 
added  in  excess  will  at  first  throw  down  both  the  oxide  of  iron  and  alumina,  but 
will  afterwards  re-dissolve  the  alumina,  and  leave  only  the  oxide  of  iron.  This 
is  to  be  collected  on  a  filter,  washed,  dried,  heated  to  redness,  and  weighed. 
Every  100  grains  of  this  peroxide  of  iron  are  equal  to  89*78  grains  of  protoxide, 
in  which  state  it  had  most  probably  existed  in  the  original  solution. 

To  the  potash  solution  muriatic  acid  is  added  till  the  alkali  is  saturated,  or  till 
the  solution  reddens  Utmvs  paper  *  when  the  addition  of  ammonia  precipitates 
the  alumina.  A  s  it  is  difficult  to  wash  this  precipitate  perfectly  free  from  potash,  it 
is  better  to  dissolve  it  again  in  muriatic  acid,  and  to  re-precipitate  it  by  caustic 
ammonia.  When  well  washed,  dried,  and  weighed,  this  precipitate  gives  the  true 
quantity  of  alumina  present  in  the  portion  of  salt  submitted  to  analysis. 

e.  Estiniatioih  of  the  Manganese. — To  the  ammoniacal  solutions  from  which 
the  oxalate  of  lime  has  been  precipitated  ('■),  a  solution  of  hydro-sulphuret  of 
ammonia  is  to  be  added.  The  manganese  will  fall  in  the  form  of  a  flesh  red 
sulphuret.  When  this  precipitate  has  fully  subsided,  it  must  be  collected  on  the 
filter  and  washed  with  water  containing  a  very  little  hydro-sulphuret  of  ammo- 
nia. The  filter  is  then  put  into  a  glass  or  porcelain  basin,  the  precipitate  dis- 
solved off  by  dilute  muriatic  acid,  and  the  solution  filtered,  if  necessary.  A  so- 
lution of  carbonate  of  potash  then  throws  down  carbonate  of  manganese,  which 
is  collected,  dried,  and  heated  to  redness  in  the  air.  Of  the  brown  powder  ob- 
tained 100  grains  indicate  the  presence  of  93'84  grains  of  protoxide  of  manganese 
in  the  salt  or  solution  under  examination. 

/.  Estimation  of  the  Magnesia. — If  no  potash  or  soda  be  present  in  the  residual 
solution,  the  determination  of  the  magnesia  is  easy.  A  few  drops  of  muriatic 
acid  are  added,  and  the  whole  gently  heated,  and  afterwards  filtered,  to  separate 
the  sulphur  of  the  excess  of  hydro-sulphuret  of  ammonia  previously  added.  The 
solution  is  then  evaporated  to  dryness,  and  the  dry  mass  heated  to  redness  to 
drive  off  all  the  ammoniacal  salts  previously  added.  A  few  drops  of  diluted  sul- 
phuric acid  are  added  to  what  remains,  to  change  the  whole  of  the  magnesia 
into  sulphate,  the  mass  again  heated  to  redness  and  weighed.  One  hundred 
grains  of  this  sulphate  indicate  the  presence  of  3401  grs.  of  pure  magnesia. 

But  if  potash  or  soda  be  present — the  weight  of  which  it  is  desirable  to  deter- 
mine— the  simplest  method  is  to  take  a  fresh  portion,  15  to  20  grains,  of  the 

*  Litmus  paper  is  paper  stainetl  by  dipping  it  into  a  soluUta  of  litmus,  a  vegetable  blue  co 
lour,  prepared  and  sold  fortl"e  purpose  of  detecting  the  prt&'xice  of  free  acids,  by  which  it 
is  reddened. 


36  or    THE    SOLUBLE    .^J^L'.NK    xMATTEU    IN    THE    SOIL.  lAppCud^X^ 

saline  matter  under  examination.  If  any  sulphuric  acid  be  present  in  it  add  ni- 
trate of  baryta  drop  by  drop  to  the  solution  till  the  whole  of  the  acid  is  exactly 
thrown  down — if  possible,  no  excess  of  baryia  being  left  in  the  solution — then 
precipitate  the  alumina  and  oxides  of  iron  and  manganese,  and  the  lime,  if  any 
of  these  be  present,  and,  finally  evaporate  to  dryness,  and  heat  to  redness  as  be- 
fore. The  dry  mass  is  now  to  be  dissolved  in  water,  adding,  -if  necessary  to 
complete  the  soliUion,  a  few  drops  of  jiiuriD.ic  acid.  A  quantity  of  red  oxide  of 
mercury  is  then  to  be  added  to  the  concentrated  solution,  and  the  whole  boiled 
down  to  dryness.  AVater  now  dissolves  out  the  potash  and  soda  only,  and 
leaves  the  magnesia  mixed  with  oxide  of  mercury.  I'his  is  to  be  collected  on 
a  filter,  washed — not  with  too  much  water — and  heated  to  redness,  when  the 
magnesia  remains  pure,  and  may  be  weighed. 

g.  Es-iniaiion  of  the  Pot;tsk  ani  S'xta. — The  solution  containing  the  potash 
and  soda,  is  to  be  evaporated  to  dryness,  and  heated  to  redness  to  drive  off  any 
mercury  it  may  contain.  The  weight  of  the  mass  which  consists  of  a  mixture 
of  chloride  of  potassium  with  chloride  of  sodium  (coinmon  salt)  is  accurately 
determined,  it  is  then  dissolved  in  a  small  quantity  of  water,  and  a  solution  of 
bi-chloride  of  platinum  added  to  it  in  sufficient  quantity.  Being  evaporated  by 
a  very  g  ntle  heat  nearly  to  dryness,  weak  alcohol  is  added,  which  dissolves  the 
chloride  of  sodium  and  any  excess  of  salt  of  platinum  which  may  be  present. 
The  yellow  powder  is  collected  on  a  weighed  filter,  washed  well  with  spirits, 
dried  by  a  gentle  heat  and  weighed  on  the  filter.  Every  100  grains  indicate 
the  presence  of  19'33  grains  of  potash,  or  3056  grains  of  chloride  of  potassium. 
The  quantity  of  chloride  of  sodium  is  estimated  from  the  loss.  The  weight 
of  the  chloride  of  potassium  above  found,  is  deducted  from  that  of  the  mixed 
chlorides  previously  ascertained,  the  remainder  is  the  weight  of  the  chloride  of 
sodium.  Every  100  grains  of  chloride  of  sodium  (common  salt)  are  equiva- 
lent to  53-29  of  soda. 

k.  EsUmation  of  the  Amnioiria. — If  ammonia  be  present  in  the  solution  along 
with  potash  and  other  substances,  the  method  by  which  it  can  be  moist  easily 
estimated  is  to  introduce  the  solution  into  a  large  tubulated  retort,  to  add  water 
until  the  solution  amounts  to  nearly  an  English  pint — then  to  introduce  a  quan- 
tity of  caustic  potash  or  caustic  baryta,  and  to  distil  by  a  gentle  heat  into  a 
close  receiver,  containing  a  little  dilute  muriatic  acid,  until  fully  one  half  has 
passed  over,  Bi-chloride  of  platinum  is  then  to  be  added  to  the  solution, 
which  has  come  over,  previously  rendered  slightly  acid  by  muriatic  acid,  and 
the  whole  is  evaporated  nearly  to'dryness  by  a  very  gentle  heat.  Dilute  alco- 
hol is  then  added  to  wash  out  the  excess  of  the  salt  of  platinum,  and  the  yellow 
powder  is  collected  on  a  filter,  washed  with  spirit,  dried  by  a  very  gentle  heat, 
and  weighed.  One  hundred  grains  indicate  the  presence  of  7-69  grains  of 
ammonia. 

Or  the  yellow  powder,  without  being  so  carefully  dried,  may  be  heated  to  red- 
ness, when  only  metallic  platinum  will  remain.  One  hundred  grains  of  this 
metallic  platinum  indicate  the  presence  of  17  39  grains  of  ammonia. 

i.  Estimation  of  the  Phosplioric  Acid. — If  phosphoric  acid  be  present  in  the 
solution,  it  will  be  contained  in  the  precipitate  thrown  down  by  ammonia  {d). 
As  it  will  never  be  found  but  in  very  small  quantity,  the  rigorous  determination 
of  its  amount  is  a  matter  of  considerable  difliculty.  The  following  method 
already  described  (13°,  //,)  may  be  adopted.  The  precipitated  alumina,  oxide 
of  iron,  &c.,  thrown  down  by  ammonia,  after  being  dried,  are  to  be  mixed  with 
three  times  their  weight  of  pure  dry  carbonate  of  soda,  and  fused  together  in  a 
platinxim  crucible.  The  fused  mass  is  then  to  be  treated  with  cold  distilled 
water  till  every  thing  soluble  is  taken  up.  The  filtered  solution- is  next  te  be 
gently  heated  and  exactly  neutralized  with  nitric  acid,  when  a  solution  of  ni- 
trate of  silver  Avill  throw  down  a  ivhite  precipitate  of  phosphate  of  silver,  which 
is  to  be  collected,  dried,  and  weighed.  Every  hundred  grains  of  it  are  equal  to 
23-51  of  phosphoric  acid,  c '  48*50  of  bor.3  earth. 


No.   v.}  OP   THE    SOLUBIiE    SALINE    MATTER   IN   THE    SOIL.  37 

Or  the  filtered  solution  may  be  treated  with  muriatic  acid,  ammonia  added  in 
excess,  and  then  a  solution  of  chloi'ide  of  calcium.  Bo7i/;  earlli  will  fall,  which 
is  to  be  collected,  washed,  heated  to  redness,  and  weighed.  One  hundred 
grains  of  it  contain  4845  of  piiosphoric  acid.  Tlie  former  method  is  probably 
tiie  better,  but  neither  of  them  will  give  more  than  an  approximation  to  the  truth. 

I'hat  portion  of  the  fused  mass  wliich  cold  water  has  refused  to  take  up  is  to 
be  dissolved  in  mui-iatic  acid,  and  again  precipitated  by  ammonia.  The  clear 
solution  which  passes  through  is  to  be  added  to  the  first  ammoniacal  solu- 
tion (r),  from  which  the  lime  is  not  yet  thrown  down,  as  when  little  alumina 
and  oxide  of  iron  are  present,  a  small  portion  of  lime  and  magnesia,  if  con- 
tained in  the  salt  under  examination,  may  have  fallen  along  with  them  in  com- 
bination with  phosphoric  acid. 

The  alumina  and  oxide  of  iron  which  rest  on  the  filter  are  to  be  separated 
and  estimated  as  already  described  (./). 

k.  Esthnaiion  of  Ike  Curijo7uc  Add. — The  lime  and  magnesia  dissolved  by 
cold  diluted  muriatic  acid  are  partly  in  combination  with  cai-bonic  acid  and 
partly  with  the  humic,  ulmic,  and  other  j^egetable  acids.  To  determine  the 
carbonic  acid,  100  grains  of  the  soil  dned  at  "il^^,  are  to  be  introduced  into  a 
small  weighed  flask,  and  then  just  covered  by  a  weighed  quantity  of  cold  di- 
luted muriatic  acid.  After  12  hours,  when  the  action  has  ceased,  a  small  tube 
is  to  be  introduced  into  the  flask  and  air  sucked  through  it  till  the  whole  of  the 
carbonic  acid  is  drawn  out  of  the  flask.  The  loss  of  weight  will  indicate  the 
amount  of  carbonic  acid  very  nearly.  It  would  be  more  rigorously  ascertained 
by  fitting  into  the  mouth  of  the  flask  a  tul^e  containing  chloride  of  calcium, 
and  then  heating  the  solution  to  expel  the  carbonic  acid. 

Kvery  hundred  grains  of  carbonic  acid  indicate  the  presence  of  77-24  grains 
of  lime  in  the  state  of  carbonate.  The  weight  of  lime  in  this  state,  deducted 
from  the  whole  weight  obtained  as  above  (c),  gives  the  quantity  which  is  ii 
combination  with  othev  organic  acids. 

IV. or    THE    INSOLUBLE    EARTHY    MATTER    OF    THE    SOIL.  ^ 

15^'.  When  the  soil  has  been  washed  with  distilled  water  as  above  directed — 
it  is  to  be  treated  in  the  cold  with  diluted  muriatic  acid — and  allowed  to  stand 
with  occasional  stirring  for  1-2  hours.  By  this  means  the  carbonates  of  lime, 
magnesia,  and  iron,  and  the  phosphates  of  lime,  and  alumina,  are  dissolved — 
with  any  lime,  magnesia,  oxide  of  iron,  or  alumina,  which  may  have  been  in 
combination  with  organic  acids.  The  iron,  alumina,  and  phosphoric  acid  are 
to  be  precipitated  by  ammonia,  the  lime  by  oxalate  of  ammonia,  and  such  other- 
steps  taken  as  may  be  necessary,  according  to  the  methods  already  described. 

lo^^.  The  undissolved  portion  may  now  be  treated  with  hot  concentrated 
muriatic,  kept  warm  and  occasionally  stirred  for  two  or  three  hours,  and  the 
solution  afterwards  evaporated  to  dryness.  The  dry  matter  is  then  to  be 
moistened  with  a  few  drops  of  muriatic  acid,  and  subsequently  treated  with 
water.  What  remains  undissolved  is  silica,  which  must  be  collected  on  a 
filter,  dried,  heated  to  redness,  and  weighed. 

The  solution  may  contain  oxide  of  iron,  alumina,  lime,  magnesia,  potash, 
and  soda.  Any  of  the  four  last  substances,  which  may  be  detected  in  it,  have 
most  probably  existed  in  the  soil,  in  combination  with  silica — in  the  state  of 
silicates. 

17°.  But  the  soil  may  still  contain  alumina,  not  soluble  in  hot  muriatic  acid. 
To  ascertain  if  this  be  the  case,  and  to  separate  and  determine  this  portion  of 
the  alumina,  if  present,  either  of  two  methods  may  be  adopted. 

a.  The  residual  soil  may  be  drenched  with  concentrated  sulphuric  acid  and 
heated  for  a  considerable  time  till  the  sulphuric  acid  is  nearly  all  driven  off. 
On  treating  with  water,  and  adding  ammonia  to  the  filtered  solution,  alumina, 
and  oxide  of  iron,  if  any  have  been  present,  will  be  thrown  down.  If  any 
alumina  be  thus  separated,  tks  treatment  with  sulphuric  acid  must  be  repeat- 


38 


OF   THE    SOLUBLE    SALINE   MATTER    IN   THE    SOIL. 


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No.  V.\  or   THfc-    SOLUBLE    SALINE    MATTER   IN   THE    SOIL.  39 

ed,  till  on  treating  with  water  and  ammonia,  as  before,  no  more  alumina  ap- 
pears. 

b.  Or  that  portion  of  the  soil  on  which  hot  muriatic  acid  refuses  to  act  may 
be  mixed  with  twice  its  weight  of  carbonate  of  soda,  and  heated  in  a  platinum 
crucible  till  the  whole  is  completely  fused.  The  mass  is  then  to  be  treated  with 
diluted  muriatic  acid  till  every  thing  soluble  is  taken  up,  the  filtered  solution 
evaporated  to  dryness,  the  dry  mass  moistened  with  muriatic  acid,  and  again 
treated  with  water.  If  any  thing  is  left  undissolved  it  will  be  silica,  and  if  any 
alumina  be  contained  in  the  solution,  it  will  be  precipitated  by  ammonia,  and 
may  be  collected,  washed,  dried,  and  weighed,  as  already  described.  The  so- 
lution may  also  be  tested  for  magnesia,  and  if  any  be  present  it  may  be  sepa- 
rated by  the  process  already  explained. 

The  former  of  these  two  methods  is  to  be  preferred  as  the  simpler,  though  it 
will  also  require  considerable  care  and  attention.  That  which  the  sulphuric  acid 
leaves  behind  must  be  washed,  dried,  heated  to  redness,  and  weighed.  It  will  be 
found  to  consist  chiefly  of  quartz  sand,  and  finely  divided  siliceous  matter. 

The  accuracy  and  care  with  which  the  whole  of  these  processes  have  been 
conducted  is  tested  by  adding  together  the  weights  of  the  several  substances 
that  have  been  separately  obtained.  If  this  sum  does  not  differ  more  than  one 
per  cent,  from  the  weight  of  the  soil  employed,  the  results  may  be  considered 
as  deserving  of  confidence.  One  of  the  points  in  which  a  beginner  is  most 
likely  to  err,  is  in  the  washing  of  the  several  precipitates  he  collects  upon  his 
filters.  As  this  is  a  tedious  operation,  he  is  very  likely  to  wash  them,  at  first, 
only  imperfectly,  and  thus  to  have  an  excess  of  weight  when  his  quantities  are 
added  together — whereas  a  small  loss  is  almost  unavoidable.  The  precipitates 
should  always  be  washed  with  distilled  water,  and  the  washing  continued  until 
a  drop  of  what  passes  through  leaves  no  stain  when  dried  upon  a  bit  of  glass. 


No.  VI. 

ACTION   OF  GYPSUM. — {See  pages  333-34.) 

In  the  text  I  have  stated  what  appear  to  me  the  most  probable  effects  which 
gypsum  is  fitted  to  produce  upon  the  soil.  Some  of  the  numerous  opinions  that 
have  been  entertained  upon  this  point  are  thus  summed  up  by  Hlubeck  : — 

"  According  to  i^oZ^?^e?•,  the  action  of  gypsum  depends  upon  the  power  pos- 
sessed by  lime  to  form  with  the  oxygen  and  carbon  of  the  atmosphere  compounds 
which  are  favourable  to  vegetation  ;  accoiniing  to  Ritckert,  it  acts  like  any  other 
food ;  according  to  May.r  and  Brown,  it  merely  improves  the  physical  proper- 
ties of  the  soil ;  while,  according  to  R:U,  it  is  an  essential  constituent  of  the  plant. 
Hedwi g  caWedi  gy^sxxm  the  saliva  and  gastric  juice  of  plants  ;  Huviholdt ,  Gir- 
tanir,  and  Albc.rl  ^Pkaer  considered  it  as  a  stimulant  by  which  the  circulation 
of  plants  is  promoted  ;  and  CfiapUil  ascribed  its  action  to  a  supposed  power  of 
supplying  water  and  carbonic  acid  to  plants.  Davy  regarded  it  as  an  essential 
constituent  of  plants,  because  it  acts  only  where  gypsum  is  wanting  in  the  soil, 
while  other  English  agriculturists  have  supposed  it  to  promote  fermentation  in 
the  soil.  According  to  Laxihender ,  it  acts  as  an  exciting  power  without  mixing 
itself  with  the  sap  of  the  plant;  according  to  Lieblg,  it  fixes  the  ammonia  of  the 
atmosphere  ;  and,  according  to  Brcfonnot  and  Sprcngel,  it  supplies  sulphur 
for  the  formation  of  the  legumin  of  the  leguminous  plants  (the  most  probable 
view)." — Erndhrung  der  PJlanzcn,  p.  70,  note. 

To  the  above  extract  I  may  add,  tiiat  Mr.  Cuthbert  Johnson  ^o  long  known 
for  his  many  valuable  writings  upon  agriculture,  in  following  out  the  above  idea 
of  Reil  and  Davy  in  a  recent  paper  on  the  use  of  gypsum  (Jour,  of  the  Royal 
28° 


40  ACTION  or  GYPSUM.  [Appeiultz, 

Agr.  Society,  ii.,  p.  108,)  has  stated  that  a  crop  of  clover  or  sainfoin  contains  IJ 
to  2  cwt.  of  gypsum  per  acre,  exactly  the  quaniiiy  which  the  fa viiiers  of  Kent  and 
Hampshire  find  it  useful  to  apply  to  their  grass  lands  every  year.  This  state- 
ment aftords  a  vary  simple  explai\aiion  of  the  use  of  gypsum,  and  one  which 
at  first  sight  leaves  nothing  to  be  desired.  But  it  proves  too  much,  for  it 
supposes  the  whole  of  the  gypsum  which  is  laid  upon  liie  grass  or  clover 
field  to  be  removed  year  by  year  in  the  crop,  and  makes  no  allowance  either  for 
the  quantity  which  must  necessarily  be  carried  off  by  the  rains,  or  for  that 
which  must  be  sometimes  at  least  laid  on  in  the  forai  of  farm-yard  or  other 
similar  manure.  Nor  does  the  result  i^f  analysis  confirm  the  above  statement 
as  to  the  quantity  of  gypsum  contained  ir..  the  crop  of  clover  or  sainfoin.  By 
referring  to  page  220,  it  will  be  seen  that  1000  lbs.  of  dry  hay  do  not  con- 
tain, on  on  average,  more  than  4  lbs.  of  sulphuric  acid — equal,  supposing  it  all 
to  be  in  combination  with  lime,  to  8|  lbs.  of  gypsum.  Or  a  crop  of  1^  tons  of 
hay  contains  the  elements  of  about  30  lbs.  of  gypsum — only  about  a  sixth 
part  of  what  is  usually  added  as  a  top-dressing  to  the  land. 


No.  YIL 

SUGGESTIONS  FOR  EXPERIMENTS  WITH  THE    SOLUBLE   SILICATES 
OF  POTASH    AND   SODA. 

In  the  text  (pp.  207  and  349,)  1  have  had  frequent  occasions  to  refer  to  the  pre- 
sence in  the  soil  of  the  silicates  of  potash  and  soda,  and  to  their  supposed  action 
in  supplying  silica  to  the  stems  of  the  grasses  and  of  the  corn- bearing  plants. 
It  would  be  interesting  in  a  theoretical  point  of  view,  to  ascertain,  by  experi- 
ment, more  fully  than  has  hitherto  been  done,  how  far  the  application  of  tliese 
substances  to  the  growing  crops  would,  as  a  general  rule,  improve  or  otherwise 
aifect  their  growth.  But  as  those  experiments  which  have  already  been  made 
(page  349),  afford  a  strong  presumption  in  favour  of  their  economical  value, 
it  becomes  a  matter  of  practical  interest  also  to  iijvesligate  their  apparent  effects 
upon  each  of  our  cultivated  crops. 

These  experiments  are  placed  within  the  reach  of  the  practical  farmer  during 
the  ensuing  season,  by  the  introduction  of  the  above  compounds  into  the 
market  at  a  reasonable  rate  (page  363).  1  therefore  subjoin  a  few  sugges- 
tions for  experiments  with  these  silicates,  in  the  hope  that  some  of  the  many 
zealous  and  intelligent  practical  men,  wiio  are  now  directing  their  attention  to 
the  applications  of  chemical  science  to  agriculture,  may  be  induced  to  enter 
upon  this  field  of  inquiry  during  the  ensuing  spring. 

1  °.  In  order  to  convey  silica  into  the  plant,  it  appears  to  be  chemically  indif- 
ferent whether  the  silicate  of  potash  or  that  of  soda  be  placed  within  reach  of 
its  roots.  But  as  the  silicate  of  soda  can  be  manufactured  very  much  cheaper 
than  that  of  potash,  it  is  desirable  above  all  to  try  the  effects  of  this  compound 
— upon  the  grasses  and  corn-bearing  plants  especially. 

2°.  But  as  in  the  ashes  of  most  plants  potash  is  found  in  larger  quantity  than 
soda,  it  is  possible  that  the  effect  of  the  silicate  of  potash  upon  some  soils  may 
be  so  much  greater  than  that  of  the  salt  of  soda  as  to  counterbalance  the  dif- 
ference of  expense.  Hence  the  propriety  of  extended  trials  with  this  com- 
pound also. 

3°.  But  as  in  the  ashes  of  all  our  cultivated  plants  both  potash  atid  soda  are 
found,  it  may  be  that  a  mixture  of  the  two  silicates  may  act  better  than  either 
alone.  It  will  be  proper,  therefore,  to  apply  such  a  mixture  in  difTerent  pro- 
portions, and  to  compare  it  effects  with  those  of  each  of  the  silicates  laid 
on  singly. 


No.  VIII.]  OF   THE    SOLUBLE    SILICATES    OF    POTASH  AND   SODA. 


41 


The  first  series  of  comparative  experiments-,  therefore,  would  be  as  follo^rs: 

The  ap2)lication  may  be  frora  1  cwt.  to  IJ 
cwt.  per  acre,  laid  on  as  a  top-dressing  in 
moist  weather  early  in  the  spring.  Or  it 
may  be  mixed  with  a  large  quantity  of  wa- 
ter, and  applied  with  a  water-cart.     In  either 


Silicate  of 
Soda. 


'^Silicate  of, 
P(jlash,     ! 

%  Silicate  of  I 
Soda. 


ci-    .     r   ^^  ^''f  *'f  °^    case  it  ought  to  be  in  the  state  of  a  fine  powder, 
bilicate  of         Potash,  i>    .     i  r        i   .1        i  i-     .•  ^3  1 

Potash.      }i  Silicate  of        t>ut  altliough  the  ibove  applications  produce  a  bene- 
Soda.         ficial  effect  upon  the  crops,  it  will  not  necessarily  follow 

that  the  silica,  which  the  silicates  contain,  has  had  any 

share  in  bringing  about  the  good  result.  By  mere  expo- 
sure to  the  air  for  a  length  of  time  tiie  potash  or  soda  of  those  silicates  will  absorb 
carbonic  acid  from  the  atmosphere,  and  be  converted  into  carbonates.  The 
same  will  take  place  more  rapidly  still  in  the  soil,  where  carbonic  acid  abounds 
This  conversion  of  the  alkali  into  carbonate  will  set  free  a  large  part  of  the 
silica — in  a  state  it  is  true  in  which  it  is  in  some  degree  soluble  in  water  (page 
206,) — but  in  whicn,  nevertheless,  it  will  find  its  way  into  the  plant  with 
much  more  difficulty  than  if  it  had  remained  in  the  state  of  a  soluble  silicate. 

Now  as  the  carbonates  of  potash  and  soda  are  known  to  promote  vegetation 
(page  '>i28), — though  even  with  these,  sufficient  trials  have  not  yet  been  made 
— it  is  possible,  as  1  have  remarked  above,  that  a  good  eifect  may  follow  the 
application  of  the  sihcates,  and  yet  it  maybe  altogether  due  to  the  action  of  the 
carbonates  which  are  formed  by  their  decomposition.  It  is  of  consequence  to 
ascertain  if  this  really  be  the  case,  because  the  quantity  of  carbonates  which 
would  be  formed  by  the  decomposition  of  the  silicates  could  be  laid  on  directly 
at  one  lialf  of  the  price  at  which  the  silicates  can  as  yet  be  sold. 

The  second  series  of  comparative  experiments,  therefore,  which  it  would  be 
interesting  to  try,  would  be  such  as  the  following  ;  — 

The  quantities  here  indicated  are  bj^  the  acre — thai 
of  carbonate  of  soda  is  given  so  great,  because  this  salt 
contains  upwards  of  three-fifths  its  weight  of  water  (see 
p.  215.) 

Another  consideration  ought  not  here  to  be  omitted. 
Nature,  as  has  been  frequently  illustrated  in  the  text, 
feeds  her  plants  with  a  mixture  of  many  different  sub- 
stances, and  by  the  aid  of  such  mixtures  they  always 
thrive  the  best.  I'he  full  benefit  of  the  silicates,  when 
applied  alone,  will  be  experienced  only  when  every  oth- 
er ingredient  which  the  plant  requires  is  already  present  in  the  soil,  and  in  suf- 
ficient abundance.  But  this  can  rarely  be  the  case.  Its  success  will  be  more 
sure,  therefore,  if  it  be  applied  in  a  state  of  mixture  with  other  saline  substances 
which  are  known  to  be  more  or  less  useful  to  vegetation,  and  which  will  not, 
upon  admixture,  decompose  these  silicates.  Such  are  common  salt  and  the 
sulphate  and  nitrate  of  soda. 

A  third  series  of  comparative  experiments,  therefore,  might  be  made,  in  which 
from  1  to  1 1  cwt.  per  acre  of  the  following  mixtures  might  be  applied : — l'^. 
Equal  weights  of  common  salt,  of  dri/  sulphate  of  soda,  of  nitrate  of  soda,  and 
of  silicate  o^  potash;  2°.  Equal  weights  of  the  same  substances,  omitting  the 
silicate  of  potash ;  3°.  Equal  weights  of  common  salt,  oi  dry  sulphate  of  soda, 
of  nitrate  of  potash,  and  of  silicate  of  soda;  and  4'-\  Equal  weights  of  the  same 
substances,  omitting  the  silicate  of  soda,  or  substituting  carbonate  of  soda  in 
its  stead. 

The  sulphate  of  magnesia  (Epsom  salts)  or  of  lime  (gypsum)  can  not  be 
safely  used  along  with  the  silicates,  as  the  magnesia  or  lime  they  contain  may 
decompose  the  silicates — forming  sulphate  of  potash  or  soda  and  silicate  of 
magnesia  or  lime,  in  which  the  silica  is  insoluble,  and  could  not,  therefore,  until 
a  further  chemical  change  took  place,  find  its  way  into  the  roots  of  the  plant. 


Silicate  of 
Potash, 
I  cwt. 


Silicate  of 
Soda, 
1  cwt. 


Crude 
Potash  or 
Pearlash, 

75  lbs. 


Crystallized 

Carbonate 

of  Soda, 

150  lbs. 


BXPERIMENTS   ON  TURNIPS. 


[Apyendtz, 


No.  VIII. 


RESULTS  OF  EXPERIMENTS    IN    PRACTICAL  AGRICULTURE, 
MADE    IN    1842. 

I  have  much  gratification  in  laying  before  my  readers  the  results  of  a  second 
year's  series  of  experiments  undertaken  in  consequence  of  suggestions  thrown 
out  in  previous  parts  of  this  Appendix,  or  of  opinions  expressed  in  the  body  of 
the  work.  It  is  one  of  the  numerous  good  results  which  have  followed  from  the 
issue  of  these  Lectures  in  a  periodical  form  that  I  have  the  pleasure  of  incorpo- 
rating in  the  same  volume  the  results  of  experiments  made  during  two  succes- 
sive years.  No  one  who  studies  with  care  the  experiments  which  follow,  and 
the  few  remarks  I  have  appended  to  them,  will  hesitate  in  pronouncing  them  to 
be  as  a  whole  the  most  valuable  contributions  to  accurate  expei-imental  agricul- 
ture ever  hitherto  published.  The  results  are  not  all  equally  important,  nor  all 
equally  instructive,  but  they  are  the  first  fruits  of  a  new  line  of  research,  which 
will  lead  us  hereafter  to  the  discovery  of  important  general  truths.  They  show 
that  practical  men  are  now  on  the  right  road,  and — spreading  as  scientific  know- 
ledge now  is  among  the  agricultural  body — 1  trust  there  is  no  fear  of  their  here- 
after being  prevented  from  pursuing  it. 


A.— EXPERIMENTS  ON  TURNIPS. 
I.   The  first  series  of  experiments  was  made  with  the  view  of  obtaining  an- 
swers to  these  two  questions : 
1°.    What  are  the  relative  effects  of  different  saline  substances  upon  the  turnip  crop 

under  the  same  circwnistaTices  7  and 
2°.  How  far  may  these  substances  be  employed  alone  to  supersede  farm-yard  manure 
in  the  culture  of  turnips  7 

Turnips  grown  in  Salter's  Bog. — Field  furrow-drained  and  subsoil  ploughed.     Manures  ap- 

flied  partly  in  drills  before  sowing  on  1st  June,  and  partly  as  top-dressing  on  28th  July, 
842.  The  salt  and  nitrate  of  soda  last  applied  were  dissolved  in  water ;  the  others  applied 
dry.     TTie  quantity  of  land  in  each  plot  was  one-thirteenth  of  an  acre. 


) 


No. 

Description  of 
Dressing. 

Manure  appUed. 

Produce 
weight 
ofbulbs. 

sts.    lbs. 
43    11 
23      0 

66    10 

36      6 

45  8 

35    12 
29      7 
39    12 

46  3 
61      6 

9      9 

Remarks.             | 

The  rest  of  the  field, 
grown    with     farm-yardi 
manure,  was  a  fair  ave-| 
rage  crop.     Those  expe- 
rimented   upon  were    a 
complete    failure,  owing 
partly,  no  doubt,  to  the 
severe  droueht  of  the  sea- 
son, but   chiefly    to    the 
want  of  farmyard  dung. 
The  seeds  brairded  bad- 
ly, and  the  drills   were 
blanky  throughout.    Few 
of  the  plants  reached  any 
size,  and  the  best  of  them 
were  inferiorto  the  plants 
immediately  adjoining- 
sown  at  the  same  lime,  & 
similarly  treated,  except 
as  respects  the  manuring. 

IslJune. 

28thJuly 

Total. 

1 
2 

'J 

5  i 

e' 

7^ 

8 

9 
10 

11 

Nothing 

Common  Salt 

Common  Salt 

2 

67 
2 

67 

67 

67 

8 

bush. 

u 

lbs. 

6 
4   ? 

6 

^\ 

6 
6 

9 
bush. 

I 

lbs. 
1 

Si 

17 
bush. 
2i 

Nitrate  of  Soda.   ... 

Nitrate  of  Soda 

Rape-dust      

Nitrate  of  Soda 

Sulphate  of  Soda 

Sulphate  of  Soda 

Sulphate  of  Soda 

Rape-dust....    .... 

Soot 

The  foregoing  experiments  were  made  at  the  suggestion  of  Lord  Blantyre  on 
the  home  farm,  at  Lennox  Love,  near  Haddington,  and  have  been  reported  to 
me,  at  his  Lordship's  request,  by  Mr.  William  Goodlet,  under  whose  immedi- 
diate  superintendence  the  whole  were  conducted. 

The  reader  will  not  suppose^  because  they  proved  what  are  commonly  called 


No.   VIIL]  EXPERIMi-NTS   ON   TURNIPS.  43 

failures,  that  therefore  they  are  of  no  value.  On  the  contrary,  they  so  far  satis- 
factorily answer  the  questions  they  were  intended  to  solve.     They  show 

1°.  That  saline  manures  in  that  locality  cannot  economically  take  the  place 
of  farm-yard  manure,  even  for  a  single  season, 

2°,  That  saline  manures  are  even  hurtful  in  the  present  condition  of  the  land, 
when  employed  alone — producing  a  smaller  crop  than  if  no  manure  had  been 
applied  at  all,  and  some  of  them  in  a  remarkable  degree.  This  appears  to  be 
especially  the  case  with  common  salt,  which  at  the  rate  of  1  cwt.  an  acre  reduced 
the  crop  of  bulbs  nearly  to  one-half  of  what  was  yielded  by  the  unmanured  por- 
tion of  the  field.  It  is  still  more  striking  that  nitrate  of  soda  applied  at  the  same 
rate  should  diminish  the  crop  though  in  a  less  degree  than  common  salt — and 
that  soot  should  almost  kill  it  entirely,  and  that  15  cwt.  of  rape-dust  per  acre 
should  produce  scarcely  any  effect.  In  regard  to  guano,  it  was  applied  in  too 
small  quantity  to  do  all  the  good  of  which  it  was  capable  had  it  been  laid  on 
more  largely.  If  6  or  8  cwt,  instead  of  IJ  cwt.  per  acre  had  been  used,  the  crop 
would  probably  have  equalled  that  obtained  by  the  use  of  farm-yard  manure. 

There  is  no  doubt  that  to  the  extreme  drought  of  the  season,  as  Mr.  Goodlet 
observes,  must  be  ascribed  the  injury  or  actual  lessening  of  the  crop,  in  this  case, 
by  the  use  of  saline  manures.  The  drought  brings  up  the  saline  matters  to  the 
surface,  and  thus  enables  it  to  encrust,  and  weaken,  or  entirely  kill,  the  growing 

giants.     The  want  of  rain  in  1842  w^much  more  felt  in  the  Eastern  part  of 
cotland  than  in  the  West,  where  the  greater  part  of  the  succeeding  experi- 
ments were  made,  and  where  occasional  showers  refreshed  the  land. 

One  other  observation  I  may  make.  Had  the  saline  matters  been  mixed 
with  a  fair  proportion  of  farm-yard  manure,  it  is  probable  that  even  on  this  field 
the  effects  would  have  been  very  different.  One  reason  for  this  expectation  is, 
that  the  plants  being  kept  in  a  rapidly  gi-owing  state — partly  use  up,  and  even 
eagerly  appropriate,  a  large  portion  of  the  saline  matter  as  it  rises  to  the  surface 
— and  by  their  strength  are  enabled  to  resist  the  injurious  action  of  any  excess, 
which  in  ordinary  circumstances  is  likely  to  remain.  The  reader,  however, 
will  not  ask  why  the  experiments  were  not  so  made — for  he  has  already  seen 
that  their  object  was  to  ascertain  the  effect  of  saline  manures  applied  ahne. 
From  their  results,  however,  he  will  draw  for  himself  the  important  practical 
rule,  that  in  ordinary  circmnstances  it  is  imsafe  to  trust  his  turnip  crop  to  sali^ie 
manures  alone — that  they  may  assist  the  action  of  farm-yard  or  other  similar 
mixed  manures,  but  cannot  supply  their  place.  But  upon  this  point  the  suc- 
ceeding series  of  experiments  throw  much  further  hght, 

II.  The  special  object  of  the  following  four  series  of  experiments  was  to  as 
certain — 

1°.  The  relative  effects  chiejiy  of  various  mixed  manures  upon  several  varieties 
of  turnips;  and 

2°.  Whether  any  of  these  mixtures  could  alone  be  economically  used  to  supersede 
farm-yard  manure. 

They  were  made  at  the  home-farm  at  Barochan,  near  Paisley,  under  the 
direction  and  superintendence  of  Mr.  Fleming,  whose  excellent  experiments, 
made  in  1841,  are  recorded  in  a  previous  part  of  this  Appendix  (pp.  17  to  24). 
Mr.  Fleming  describes  himself  as  much  indebted  to  his  overseer,  Mr.  Gardiner, 
without  the  aid  of  whose  zeal,  intelligence,  and  careful  superintendence,  so 
numerous  a  body  of  experiments  could  neither  have  been  made,  nor  the  results 
accurately  ascertained. 

1°.  Comparative  Experiments  writh  various  substances  used  as  manures,  for  growing 
Swedish  Turnips :  seed  sown  6th  June,  bulbs  lifted  25th  Nov.,  1842. 
Remarks.— The  land  is  a  light  loam,  loose  in  texture,  and  of  a  light  brown  colour.  Sub- 
soil hard,  and  full  or  small  stones  :  it  is  of  as  nearly  as  possible  the  same  quality.  The  tur- 
nip seed  was  all  sown  upon  the  same  day.  Rain  came  on  the  night  after  sowing,  and  in 
consequence  the  crops  brairded  well,  and  came  away  strong.  Those  which  show  the  great- 
est weight  in  the  Table  kept  the  lead  of  the  others  all  the  season.  The  numbers  of  the 
plots  in  the  Table  are  placed  in  the  order  in  which  they  followed  each  other  on  the  ground. 
The  crop  would  probably  have  been  larger  bad  there  been  more  rain. 


i 


44 


EXPERIMENTS    ON   TURNIPS. 


[AppendtXt 


No. 


ORCHARD  FIELD. 

Description  of  Manures  used. 


Quantity 
applied 

per 

imperial 

Acre. 


Produce  {  Produce  ot 
of  Bulbs,  |Bulb9,  loppe 
topped  dt 

tailed,  per 

imp.  Acre. 


and  tailed,  per 

imperial 

acre. 


Ccst  of  Manure 
per  imperial 

Acre,iuclading 
carriage  and 
putting  on. 


jPeat  and  Night-soil,  mixed. . , 

[Gypsum 

jCarbonate  of  Lime 

iSulphate  of  Ammonia 

JQuicklime , 

Soot , 

[Sulphur  

limitation  of  Daniel's  mixture. 

I  Wood  Charcoal  Powder 

Fresh  Animal  Charcoal 

[Exhausted  Animal  Charcoal. . 

iTurnbuU's  Humus. 

Bones  diss,  in  Muriatic  Acid. . 

iBaroehan  Artificial  Guano 

iTurnbuU's      do.         do 

INatural  Guano 

jSalt  and  Quicklime,  mixed, , 

I        3  months  old ' 

iSoot 

Potash  and  Lime  mixed,  14  , 

I        months  old ' 

iQuick  lime   

j  Wood-ashes 

jBone  dust 

JRape-dust 

jWooilen   Rags 

Farm-yard  dung 

Nothing 


lbs. 

4800 
4060 
4640 


20  tons. 

5  cwt. 
20  bush. 

1  cwt. 
20  bush.  I }   4320 
20  bush. 

6  lbs. 
50  bush. 
50  bush. 
10  cwt. 
10  cwt. 
50  bush. 
10  cwt. 

3  cwt. 
3  cwt. 
3  cwt. 


50  bush. 

50  bush. 

50  bu^ 

50  bush. 
50  bush. 
40  bush. 

1  ton. 

1  ton. 
20  tons. 


3980 
4400 
4240 
5920 
5560 
4800 
5200 
4960 


6560 

4240 

4480 

4400 

3200 
3600 
4160 
4000 
3920 
5200 
3440 


tons.  cwt.  qrs. 
17   2   3 
14  11   2 
16  U   2 


14  J3 

15  14 
15  2 
21  2 
19  17 
-7  2 
18  11 
17  14 
14  11 
23  8 


15      8      2 


15  2  3 

16  0  0 
15  14  I 

11  8  i. 

12  17  . 
14  17  1 
14  5  3 
14  0  0 
18  11  2 
12  5  3 


£.  s.  d. 

6  12  0 

0  12  6 

0  3  0 

1  12  0 


0  2 
0  15 
2     10 


0  15 

1  0 
1     17 


0  9  9 

1  5  0 
5  10  10 

8  10  0 

9  9  0 
10  10  0 


2°.  Results  of  Experiments  with  various  Substances  used  as  manures  for  growing  .fiar/t; 
Liverpool  Yellow  Turnips,  sown  9th  June,  and  lifted  2d  December,  1842.  The  quantity  of 
land  in  eacfi  plot  was  one  eighth  of  an  imperial  a-cre. 


No. 


BERRIE  KNOWES  FIELD. 

Description  of  Manures  used. 


Natural  Guano  at  25s. 

Wood-ashes 

Barochan  Artificial  Guano 

Wood-ashes 

Rape-dust 

Turnbull's  Artificial  Guano 

Wood  ashes 

Soil  simple 

Turnbull's  Humus 

Bone-dust 

Potash  &  Lime  mixed,  14  mos.  old 
Salt  &  Lime  mixed,  3  mos.  old.... 

Sulphate  of  Magnesia , 

Sulphate  of  Ammonia 

Nitrate  of  Soda , 

Sulphate  of  Ammonia 

Wood-ashes , 

Nitrate  of  Soda. 

Sulphate  of  Magnesia , 

Wood-ashes 

Sulphate  of  Ammonia 

Sulphate  of  Magnesia 

Lime  and  Potash , 

Turnbull's  Artificial  Guano 

Barochan  Artificial  Guano 

Soil  simple 


Quantity  of 
Manure  ap- 
plied per  im- 
perial Acre. 


5  cwt. 
20  bush. 

5  cwt. 
20  bush. 
15  cwt. 

5  cwt. 
20  bush. 

50  bush. 
30  bush. 
50  bush. 
50  bush. 

1  cwt. 

1  cwt. 

1  cwt. 
56  lbs. 
40  bush. 
56  lbs. 
28  lbs. 
40  bush. 
84  lbs. 
40  lbs. 
20  bush. 

5  cwt. 

6  cwt. 


Cost  per  Acre. 

including 
carriage  and 
putting  on. 


6 
2 
0    10 


Produce  of  ] 

Bulbs,  tot 

)ped 

and  tailed,  per] 

impe 

rial/ 

Icre. 
qrs. 

tons. 

cwt. 

32 

2 

2 

21 

2 

3 

24 

11 

2 

18 

5 

3 

n 

8 

2 

13 

14 

1 

17 

2 

3 

14 

5 

3 

18 

17 

1 

14 

17 

1 

24 

11 

2 

27 

2 

3 

20 

17 

2 

11 

11 

2 

16 

14 

1 

21 

4 

1 

24 

2 

1 

12 

17 

1 

No.  VJIL] 


EXPERIMENTS    ON   TURNIPS. 


Remarks.— The  soil  is  a  light  hazel  loam  incumbent  upon  sand-stone  rock.  It  was 
trenched  with  the  spade,  in  the  spring  of  1842,  out  of  pasture  grassj  to  the  depth  of  16  inches, 
and  the  rock  quarried  out  when  it  came  nearer  the  surface  than  that  depth,  it  was  again 
pointed  over  before  sowing,  after  which  the  drills  were  made  upon  the  flat  surface  with  the 
hoe,  at  the  distance  of  17  inches  between  them,  the  manure  sown  in  by  the  hand,  and  co- 
vered up,  the  seed  sown  and  rolled  in.  The  weather  was  very  dry  at  the  time  they  were 
sown,  and  continued  so  till  about,  the  20th  June,  accompanied  with  east  winds  and  bright 
sunshine.  They  brairded  moderately  well,  and  most  of  them  came  away  strong  and 
healthy.  In  examining  them,  and  in  the  working  them,  which  was  done  by  the  hand-hoe, 
many  of  them  showed  a  remarkable  difference  from  the  others  ;  particularly  No.  1  was  pre- 
eminent above  the  others  for  size  of  bulbs  and  strength  of  foliage.  Many  of  the  bulbs  were 
11  lbs.  in  weight ;  those  with  tlie  saline  and  alkaline  manures,  such  as  Nos.  8,  9,  10,  and  12, 
were  much  smaller  in  bulbs  ard  leaves  than  No.  1,  but  were  remarkable  for  firmness  and 
solidity  of  bulbs.  No.  11  was  larger  in  size  both  of  bulbs  and  leaves,  but  soft  and  light  in 
weight.  No.  7  liari  very  firm  solid  bulbs,  as  had  also  Nos.  2  and  4.  The  numbers  of  the 
plots  given  in  the  Table  indicate  the  order  in  which  they  were  grown  in  the  field. 
The  Barochan  Artificial  Guano  consisted  of 

Bones  dissolved  in  Muriatic  Acid 2  cwt.  i  Nitrate  of  Soda 28  lbs. 

Charcoal  powder .,.2cwt.  j  Sulphate  of  Soda  and  ;^^.  ,^,. 

Sulphate  of  Ammonia 1  cwt.  I  Sulphate  of  Magnesia   \  luins. 

Common  Salt  and  Gypsum,  each 1  cwt.  |  

Wood-ashes 5  cwt.  |  12  cwt.  1  qr.  20  lbs. 

See  note  to  page  47. 


3°.  Experiments  with  various  Manures  on  nine  Acres  of  Turnips  on  the  Farm 
at  Crooks,  1842. 


6 

Date  of 
Sowing. 

Quantity 

ofLaud 

per  Scotch 

acre. 

Manures,  and  quantities  applied  to 
the  land  sown,  per  Scotch  ,acre. 

Produce 

in  Tons 

per  Scotch 

acre. 

Kinds 

of 
Turnip. 

Value 
of  ma- 
nures 
applied. 

1 

2 
3 
4 
5 
6 

May  28. 

May  30. 
June  6. 
June  11. 
June  15. 
June  17. 

A. 

1 

1 
1 
0 

1 
1 
J 

R. 

1 

0 
2 
3 
0 

1 

1 
1 

Rape-dust  5  cwt.  Humus  25  bushels. 
Bone-dust  12  bushels.  Peat  ashes  5 
carts  .    . 

22 

20 

24 

19 

20 

IS 
14 
12J 

Swedes. 

Do. 
Yellow. 

Do. 

Do. 

Do. 

Do. 

White. 

£.    s. 

4    15 
4    10 
10    15 
10      0 

3  5 

2    15 

4  2 

5  12 

Rape  dust  5  cwt.,   Bonos   10  bushels, 
Humus  25  bush.,  Ashes 5  carts.. .. 

Johnstone  lowndung  30  tons  at  6s., 
Bones  14  bu*;!)   at  2s    6d 

Farm- yard  dung  25  tons  at  7s.,  Bones 
10  bush,  at  vs.  6d 

Artificial  Guano  (No.  1.,  p.  50)  2  cwt., 
Humus  40  bush..  Peat  ashes  5  carts. 

Natural    Guano    1  cwl  ,    Humus  40 

7 

8 

June28. 
July  4. 

Humus  57  bush.,  Bones  10  bush 

Artificial  Guano  mix.,  (No.  11.,  p.  50.) 

Remarks. — No.  1.  Soil  a  stiff  loam,  moist,  and  in  good  order  ;  when  the  seed  was  sown 
It  brairded  well,  and  came  away  at  once. 

No.  2.  Soil  rather  lighter  than  the  former;  seed  brairded  well,  and  came  away  at  once. 

No.  3.  Soil  the  same  as  above  ;  brairded  quickly  in  consequence  of  a  shower  of  rain. 

No.  4.  Soil  lighter  than  No.  3;  a  bad  braird,  and  turnips  long  of  springing  for  want  of  rain 

No.  5.  Soil  as  above  ;  long  of  brairding  in  consequence  of  want  of  rain. 

No.  6.  Soil  as  above  ;  and  like  No.  5,  still  very  dry  for  want  of  rain  ;  a  late  braird. 

No.  7.  Soil  lighter,  mixed  with  peat ;  no  rain — bad  braird. 

No.  8.  Soil  heavy  clay  loam  ;  no  rain,  and  a  bad  braird. 

The  two  latter,  from  drought  and  late  sowing,  did  not  grow  much  till  the  end  of  Sep- 
tember ;  and  when  checked  by  frost  in  the  beginning  of  November,  were  still  growing 
vigorously. 

N.  B— The  land  was  of  different  qualities,  the  seed  also  sown  at  different  times,  and  in 
very  different  states  of  the  atmosphere,  with  respect  to  moisture,  yet  the  average  produce 
was  good  ;  and  although  it,  is  not  easy  to  say  which  of  the  artificial  manures,  imder  such 
circumstances,  was  actually  the  best,  the  general  result  shows  that  any  of  these  used  will 
produce  on  my  land  a  good  average  crop  of  turnips,  and  at  a  less  expense  than  farm-yard 
manure,  and  tends  to  confirm  the  correctness  of  various  experiments  tried  by  me  on  a 
smaller  scale.  The  measurements  having  been  made  by  the  Scotch  chain,  I  have  not  al- 
tered them.  No.  8  would  probably  have  been  the  best  turnips,  had  they  been  sown  earlier, 
and  bc«n  assisted  by  a  fall  of  rain. 


4b 


EXPERIMENTS  ON  TURNIPS. 


[Appendix^ 

49.  Results  of  Experiments  with  different  mixed  manures,  in  growinjT  White  Globe  Tur- 
nips,  on  new  trenched  land,  Bucklather  Field.  Sown  13th  July,  aiid  liUed  IGth  December, 
1842. 


Description  of  Manure  used. 


TurnbuU's  Humus 

TurnbuU's  improved  Bones 
3  Barochan  artificial  Guano. . . . 
4lNatural  Guano 


Quantity 

per 

imperial 

Acre. 


60  bush. 
5  cwt. 
5  cwt. 
5  cwt. 


Price  of 

Manure 


per 
Acre. 


Weight  in 
imperial 
pounds  pr. 
>sth  Acre. 


£.  s.  d. 

3      0  0 

1  10  0 

2  10  0 
6      5  0 


Weight  in, 
Tons,  &C.1 
per  impe- 1 
rial  Acre. 


lbs. 

5950 

4900 

6300 

9170 


tons.  cwL 

21  5    i 
17    10    I 

22  10    I 
39    15    1 


The  Natural  Guano  was  purchased  December,  1841,  when  the  [.rice  was  jE25  per  ton.  It 
can  now  be  had  for  jei2. 

Remarks. — The  land  was  trenched  18  inches  deep,  and  completely  drained  at  the  dis- 
tance of  18  feet,  with  tile  drains  laid  30  inches  deep,  in  Feb.  1842.  Previous  to  this  it  was  in 
a  wet,  sour  state.  It  was  again  pointed  over  with  the  spade,  and  the  drills  made  for  the 
manures  with  the  hoe  upon  the  level  surface.  The  manures  were  then  sown  in  the  bottom 
of  the  drills  with  the  hand,  and  a  little  earth  being  put  over  them,  the  seed  was  sown, 
covered,  and  rolled.  The  weather  had  been  dry  for  some  time  before  sowing,  but  rain 
came  on  that  day  ,  they  brairded  quickly,  and  continued  to  grow  till  lifted — the  field  being 
well  sheltered.  The  tops  of  Nos.  2,  3,  and  4  were  of  a  dark  green  colour,  and  remarkably 
luxuriant,  many  of  the  bulbs  weighing  from  5  to  aibs.  No.  I  was  of  a  lighter  green,  but 
strong  and  healthy,  and  many  of  the  bulbs  of  this  lot  were  5  and  6  lbs.  The  bulbs  of  all  of 
them  were  finely  shaped. 


III.  The  object  of  the  two  following  series  of  experiments  was  the  same  as  in 
those  of  Mr.  Fleming. 

1°.  Results  of  comparative  experiments  upon  Swedes  and  other  Turnips  made 
on  the  home  farm  of  Mr.  Alexander,  of  Southbar,  near  Paisley,  in  1842. 

The  soil  of  the  field  was  a  deep  loam,  with  a  slight  admixture  of  peat — the 
subsoil  was  partly  a  light  clay  and  partly  a  sandy  gravel.  It  was  thoroughly 
tile-drained  and  subsoiled  to  the  depth  of  fourteen  inches. 


No. 


Kind  of  Manures. 


Quantity 

per 

imperial 

Acre. 


Swedes,  sown  Sth  May. 

Bone-dust i32bush. 

Bones il6  bush. 

Ash-dung 1 12  tons. 

Farm-yard  dung 32  tons. 

Mixture  of  Yellow  if  White,  sown  2Qth  July. ' 

Guano I  3^  cwt. 

Guano 2  cwt. 

Farm-yard   manure 8  tons. 


Cost  per 

imperial 

Acre 


£.  8. 

4  8 

5  8 
11    4 

3  10 
'   4  16 


Produce 
in  bulbs 


per  imp.  | 
Acre.      I 


24  tons. 
28  tons. 
30i  tons. 

20  tons. 
24  tons. 


Mr.  Alexander  adds,  I  must  here  notice  particularly  the  result  of  the  last  two  experi- 
ments. The  seed  sown  was  a  mixture  of  yellow  and  white,  and  I  he  period  of  sowing  as 
late  as  the  10th  July.  The  weather  at  the  time  being  favourable,  they  brairded  quickly, 
grew  with  great  vigour,  and  when  all  the  other  turnips  in  the  field  became  affected  with 
mildew  they  stood  as  green  as  ever.  This  (viz.,  the  non-mildewing)  I  attribute  greatly  to 
the  guano,  as  well  as  to  the  late  sowing,  never  before  having  seen  such  a  weight  of  turnips 
produced,  sown  so  late  in  the  season.  I  applied  other  artificial  manures  on  both  of  these 
fields  with  a  due  proportion  of  dung,  varying  the  quantities  and  modes  of  application,  as  ap- 
peared to  me  best  to  test  their  qualities,  but  as  the  comparative  effect  is  so  difficult  to  decide 
upon,  I  can  only  here  observe,  with  any  certainty,  that  though  the  turnips  brairded  quicker 
when  the  dung  was  assisted  with  these  manures,  particularly  where  TurnbuU's  humus  was 
applied,  the  crops  afterwards  did  not  appear  tome  to  be  materially  aided. 

2°.  Result  of  experiments  upon  Yellow  Turn-ips  made  by  Mr.  Alexander,  of 
Southbar,  at  Well  wood  Farm,  Muirkirk,  Ayrshire,  1842. 

The  nature  of  the  soil  on  which  the  experiments  were  made  was  reclaimed  moss 
(then  about  2  feet  deep),  having  a  clayey  subsoil,  but  which  had  been  thoroughly 
drained  with  tiles  at  fifteen  feet  apart.    The  field  had  produced  white  and  hay 


No.    VIII.]  KXPERIMKNTS    ON    TURNIPS.  47 

crops,  but,  as  far  as  known,  had  never  been  previously  green-cropped.  The  whole 
of  it  received  the  same  labour,  preparatory  to  sowing,  and  the  weather  during  the 
operation  (-which  lusted  four  days)  was  the  same,  ilius  giving  to  each  experiment 
an  equal  chance.  I'he  peiiod  of  sowing  was  from  the  15th  to  19th  of  May ;  the 
turnip  seed  used  was  Skirving's  improved  purple-topped  yellow;  the  dung  used 
was  the  produce  of  the  farm,  and,  with  the  exception  of  the  foreign  guano,  all  the 
other  manures  applied  were  those  manufactured  and  sold  by  Mr.  Turnbull,  of 
Glasgow.     7%(?  extent  of  ground  for  each  expcrijueni  was  one  acre,  Scotch  measure. 


No. 


Kind  of  Manure. 


Farm-yard  DuHg. . . 

Humu.s 

Farm-yard  Dung. . . 

Hnmu's'   . 

Artificial  Guano. ... 
Farmyard  Dung. . , 

Prepared  Bones' 

Farm-yard  Dung 

Humus 

Improved  Bones. . . 

Artificial  Guano 

Ammoniacal  Salts.. 

Artificial  Guano 

Guano 


Quantity 

per 
imperial 
Acre. 


12  tons. 

2  cwl. 
12  tons. 

\i  cwt. 

12  tons. 
2^  cwt. 
12  tons. 
90  lbs. 
90  " 


45 
31  cwt. 
3l 


31  cwi 

3|    " 


Cost  of      Produce 
Miuiure    j  in  Bulbs 
per  impe-  per  impe- 
rial   Acre,  rial  Acre. 


0  7 
0  6 
4  4 
U  15 
4    4 


24 


20 


9i  « 

28    " 


Cost  for 
Manure 
per  ton. 


s.     d. 
3       3i 


IV.  Effect  of  Gypsum  on  the  Turnip  Crop. 

In  1841,  Mr.  Burnet  of  Gadgirth,  near  Ayr,  applied  a  top-dressing  of  gypsum 
to  part  of  a  field  of  turnips,  and  found  that  it  naarly  doubled  the  crop.  « 

In  1842,  Mr.  Campbell,  of  Craigie,  in  the  same  neighbourhood,  "dressed  a 
six  acre  field,  with  the  exception  of  a  few  rows,  with  two  cwt.  of  unburned 
gypsum  per  acre.  The  crop  over  the  whole  was  excellent,  but  there  was  no 
perceptible  difference  between  the  dressed  and  the  undressed  part." 

How  are  these  discordant  results  to  be  reconciled  1  The  following  questions 
suggest  themselves  as  worthy  of  investigation — 

1°.  Is  gypsum  realty  propiiioiis  to  the  turnip  crop, — and  to  every  variety  alike? 

2°.  Are  the  unlike  results  above  obtained  to  be  ascribed  to  the  abundant  pre- 
sence, in  the  one  case,  of  gypsum  in  the  soil,  or  in  the  manure  ploughed  in, 
and  its  absence  in  the  other — or  to  the  variety  of  ttirnip  cultivated  1 — or 

3°.  Can  the  sea-spray  supply  gypsum  to  Mr.  Campbell's  estate,  which  is 
within  two  miles  of  the  coast,  while  it  is  less  bountiful  to  that  of  Mr.  Burnet, 
which  is  six  miles  inland  1 


B.— EXPERIMENTS  ON  POTATOES. 

I.  Results  obtained  by  Mr.  Campbell,  of  Craigie. 

Four  equal  drills  of  potatoes  were  treated  as  follows: — 

J  °.  Guano,  3  cwt.  per  aCre produce  5  pecKs, 

2°.  Farm-yard  dung,  40  cubic  yards  per  acre  .  .  .  produce  6  do. 
3°.  Do.,  top-dressed  afterwards  with  60  lbs.  of  nitrate  of  soda,  produce  6  do. 
4°.  Do.,  top-dressed  with  160  lbs.  sulphate  and  nitrate,  mixed,  produce  6    do. 


*  TurnbuWs  Humus  is  formed  from  urine  and  night-soil  mixed  with  gypsum  and  char- 
coal and  then  dried. 

Turnbull^ s  prepared  Bones  are  bones  and  flesh  dissolved  in  muriatic  acid,  and  mixed 
with  about  an  equal  quantity  of  charcoal  in  powder. 

TurnbulVs  Artificial  Guano  is,  I  believe,  prepared  bones,  with  a  little  salt  and  sulphate  of 
ammonia  prepared  from  urine,  and  dried  wiL;  i.  stove-heat. 


4.S 


EXPERIMENTS    ON    TURNIPS. 


[Appendix^ 


The  above  result  is  favourable  to  guano,  considering  that  it  was  applied  in 
such  small  quantity ;  but  why  did  the  saline  manures  produce  no  effect — was 
it  because  of  the  drought  of  the  season,  or  was  it  because  Mr.  Campbell's  land 
is  already  amply  supplied  with  salts  of  soda  from  its  vicinity  to  the  sea'?  (see 
Lectures,  pp.  344and34G).  These  experiments  are  not  unworthy  of  repetition 
on  a  larger  scale. 


II.  Some  very  striking  results,  obtained  by  top-dressing  potatoes  with  saline 
manures  on  a  small  scale,  were  described  by  ivlr.  f'leming,  of  Barochan,  in 
1841,  and  are  recorded  in  the  preceding  part  of  this  Appendix  (p.  20).  The 
following  three  series  of  experiments,  made  under  the  direction  and  superin- 
tendence of  the  same  gentleman,  have  been  made  upon  a  larger  scale,  and  with 
the  view  of  throwing  light  upon  a  greater  number  of  interesting  points — 

The  object  of  the  first  series  was  to  ascertain  the  effect — 

1°.   Of  (li[;'erent  mixed  manure:^,  when  applied  alone  to  the  potato  crop. 

^°.   Their  relative  effects  on  diffei'ent  varieties  of  potato. 


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No.  VIII.] 


EXPERIMENTS    ON   POTATOES. 


40 


2°.  The  object  of  the  two  followmg  series  of  experiments  was  to  ascertmn — 
1°.  The  relative  effect  of  different  saUri/;  subslances  applied  along  wUh  f ami-yard 
manure;  and — 2°.  Whether  tlie  effects  were  greater  when  mixed  with  the  ma- 
nure at  the  time  of  planting,  or  when  subsequently  applied,  as  a  top-dressing,  to 
the  growing  plants. 

1°.  Result  of  Experiments  with  saline  substances  in  top-dressing  Eoxly  American 
Potatoes.  Planted  18tli  April,  top-dressed  1st  June,  and  lifled  28th  Sep- 
tember, 1842.  Low  Field,  Barochan.  T!ie  quantity  of  land  in  each  plot 
was  one-eighth  of  an  imperial  acre. 


Cost  of 

Quantity 

Produce 

Produce  in 

Produce  in 

dressings  pr. 

Description  of 

of  dressing 

in  pecks 

bolls  of  5 

tons,  &c., 

imp.  acre, 

No.           Top-dressing. 

applied 

of  35 

cwt.  each 

per  imperial 

including 

per 

pounds 

per  imperial 

acre. 

carriage  and 

imp.  acre. 

each. 

acre. 

putting  on. 

cwt. 

pecks. 

bolls. 

ins.  cwt.  qrs. 

£.     s.     d. 

1      Nitrate  of  Soda 

li 
li 

126 

64 

16      -    - 

1     11    0 

2     Sulphate  of  Ammonia. 

116 

58 

14      10    — 

1    11    0 

3     Sulphate  of  Magnesia 

1^ 

106 

53 

13        5    - 

0    12    6 

4     Nitrate  of  Potash 

l| 

148 

74 

18      10    — 

2      3    0 

5     Nothing  but  Dung 

40  cubic  yds. 

98 

49 

12      15    — 

0      0    0 

P  S  Sulphate  of  Soda 

^f  Nitrate  of  Soda 

1( 

144 

72 

18      —    — 

1      4    9 

7      Sulphate  otSoda 

2 

SO 

49 

12      15    — 

0    15    0 

o^  Sulphate  of  Soda ^ 

I  Sulphate  of  Ammonia. 

1( 

151 

75i 

18      17      2 

1      4    9 

q  ]  Sulphate  of  Magnesia. . 
^}  1  Nitrate  of  Soda 

1          ? 

180 

90 

22      10    - 

1      9    0 

Remarks. — The  soil  is  a  light  loam  of  good  quality,  subsoil  hard,  stoney  till,  and  retentive 
of  water.  The  potatoes  were  planted  with  the  spade  at  the  distance  of  26  inches  between 
drills.  The  manure,  farm-yard  dung  at  the  rate  of  40  cubic  yards  per  acre,  spread  in  the 
bottom  of  the  drills — cutsets  laid  on  this  and  covered  up.  (The  cut  tubers  planted  were 
the  produce  of  those  top-dressed  last  season  (see  Appendix,  page  20).  Came  away  strong 
and  healthy,  of  a  dark  green  colour,  and  were  very  remarkable  fn>m  the  contrast  whicli 
they  presented  to  the  same  variety  of  Potato — planted  alongside  this  experimental  ground 
• — that  had  not  been  dressed  last  season.  These  last  came  away  weak,  and  of  a  yellowish 
green  colour,  and,  under  the  some  treatment  in  every  respect,  did  not  produce  so  good  a 
crop  by  15  twlls  per  acre).  Nos.  1,  2,  4,  6,  8,  and  9,  had  all  the  same  effect  in  altering  the 
colour  of  the  stems  and  leaves  to  a  darker  green.  Nos  3  and  7  had  not  that  effect,  but  No. 
3  added  greatly  to  the  produce.  No.  7  made  no  visible  SiHerMion^  but  hurTied  the  tops  se- 
verely  at,  the  time  of  dressing,  as  did  most  of  the  others  this  dry  season ;  this  burning  was  in 
most  cases  only  temporary. 

2°.  Results  of  Experiments  with  different  saline  subHances,  mixed,  with  farm- 
yard dung  at  the  time  of  planting,  in  growing  Early  American  Potatoes. 
Planted  29th  April,  and  lifted  31st  i^ugust,  1842.  The  quantity  of  land  in 
each  plot  was  one-eighth  of  an  imperial  acre. 


Cost  of  Salts 

Quantity 

Produce 

Produce 

Produce 

used,  per 

Description 

applied  per 

in  pecks 

in  bolls,  of 

in  tons, 

acre,  inclu- 

No. 

of  Manure  and  Salts, 

imperial 

of  35  lbs. 

5cwL 

&c.,  per 

ding  patting 

acre. 

each. 

each, per 
acre. 

acre. 

on,exclu8ive 
of  Dung.* 

Pecks. 

Bolls. 

tns.  cwt  qrs. 
8    17      2 

£.    s.    d. 

1  Farm-yard  Dung  alone.. 

2  Com.  Salt,  added  to  Dung 

35  cubic  yds. 

71 

35^ 

2  cwt. 

70 

3b 

8    15      0 

0     4    0 

3   Nitrate  of  Soda,        do. 

H" 

99 

49 

12    r    2 

1    12    0 

4   Sulph.  of  Magnesia,    do. 

2"  « 

91 

45 

ir    7     2 

0    17    0 

5  iSulph.  of  Ammonia,  do. 

6  iSulph.  of  Soda,           do. 

H  " 

107 

53i 

13      7      2 

1    12    0 

2    «' 

64 

32' 

8      0      0. 

0    17    0 

7 

SiUcate  of  Potasht     do. 

1    « 

120 

60 

15      0      0 

'  Dung  5s.  6d.  per  cubic  yard,  exclusive  of  cartage  and  spreading. 

t  The  silicate  of  potash  or  soluble  glass  was  directly  prepared  from  caustic  potash  an<J 
sand  or  silex  fug^d  together. 


50 


EXPERIMENTS    ON   POTATOES. 


[Appendix, 


Remarks.— The  soil  upon  which  the  above  were  grown  was  a  subsoil,  the  upper  soil 
having  been  taken  off  at  different  times.  It  was  trenched  two  feet  deep  in  the  Spring  of 
1841,  and  which  had  to  be  done  with  t)ie  mattoclc,  it  being  too  liard  for  the  spade  alone,  it 
was  cropped  that  season  with  potatoes,  manured  with  40  cubic  yards  of  compost  of  weeds, 
cut  grass,  and  half-rotten  leaves.  It  was  eigain  trenched  to  the  same  depth  after  the  crop  of 
potatoes  was  lifted ;  and  was  again  planted  in  the  Spring  of  1842  with  potatoes,  manured 
with  35  cubic  yards  of  farm-yard  dung,  mixed  in  the  proportions  stated  with  the  above  salts. 
The  potatoes  were  planted  with  the  spade,  at  the  distance  of  two  feet  between  the  drills,  the 
manure  being  put  in  the  bottom  of  the  drills,  the  salts  sown  by  the  hand  above  it,  and  then 
all  mixed  together  with  a  dung  fork.  The  cut  sets  were  laid  upon  the  mixture,  and  covered 
up.  As  was  remarked  in  1841,  the  potatoes  with  No.  3  tvere  eight  to  ten  days  brairded  before 
the  others ;  also  Nus.  5  and  7  were  earlier  than  the  others,  those  three  being  all/airly  up  in 
drills  before  the  others  made  their  ajipearance  through  the  grmmd.  Nos.  2,  4,  and  6  were  la- 
test, and  very  irregular  in  coming  up,  and  upon  examining  the  drills  a  few  of  the  sets  ap- 
peared to  have  been  burned.  There  was  a  marked  dissimilarity  in  the  stems  and  leaves  of 
these  potatoes  through  the  summer.  Nos.  3,  5,  and  7,  were  all  of  a  darker  green  colour  and 
stronger  than  the  others.  "No.  7  was  remarkable' for  intenseness  of  colour  and  length  of 
stems,  so  much  so  that  it  appeared  to  be  a  different  variety  of  potato.  Ho.  4  was  fully  beU 
ter  in  appearance  thun  Nos.  2  and  6,  which  were  of  a  yellowish  green  colour  and  had  a 
stunted  appearance  all  the  season. — When  this  ground  was  first  broken  up,  a  pound  of  it 
was  boiled  in  pure  rain  water  and  filtered,  which  was  then  evaporated,  the  residue  weighed 
4^  grains,  mostly  soluble  salts,  but  hardly  a  trace  of  common  salt. 

3°.  The  following  experiments  were  made  with  the  view  of  determining  how 
far  eMnomical  mixtures  might  be  made  to  supasede  fann-yard  manure  in  the 
growth  of  potatoes : — 
1°.  Account  of  an  Experiment  in  growing  Potatoes  (Irish  Pink  Eyes)  with  the  following 

mixture  of  substances,  instead  of  farmyard  dung,  planted  20th  April,  1842, 


No. 

Ingredients. 

• 
Quantity  in- 
tended to  ma- 
nure four 
acres. 

Cost  of 
Substances 

for 
four  acres. 

1 
2 
3 
4 
5 
6 

I. 

9 
10 

Rape-dust 

cwts.  qrs.  lbs. 

5  0      0 
2      0      0 
0      2    24 
2      0      0 

0  2      0 

1  2      0 
1      2      0 
0      2      0 
0      0      2 

6  2      0 

£.     s.    d. 
1    10     0 
0    12     0 
0      6      0 
0      1      6 
0    10      0 
0      2      3 
0      9      0 
0    10      0 
0      1      0 

Bones  dissolved  in  Muriatic  Acid. 

Carbonate  of  Lime 

Nitrate  of  Soda 

Dry  Moss-Earth 

20      0    26 

4      1      9 

Remarks. — The  above  mixture  was  sown  in  the  drills  at  the  rate  of  about  5  cwts.  per  im- 
perial acre,  at  a  cost  of  little  more  than  jEl.  sterling,  and  produced  a  fair  crop  of  potatoes  of 
a  remarkably  fine  quality,  43  bolls  per  acre  of  imperial  Renfrewshire  measure,  weighing  5 
cwt.  each,  upon  a  poor  and  light,  although  new  soil,  but  not  worth  more  than  25s.  per  acre. 
Great  caution  is  required  in  using  this  mixture,  as  it  is  very  apt  to  bum  the  cut  sets  if  laid 
directly  upon  them.     A  little  earth  should  be  put  between  the  cut  potato  and  the  manure. 

2°.  The  following  mixture  was  made,  and  lay  together  for  five  weeks,  when  it  was  sown  in 
the  bottoms  of  potato  drills  upon  a  poor  tilly  soil,  and  White  Don  Potatoes  planted  with  it 
30lh  April,  l&i2. 


No. 

1 
2 
3 
4 
5 
6 
7 

Ingredients. 

Quantity  mixed 

to  manure  one 

acre. 

Cost  of  Sub- 
stances for 
one  acre. 

Saw-dust,  mostly  from  Alder 

Potash  &  Lime  mixed,  14  mos.  old 
Common  Salt 

cwts.  qrs. 

1        2 
1        0 
0       2 
0        2 

bush. 
40 
10 

£.     s.    d. 

0      7      6 

0  2     3 

1  0      0 
0      3      6 
0      4      0 
0    10      0 

Sulohate  of  Ammonia 

Sulphate  of  Soda. 

Sulphate  of  Magnesia. ........... 

Coal  Tar,  20  gajlonsi  say 

3        2 

50 

2      7      3 

No.   VIIL]  EXPERIMENTS   ON   POTATOES.  61 

Remarks.— The  potatoes  planted  with  the  above  mixture  came  quickly  t^lirough  the 
ground,  and  were  very  luxuriant  in  foliace.  They  were  lifted  15th  October,  after  being  cut 
down  by  frost  whilst  still  unripe  and  growing.  On  being  taken  up,  they  were  found  to  yield 
a  produce  of  56  bolls  of  Renfrewshire  measure,  weighing  5  cwts.  each,  per  acre,  of  very 
fine  potatoes,  many  of  which  weighed  from  24  to  30  oz.  each. 

N.  B  —This  mixture,  alter  being  put  together,  fermented,  and  was  frequently  turned,  but 
kept  dry. 

The  several  series  of  experiments  made  upon  potatoes  by  Mr,  Fleming  are 
deserving  of  careful  consideration,  and  many  of  them  of  judicious  repetition. 
They  are  all  well  contrived  or  devised,  and  each  series  skilfully  arranged. 

In  agricultural  experiments  it  is  of  the  greatest  possible  consequence  that  the 
practical  man  should  have  a  clear  and  definite  object  distinctly  in  view.  If  so, 
his  experiments  may  be  signally  successful  in  his  own  estimation,  while,  eco- 
nomically considered,  they  may  be  total  failures.  This,  as  we  have  seen,  was, 
to  a  certain  extent,  the  case  with  the  first  series  of  experiments  made  upon  Lord 
Blantyrc's  farm,  as  above  detailed  (p.  42).  The  applications  in  some  instances 
lessened  the  crop,  but  the  result,  nevertheless,  threw  considerable  light  upon  the 
questions  which  the  trials  were  intended  to  solve. 

In  making  an  experiment,  the  practical  farmer  asks  a  question  of  nature; — in 
arranging  the  form  and  details  of  his  experiment,  he  is  putting  together  the 
words  by  which  his  question  is  to  be  expressed.  If  his  question  be  clearly  put, 
nature  will  give  him,  sooner  or  later,  a  clear  and  distinct  answer — if  he  have 
skill  enough  in  nature's  language  to  understand  what  she  has  said  to  him.  I 
say,  sooner  or  later,  for  it  may  be  sometimes  necessary  to  repeat  the  question, 
either  because  something  has  intervened  to  prevent  nature,  so  to  spe£ik,  from 
hearing  his  question, — because  it  has  not  been  accurately  expressed — or  because 
something  in  the  seasons,  or  otherwise,  has  prevented  her  answer  from  being 
clearly  understood — perhaps  from  bein^  heard  or  read  at  all.  Circumstances 
may  even  prevent  the  answer  from  bemg  given  until  a  second  summer  come 
round,  when,  if  we  are  not  on  the  alert,  it  may  never  be  received  at  all. 

The  above  experiments,  as  well  as  those  which  follow,  form  an  excellent 
study  for  the  practical  farmer  in  reference  to  this  matter.  Eveiy  series  is  plan- 
ned with  a  view  to  a  given  end,  the  circumstances  are  carefully  noted  before, 
during,  and  at  the  close  of  each  of  the  several  trials,  and  the  answers  are  re- 
corded with  a  very  praiseworthy  degree  of  accuracy.  I  shall  place  together,  in 
one  view,  the  most  important  of  the  deductions  to  which  the  experiments  of 
1842  appear  to  have  led,  when  I  shall  have  laid  before  the  reader  the  whole  of 
the  tables  which  have  as  yet  been  placed  in  my  hands. 

C— EXPERIMENTS  UPON  BARLEY. 

The  object  of  the  following  experiments,  also  made  by  Mr.  Fleming,  was  to 
ascertain  the  relative  effect  of  different  saline  stbbstances,  when  applied^  as  top- 
dressings,  to  a  crop  of  white  barley. 

The  results,  as  shown  in  the  last  column,  are  sufficiently  interesting. 

Results  of  Experiments  with  various  substances  used  as  top-dressings  upon 
Barley  (common  white).  The  Barley  sown  l4th  April,  top-dressed  6th 
May,  and  cut  down  25th  August,  thrashed,  cleaned,  measured,  and  weighed 
5th  October,  1842.  The  quantity  of  land  in  each  plot  was  one-eighth  cf  an 
imperial  axrt. 

Remarks.— The  soil  of  this  field  is  a  light  loam,  as  nearly  as  possible  uniform  in  quality, 
and  had  lain  about  ten  years  in  pasture  previous  to  the  spring  of  1842,  when  it  was  £ul 
trenched  with  the  spade  twelve  inches  deep.  It  had  been  thorough-drained  with  tiles  some 
years  before  breaking  up.  After  being  trf  r*ched,  it  was  dressed  over,  except  where  the  ex- 
periments were,  with  two  chaldrons  of  linift  per  acrefslaked  with  water,  in  which  common 
salt  had  been  dissolved,  and  before  sowing  the  barley,  with  the  exception  of  the  experiment 
ground,  it  v/as  top-dressed  over  with  two  and  a  half^cwfs.  of  Tumbull's  artificial  guano  per 
acre,  harrowed  in,  aa  was  also  the  top-dressing  No.  3  in  the  table  of  experiments.  The  bar- 
ley was  sown  broadcast,  2i  bushels  per  acre.  Owing  to  the  extraordinary  drought  at  time 
of  sowing,  it  did  not  braird  well  till  rain  came  ;  after  which  it  made  rapid  progress.  Advan- 
tage was  taken  of  heavy  rains  to  put  on  the  top-dressings,  all  of  which  were  sown  at  the 
time  above  stated,  viz.,  6lh  May,  except  No.  4,  which  was  not  sovm  till  the  Ifth,  at  which 


52 


EXPERIMENTS  UPON  BARLEY, 


[Appendix 


No. 


RoDBN  Hill  Field. 

Description 
of  Top-Dressings. 


Nitrate  of  Soda 

Common  Salt 

Sulphate  of  Soda 

Sulphate  of  Magnesia 

Natural  Guano,  at  253 

Nitrate  of  Potash 

Common  Salt 

Nothing 

TurnbuU'a  Artificial  Guano. 


^   3    «     C    Q.        S 


:  >  .5  =  '  °  c 


lbs  lbs. 
Hi  1821 
21 

7 
42 
14 
42 


42 


1638 

2192 
1665 
1735 
1620 
1925 


364 

378 
432 
255 
378 
325 
a34 


^-.- 

i.  *- 

, 

£  <ui^ 

c? 

?«tc 

-.n 

45 

■-t?; 

Q 

^ir,c 

o 

III 

11 

lbs. 

lbs. 

s.  d.   1 

500 

56 

2  0?! 
0  2i  1 

491 

55 

1  6  ; 

0  5i 

589 

54 

9  7 

590 

54 

3  6 

495 

57 

0  6| 

425 

55 

480 

54 

8  0 

sS 


cf« 


54    54 

64      0 
37    42 


49    26 


time  there  teas  little  rain,  and,  in  consequence,  it  burned  the  pl.a7its,  of  which  they  did  not  re- 
cover all  the  season,  and  the  ground  got  full  of  weeds.  No.  5  burned  the  plants  also,  but 
they  recovered  quickly,  and  gave  a  good  return.  Asicas  remarked  he/ore,  icherever  cvrnmon 
salt  was  put  on  as  a  top  dressing  on  grain  crops,  either  oficheat,  barley,  or  oats,  and  on  what- 
ever description  of  soil  upon  this  estate,  the  grain  was  invariably  heavier  per  bushel,  and  had 
fewer  weuks  or  tails  in  proportiu7i  to  the  quantity  of  grain  per  acre,  than  any  of  the  other 
dressings  apj)lied  here.  From  the  frequent  mention  of  spade  culture  in  these  experiments, 
many  may  consider  that  they  were  upon  a  very  small  scale,  which  is  not  the  case,  the 
greater  proportion  of  Ihem  being  very  extensive.  Mr.  Fleming,  to  give  employment  to  the 
destitute  labourers,  having  dug  and  trenched  about  thirty  acres  of  land  instead  of  ploughing 
it,  which  accounts  for  the  frequent  mention  of  spade  culture,  which,  when  it  can  be  got  ex- 
ecuted at  a  moderate  rate  (particularly  trenching  at  j£4.  oer  acre),  is  very  advantageous, 
and  seems  superior  to  trench  ploughing.  •  A.  F.  Gardiner. 

D.— EXPERIMENTS  UPON  OATS. 

The  first  of  the  following  series  of  experiments  was  made  at  Lennox-Love, 
at  the  request  of  Lord  Blantyre,  the  second  at  Barochan,  under  the  direction 
of  Mr.  Fleming.  The  general  object  of  both  was  the  same — to  ascertain  the 
relative  effect  of  different  salnie  siibsta7ices  applied  as  top-dressings  vpan  young 
oats;  but  those  of  Mr,  Fleming  have,  besides,  t/ie  special  object  of  ascertaining  the 
effect  of  certain  mixtures  upon  oats  token  grown  upon  mossy  land. 
1°.  Oats,  second  crop,  after  old  lea.  Soil  sharp  loam ;  subsoil  clay  resting  on  sand-stone 
rock.  Oats  sown  14th  March;  top-dres.sings  applied  13th  May  ;  crop  cut  27th  Aug. ;  and 
thrashed  9th  Sept. ,  1842.  The  gtiantity  of  land  in  each  plot  was  one-eighth  of  an  imperial  acre. 


Quarry  Park, 

Lennox-Love. 

Description  of 
Dressing. 


Nothing 

Common  Salt 

Common  Salt 

Rape-dust 

Nitrate  of  Soda 

Nitrate  of  Soda 

Rape-dust 

Nitrate  of  Soda.   , . 
Sulphate  of  Soda, . . . 
Sulphate  of  Soda. . . . 
Sulphate  of  Soda 

Rape-dust 

Rape-dust 

Guano 

Soot 

Waste  water  from  gas 
work  diluted  with  4 
times  itsbuUc  of  water 


St  ^ 

<3  ea 


lbs. 

14 

112  ( 
14 

112? 

l\ 

14 

112? 
224 
28 
4  bush. 

6gejls. 


o 
s.  d 

0  4 
70 


St 


Weight  taken  from 
Thrashing  Mill  of 

s 


lbs. 
672 


3  1     588 


|0 

1  0 

7  5 

14  0 
5  0 
4  0 


616 

504 
504 

672 

616 
938 
532 

700 


224  26 
351  30 
193    11 


273    15     390   22 


40i 


btishs. 
6-75 
6-00 

5-95 

519 

556 

4-81 

4  82 

6-56 

5-62 
8-75 
512 

7  00 


bush.  bush. 


£"2 


2« 


h  S  cfl  u  o  3 


2-00 


•75 

•80 

1-56 

119 

194 

Fas 

•19 
113 

1-63 


No.  VIIL] 


EXPERIMENTS   UPON    OATS. 


53 


2°.  Results  of  ExperiEJents  itn'th  various  substances  used  as  top-dressings  upon  Oats  (Sandy 
Oats),  sown  16th  April,  upon  drained  peat  moss  Nos.  2,  3,  and  5  top-dressed  on  the  same 
day  ;  No.  1  dressed  6th  May,  cut  down  14th  September,  and  thrashed,  cleaned,  and 
weighed  6th  Oct,.  1842.     The  quantify  of  land  in  eachplot  was  one-eighth  of  an  imperial  acre. 


No. 


SHAW  PARK  FIELD,  BAROOHAN. 

Description  of  Dressing. 


0.3 


— •  <u  ~ 
•5  ? 


si's 

seal's 


^.2 

m 

o2 

•S  '^  CO 


2  53 

is 


«  be*: 


^« 


Sulphate  of  Ammonia 12J  lbs. 

Water 20  galls. 

Sulphate  of  Soda 21  lbs. 

Nitrate  of  Soda 9^  lbs. 

Bones    dissolved    in   Muriatic 

Acid 42  lbs. 

Nothing 

Sulphate  of  Ammonia 7  lbs. 

Silicate  of  Potash 14  lbs. 

Sulphate  of  Soda  14  lbs. 

iBones    dissolved   in    Muriatic 

I     Acid !l41bs. 


1105 

1220 

1340 
960 

1600 


270 
305 


320 
210 


350 


Jbs. 
420 

450 


4S0 

320 


s.    d. 
2    6 


1  8, 

2  0' 


1  41 

2  0  I 
1    2^ 


bush. lbs 
52    18 


61      0 


60    40 
43      3 


65 


Remarks. — The  soU  upon  which  the  above  were  grown  is  moss,  rather  deeper  in  some 
parts  than  others,  incumbent  upon  gravel  of  a  stiff  retentive  quality.  It  had  been  partly 
drained  some  years  ago,  but  owing  to  the  nature  of  the  soil  the  drains  did  not  act  well.  In 
the  spring  of  1842,  it  was  again  dra,ined  with  tiles,  and  trenched  over  with  the  spade  to  the 
depth  of  16  inches(»nd  some  of  the  gravel  subsoil  brought  up  among  the  moss.  The  ground 
being  divided  into  lots  for  the  purpose,  the  top-dressings  Nos.  2,  3,  and  5  were  sown  on  the 
16th  April,  and  slightly  harrowed  in ;  the  oats  were  then  sown  and  harrowed  in  No.  I  was 
made  from  160  lbs.  sulphate  of  ammonia  dissolved  in  100  galls,  of  water  (proportions  for  an 
imperial  acre),  and  sprinkled  upon  the  oats  during  the  time  of  rain  on  6th  May.  No.  5  was 
sown  upon  a  lot  where  the  moss  was  fully  the  deepest.  They  all  brairded  well ;  Nos.  2  and 
5  coming  rather  earlier  than  the  others,  and  of  a  darker  colour,  particularly  No.  2.  No.  1, 
after  being  watered  with  the  solution,  became  also  of  a  darker  green,  but  neither  Nos.  1  nor 
2  were  so  strong  in  the  straw  as  Nos.  3  and  5,  boih  of  tchich  were  remarkable  for  strength  and 
luxuriance,  especially  No.  5,  which  kept  the  lead  of  the  others  all  the  season. 

E.— EXPERIMENTS  UPON  WHEAT. 
The  following  three  Experiments  upon  wheat  exhibit  very  interesting  results  : 
1°.  The  first  series  was  made  on  the  home  farm  of  Lord  Blantyre  at  Lennox 
Love,  and  was  intended  to  ascertain  the  relative  effects  in  that  locality  of  differ- 
ent, chiejb/  saline,  manures  applied  as  top-dressings  to  spring  wheat. 


iNo. 


Lbnnox-Lo  vs. 

Description  of 
Dressing. 


Nothing 

Common  Salt 

Common  Salt.... 

Rape-dust 

Nitrateof  Soda. . . 
Nitrate  of  Soda... 

Rape-dust 

Nitrate  of  Soda. 
Sulphale  of  Soda. 
Sulphate  of  Soda. 
Sulphate  of  Soda 

Rape-dust 

Rape-dust 

Guano 

Soot 


MANUKES.     i 

>\    . 

.tiT3 

^ 

11 

o 

lbs. 

s.  d. 

14 

0  4 

112  ( 

70 

14 

3  1 

uU 

8  7 

?( 

2  0 

14 

1  0 

112  ( 

7  5 

224 

14  (J 

28 

50 

4  bush. 

40 

lbs. 
10.36 
1003 

1148 

1120 

1176 

.1078 

896 

990 

1106 
1092 
1036 


Weight,  taken  from 
Thrashing  Mill  of 


363^ 
394 

364 

286i 

3391- 

399 
367 
361 


lbs.  lbs. 
154  61i 
92 


■5  2 


bushs. 
5-9'-i6 
5-750 

6-250 

5  970 
6375 

6  000 

4-750 

5-562 

6-.381 
6.000 
5-939 


2  5 


J-   Of  — 


2-2     ^L 


o  _ 

S :?  =  ? 


1 1-  ® 


bush. 


•29 

•014 

419 

-044 


•425 
•044 


bush. 
•206 


1-206 


54  EXPERIMENTS  CPON  WHEAT,  [Appendix 

Remarks.— Spring  Wheat  after  Turnips,  South-Lawn.  Soil  loamy  clay ;  subsoil  clay 
Drained  every  furrow  before  breaking  up  from  old  grass  in  the  autumn  of  1839 ;  ploughed 
deep  and  subsuiled  in  spring  of  1841.  Wheat  sown  5th  February,  1842 ;  manures  applied  I3th 
May;  crop  cut  24th  August;  and  thrashed  10th  September,  1842.  The  quantity  of  land  in 
each  plot  was  one-eighth  of  an  imperial  acre. 

2°.  The  object  of  the  second  series,  made  at  Barochan,  was  to  ascertain  tho 
relative  effect  of  certain  mixed,  chiefly  saline ^  manures  applied  as  top-dressings  to 
winter  wheat. 

Results  of  Experiments  with  various  substances  used  as  top  dressings,  upon  Winter  Wheat. 
Dressed  9th  May,  and  cut  7th  September,  1842.  The  quantity  of  land  in  each  plot  teas  one- 
sixteenth  of  an  imperial  acre. 


No. 


crook's  farm, 
barochan. 

Description  of 
Top  Dressings. 


Nothing 

Natural  Guano.. . 
Turnbull's    Artificial 

Guano 

Common   Salt 

Sulphate  of  Soda. . . 

Nitrate  of  Soda 

Common  Salt 

Dissolved  Bones. . . 

Rape-dust 

Sulphate  of  Magnesia 


3f.S 


510 


^  2  «^ 

.2."  .  w 


lbs. 
95 
115 


80 
101 

90 

110 


lbs. 
160 
230 

175 
150 

190 
170 
200 


s.  d. 
0  0 
4    4^ 


0 

4 

so 

s? 

}\ 

OS 

so 

4j> 

^0 

T^ 

S2 

T} 

^0 

6^ 

11       !|l 

^  00  -es 


3  £  t3 


bush.  lbs. 

24  56 

30  40 

24  56 

21  27 

26  30 

%  54 

28  24 


lbs. 
2560 
3680 

2800 
2400 

3040 
2720 


Remarks. — The  soil  is  a  heavy  loam,  incumbent  upon  a  deep  clay.  The  wheat  was  sown 
at  the  end  of  November,  1841,  after  a  crop  of  yellow  turnips.  The  turnips  were  manured 
with  20  tons  of  town  dung  per  acre.  Owing  to  the  severity  of  the  winter  of  1841  and  spring 
of  1842,  the  plants  were  very  thin  upon  the  ground.  In  April,  1842,  it  was  sown  down  with 
grass  seeds,  harrowed  and  rolled,  after  which  it  tillered  and  gradually  recovered.  At  the 
time  the  dressings  were  put  on  there  was  rain,  but  in  general  it  teas  dry  weather  after,  and 
in  consequence  the  top-dressings  did  not  produce  such  great  results  as  they  did  in  1841.  The 
field  was  examined  from  time  to  time,  and  the  appearance  of  each  experiment  as  noted 
down  is  fully  borne  out  by  the  results  given  in  the  table,  viz. : — No.  1  was  taller  in  the  straw, 
longer  in  the  ear,  and  of  a  darker  green  colour  than  any  of  ihe  others  ;  No.  6  was  next,  and 
No.  4  was  third.  In  point  of  appearance  there  was  in  the  others  no  perceptible  difference 
from  the  general  crop,  except  No.  3,  which  appeared  to  have  checked  the  growth  of  the 
plants,  and  from  this  ch^ck  they  scarcely  recovered  all  the  season.  It  is  however  remarka- 
ble that  wherever  common  salt  was  applied  the  grain  was  heavier  per  bushel.  It  will  be 
observed,  with  reference  to  the  experiment  upon  wheat  grown  on  this  land  last  year,  that  the 
application  of  common  salt  had  a  very  great  effect,  and  would  probably  have  also  benefitted  the 
general  crop  this  year,  had  it  not  been  for  the  extraordinary  drought  of  the  season  (see  Appen- 
dix, p.  17.) 

3°.  The  object  of  the  third  series,  made  by  Mr.  Burnet,  of  Gadgirth,  nea 
Ayr,  was  the  same  as  those  of  Mr,  Fleming.  The  mixtures  employed,  how- 
ever, were  different,  and  the  tabulated  results  are  at  least  equally  interesting, 
and  satisfactory. 

Results  of  Experiments  with  mixed  Manures  used  as  top-dressings  upon  Winter  Whea 
(Eclipse  variety),  sown  29th  October,  1841,  and  reaped  15th  August,  1342.     The  quantity 
of  land  in  each  plot  was  one-fourth  of  an  imperial  acre. 
The  soil  a  loam,  with  subsoil  of  clay ;  tile-drained  and  trench-ploughed.    Had  been  in 

beans  the  year  previous,  and  had  no  manure  with  that  crop  nor  with  the  wheat,  except  the 

above  applications,  harrowed  in  in  spring.    No.  6^  at  a  cost  of  JE2.  4s,,  has  produced  an  m> 

crease  over  No.  1  of  £6.  19s.  3i.  being  a  ^-ain  of  i,4.  15s.  3d. 


^o.  viii.\ 


EXPERIMENTS    UPON   WHEAT. 


55 


GADGIRTH, 
NEAR    AYR. 

2 

c 
O 

c 

i 
> 

c 
.2 

s 

"3, 

2^ 

•is 

Manures  applied 

"o 

o 

o'S 

s. 

a.  . 

-o 

■g 

§-£ 

o^ 

c 

2 

16lh  April. 

i 
1 

j3 

.a 
.£.0 

4) 

i 

II 

11 

ll 

cwt  qrs  lbs 

cwt  qrs  lbs 
4  3  23i 

cwt  qr«  lbs 

lbs. 

lbs. 

bshl.  lbs 

L.  s. 

L.   8. 

s.   d. 

L.  s. 

lbs.  j 

1 

No  application.. 

7  1   18i 

4  0  16 

6li 

9 

31  38 

11     1 

9E 

2 

Guano  §  cwt.    & 

I 

Wood-aslies 

7  2  18 

5024 

4  1     9 

61^ 

10 

32  20 

11     6 

0    6 



2    0 

88  i 

3 

Arlificiai    Guano 
I  cwt.   «fe  Wood 

1 
i 

ashes  i  cwt  . . . . 

6  3  25 

5  0  17 

4  1  10 

591 

9 

32  24 

11    6 

0    5 



1  12 

88 

4 

Sulpli.  of  Ammo- 
nia f^  cwt., Wood- 

ashes  Icwt 

8  3  21 

6  2    7 

5  1  lOi 

60 

17 

39  54 

14    0 

2  19 

63 

2    0 

85 

5 

Snlph.  of  Ammo- 
nia A  cwt.,  Sulph. 
of  Soda  ^  cwt.. 
&  Wood-ashes  1 

cwt 

11  0  18i 

7  0    9i 

6  2    8§ 

60 

13 

49    6 

17    4 

6    3 

16  9 

2  16 

81 

C 

Sulph.  of  Ammo- 

nia 1  cwt.,  Com- 

mon Salt  ^  cwt , 

«fc  Wood-ashes  1 

cwt 

11  1    4 

7  1  24 

6  2    6J 

60 

9 

49    0 

17    3 

5    2 

17  3 

2    4 

84 

7 

Sulph.  of  Ammo- 
nia ^cwt.,  Nitrate 
of  Soda  i  cwt., 
&  Wood-ashes  1 

cwt 

11  0    5 

7  0  23 

6  1  25       591 

11 

48  20 

16  18 

5  17 

16  li 

3    4 

70 

8 

TurnbuU's   Gua- 

no  1  cwt.,  Sulph. 

of  Lime    I  cwt., 

&  Wood-ashes.  1 

cwt 

8  0    6     .^i  2    fi 

4  2    2 

60 

23 

33  44 

11  16 

)  15 

2A 

I  16  81   i 

F.— EXPERIMENTS  UPON  PASTURE  AND  OTHER  GRASSES. 

I.  Experiments  made  by  Mr.  Alexander,  at  Wellwood,  in  1842. 

A.    On  crops  of  meadow  and  rye  grass  hay. 

\°.  One  Scots  acre  of  well-drained  mossy  meadow,  and  full  of  timothy  grass, 
was  top-dressed  during  the  last  week  of  April,  with  1  cwt.  improved  bones,  \ 
cwt.  glauber  salts,  \  cwt  of  charcoal,  all  well  mixed  with  ashes.  Result. — 
Crop  much  improved,  and  came  to  180  Ayrshire  stones  (of  24  lbs.)  per  acre. 
I  may  mention  that  this  meadow  suffered  generally  much  from  the  severe 
drought ;  the  above  kept  its  growth  best. 

2°.  One- Scots  acre  of  well-drained  mossy  meadow,  full  of  timothy  grass,  was 
toprdressed  dming  the  last  week  of  April,  with  1  cwt.  of  artificial  guano,  12 
bushels  of  humus,  well  mixed  with  a  quantity  of  ashes.  Result. — Not  so 
good;  more  affected  by  drought;,  crop  160  stones  per  acre ;  the  rest  of  the  un- 
dressed meadow  land,  on  an  average,  140  stones  per  acre. 

3°.  Three  acres  of  rye  grass  hay,  upon  a  very  light  sharp  soil,  was  top-dressed 
during  the  last  week  of  April,  with  3  cwt.  of  artificial  guano,  2  J  cwt.  of  improved 
bones,  1  cwt.  of  charcoal,  all  mixed  with  a  quantity  of  ashes.  Result. — I  can- 
riot  pronounce  that  the  hay  on  the  three  acres  was  increased  in  bulk ;  the  crop 
was  a  light  one  on  the  whole  field,  owing  to  the  severe  drought,  and  the  very 
dry  nature  of  the  soil  this  season,  therefore,  gave  this  experiment  no  fair  trial. 
I  would  say,  however,  that  I  have  rarely  seen  such  an  appearance  of  white 
clover  since  the  hay  was  cut,  and  particularly  on  the  dressed  land, 
• 

39 


56 


EXPERIMENTS    UPON    FaSTUUE    GRASS. 


lAppendtr, 


B.    On  pasture  grass. 

Three  years'  old  lea.  The  extent  2  acres  3  roods  Scots  measure,  divided  into 
three  equal  parts,  and  the  manures  applied  during  the  last  week  of  April. 

No.  1.  Dressed  with  J  cwt.  of  ammoniacal  salts,  1  cwt.  of  sulphate  of  sodei 
(glauber  salts). 

No.  2.  Dressed  with  \  cwt  of  ammoniacal  salts,  ^  cwt.  of  e;lauber  salts,  |  cwt. 
of  common  salt. 

No.  3.  Dressed  with  i  cwt.  of  ammoniacal  salts,  |  cwt.  of  glauber  salts,  ^  cwt. 
of  nitrate  of  soda. 

Results. — Nos.  I,  2,  and  3  were  much  alike ;  in  all  the  three  cases  the  vege- 
tation was  quickened  and  improved;  but,  as  is  always  the  case  with  experi- 
ments on  pasture,  unless  the  cattle  were  kept  off  for  the  whole  season,  and  the 
produce  cut,  it  is  not  easy  to  say  how  far  the  above  application  went  to  improve 
the  grass ;  but  certainly  the  small  field  did  wonders — for  it  pastured  fifteen  early 
calves  nearly  all  the  season, 

II,  The  following  carefully  conducted  series  of  experiments  were  made  by 
Mr.  Fleming,  of  Barochan,  with  the  view  of  determining  the  relative  effect  of 
saline  substances  upon  the  weight  of  the  hay  crop,  on  the  field  where  the  experi- 
mental wheat  of  1841  was  grown: — 

Result  of  Experiments  tried  upon  sown  Grass,  cut  for  Hay  on  30th  June,  1842,  Crook's 
Farnni,  where  the  Wheat  grew  in  1841.  (See  preceding  partof  this  Appendix,  p,  19.) 
The  quantity  of  land  in  each  plot  teas  one-sixteenth  of  an  imperial  acre. 


No. 


crook's  farm,  barochan. 
Description  of  Dressing. 


Nothing 

Sulphate  of  Soda 

Common  Salt 

Nitrate  of  Soda 

Sulphate  of  Soda 

Nitrate  of  Soda,  mixed.. . . 

Natural  Guano 

Silicate  of  Potash « . 

Gypsum 

Sulphate  of  Ammonia. . . . , 

TurnbuU's  Guano , 

Common  Salt 

Soot 

Hay  of  Barley  Land,  ma 
nured  with  Bane-dust,  1841 


lbs. 

21 

21 

')  ' 

14 

14     I 
1  bushel  \ 


s-i 


<a  3 


III 


£13  s  i,  M  c 


lbs. 
710 
484 
672i 
1125 
515 
932i 
757i 

820 
595 

795 


lbs. 
11,360 
7,740 
10,960 
18,100 

8,240 

14,920 

12,120 

13,120 
9,520 

12,720 


M^l 


6640 


186 
3560  256i 
760  198 

1760 '225 

—    186 

1360,228 


940   15,840  3680  305     324i       6    14 


o2  ^ 


275 
3.37 
262 
312 

362 

275 

262 

275 
312 

287 


o     eo 


tns.cwt.qrs. 


13    2 


Remarks.— Nos.  1,2,  3,  4,  5,  and  8,  were  all  dressed  on  the  9th  of  April,  the  weather  be- 
ing very  dry  at  the  time,  and  their  effects  were  hardly  perceptible  ;  but  in  the  last  week  of 
April  Nos.  3  and  4  ehowed  an  improvement  over  the  others.  We  had  heavy  rains  the  first 
week  of  May,  and  by  the  7th  of  May  the  nitrate  of  soda  (No.  3)  could  be  seen  at  a  distance  by 
the  alteration  of  the  colour  to  dark  green,  and  its  height  above  the  others  ;  upon  that  day 
Nos.  1  and  2  shewed  no  visible  alteration  from  the  ur.  Iressed.  No.  3  was  the  best  of  any  : 
taller,  and  of  a  dark  green  colour,  and  thicker  swardeo.  No.  4  showed  little  or  no  alteration 
in  colour,  but  was  fully  lofiger  than  the  general,  crop,  and  presented  the  remarkable  appearance, 
aa  did  No.  1,  in  being  nearly  all  Festuca  Rubra,  irilh  hardly  any  ryegrass,  although  of  this 
grass,  viz.  (Festuca  Rubra),  none  was  sown  ;  the  field  having  been  sown  with  rye  grass,  tim- 
othy, and  red  clover.  No.  5  darker  than  No.  4  in  the  colour,  and  good  ;  but  No.  8  hardly  im- 
proved. Nos.  6,  7,  9,  and  10,  were  dressed  upon  the  7th  of  May.  The  men  in  ploughing  up 
the  stubble  of  1841  found  that  the  ridges  which  were  top-dressed  that  season  with  nitrate  of 
soda,  were  more  difficult  to  plough,  from  the  strength  and  depth  of  the  grass  roots,  than  the 
ridges  undressed,  each  alternate  ridge  only  having  been  dressed. 

Prices  of  Manures. — Sulphate  of  soda,  7s.  per  cwt. ;  Nitrate  of  soda,  JEI.  per  cwt. ;  Natu- 
ral Guano,  25s.  per  cwt.  ;  Artificial  Guano,  8s.  per  cwt. ;  Silicate  of  Potash  or  Soluble  Glass, 
I63.  per  cwt. '  Sulphate  of  Ammonia,  £1.  per  cwt. 


No.    VIII.]  EXPBniMENTS  UPON  MIXED  CROPS.  67 

G.— EXPERIMENTS  UPON  MIXED  CROPS. 

The  following  interesting  experiment  was  made  by  Mr.  Alexander,  for  the 
purpose  of  ascertaining  the  effect  uf  a  mixture  of  gypsum  and  common  salt  upon  a 
mixed  crop  of  oats,  beans,  and  peas : — 

Result  of  an  experiment  upon  the  effect  of  gypsum  and  common  salt,  applied 
as  a  top-dressing  at  Wellwood,  Muirkirk,  1842. 

Four  Scotch  acres  of  strong  soil,  bordering  on  clay,  broken  up  ft-om  two-year- 
old  pasture,  were  sown  with  oats,  beans,  and  peas  (which  is  called  in  Scotland 
mashlem,  and  is  a  first-rate  fodder  for  dairy  stock).  They  all  came  well  up,  but 
worming  and  other  causes  injured  the  crop  so  much  that  I  had  serious  intention 
of  ploughing  it  up,  and  sowing  turnips.  Instead  of  doing  so,  I  top-dressed  the 
whole  four  acres  with  the  following  substances,  well-pounded  and  mixed  to- 
gether, and  this  being  done  immediately  before  copious  rains,  the  mixture  was 
washed  into  the  soil : — 13  cwt.  gypsum  (from  TurnbuU),  which,  with  carriage, 
cost  8s.  ;  4  cwt.  common  salt,  which,  with  caniage,  cost  8s. ; — this  and  the 
gypsum,  16s.     Cost  of  top-dressing,  4s.  per  acre. 

The  effect  was  like  magic  ;  the  plants  immediately  assumed  a  deeper  green 
colour,  and  grew  wonderfully,  and  this  field  took  the  lead  of  all  my  other  oats, 
and  when  reaped  the  field  generally  was  the  best  I  had.  Oats,  beans,  and  peas 
were  all  particularly  well  filled.  I  may  state  further,  that  after  the  dressing  it 
stood  the  severe  drought  better  than  any  of  my  other  crops.  Wellwood  is  23 
miles  from  the  sea,  and  550  feet  above  it. 

From  other  experiments  which  I  had  before  made,  but  which  I  shall  not  fur- 
ther enter  on  here,  I  am  convinced  that  common  salt  is  a  great  auxiliary  in  that 
locality  (if  not  to  most  others  distant  from  the  sea),  and  it  ought  to  be  far  more 
extensively  used. 

H.— EXPERIMENTS  UPON  BEANS. 

The  following  experiments  were  made  by  Mr.  Alexander,  of  Southbar,  at  his 
farm  of  Wellwood,  m  Ayrshire,  with  the  view  of  ascertaining  the  relative  appa- 
rent effects  of  different  saline  top-dressings  upon  beans  at  different  periods  oj 
their  growth : — 

Experiments  made  at  Wellwood  upon  a  crop  o? beans  (1842). 

The  ground  was  manured,  previous  to  sowing,  with  15  tons  of  farm-yard 
dung  per  Scotch  acre,  and  the  other  manures  applied  when  the  beans  tCere  about 
two  jn/:hes  high  (they  were  sown  in  broad-cast).  The  extent  of  ground  was  2^ 
acres  Scots  measure,  divided  into  four  equal  proportions. 

No.  1.  Dressed  with  §  cwt.  of  sulphate  of  soda,  i  cwt.  of  nitrate  of  soda. 
Result. — The  effect  of  the  dressing  was  seen  soon  after  application,  by  deep- 
ening the  colour  of  the  plants.  The  beans  were  deficient  in  straw,  but  remark- 
ably well  podded  and  filled. 

No.  3.  Dressed  with  ^  cwt.  of  sulphate  of  soda,  1  cwt.  of  gypsum.  Result. 
— More  straw  than  the  foregoing,  and  rather  better  crop. 

No.  3.  Dressed  with  i  cwt.  improved  bones,  i  cwt.  artificial  gl^ano,  3  bushels 
TurnbuU's  humus.     Result. — About  the  same  as  No.  1. 

No.  4.  At  first  not  dressed ;  but,  in  consequence  of  being  weakly,  was  after- 
wards top-dressed  with  3  cwt.  of  gypsum,  and  1  cwt.  of  common  salt,  done  in 
consequence  of  the  highly  beneficial  effect  produced  on  the  four  acres  of  mashlara 
crop  above  alluded  to.  Result. — Though  done  so  late  that,  the  beans  were  already 
coming  into  flower,  it  helped  them  much,  and  they  ended  as  well  as  any  of  the 
above.  It  may  here  be  remarked,  that  all  the  beans  were,  particularly  for  that 
high  district,  heavy,  being  on  trial  soon  after  mowing  65  to  66  lbs.  per  bushel. 

I.  Observations  upon  the  effect^  the  top-dressings  applied  m  1841  upon  the  crop 
^    0/1842. 
The  following  remarks  are  quite  as  interesting  as  any  thing  contained  in  the 
numerous  experiments  made  this  year  at  Barochan  by  Mr.  Fleming's  skilful 


\ 


58  EXPERIMENTS  UPCN  MIXED  CROPS.  [Appendix, 

overseer.  They  are,  I  believe,  the  first  syslemntic  series  of  observations  of  the 
Kind  yet  published.  They  are  valuable,  therefore,  as  the  first  steps  in  the  line 
oi prolonged  observations  upon  the  same  land  made  during  successive  seasons, 
by  which  prolonged  observations  only  can  we  hope  to  eliminate  the  effect  of 
our  variable  seasons,  and  to  arrive  at  true  deductions  in  regard  to  the  kind  and 
amount  of  effect  which  this  or  that  manure  is  fitted  to  produce. 

I  do  hope  that  Mr.  Gardiner,  who  is  capable  of  observing  so  well,  and  of 
experimenting  so  accurately,  will  not  lose  the  opportunity  which  the  present 
year  will  afford  him  of  continuing  these  important  observations: — 

1°.  Top-dressings  upon  hay,  Covenlea  field  (see  Appendix,  p.  17).  On 
looking  over  this  field  at  different  times,  and  particularly  early  last  sprijig,  the 
square  on  which  nitrate  of  soda  and  bones  mixed  had  been  sown  was  earlier, 
and  of  a  darker  green  colour,  than  any  of  the  rest  of  the  field,  and  when  stocked 
with  cattle,  the  portion  top-dressed  was  more  relished,  and  consequently  always 
eaten  quite  bare. 

•  2°.  Upon  part  of  the  pleasure-ground — soil  a  very  stiff  blue  clay — nitrate  of 
soda  was  sown  at  the  rate  of  160  lbs.  per  aci-e.  After  this  application  white 
clover  came  up  very  thick  and  strong,  and  it  was  cut  three  different  times  with 
the  scythe,  and  each  time  it  came  up  stronger  and  thicker  than  the  surrounding 
grass,  whilst,  before  dressing,  it  was  the  weakest,  and  this  season,  1842,  it  is 
better,  and  the  portion  dressed  still  easily  distinguished. 

3°.  The  field  at  Crook's  fai-m  (see  Appendix,  p.  17),  which  had  been  top- 
dressed  with  nitrate  of  soda  applied  on  each  alternate  ridge,  on  being  ploughed  up 
from  hay  stubble  was  found  tougher  upon  the  dressed  ridges,  the  grass  roots 
being  stronger  and  deeper  in  the  soil  of  those  ridges  which  had  been  dressed. 

4°.  At  p.  21  of  this  Appendix  an  experiment  upon  moss-oats  is  recorded. 
This  was  sown  down  with  a  mixture  of  grass  and  clover  seeds,  and  cut  for  hay 
this  season,  1842.  In  examining  the  hay  crop  some  of  the  dressings  on  the  oats 
of  last  year  seemed  to  have  had  a  good  eflfect  on  the  hay  crop  of  this  year.  Nos. 
1  and  2  were  the  worst  of  any;  No.  3  very  little  better,  rather  more  clover ;  No. 
4  excellent,  very  thick  of  red  and  white  clovers  and  rye-grass,  and  the  hay  was 
of  a  good  quality  ;  No.  5  a  little  better  than  No.  3,  but  far  from  being  equal  to 
No.  4;  No.  6  the  best  of  any,  full  of  red  and  white  clovers  and  rye-grass,  and 
had  three-fourths  more  hay  upon  it  than  all  the  others,  except  No.  4  ;  No.  7  not 
better  than  the  undressed ;  Nos.  6  and  4  presented  a  most  remarkable  appearance 
compared  with  the  others,  and  any  person  seeing  them,  and  not  knowing  the 
circumstances  of  the  case,  would  have  said  that  these  two  portions  only  had 
been  cultivated,  whilst  the  rest  had  been  left  in  a  state  of  nature.  After  being 
cut  for  hay,  the  aftermath  of  these  two  portions  still  presented  the  same  difference 
of  appearance  in  the  sward,  and  they  continue  of  a  better  colour. 

A.  F.  Gardiner. 


.  GENERAL  REMARKS  ON  THE  ABOVE  EXPERIMENTS  OF  1842. 

However  valuable  the  above  experiments  may  be,  and  however  interesting 
the  results  to  which  some  of  them  may  appear  to  lead,  it  is  of  importance  to 
bear  in  mind — 

1°.  That  they  are  the  results  only  of  a  ringle  season,  and  tliat  a  remarkably 
dry  one. 

2°.  That  they  show  the  eflfect  of  the  substances  employed  in  certain  localities 
only — the  localities  differing  in  the  nature  of  their  soil — m  their  distance  from, 
and  height  above,  the  sea — and  in  the  average  fall  of  rain  to  which  they  are 
subject. 

3°.  That  the  results  are  obtained  by  trials  upfn  certain  varieties  of  each  crop 
only,  and  may  not  be  obtained  even  on  the  same  spots  with  other  varieties — of 
turnips  for  example,  of  potatoes,  oats,  wheat,  or  barley. 

4°.  And  that  other  causes,  not  yet  noted,  may  have  existed  of  sufficient  in- 


No.   VJIL]  •     EXPERIMENTS   UPON   TURNfPS.  69 

fluence  to  prevent  the  exact  results  from  being  obtained  upon  a  repetition  of  the 
experiment. 

5°.  Above  all,  it  must  be  borne  in  mind  that  we  are  yet  in  the  first  infancy  of 
accurate  experimental  agriculture — that  it  will  take  many  careful  repetitions  of 
our  experiments  before  we  can  ehminate  the  effects  of  the  seasons — of  the  alti- 
tude of  our  farms,  their  distance  from  the  sea,  the  falls  of  rain  to  which  they 
are  subject,  and  the  kind  of  soil  of  which  they  consist.  In  the  mean  time  our 
most  careful  deductions  must  be  considered  as  partial  only,  and  as  open  to  doubt 
—as  facts  by  the  combination  and  comparison  of  which  we  are  hereafter  to  ar- 
rive at  more  general  truths. 

With  these  preliminary  observations,  I  turn  to  the  experiments  themselves — 

A. — The  experiments  upon  turnips. 

The  first  series,  those  of  Lord  Blantyre — except  the  general  answer  that  saline 
substances  cannot  replace  farm-yard  raanure — afford  no  very  satisfactory  results. 
They  exhibit,  indeed,  some  striking  circumstances — such  as 

1°.  That  100  lbs.  of  salt  per  acre  may,  in  a  diy  season,  reduce  the  natural  or 
unaided  produce  of  ti^rnips  one-half— and  that  the  same  weight  of  nitrate  of  soda 
may  reduce  it  one-fourth!  » 

2°.  That  in  such  a  season  as  much  as  16  cwt.  of  rape-dust  per  acre  may  be 
applied,  one-half  drilled  in,  and  one-half  as  atop-dressing,  without  producing  any 
sensible  benefit. 

3°.  That  the  same  may  be  the  case,  if  eight  cwt,  of  rape-dust  be  drilled  in, 
and  half  a  cwt.  of  nitrate  of  soda  be  afterwards  applied  as  a  top-dressing — 
while  if  the  same  weight  of  common  salt  be  used  as  a  top-dressing  "instead, 
the  crop  will  be  increased  one-half 

These  results  are  too  anomalous  to  be  considered  for  the  present  as  more  tha* 
accidental.  They  may  possibly  be  explained  either  by  the  different  degrees  (A 
moisture  of  the  several  parts  of  the  field  in  which  the  mixtures  were  applied-— 
or  on  the  supposition,  which  is  very  probable,  that  in  the  concentrated  state 
some  of  these  saline  substances  are  more  hurtful  to  the  groacin/r  plant  than  others. 
It  is  to  be  regretted  that  the  season  was  so  unpropitious  to  this  series  of  experi- 
ments, for  though  the  following  experiments  of  Mr.  P'leming  afford  some  valuable 
information,  further  knowledge  still  is  wanted  in  regard  to  the  relative  effects  of 
different  saline  substaiices  upon  the  growth  of  turnips,  where  no  fermentible  ma-, 
nure  is  applied. 

4°.  In  these  experiments,  a  striking  contrast  is  presented  between  the  effects 
of  rape-dust  and  those  of  guano,  16  cwt.  per  acre  of  the  former  gave  only  3 J 
tons  of  turnip  bulbs,  while  2  cwt.  per  acre  of  the  latter  gave  5  tons.  It  appears, 
therefore,  that  rape-dust  requires  moist  weather  or  occasional  rain,  while  guano, 
even  in  very  dry  seasons,  will  prodAtce  a  considerable  effect.  This  is  consistent  with 
what  we  know  of  the  employment  of  the  latter  substance  as  a  manure  on  the 
arid  plains  of  Peru. 


II.  The  next  four  series  of  experiments,  those  of  Mr.  Fleming,  are  rich  in  re- 
sults and  suggestions, 

1°,  Limits  of  error. — The  first  observation  which  a  careful  examination  of 
them  will  lead  the  reader  to  make — and  it  appears  to  me  to  be  a  very  important 
one  in  reference  to  all  future  experiments  of  this  kind — is  suggested  by  the  se- 
cond series — those  upon  early  yellow  turnips,  p.  44. 

In  this  series  there  are  included  two  plots  (Nos.  5  and  18),  upon  which  no 
manure  was  used.  Upon  one  of  these  the  produce  amounted  to  12  tons  17  cwt., 
upon  the  other  to  11  tons  8  cwt.  only — being  a  difference  of  U  tons,  or  one- 
eighth  of  the  whole.  This  difference  between  two  equal  portions  of  the  same 
field,  apparently  similar  in  soil,  could  scarcely,  I  think,  have  been  anticipated, 
and  it  shews  that — where  the  produce  obtained  by  the  application  of  two  tinlike 
w^nures,  to  this  turnip  crop,  does  not  differ  7nore  than  1  i  tons  per  acre,  the  effects 


60  EXPERIMENTS  UPON   TURNIPS.  [AppCndix, 

of  the  two  manures  may  be  cmisidered  as  practically  equal — since  this  amount  of 
QilTerence  may  have  arisen  from  the  unlike  qualities  of  the  two  plots  of  land,  to 
which  the  manures  were  respectively  applied. 

This  is  an  important  practical  rule  for  enabling  us  to  judge  accurately  in 
regard  to  the  true  effect  of  the  several  manures  employed  in  the  series  of  experi- 
ments (p.  44)  referred  to,  but  the  fact  itself  suggests  also  an  important  modifi- 
cation in  the  mode  of  conducting  all  similar  comparative  experiments  in  future. 

In  my  previously  published  Suggestions,  I  have  recommended  the  setting 
apart  o^  one  undressed  portion  only  of  the  field  on  which  the  trials  were  made — 
considering  that  the  produce  of  this  portion  would  represent  the  average  fertility 
of  the  whole  undressed  part  of  the  field  But  these  experiments  of  Mr.  Flem- 
ing seem  to  shew  that  this  opinion  cannot  safely  be  entertained.  It  appears  to 
be  necessary,  therefore,  in  all  future  experiments  from  which  accurate  deduc- 
tions are  intended  to  be  drawn — that  two  undressed  plots,  at  least,  should,  in  earn 
case,  be  measured  out,  and  their  relative  produce  ascertained,  in  order  to  afford  a 
trust-worthy  average  of  the  unaided  fertility  of  the  land. 

Suggestion  I. — For  the  clearing  up  of  this  point,  however,  it  would  be  very 
desirable  to  institute  a  series  of  weighings  of  the  produce  of  equal  portions  of 
land,  in  several  different  parts  of  the  same  field,  the  whole  of  which  has  been 
tilled  and  manured  in  the  same  way.  This  would  throw  some  certain  and  sat- 
isfactory light  upon  the  amount  of  variation  which,  from  natural  causes,  may 
take  place  in  the  same  crop,  grown  upon  different  parts  of  the  same  field,  and 
under  the  same  circumstances.  We  should  thus  be  enabled  to  allow  for  the 
influence  of  natural  causes  upon  the  results  of  such  experiments  as  are  made, 
with  the  view  of  determining  the  true  action  of  the  different  manures  we  apply. 

Suggestion  II. — But  if  some  slight  difference  in  the  soil,  which  the  eye  cannot 
detect,  be  capable  of  materially  affecting  the  natural  produce  of  the  unmanured 

{)arts  of  a  field,  it  may  also  be  suflSicient  to  modify — that  is,  to  increase  or  to 
essen — the  effects  produced  by  the  saline  and  other  manures  we  apply  to  the 
diflferent  parts  of  the  same  field.  It  suggests  itself,  therefore,  as  the  more  pru- 
dent and  wary  course  of  experiment  to  dress  two  plots  at  least  with  each  of  the 
manures  whose  relative  virtues  we  are  desirous  of  testing,  and  these  in  different 
parts  of  the  piece  of  land  upon  which  our  trials  are  made.  The  mean  produce 
of  the  two  or  more  plots  we  thus  dress,  compared  with  the  mean  produce  of 
those  to  which  no  dressing  has  been  given,  will  indicate  more  nearly  the  aver- 
age eflfect  of  the  manure  we  have  been  tiying,  upon  the  given  soil  and  crop. 

The  reader  will  perceive  in  the  new  precautions  thus  indicated,  one  of  those 
practical  results  which  year  by  year  will  necessarily  flow  from  the  continuation 
of  the  train  of  inductive  experimental  research,  now,  I  hope,  fairly  entered  upon 
by  the  practical  agriculture  of  our  country. 

2°.  Guano. — Among  the  other  experiments  upon  turnips  here  stated,  those 
upon  guano  are  the  most  practically  successful.  Thus,  per  acre,  without  any 
farm-yard  manure 

3    cwt.  of  guano  alone  gave  23  tons    S  cwi.  oi  Swedes         .        .        (p- 44)- 

m    blkl^fwooTles  I  ^^  '»-    2  =-■  or  Early  VeUo,.        .         (p.  44). 

5    cwt.  of  guano  alone  32  tons  15  cwt.  of  White  Globes        .        (p.  46). 

3i  cwt.  do.  20  tons    0  cwt.  of  Yelhno  t^  White  mixed  f  p.  46}. 

3j  cwt.  do.  28  tons    0  cwt.  oi  Purple-topped  Yellow   (p  47). 

These  results  are  very  gratifying,  since  they  seem  to  shew  that  for  the  turnip 
crop  this  light  and  portable  manure  may  be  substituted  with  safety  for  fann- 
yard  dung.  But  they  are  more  gratifying  in  connection  with  the  large  reduction 
which  has  lately  taken  place  in  the  price  of  this  substance.  In  norte  of  the 
cases  above  mentioned  did  the  quantity  applied  exceed  5  tons  per  acre.  This 
quantity  may  now  be  purchased  for  three  guineas,  though  when  these  experi- 
ments were  undertaken  it  cost  -CG   5s. 

It  is  no  small  matter  of  congratulation,  tha.  this  important  reduction  has  been 


No    VIIl.]  EXPERIMENTS   UPON    TURNIPS.  61 

mainly  brought  about  by  the  expression  of  scientific  opinion,  and  by  the  readi- 
ness with  which  various  persons,  manure-manufacturers  and  others,  have  put 
in  practice  the  suggestions  contained  in  the  preceding  part  of  this  Appendix 
(p.  26),  for  the  formation  of  an  artificial  mixture  in  imitation  of  the  natural 
guano.  The  fear  of  competition  produced  its  natural  effect  upon  the  market, 
and  led  the  importers  of  this  substance  to  content  themselves  with  a  smaller 
profit.  It  is  to  be  hoped  that  the  more  extended  sale  which  has  followed  the 
reduction,  will  leave  the  spirited  merchants  who  first  brought  it  into  the  country 
no  reason  to  regret  the  diminution  in  price.  The  benefits  which  the  practical 
agriculturist  derives  from  one  such  reduction  as  this  are  not  all  at  first 
sight  perceptible.  The  demand  for  guano  has  so  greatly  lessened  the  call  for 
rape-dust,  that  it  has  also  fallen  in  price  from  £8  to  £5  10s,  per  ton.  Thus 
ramified  and  extended  are  the  results  of  a  single  chemical  investigation — or  the 
publication  of  a  single  well-founded  scientific  opinion. 

3*^.  Artificial  Chtano. — In  connection  with  this  subject  it  is  important  to  as- 
certain to  what  extent  the  attempts  to  manufacture  a  substitute  for  the  natural 
guano  have  been  attended  with  success — in  so  far  as  the  turnip  crop  is  concern- 
ed. The  only  comparative  results  which  the  above  experiments  present,  are  the 
following — those  upon  Swedes  being  obtained  by  the  use  of  o  cwt.  of  each 
mixture,  those  upon  the  yellow  and  white  turnips  by  the  use  of  5  cwt.  of  each: — 

Swedes.  Early  Yellow.  White  Globe. 

1°.  Nothing  .        .         .     12  tons  5  cwt.    12  tons  17  cwt.    — tons — cwt. 

2°.  Natural  guano  .  .  23  "  8  "  32  "  2  "  32  "  15  " 
3°.  Barochan  artificial  guano  17  "  14  «  24  "  2  "  22  "  10  " 
4°.  Turnbull's  artificial  guano  14     "  11    "      21     "      4    "      —    «    _    «' 

These  results  show  that,  when  equal  quantities  are  employed,  equal  results 
are  not  obtained  from  the  natural  guano  and  from  the  artificial  mixtures. 
It  also  appears  that  Mr.  Fleming's  mixture  is  much  more  efficacious  than  ths^ 
of  Mr.  Turnbull.  They  are  made  up,  with  some  modifications,  after  the  recipk 
given  in  the  preceding  part  of  this  Appendix  (p.  25),  but  are,  no  doubt,  suscep- 
tible of  improvement.  It  is,  indeed,  one  of  the  indirect  benefits  which  will  re- 
sult from  the  introduction  of  this  foreign  manure,  that  it  will  stimulate  to  expe- 
riments, by  which  we  shall,  no  doubt,  at  last  successfully  imitate  it — and  wili 
lead,  at  the  same  time,  to  a  more  general  and  thorough  understanding  of  the 
principles  upon  which  mixed  manures  ought  to  be  compounded,  and  of  the 
mode  of  preparing  them  with  the  greatest  possible  economy.  Many  crude  mix- 
tures may  be  made  at  first,  by  dealers  in  manure  and  others,  and  many  instan- 
ces of  want  of  success  may  occur,  but  now  that  we  have  adopted  the  system  of 
recording  results,  whether  apparently  successful  or  the  contrary,  there  is  little  fear 
of  our  arriving  at  satisfactory  and  economical  truths  at  last. 

Suggestion  III. — In  experiments  made  for  the  purpose  of  aiding  the  real  ad- 
vance of  scientific  agriculture,  I  would  suggest  that  no  mixture  should  be  used  of 
which  the  composition  is  not  exactly  knowji — which,  therefore,  has  not  been  either 
made  by  the  experimenter  himself  or  by  some  dealer  upon  whose  honor  perfect 
reliance  is  to  be  placed.  The  use  of  the  random  mixtures  now  sold  under  so 
many  different  names,  however  successful  they  may  be  in  this  or  that  case,  can 
never  lead  to  the  discovery  of  useful  agricultural  principles,  and,  therefore,  are 
unworthy  of  the  attention  of  the  cultivator  of  inductive  experimental  agriculture. 

i°.  Sulphate  of  ammonia. — These  remarks  lead  me  to  notice  the  effect  ascrib- 
ed in  Mr.  Fleming's  second  table  (p.  44),  to  sulphate  of  ammonia — one  cwt. 
of  which  nearly  doubled  the  crop.     Thus — 

The  unmanured  soil  gave        .         .         12  tons  17  cwt. 
With  1  cwt.  of  sulphate  of  ammonia        24    "     11     " 

l^his  is  exactly  equal  to  the  effect  produced  by  15  cwt.  of  rape-dust  at  a  cost  of 
X(i  iOs.  But  the  sulphate  of  ammonia  here  employed  was  that  prepared  by 
the  Messrs.  Turnbull,  of  Glasgow — which  is  not  merely  sulphate  of  ammonia, 
but  a  variable  and  undetcrvmied  mixture.    It  is  prepared  from  urine,  and  I  be- 


I 


62  EXPERIMENTS  UPON  TURNIPS.  [Appendix 

lieve  is  contaminated  also  with  a  considerable  proportion  of  saline  substances 
artificially  added  to  it.  That  it  contains  many  substances  useful  to  plants  there 
can  be  no  doubt,  and  that  it  may  prove  a  valuable  manure  is  exceedingly  pro- 
bable, but  imdcr  its  present  name  it  can  only  lead  to  false  deductions  in  expe- 
rimental agricultui'e — and  the  use  of  it,  therefore,  in  comparative  tiiajs  such  as 
these  we  are  now  discussing,  ought  to  be  avoided.  It  is  only,  as  I  have  already 
said,  from  the  use  of  pure  substances  mixed  in  known  proportions,  iJiat  valuar 
ble,  because  undoubted,  conclusions  can  be  drawn.  It  is  in  vain  co  attempt  to 
eliminate  the  effects  of  diversity  of  soil  and  climate,  if  new  causes  of  diversity 
are  introduced  by  tlie  very  substances  with  which  our  experiments  are  made. 

5°,  Bones  dissolved  in  muriatic  acid. — The  action  of  bones  is  not  in  general 
exhausted  in  a  single  season.  If  they  are  in  the  state  of  fine  dust,  they  decom- 
pose more  quickly  and  cease  to  act  in  a  shorter  space  of  time.  By  dividing 
them  still  more  minutely,  or  by  solution  in  an  acid,  it  has  been  thought  that 
their  apparent  efficacy  might  be  increased.  Mr.  Fleming,  in  1841,  made  some 
experiments  which  seemed  to  justify  this  conclusion.  In  the  present  tables 
other  results  are  exhibited,  which  favovu  the  same  opinion.  I  place  togethei 
here  the  results  upon  potatoes,  as  well  s,s  upon  turnips,  for  the  purpose  of 
comparison : — 

Bone^ust.         Bones  in  rmtriatic  add. 


16CWT. 

18  CWT. 

3  CWT. 

10  CWT. 

tons.  cwt. 

tons.  cwf. 

tons.  cwt. 

tons.  cwt. 

Swede  Turnips 

14    17 

—     — 

—     — 

18    11 

White  Don  Potatoes 

—    — 

9     15 

12    15 

—    — 

These  results,  the  only  ones  contained  in  our  tables  which  can  be  compared 
together,  are  both  greatly  in  favour  of  the  dissolved  bones,  in  so  far  as  the  action 
upon  the  first  crop  is  concerned.  It  will  require  longer  obsei-vation  to  deter- 
mine in  which  form  the  same  weight  of  bones  will  produce  the-.more  lasting 
effects — and  will  be  the  more  economical  on  the  whole. 

6°.  NP'Tate  of  soda. — The  effect  of  1  cwt.  of  this  salt  per  acre  upon  the  early 
yellow  turnip  is  very  remarkable  (p.  44),  having  given  upwards  of  27  tons  of 
bulbs,  at  a  cost  of  25s.  It  is  to  be  regretted  that  no  similar  experiment  is  re- 
corded upon  the  other  varieties  of  turnip,  either  by  Mr.  Fleming  or  by  Mr.  Al- 
exander. In  the  text  (Lecture  XV.,  p.  335  to  p.  342)  an  abstract  of  all  the  pub- 
lished results  hitherto  obtained  by  the  use  of  nitrate  of  soda  will  be  found  in  a 
tabulated  form. 

7°.  Lime. — An  interesting  result  in  Mr.  Fleming's  first  table  may  hereafter 
lead  to  some  satisfactory  experimental  determinations  of  the  points  considered 
still  doubtful  in  regard  to  the  form  in  which,  and  the  time  when,  lime  may 
be  most  efficaciously  applied,  in  reference  to  the  culture  of  particular  crops.  He 
caused  carbonate  of  lime  and  caustic  (newly  slaked  1)  lime  to  be  sown  in  the 
drills  without  manure,  and  the  effect  upon  the  crop  of  Swedes  was  as  follows : 
Soil  unmanured  .....  12  tons  5  cwt. 
Carbonate  of  lime,  20  bushels  .         .         16      "    11    " 

Caustic  lime,  50  bush  els  .         .         11      "     8    " 

The  immediate  effects  of  lime  applied  in  these  two  forms  was  veiy  different — 
the  caustic  lime  lessened  the  turnip  crop,  while  the  carbonate  increased  it  by 
4f  tons.  This  effect  most  probably  arose  from  the  lime,  in  its  caustic  state, 
taking  from  the  soil  the  carbonic  and  other  organic  acids  from  which  the  roots 
in  the  early  infancy  of  the  plant  would  have  derived  a  portion  of  their  nourish- 
ment, and  thus  retarding  and  stunting  their  growth.  At  all  events  the  experi- 
ment seems  to  indicate  that  lime  ought  to  be  in  the  state  of  carbonate— the  mild 
state — more  or  less  entirely,  if  it  is  intended  to  benefit  the  crop  to  which  it  is 
immediately  applied.  When  mixed  .with  manure,  however,  where  vegetable 
matter  abovinds  in  the  soil,  or  where  the  lime  is  merely  harrowed  into  the  sur- 
face— in  all  which  cases  it  will  readily  become,  in  a  great  measure,  saturated 
with  carbonic  acid — the  skilful  fanner  will  understand  that  the  deduction  drawn 
from  the  pre^ding  experiment  will  not  apply. 


No.  VIIL]  EXPERIMENTS  UPON   TURNIPS.  G3 

8°.  Rape-dust — The  results  exhibited  in  this  year's  experiments,  generally, 
are  not  so  favourable  to  the  employment  of  this  substance  as  was  to  be  expect- 
ed. The  reason,  however,  is,  probably,  that  which  has  already  been  suggested 
in  discussing  the  results  obtained  at  Lennox  Love — that  rape-dust  requires  a 
moist  soil  or  occasional  showers.  But  this  itself  is  an  important  jrrobable  deduction. 
The  reader  will  find  a  comparative  view  of  the  whole  of  the  results  with  this 
substance  in  the  text  (see  Lecture  XVII.) 

9°.  Animal  Charcoal. — The  effect  of  animal  charcoal  upon  Swedes  in  Mr. 
Fleming's  experiments  is  only  inferior  to  that  of  guano.  It  is  certainly  deserv- 
ing of  further  trials,  and  especially  in  comparison  with  what  is  called  exhausted 
animal  charcoal — that  which  has  already  been  used  in  the  refining  of  sugar. 
In  France,  the  latter  is  said  to  be  prefen-ed  to  the  former,  and  to  be  sold  by  the 
sugar  refiners  at  a  higher  price  than  they  pay  for  it  in  the  recently  prepared 
state. 

10°.  Other  mixed  manures. — In  regard  to  other  mixed  manures,  the  reader 
will  find  much  practical  information  by  the  study  especially  of  No.  3  of  Mr. 
Fleming's  tables,  p.  45 ;  and  of  Nos.  1  and  2  of  those  of  Mr.  Alexander,  p.  46. 
These  are  the  more  worthy  of  the  attention  of  the  practical  man,  since  Mr.  Flem- 
ing considers  himself  justified  in  remarking  as  the  general  result  of  the  experi- 
ments in  p.  45,  thai  any  of  the  mixtures  used  will  in  his  land  produce  an  ave- 
rage crop  of  turnips  at  a  less  expense  than  fann-yard  manure.  This  is  the  kind 
of  result  which  it  ought  to  be  the  ambition  of  every  practical  man  to  work  out 
for  himself  upon  his  own  land. 

11°.  Size  and  weight  of  Jndbs. — There  remains  only  one  other  topic  in  con- 
nection with  these  experiments  to  which  space  will  permit  me  at  present  to  ad- 
vert. In  the  remarks  upon  the  table  inserted  in  p.  44,  it  is  stated  tliat  the  tur- 
nips on  the  plots  dressed  with — 

Guano  and  wood-ashes — were  pre-eminent  for  size  of  bulbs. 

Sulphate  of  ammonia — large  in  buW),  bid  soft,  and  light  in  weight. 

Potash  and  lime,  salt  and  lime,  sulphate  of  magnesia,  nitrate  of  ^oAsl—sttuUI 

in  bulb  J  but  firm  and  solid. 
Bone-dust   and  the  artificial  guanos — both  containing  bones — Vie  bulbs  firm 

OMi  soli'i,  but  not  remarkable  in  siz':. 
Now  upon  the  solidity  of  the  bulb — other  things  being  equal — it  may  be  pre- 
sumed that  tlie  relative  nourishing  properties  of  different  species  of  turnip  will 
materially  depend.  The  quantity  of  water  which  different  specimens  of  the 
same  variety  of  turnip  contain  varies  from  79  to  91  per  cent. — that  is,  sovie  tur- 
nips of  the  same  species  contain  only  four-fifths,  whi.k  others  contain  upwards  of 
nine-tenths  of  their  weight  of  wrotcr'.  In  other  words,  the  same  variety  of  turnip 
may  contain  such  unlike  quantities  of  water,  that  2  tons  grown  on  one  spot 
may  not  contain  more  than  1  ton  grown  in  another.  The  weight  of  bulbs,  there- 
fore, is  no  safe  criterion  of  t}ie  quantity  of  food  raised  on  different  parts  of  the 
same  field — where  the  general  treatment,  or  the  substances  applied  to  aid  the 
growth,  have  been  different. 

Now  in  the  above  experiments  the  guano  gave  32  tons  of  very  large,  the  sul- 

fihate  of  ammonia  24  of  soft,  and  the  nitrate  of  soda  21  of  small  and  solid  bulbs, 
t  is  probable,  therefore,  that  the  actual  quantity  of  food  raised  by  the  aid  of  the 
nitrate  of  soda  was  much  greater  than  even  by  the  natural  gueino.  It  may  also 
have  been  that  the  I4j  tons  of  solid  bulbs  given  by  the  sulphat||of  magnesia, 
or  the  12^  raised  from  the  land  without  manure  at  all,  may  have  contained  as 
much  nutriment  as  the  24  tons  of  soft  bulbs  raised  by  the  sulphate  of  ammonia. 
Suggestion  IV. — The  bare  possibility  of  such  a  circumstance  as  the  last, 
shows  how  little  absolute  confidence  we  can  place  in  the  numerical  results  as 
yet  obtained,  considered  as  evidences  of  the  greater  or  l-ess  amount  of  food,  which 
the  use  of  this  or  tliat  kind  of  manure  will  enable  us  to  raise  from  a  given  ex- 
tent of  land.  It  suggests,  also,  the  necessity  of  a  further  determination  of  the 
relative  quantity  of  water  contained  in  our  experimental  turnip  crops.  This 
will,  without  difficulty,  be  effected  by  selecting  three  or  four  turnips  of  different 

29* 


White  Don. 

Red  Don. 

Connaught  Cups. 

1  tons  1  cwt. 

6  tons  15  cwt. 

5  tons  15  cwt. 

18     "      9   '* 

(<      (( 

(J      (( 

(t    «{ 

14    "       6    " 

13    "      14    " 

12    "      6   " 

10    "       0    " 

13    «        0    '' 

64  EXPERIMENTS  UPON  POTATOES,  [Appendix^ 

sizes  from  each  sample — cutting  a  slice  from  either  side,  and  one  from  the  mid- 
dle of  each  turnip — weighing  the  whole — drying  them  then,  first  in  the  air, 
afterwards  before  a  gentle  fire,  and  lastly  in  an  oven  so  hot  as  not  to  brown  white 
paper  or  dry  flour,  and  then  weighing.  The  loss  being  the  weight  of  the  water 
m  the  turnips,  will  enable  the  experimenter  to  determine  the  relative  quantities 
of  food  raised  upon  his  different  plots,  and  therefore  the  relative  value  of  his 
different  applications  or  methods  of  culture. 

In  this  suggestion  the  re*ler  will  perceive  another  of  those  precautions  which 
the  prosecution  of  our  experimental  inquiries  renders  necessary — future  years 
will  suggest  others — but  the  increase  of  trouble  will  not  deter  the  zealous  la- 
bourer in  this  important  field — for  the  more  precautions  and  difficulties  multiply, 
the  greater  the  honour  will  be  to  those  who  by  perseverance  shall  successfully 
overcome  them. 

B. —  The  Experime7ds  upon  Potatoes. 

Nearly  all  the  experiments  in  the  first  table  of  results  (p.  48)  were  made  with 
mixed  manures. 

1°*  Chiano  and  rape-dust. — Among  these  the  effect  of  guano  is  again  striking, 
and  upon  two  of  the  varieties  gi-eatly  exceeds  that  of  rape-dust.  Thus,  the  pro- 
duce of  the  three  varieties  tried  was — 

Unaided  soil   . 
"With  3  cwt.  guano  . 
With  4  cwt,  guano  . 
With  1  ton  of  rape-dust .  12 

We  are  not  enabled,  by  the  experiments  before  us,  to  compare  its  effect  with 
that  of  farm-yard  manure. 

A  curious  question  suggests  itself  upon  the  inspection  of  the  above  numbers 
— one  which  could  scarcely  have  arisen  in  our  minds,  had  not  differences  such 
as  the  above  presented  themselves  among  the  results  of  our  experiments. 
Nothing  is  more  common  than  to  ask  which  of  several  varieties  of  potato  is  the 
more  prolific — and  a  practical  man  who  has  made  the  trial  has  no  difficulty  in 
giving  an  immediate  answer  to  the  question.  But  the  experiments  of  Mr.  Flem- 
ing seem  to  say  that  the  relative  iceight  of  crop  yielded  by  each  of  tico  or  more  va- 
rieties of  potato,  depends  upon  the  icay  in  which  you  treat  or  manure  them.  With 
one  treatment  a  variety  (A),  with  another  a  variety  (B),  will  give  the  heaviest 
crop.     Thus,  our  three  varieties  gave  with — 

White  Don.  Red  Don.  Connauglil  Cups. 

Natural  guano    .     18  tons    9  cwt.       14  tons    6  cwt,         13  tons  14  cwt, 
Rap^dust  .        .     12     "      6   "  10     "       0     "  13     "      0    " 

Both  substan«es  agree  in  saying  that  the  whit^.  is  considerably  more  prolific 
than  the  red  Don.  But  while  the  guano  adds  that  both  Dons  are  more  prolific 
than  the  Cups,  tlie  rape-dust  pronounces  the  latter  variety  to  be  superior  to  either 
of  the  former.  Now  it  may  have  happened  tliat  in  the  last  case  of  the  three,  the 
rape-dust,  from  some  circumstance  not  noticed,  may  have  acted  better  than  in 
the  other  two  cases,  and  that  in  this  way  the  discordance  may  have  arisen.  Un- 
fortunately, however,  there  are  upon  record  no  other  experiments  made  upon 
any  two  of  the  varieties  of  potato  with  otlier  substances  used  in  Uke  proportion 
— By  which  t||^  question  might  have  been  in  some  measure  solved.  But  the 
interesting,  and  as  it  may  hei-eafter  prove,  important  inquiry  suggests  itself—- 
what  is  the  order  of  relative  productiveness  of  the  several  varieties  of  the  same  culti- 
vated plant,  when  they  are  severally  dressed  or  manured  vdth  this  or  with  that  sub- 
stance? This  question  will,  no  doubt,  hereafler  lead  to  extended  series  of  very 
refined  experimental  inquiries,  from  which  not  only  much  knowledge  but  much 
practical  benefit  may  be  derived. 

Suggestion  V. — It  may  be,  for  instance,  that  a  given  variety  of  potato,  turnip, 
oat,  barley,  &c,,  is  more  valuable  as  food,  more  agreeaole  tc  the  taste,  or  bring* 


No.   VIII.]  EXPERIMENTS    UPON    POTATOES,  65 

a  better  price  in  the  market — but  by  the  ordinary  modes  of  cull'uie  is  the  least 
productive  of  those  generally  cultivated.  It  would  then  be  not  only  an  interest- 
ing, but  an  important  economical  question  to  ask — could  this  variety  be  render- 
ed more  productive  by  a  different  mode  of  treatment — one  especially  adapted  to 
its  own  nature  7  Would  the  practical  man  not  rejoice  to  think  that  such  a  result 
could  be  brought  about  by  the  aid  and  suggestions  of  science  1  Yet  this  is  the 
result  to  which  the  refined  series  of  experiments  suggested  by  the  question 
abov^e  proposed  may  possibly  lead. 

May  I  venture  to  hope  that  some  of  my  more  zealous  readers  will  be  induced, 
during  the  present  or  succeeding  summer,  to  make  trials  of  the  relative  effects 
of  the  same  saline  or  other  known  substances  and  mixtures,  upon  different  varie- 
ties of  the  same  crop — of  potatoes,  turnips,  wheat,  &cc.,  in  circumstances  other- 
wise equal,  in  some  such  form  as  the  following  : 

Variety  A.  Variety  B.  Variety  C.         Variety  D.  Variety  E. 

Substances.  Substances.  Substances.  Substances.  Substances. 

A.  I  B.  I  C.  A.  I  B.  I   C.  A.  I  B.  I  C.  J^-   |  ».  |  C.  A.  |  B.  |  C. 

The  results  if  carefully  ascertsiined  are  sure  to  lead  to  good,  if  they  should 
not  be  successful  at  once  in  solving  the  problem  above  proposed. 

3°.  Solidity  and  size  of  the  potatoes. — Nothing  is  said  in  the  observation  of 
Mr.  Fleming,  or  his  overseer,  in  regard  to  the  size  or  solidity  of  the  different 
varieties  of  potato,  or  of  the  different  samples  of  the  same  variety  on  which  the 
experiments  were  made.  Yet  in  connection  with  the  remarks  1  have  already 
offered  upon  these  qualities  of  the  turnip,  it  is  proper  to  add  that  the  potato  is 
subject  to  similar  variations  in  the  proportion  of  water  it  contains — and,  there- 
fore, in  the  relative  amount  of  nourishment  capable  of  being  afforded  by  equal 
weights  of  its  different  varieties. 

Some  potatoes  contain  less  than  70,  others  upwards  of  80  per  cent,  of  water, 
so  that  while  100  tons  of  one  sample  will  give  only  20  tons  of  nourishment,  the 
same  weight  of  another  will  give  30  tons,  or  one  half  more.  In  general,  such 
as  grow  on  heavy  or  clay  soils,  or  such  as  are  less  ripe,  contain  the  most,  while 
those  which  have  been  planted  upon  sandy  spots,  or  are  fully  ripe,  contain  the 
least  water.  But  the  effect  produced  by  different  soils  we  tsegin  now  to 
see  may  be  produced  by  different  methods  of  dressing  or  medicating  our  crops 
also. 

Suggestion  VI.  —It  would  be  interesting  to  determine,  therefore,  by  actual 
experiment,  the  relative  proportions  of  water  contained  in  the  produce  of  the 
several  experimental  patches  of  potato  ground  upon  the  same  field,  when 
equally  ripe,  or  when  dug  up  on  the  same  day.  This  would  afford  us  the 
means  of  approximating-^still  more  closely  to  the  true  econojnical  action  of  our 
different  manures  upon  the  potato  crop.  It  may  turn  out  that  in  certain  cases 
the  increase  of  produce,  as  indicated  by  a  greater  weight,  is  only  apparent, 
while  the  increased  amount  of  food  raised  may  in  other  cases  be  considerable, 
though  the  balance  indicates  no  increase  of  weight. 

Did  we  know  the  relative  proportions  of  water  in  the  several  samples  of  the 
three  varieties  of  potato  raised  by  Mr.  Fleming  by  the  aid  of  guano,  and  of 
rape-dust,  already  compared  together,  our  conclusion  in  regard  to  their  relative 
productiveness,  when  treated  by  either  substance,  might  be  materially  altered. 
I  hope,  therefore,  that  this  point  also  will  hereafter  arrest  the  attention  of  some 
of  our  experimentalists. 

4°.  Permanent  effects  of  saline  manures  on  tlve  future  productiveness  of  the 
seed. — Recommending  to  my  practical  readers  a  careful  consideration  of  the 
effects  of  an  admixture  of  wood-ashes  with  the  several  dressings  applied  to  the 
turnip  and  potato  crop,  I  pass  on  to  the  two  following  series  of  experiments 
with  saline  manures  upon  the  potato  crop,  as  given  on  p.  49.  These  two  series 
are  well  conceived,  and  the  results  veiy  instructive.  Of  these  results  the  one 
which  seems  to  me  most  deserving  if  the  attention  of  the  practical  man  is  con- 


66  EXPERIMENTS    UPON    POTATOES.  [AppeTuHx, 

tained  in  a  few  words,  thrust  in  as  it  were,  among  the  remarks  appended  to  the 
table  (1°,  p.  49.)  In  the  later  printed  copies  I  have  caused  them  to  be  put  in 
italics,  with  the  view  of  bringing  them  into  notice.  If  the  reader  will  turn  to  p. 
20  of  this  Appendix,  he  will  find  a  remarkable  experiment  recorded,  in  which, 
by  top-dressuig  well-manured  potatoes,  with  a  mixture  of  ^  of  nitrate  and  |  of 
sulphate  of  soda,  the  enormous  crop  of  30  tons  an  acre  was  obtained  from  the 
small  plot  experimented  upon.  Some  of  these  potatoes  were  kept  for  seed,  and 
planted  alongside  of  others  of  the  same  variety,  which  had  not  been  so  dressed, 
and  tlie  result  is  stated  in  the  few  words  above  referred  to — "  These  last,  v.nder 
the  same  treatment  in  every  respect,  did  not  produce  so  good  a  crop  by  15  boUs  (3| 
tons^  per  acre" 

In  so  far,  therefore,  as  this  experiment  is  tc  be  relied  upon — for  we  must  not 
be  hasty  in  drawing  general  conclusions — it  appears  that  the  benefit  to  be  de- 
rived from  a  skilful  treatment  of  the  potato  plant  does  not  terminate  with  the 
greater  immediate  crop  we  reap,  but  extends  also  into  future  years,  improving 
the  seed  and  rendering  its  after-culture  more  productive. 

Suggestion  VII. — This  idea  is  worth  pursuing,  were  it  only  for  the  purpose 
of  making  out  the  possible  existence  of  so  important  a  physiological  law — how 
much  more  when  it  appears  so  pregnant  with  important  practical  results.  But 
thus  it  is  in  all  cases,  that  the  prosecution  of  experimental  research,  with  im- 
mediate reference  either  to  purely  scientific  or  to  purely  practical  results,  ends 
in  improving  and  benefitting  both  abstract  science  and  economical  practice. 

I  am  unwilling  to  follow  out  or  to  reason  upon  this  possible  law,  as  if  it 
were  really  established ;  but  the  possibility  of  its  tmth  appears  to  throw  light 
upon  such  questions  as  this — why  the  seed  must  occasionally  be  changed  if 
large  crops  are  to  be  continually  reaped.  One  soil  may  be  adapted  to  give  the 
plant  a  large  supply  of  this  or  that  substance  in  which  the  other  soil  is  com- 
paratively deficient ;  audit  maybe  possible  to  medicate  our  seed-corn,  while 
growing,  so  as  to  give  it  the  qualities  which  at  present  it  can  acquire  only  by  a 
change  of  soil. 

All  this,  however,  can  be  only  determined  by  experiment,  and  the  intelligent 
reader  will  net  fail  to  be  stmck  with  the  remarkable  richness.of  these  fii-st  trials, 
in  suggestions  for  future  carefully  conducted  experimental  researches. 

5°.  How  should  saViTie  manures  be  applied  to  the  potato  crop? — Ought  they  to 
be  mixed  with  the  manure,  or  to  be  applied  as  a  top-dressing  %  Mr.  Fleming's 
experiments  do  rtot  fully  solve  this  question  ;  because  the  soil  on  his  two  fields 
was  very  unlike  in  quality.  Thus  with  manure  alone  the  one  field  produced 
12  tons  15  cwt.,  the  other  only  8  tons  17  cwt  per  acre.  A  perfectly  satisfactory 
solution  of  the  question  can  be  obtained  only  by  experiments  with  the  same  sub- 
stances, upon  the  same  soil,  and  with  the  same  variety  of  potato.  Yet  the  experi- 
ments now  before  us  add  considerably  to  our  knowledge  vipon  this  point,  and 
such  of  them  as  are  capable  of  being  compared  together  are  much  in  favour 
of  mixing  the  saline  substances  with  the  7namire.  Thus  apphed  in  nearly 
equal  proportions  by  both  methods,  nitrate  of  soda,  sulphate  of  magnesia,  and 
sulphate  of  ammonia,  gave  the  following  results  : — 

FIRST   FIELD.  SECOND   PIEIiD, 

Top-dressed.        Mixed  with  manure, 
tons.    cwt.  tons,     cwt 

Manure  alone 12      15  8     17 

Nitrate  of  soda 1(5        0  12      7 

Sulphate  of  magnesia     ....     13        5  117 

Sulphate  of  ammonia      ....     14      10  13      7 

The  proportionate  increase,  therefore,  in  these  three  cases,  is  greatly  in  favour 
of  mixing  with  the  manure,  but  something  may  depend  upon  the  soil  and 
season ;  and,  therefore,  other  experiments  are  necessary  before  we  can  draw  a 
genered  conclusion.  It  may  prove  that  some  act  better  when  applied  in  the  one 
>yay,  and  some  in  the  other. 

6°.  Sulphate  of  soda. — With  this  substance  applied  in  either  way,  the  tingu- 


No.   VIII]  EXPEKIMEtfrS    UPON    POTATOES,   BARLEY    AND   OATS.  9 

lar  and  consistent  result  was  obtained  tliat  2  cwt.  per  acre  caused  no  alteration 
whatever  in  the  weight  of  the  produce  upon  either  of  the  two  oi|wiiich  the  tiiala 
were  made.     Of  the  respective  qualities  of  the  crops  nothing  is  stated. 

7°.  Sidphate  with  nitrate  of  soda. — The  above  result  with  sulphate  of  soda 
alone,  is  the  more  remarkable  from  the  known  effect  produced  by  this  and  other 
sulphates  when  mixed  with  nitrate  of  soda.  This  year,  also,  the  mixture  of 
nitrate  with  sulphate  of  soda  added  one-half  (G  tons  per  acre)  to  the  crop,  a 
greater  proportionate  increase  even  than  in  the  experiment  of  1841,  which  gave 
an  increase  of  8  tons  out  of  a  total  produce  of  30  tons  per  acre.  But  this 
season  Mr.  Fleming  has  tried,  with  still  greater  success,  a  mixture  of  1  cwt. 
each  of  sulphate  of  magnesia  and  nitrate  of  soda,  the  produce  rising  by  the  use 
of  this  top-dressing  to  22*  tons.  The  relative  effects  of  the  two  sulphates 
would  have  been  more  clearly  proved,  had  the  proportions  of  nitrate  of  soda 
applied  per  acre  in  the  two  mixtures  been  the  same. 

8°.  Nitrates  of  soda  and  potash. — Anotlier  interesting  fact  to  add  to  those 
alrerdy  registered  upon  the  relative  efficiency  of  these  two  saline  substances,  is 
presented  in  page  49.     One  hundred  weight  and  a  half  of— 

Nitrate  of  soda  gave 16     tons. 

Nitrate  of  potash  gave 18^  tons. 

This  difference  may  have  been  due  to  accidental  causes — or  the  18^  tons  of 
the  one  result  may  have  contained  no  more  food  than  the  16  tons  of  the  other; 
but  the  multiplication  of  accurate  experiments  will  eventually  lead  us  to  the 
trutli.  Apparent  failures  and  discordant  results  must  not  discourage  the  prac- 
tical man.  By  recording  all  trust-worthy  results,  the  light  will  almost  sponta- 
neously spring  up  at  last, 

9*^.  Silicate  of  potash. — The  results  obtained  by  the  use  of  this  substance,  and 
the  remarks  appended  to  them  (p.  50),  are  deserving  of  much  attention.  In  re- 
ference to  this  compound,  and  to  the  silicate  of  soda,  I  beg  the  reader  to  turn  to 
the  suggestions  contained  in  this  Appendix,  p.  40. 

10°.  Mixed  manures. — The  mixtures  in  page  50  will  no  doubt  be  imitated, 
and  by  those  who  can  obtain  them  oihwwn  composition,  comparative  experi- 
ments may  be  tried  with  advantage  both  to  theory  and  to  practice. 

C. — The  Experiments  upon  Barley. 

The  true  practical  value  of  the  experiments  upon  barley  will  be  shown  by 
placing  them  in  the  following  form : — 

Increase.  £    a.  d   Cost  per  bush. 

Nitrate  of  soda  with  common  salt,  gave  5    bush,  for  0  17  6    —    3s.  8d. 

Sulphate  of  soda  with  sulphate  of  magnesia,  7i  bush,  for  0  15  6  —  2s.  Id. 
Guano  (at  25s.),        ....  17    bush  for  3  18  0    —    4s.  7d. 

Co.mmon  salt, 6    bush,  for  0    4  6    —    Os.  9d. 

TurnbuU's  artificial  guano,         .         .  2    bush,  for  1     4  0    —  12s.  Od. 

The  cheapest  application,  without  doubt,  upon  this  soil,  is  common  salt. 
At  half  the  above  price  guano  would  produce  the  barley  at  2s.  3d.  per  bushel, 
and  the  larger  quantity  reaped,  together  with  the  value  of  the  straw  in  the  pre- 
paration of  manure,  may  satisfy  many  that  either  guano  or  the  mixture  of  sul- 
phates may  be  used  with  profit.  It  is  a  further  recommendation  of  tlie  common 
salt,  however,  that  it  produced  the  heaviest,  while  guano  produced  tlie  lightest 
grain. 

From  the  experiment  with  nitrate  of  potash  no  result  can  fairly  be  drawn,  in 
consequence  of  the  great  drought  of  the  season  (see  Mr.  Gardiner's  remarks). 

D. — The  Experiments  upon  Oats, 
1°.  Negative  effect  of  salitie  manures. — The  first  of  the  two  series  of  experi- 
ments above  recorded  being  made  at  Lennox  Love — like  those  made  at  the  same 
place  upon  turnips — derive  their  principal  interest  from  the  illustration  they 
Kfford  of  the  7iegat.ive  effect  of  saline  manures  upon  the  oat  crop,  under  the  in- 


68  EXPERIMENTS  UPON   OATS    AND   WHEAT.  [Appendix, 

jfluence  of  great  heat  and  drought,     I  select  the  more  simple  and  striking  cases 
of  diminution.    tThe  undressed  part  of  the  field  produced  54  bushels  per  acre 
Common  salt  diminished  this  produce  by   6  bushels. 

Nitrate  of  soda 12^      " 

Sulphate  of  soda 15|      " 

Rape-dust 9        " 

Soot I2i      " 

while  2  cwt.  of  guano  raised  the  produt  3  to  70  bushels,  being  an  increase  of  16 
bushels. 

These  results  not  only  confirm  the  deductions  which  we  have  already  drawn 
from  the  preceding  experiments  upon  potatoes  and  turnips — that  guano  will  act 
even  in  our  driest  seasons,  while  rape-dust  requires  at  least  occasional  rain — but 
they  go  further  in  showing  that,  like  the  saline  substances,  rape-dust,  and  even  soot, 
will  viateriaUy  diminish  the  oat  crop,  if  the  season  be  distinguished  try  remarkable 
drought. 

2°,  Moss  oats. — The  experiments  upon  moss  oats  (p.  53)  are  a  continuation 
and  extension  of  those  of  1841  with  greater  attention  to  accuracy  in  the  determi- 
nation of  the  produce.  The  last  column  in  the  table  speeiks  for  itself.  The 
general  produce  of  the  field  being  43  bushels  per  acre. 

Increase.  Cost  per  bush. 

Sulphate  of  ammonia  gave  ...  9  bushels  2s.  3d. 

Sulphate  of  soda  with  nitrate  of  soda  gave  18  bushels  Is.  7d. 

Bones  in  muriatic  acid  gave        ...         18  bushels  Is.  6d. 

Silicate  of  potash,  mixed  with  the  above,  gave  22  bushels  2s.  Od. 

m  the  last  two  cases  the  straw,  which  is  usually  imperfect  in  oats  grown  upon 
Mioss  land,  was  strong  and  healthy.  It  is  obvious,  therefore,  that  all  these  exper- 
iments deserve  repetition,  though,  as  here  set  forth,  the  increase  of  grain  by  Nos. 
2  and  3  was  obtained  at  the  least  cost,  and,  therefore,  to  the  economist  will  ap- 
pear most  important. 

E, — The  Experiments  upon  Wheat. 
I,  Effect  ofdro^ight. — The  first  series,  tliose  made  at  Lennox  Love,  afford  in- 
teresting illustrations  of  the  effect  of  great  drought  in  modifying  the  action  of  sa- 
line manures  and  of  rape  dust,  upon  the  wheat  crop.  The  more  prominent 
results  are  distinctly  brought  out  when  thrown  into  the  following  form.  The 
produce  of  the  undressed  part  of  the  field  being  47^  bushels  an  acre,  this  produce 
was  affected  by  the  several  substances  employed  in  the  following  manner: — 

Decrease  per  acre.     Increase  per  acre. 

Common  salt,  1  cwt H  bush.  — 

.         9i  bush,  — 

slight.  — 

—  slight. 

—  3i  bush. 

—  J  bush. 
Thus,  the  nitrate  of  soda  and  the  soot  did  no  harm,  though  the  drought  did 

not  permit  them  to  do  any  good.  Common  salt  slightly,  and  sulphate  of  soda 
largely  diminished  the  crop  of  grain — while  of  these  four  substances  the  sulphate 
was  the  only  one  which  diminished  the  yield  of  straw.  Nitrate  of  soda  and 
soot  largely  increased  it. 

On  the  other  hand,  guano  slightly  increased  the  yield  of  grain,  and  rape-dust 
added  3|  bushels  to  the  natural  produce,  both  also  augmenting  the  weight  of 
the  straw  by  about  one-tenth  of  the  whole. 

In  this  case,  then,  the  rape-dust  surpassed  in  beneficial  effect  the  natural 
guano,  though,  as  we  have  already  seen,  it  proved  greatly  inferior  to  the  latter 
when  applied  in  similar  proportions  to  oats,  potatoes,  and  turnips. 

2°,  Suggestion  VIII. — This  fact  suggests  an  interesting  inquiry.  It  is  known 
that  :>ne  of  the  most  lucrative  modes  in  which  rape-dust  has  been  hitherto 


Sulphate  of  soda,  1  cwt. 
Soot,  32  bush,     . 
Nitrate  of  soda,  I  cwt. 
Rape-dust,  16  cwt. 
Guano,  2  cwt. 


No.   VIII.]  EXPERIMENTS    UPON   OATS    AND   WHEAT.  69 

employed  as  a  manure  has  been  in  top-dressing  the  wheat  crop  (see  the  prece- 
ding part  of  this  Appendix,  p.  19).  Has  it,therefore,  some  s;7e^«a^  adaptation  to 
the  wheat  crop — which  will  account  at  once  for  its  comparative  failure  upon  oats, 
turnips,  and  potatoes,  and  for  its  superior  efficacy  to  guano  upon  the  wheat  crop 
— in  the  proportions  stated,  and  even  in  a  very  dry  summer  1  The  comparative 
efficacy  of  the  two  substances  applied  in  various  proportions  is  certainly  deserv- 
ing of  further  investigation.  It  will  be  a  gain  not  only  to  practical  but  to  theo- 
retical agriculture,  should  it  be  established  that  rape-dust  can  be  profitably 
applied  to  the  wheat  crop,  in  circumstances  when  it  would  be  thrown  away  upon 
oats  or  turnips.  By  turning  to  the  next  series,  that  of  Mr.  Fleming  (p.  54),  it 
will  be  seen  that  the  last  result  there  stated  is  also  favourable  to  the  action  of 
rape-dust  upon  the  wheat  crop.* 

3°.  Mntuaily  counteracting  injiuence  of  different  nmnures. — But  another  curi- 
ous observation  presents  itself  in  the  table  of  Lord  Blantyre's  results.  It  is  in 
the  apparent  struggle  between  the  good  and  evil  influences  of  the  rape-dust  on 
the  one  hand,  and  of  the  saline  substances  on  the  other,  when  they  we  re  applied 
together  to  the  same  plot  of  wheat  (see  Appendix,  p.  19).  Thus,  when  applied 
in  the  proportions  above  stated — 

Increase.  Decrease. 

Common  salt  gave      ....  —  IJ  bush. 

Rape-dust  gave 3j  bush.  — 

One-half  of  each  gave        .         .         .        2|  bush.  — 

Or  the  natural  effect  of  the  rape-dust  was  lessened  one-third  when  mixed  with 
the  given  weight  of  common  salt.     So,  also — 

Increase.  Decrease. 

Sulphate  of  soda  gave         ...  —  9y  bush. 

Rape-dust  gave 3j  bush.  — 

One-half  of  each  gave          ...  —  3    bush. 

Or  the  influence  of  1  cwt.  of  sulphate  of  soda  for  evil  was  one-third  greater  than 
that  of  16  cwt.  of  rape-dust  for  good — in  the  given  circumstances  of  soil,  climate, 
and  crop.  This  result,  which  at  present  seems  only  curious,  may  hereafter  lead 
to  the  establishment  qf  interesting  truths  capable  of  practical  application. 

Suppose,  for  instance,  that  upon  two  fields  rape-dust  were  applied  to  the 
wheat  crop  at  the  rate  of  16  cwt.  per  acre,  and  that  the  one  field  contained  na- 
turally in  its  surface  soil  the  proportion  of  sulphate  of  soda  employed  in  Lord 
Blantyre's  experiment,  while  the  other  contained  none — then  in  the  one  case 
the  rape-dust  would  not  only  expend  all  its  influence  in  overcoming  the  tenden- 
cy of  the  sulphate  to  lessen  the  crop, — but  would  even  seem  to  do  harm  if  the 
produce  were  compared  with  that  of  another  field,  of  apparently  similar  soil, 
near  the  surface  of  which  this  abundance  of  sulphate  did  not  exist ;  while,  in  the 
other  case,  the  rape-dust,  having  no  counteracting  influence  to  overcome,  would 
spend  itself  entirely  in  increasing  thegrowth  of  the  plant  and  the  final  yield  of 
•  grain. 

Or  suppose  an  artificial  guano  or  other  mixed  manure  artificially  prepared, 
to  contam  two  or  more  substances  which,  in  the  soil  they  are  applied  to,  have 
a  tendency  to  produce  opposite  eflfects — the  one  to  increase,  the  other  to 
diminish,  the  amount  of  produce — the  effect  of  this  conflicting  action  of  its 
component  substances  would  be  such  as  to  render  the  mixture  of  less  efficacy, 
perhaps  of  no  efficacy  at  all — it  might  be  even  injurious  to  the  crops, — although 
It  contained  substances  which,  if  applied  alone,  would  have  exhibited  a  power- 
ful fertilizing  action. 

These  two  illustrations  are  sufficient  to  show  the  kind  of  light  which  obser- 
vations, such  as  the  one  above  adverted  to,  may  hereafter  throw  upon  practical 
agriculture. 

II.  The  substance   of  Mr.  Fleming's  table  (p.  54),  may  be  thus  presented. 

*  See  also  the  subsequent  observations  on  the  experiments  upon  beans. 


70  EXPERIMENTS  UPON  WHEAT.  [Appendix^ 

The  unaided  produce  of  the  soil  was  25  bushels  an  acre,  and  the  effect  of  tlie 
dressings  as  follows : — 

Increase.        Decrease. 

Guano,  3  cwt 6    bush.  — 

Rupe-dust,  5  cwt.,  sulphate  of  magnesia,  I  cwt.  .       3^  bush,  — 

Sulphate  of  soda,  1^  cwt.,  nitrate  of  soda,  |  cwt.        1^  bush. 

Common  salt,  3  cwt —  3j  bush. 

Common  salt,  3  cwt.,  dissolved  bones,  1  cwt.      .  —  2    bush. 

Turnbull's  artificial  guano  produced  no  sensible  effect. 

Under  the  circumstances,  besides  being  favourable  to  guano,  tlie  above  re- 
sult is  also  in  favour  of  the  mixed  sulphate  and  nitrate  of  soda,  which  we  have 
seen  to  operate  beneficially  upon  so  many  otho:  cultivated  plants.  The  entire 
crop  appears  to  have  been  injured,  not  only  by  ihe  summer's  drought,  but  by 
the  severity  of  the  preceding  winter. 

In  regard  to  common  salt,  it  is  worthy  of  remark,  that  the  grain  dressed  by 
it,  whether  oats,  barley,  or  wheat,  in  Mr.  Fleming's  experiments  of  this  year, 
has  been  always  heavier  per  bushel  than  any  of  the  other  samples  tried.  This 
accords  with  the  previous  results  of  some  other  experimenters;  but  it  does  not 
agree  with  Mr.  Fleming's  observations  upon  the  wheat  of  1841,  nor  with  those 
of  Mr.  Burnet  for  184"2,  and  therefore  cannot  yet  be  considered  as  a  universal 
consequence  of  the  application  of  this  substance"  as  a  top-dressing. 

III.  The  experiments  of  Mr.  Burnet,  of  Gadgirth,  have  already  been  pajtially 
detailed  in  tlie  text  (Lecture  XVI.,  p.  362),  and  their  value  explained,  Thej 
are  important,  chiefly,  as  showing — ■ 

1°,  Economical  mixtures. — That  mixtures  can  be  prepared  which,  upon  soma 
soils,  surpass  guano  in  efficacy  and  in  economical  value,  at  its  former  price. 
The  price  being  now  reduced,  other  experiments  are  required,  yet  still  the  less 
effect  of  guano  upon  the  wheat  crop  is  in  accordance  with  the  results  of  Lord 
Blantyrc.  A  wet  season,  however,  may  alter  the  numerical  relation  which 
daese  results  exhibit.  It  will  be  observed  that  here  also  Turnbull's  guano  pro- 
duced no  sensible  effect. 

2°.  Effect  of  soda. — The  efficacy  of  the  salts  of  soda,  whether  the  sulphate, 
the  nitrate,  or  common  salt,  upon  Mr.  Burnet's  land,  ar^  also  vejy  striking — 
half  a  hundred  weight  per  acre  of  either  producing  an  additional  increase  of 
about  10  bushels  of  grain. 

3°.  YieM  of  jiour. — Into  his  tabulated  results,  Mr.  Burnet  has  introduced  a 
new  element,  and,  as  it  seems  to  me,  an  important  one  in  an  economical  point 
of  view,  namely,  the  quantity  of  fine  flour  yielded  by  equal  loeights  of  the  several 
samples  of  grain.  The  differences  presented  in  this  column  are  veiy  striking. 
Thus  100  lbs.  of  the  greiin  reaped  from  the  plot  which  was — 

Undressed,  gave 76^  lbs.  of  fine  flour. 

Dressed  with  guano 68f  lbs.         " 

With  sulphate  of  ammonia 66^  lbs.         " 

With  sulphate  of  ammonia  and  nitrate  of  soda      .     .     .     54f  lbs,         " 

It  would  be  interesting  to  learn  from  an  experienced  miller  to  what  extent 
such  differences  affect  the  money  value  of  the  grain  to  the  manufacturer  of 
flour. 

4°.  Amount  of  gluten. — Through  the  anxiety  of  Mr.  Burnet  to  "draw  as  much 
information  as  possible  from  his  excellent  experiments,  I  am  able  to  present 
another  feature  in  regard  to  the  action  of  these  saline  and  other  substances  upon 
the  quality  of  the  produce. 

It  is  known  that  the  quantity  of  gluten  contained  in  different  samples  of 
flour  is  very  unlike,  and  that  the  nutritive  property  of  the  flour  depends,  to  a  cer- 
tain extent,  upon  this  quantity  of  gluten.  It  has  also  been  stated,  as  the  result 
of  experiment,  that  the  grain  which  is  raised  by  means  of  manure  containing 
the  largest  quantity  of  nitrogen,  is  also  the  richest  in  gluten.  With  a  view  to 
these  questions,  Mr.  Burnet  transmitted  to  me  a  pound  of  each  of  the  sampki 


No.  VIII.]  EXPERIMENTS   UPON  WHEAT.  Tl 

of  flour  (see  Appendix,  p.  5),  and  upon  examination  I  found  them  to  contain 
the  following  proportions  of  gluten  : — 

Water  per  cent.      Gluten  per  cent. 
No,  1.  No  application 163  9*4 

2.  Guano  and  wood-ashes 16-15  9*3 

3.  Artificial  guano  and  do 16-8  9-6 

4.  Sulphate  of  ammonia  and  do 164  10-5 

5.  Do.,  do.,  and  sulphate  of  soda 15-7  97 

6.  Do.,  do.,  and  common  salt 157  9-6 

7.  Do.,  do.,  and  nitrate  of  soda lG-4  10-0 

8.  Turnbull's  guano,  gypsum,  and  wood-ashes  .     15-2  9-1 
These  results  are  not  without  their  interest,  for  though  they  do  not  show  any 

s^riA-mo- difference  in  the  per-centage  of  gluten,  yet  upon  the  whole  the  result  is 
in  favour  of  those  samples  to  which  the  sulpliate  of  ammonia*  had  been  ap- 
plied. One  of  these,  No.  4,  exceeded  the  undressed  grain  by  about  one  per 
cent.,  or  one-ninth  of  the  v/hole  gluten  it  contained.  Were  the  amount  of  this 
gluten  alone  therefore  to  determine  the  feeding  quality  of  the  grain,  this  sample 
might  be  considered  as  considerably  the  most  nutritious.  But  besides  the  re- 
lative proportions  of  fine  flour  which  they  severally  yielded,  there  are  other  im- 
portant considerations  which  bear  upon  this  question,  and  must  influence  our 
judgment.  These  considerations  it  would  be  out  of  place  to  present  among  the 
present  observations.  They  will  be  found  stated  in  the  text  of  the  Lectures, 
(XIX.,  p.  498  et  seq.)  where  we  treat  of  the  composition  of  wheat  and  other 
varieties  of  grain — and  of  their  respective  values  in  the  feeding  of  man  and  other 
animals. 

F. — The  Experiments  upon  Grass. 

I.  The  experiments  of  Mr.  Alexander  are  not  very  remarkable  or  conclusive. 
The  meadow,  which  was  drained  moss  full  of  timothy  grass,  gave  naturally  1 
ton  4  cwt.  of  hay,  whereas  the  one  dressing  raised  the  produce  to  1  ton  8"cwt., 
the  other  to  1  ton  11  cwt.,  per  iviperial  acre.     The  cost  is  not  stated. 

II.  But  those  of  Mr.  Fleming  are  very  interesting.  By  referring  to  page  17 
of  this  Appendix,  it  will  be  seen  that  in  1841  Mr.  Fleming  obtained  a  greatly 
increased  produce  of  hay  by  the  use  of  nitrate  of  soda.  He  informs  me  that 
in  making  the  present  experiments  he  was  desirous  of  again  testing  the  efficacy 
of  this  salt  upon  grass,  on  the  same  kind  of  land,  and  of  comparing  it  with  that 
produced  by  other  saline  substances.  lie  selected  also  a  portion  of  the  same 
field,  on  another  part  of  which  the  trials  upon  wheat  had  been  made  in  1841 
(see  Appendix,  p.  19),  with  the  view  of  ascertaining  if  any  analogy  could  be 
traced  or  difference  detected,  beliaeen  their  action  in  1841  iipon  wheat,  andj  their 
effect  in  1842  on  sown  grasses — rye-grass,  timothy,  and  red  clover.  Both  objects 
have  been  in  some  measure  attained.  I  shall  first  present  a  summary  of  the 
results. 

OP  HAY.  INCREASE.  DECREASE. 

tons  cwt.  tons  cwt.  tons  cwt. 

The  undressed  soil  produced     ..18                    0      5 

Sulphate  of  soda,  3  cwt.       ...      1       3  

Nitrate  of  soda,  IJ  cwt 2     10  12  

Sulphate  of  soda,  1  cwt i    ,       «                    ^       - 

Nitrate  of  soda,  i  cwt S  "1 

Common  salt,  3  cwt 1       6                   0      2 

Common  salt,  2  cwt ^   i     io  n      a 

Soot,  16  bushels ^11^  U      4  

Sulphate  of  ammonia,  1  cwt.     .     .      1     13  0      5  — — 

Guano,  IJ  cwt 1     18  0     10  

*  It  will  be  borne  in  mind  that  this  is  Turnbull's  sa  ;i^iate  of  ammonia,  already  adveited 
to  in  page  61  of  this  Appeodix. 


72  EXPERIMENTS   UPON    GRASS.  [AppeiUltX, 

A  mixture  of  silicate  of  potash  with  gypsum  produced  no  sensible  effect, 
neither  did  Turnbull's  artificial  guano. 

1°.  In  this  repetition  of  his  experiment,  therefore,  the  nitrate  of  soda  on  si- 
milar land  again  increased  greatly  the  produce  of  hay — giving,  at  the  first  cut- 
ting, an  excess  of  upwards  of  1  ton,  at  a  cost  of  30s. 

2°.  But  on  comparing  this  action  of  the  nitrate  upon  grass  with  its  action  in 
the  same  field  the  previous  year  upon  wheat — we  find  that  though  it  considera- 
bly increased  the  crop  of  wheat,  yet  every  additional  bushel  raised  cost  12s.  6d. 
as  the  price  of  the  nitrate  added  to  the  land  (Appendix,  p.  19).  It  appears, 
therefore,  that  upon  soils  where  the  nilrate  will  not  pay  when  applied  to  wheat,  it 
may  ye/  pay  well  when  appUcd  la  grass. 

'S^.  Again,  we  find  above  tnat  3  cwt.  of  common  salt  lessened  in  a  slight  de- 
gree the  crop  of  hay,  while,  in  1811,  IJ  cwt.  increased  considerably  the  produce 
of  wheatiu  the  same  field — the  additional  grain  reaped  from  the  salted  portion  cost- 
ing only  Gd.  a  bushel  (p.  19).  It  would  appear,  therefore,  that  on  soils  where 
aniimoa  salt  can  be  proJiLably  used  upon  wheal  it  may  do  injury  upon  hay.  The 
only  circumstance  that  renders  this  deduction  less  safe  is  that  3  cwt.  of  salt  per 
acre  were  applied  to  the  grass,  which  may  have  been  too  much  considering  the 
dryness  of  the  season. 

4°.  The  latter  remark  applies  also  to  the  sulphate  of  soda  which  was  laid  on 
at  the  rate  of  3  cwt.  per  acre.  A  less  addition  might  possibly  have  aided  the 
crop.  Yet  the  negative  influence  of  this  salt  seems  great,  since  1^  cwt.  of  nitrate' 
— itself  tending  to  increase  the  crop — was  unable  entirely  to  overcome  the  dimin- 
ishing influence  of  1  cwt,  of  sulphate. 

But  the  reason  of  this  apparent  inefficiency  of  the  nitrate,  when  mixed  with  the 
sulphate,  is  in  some  measure  explained  by  the  remarkable  fact,  that  on  both  of  the 
patches  to  which  the  sulpJude  of  soda  loas  applied,  the  grass  that  came  up  consisted 
almost  entirely  of  red  fescue  (Festuca  Rubra),  though  rye  grass,  timothy,  and  red 
cloacr  were  the  only  grasses  soion.  The  sulphate,  therefore,  must  first  have  checked 
or  entirely  destroyed  the  grasses  which  had  already  sprung  up,  and  then  have 
incited  the  dormant  seeds  of  fescue  to  germinate,  before  the  fertilizing  agency  of 
the  nitrate  could  come  into  play. 

This  effect  of  the  sulphate,  should  it  be  confirmed  by  later  experiments,  will 
establish  the  important  theoretical  principle,  that  those  substances  which,  when 
present  in  the  soil,  will  destroy  some  of  our  cultivated  grasses,  will  encourage  the 
growth  of  others;  and  the  no  less  important  practical  truth,  that  saline  substan- 
ces exercise  sucli  a  special  action  on  the  several  crops  we  grow  that  we  may 
hope  to  discover  the  means  of  aiding  the  growth  of  the  one  or  the  other  at  plea- 
sure, and  it  may  be  at  little  cost. 

Suggestion  IX. — It  is  to  be  recollected  that  in  the  case  of  Mr.  Fleming's 
field  it  may  have  accidentally  happened  that  the  seeds  of  the  fescue  particularly 
abounded  in  those  plots  to  which  the  sulphate  was  applied.  With  every  dis- 
position, therefore,  to  advance  as  rapidly  as  we  possibly  can,  I  think  it  better 
to  suspend  our  judgment  upon  this  point — until  the  following  two  series  of  ex- 
periments shall  have  been  made  in  two  or  three  different  localities  : — 

a.  By  top-dressing  any  of  the  ordinary  grasses  sown — excluding  the  fescues 
— on  four  or  more  plots,  with  i  cwt.,  1  cwt.,  2  cwt.,  and  3  cwt.  of  sulphate 
of  soda  respectively,  and  marking  the  kind  of  grasses  that  most  abundantly 
spring. 

b.  By  sowing  half  an  acre  of  one  or  more  of  the  fescues,  and  especially  the 
Rubra,  and  noting  the  effect  of  the  sulphate  applied  in  similar  proportions  upon 
as  many  patches  as  before. 

These  experiments,  it  is  obvious,  would  be  rendered  more  interesting  were 
nitrate  of  soda,  alone  and  mixed  with  the  sulphate,  tried  on  other  plots,  and  on 
both  varieties  of  grass.  I  trust  Mr.  Fleming,  whose  educated  eye  enabled  him 
to  detect  the  interesting  fact  in  question,  may  be  induced  himself  to  prosecute 
thft-subject  by  further  experiments. 

5*^.  Suggestion  X. — We  have  already  seen  i\  Jhe  above  joint  action  of  the 


-VO.   VIIL]  EXPERIMENTS   UPON    GRASS   AND  MIXED    CROPS.  73 

nitrate  and  sulphate,  another  illustration  of  the  kind  of  struggle  we  may  suppose 
to  go  on  between  substances  tending  respectively,  the  one  to  increase,  the  other 
to  diminish,  the  produce.  In  the  joint  action  of  the  common  salt  and  the  soot, 
when  applied  together,  we  have  a  further  instance  of  the  same  kind — an  increase 
of  4  cwt.  only  being  caused  by  the  application  of  16  bushels  of  soot,  when  coun- 
teracted by  an  admixture  of  2  cwt.  of  common  salt.  Applied  alone,  the  increase 
of  produce  would  probably  have  been  greater.  Will  any  one  undertake  exper- 
iments with  the  view  of  further  bringing  out  this  interesting  mutually-counter- 
acting influence  of  different  applications'? 

6°.  I  can  only  call  attention  to  tlie  large  yield  of  hay  naturally  obtained  from 
that  part  of  the  field  on  which  barley  dressed  with  bone-dust  in  1841  had  previ- 
ously grown  :  Mr.  Fleming  informs  me  that  no  sensible  difference  in  the  produce 
of  hay  was  ooserved  between  the  undressed  part  of  the  field  and  that  upon  which 
the  dressed  wheat  had  grown  in  1841,  though  the  crop  was  not  set  apart  or 
v/eighed,  as  we  might  wish  it  to  have  been. 

III.  Since  the  preceding  experiments  went  to  press  I  have  received  the  fol- 
lowing short  notice  of  trrals  upon  hay  made  by  Mr.  Campbell,  of  Islay  : — 

"  It  is  very  difficult  to  get  the  tenants  in  our  wild  part  of  the  world  to  expend 
money  in  the  purchase  of  foreign  substances,  however  beneficial ;  and  for  this 
reason  I  have  been  induced  to  try  the  substances  mentioned  below,  because, 
with  the  exception  of  sulphuric  acid,  the  others  are  to  be  got  in  abundance 
in  the  island — the  pigeons'  dung  may  be  got  in  large  quantities  in  the  caves, 
sea-ware  on  the  shore,  and  lime  is  abundant  and  excellent  in  quality.  The  ex- 
periment was  made  thus — 

WEIGHT    IN  POUNDS. 

Fresh  cut.  Dry. 

1.  Nothing 240  199 

2.  Pigeon  Dung 318  275 

3.  Sea-ware,  Lime,  and  Sulphuric  Acid  .     .     .      SOG  269 

4.  Lime  and  Sulphuric  Acid  .     .    ^    .     .     .     .      293  256 

1.  A  field  of  about  ten  acres,  lately  improved  from  heather,  was  chosen;  the 
field  was  well  drained  and  deep  ploughed,  so  as  to  raise  the  subsoil  (red  loam) 
with  the  moss.  On  its  surface  the  grass  was  sown  down  with  oats--8  cwt.  of 
each  substance  was  used  to  the  acre.  Eight  yards  square  carefully  measured 
from  the  centre  of  each  variety,  and  weighed  the  day  they  were  cut,  and  again 
on  the  day  they  were  put  into  stack.     1  he  hay  was  fully  ripe  when  cut. 

2.  The  pigeon  dung,  which  looks  like  peat-dust,  was  laid  on  exactly  as  it 
was  taken  from  the  cave. 

3.  One  ton  of  lime-shells  was  mixed  with  12  tons  fresh  sea-ware;  after  being 
twice  turned,  the  whole  of  the  sea-ware  was  consumed,  leaving  only  small  black 
particles  mixed  with  the  lime :  the  bulk  was  reduced  to  five  large  carts  (not 
weighed) ;  4  galls,  sulphuric  acid,  mixed  with  400  galls,  of  water,  were  added  to 
the  powder — a  violent  fermentation  took  place,  and  the  bulk  was  further  re- 
duced about  an  eighth. 

4.  A  ton  of  lime-shells  was  prepared  according  to  your  recommendation 
slaking  the  lime  with  the  dilute  acid. 

N.  B.  One  measure  of  this  lime  in  shells  gives  three  and  a  half  in  powder." 

G. — The  Experiments  upon  Mixed  Crops. 
Mr.  Alexander's  experiment  upon  a  field  of  mixed  oats,  beans,  and  peas,  is 
very  deserving  of  notice,  and  will,  I  have  no  doubt,  be  repeated.  Not  only  did 
the  mixture  of  gypsum  and  common  salt  increase  the  ultimate  produce — but,  as 
Mr.  Alexander-  says,  it  acted  like  magic — imparting  life  and  vigour  to  an  appa- 
rently dying  and  worthless  crop. 

H. — The  Experiments  upon  Beans. 
I.  The  principal  fact  of  importance  in  the  experiments  of  Mr.  Alexander  is 
the  effect  he  found  his  mixture  of  gypsum  and  common  salt  to  produce  upon  the 


74 


EXPERIMENTS    UPON     BKANS. 


[Appendix J 


beans  even  when  already  in  flower.  This  is  another  of  those  new  and  practical- 
ly valuable  obsei"vations  which,  year  by  year,  are  sure  to  present  themselves  to 
our  observing  experimenters  as  their  inductive  researches  are  continued, 

II.  I  am  happy  in  being  able  to  introduce  here,  though  it  reached  me  too  late  for 
insertion  among  the  other  tables,  the  following  digest  of  results  upon  beans,  ob- 
tained upon  Lord  Blantyre's  farm  at  Lennox  Love.  The  object  of  them  was 
to  SLScerlain  t/ie  relative  ejl'ect  of  certain  saline  manures,  and  of  rape-dust,  and 
guano,  upon  beans,  after  a  crop  of  oats. 

Experiments  upon  Beans,  after  a  crop  of  Oats.  The  qiiantity  of  land  in  each 
plot  was  one-eighth  of  an  imperial  acre.  Seeds  sown  25th  February  ;  manures 
applied  13th  May;  crop  cut  8th  August;  stacked  1st  September,  1842;  and 
thrashed  6th  February,  1843. 


1  MANURES.  [-^ 

Weight   taken   from 
Th^oci,:,>.T  Mill  ^f 

c 

Incr 

0 

prod 
ing 

c 
1 

ease 
f 

uce 
rain. 

a 

crease  of 
produce 
in  gi-ain. 

No. 

FORDHILL 

FIELD, 

LENNOX  LOVE. 

Description  of 
Dressing. 

•A 
1 

(5 

1 
.a 

6 

s.  d. 

U  4 

Xi 

^  6 

o 

w  3 
11 

Oq. 

lbs. 

588 

i 

n! 
PQ 

lbs 
231 

i 

lbs. 
54 

11. ij, 

J 

Ib.s. 

285 

£ 

lbs 

22[> 

■2  S: 

lbs. 

78 

1 

1     _ 

i 

1 

Common  Salt. 

Ihs. 
14 

lbs. 
65i 

bushs. 
3''i38 

bsh. 

lbs. 

bsh. 

•182 

lbs. 
31 

4j 

Common  Salt. 

Rape-dust 

Nitrate  of  Soda 
N  lit  rate  of  Sod  a 

Rape-dust 

Nitrate  ofSoda 
Sulph.  ofSoda 
Sulph.  ofSoda 

7 

112 

14 

112^ 

7  0 

630 

265 

53 

318 

230 

82 

66i 

4  000 

•282 

— 

— 

32 

3  1 

8  7 

672 
644 

276 
280 

63 
59 

339 
339 

254 
253 

79 
52 

66f 
66* 

4  134 
4210 

■414 
490 

— 

— 

22 
26 

5  j 

2  0 

686 

282 

00 

342 

2.58 

86 

66i 

4  256 

•536 

— 

— 

25 

6 

1  0 

700 

282 

73 

355 

261 

84 

661 

4-240 

•520 

— 

12 

7j 

8 

9 
10 
11 

Sulph.  ofSoda 
Rape-dust . .  . 
Rape-dust .... 

Guano 

Nothing 

Soot 

28 
4bsh. 

75 

14  {) 
5  0 

4  0 

700 

700 

728 
672 
f-86 

289 
292 

2=;o 

248 
234 

65 
61 

68 

85 
87 

35^ 

353 
348 
333 
321 

261 
260 
263 
265 

281 

85. 

87 
117 
74 

84 

67 
66| 
60  i 

66 

4  313 

4-374 
4-210 
3720 
3  545 

593 

654 
•490 

2 

•175 

20 

24 
17 

Remarks. — The  soil  of  Fordhill.  on  which  they  srew,  is  light  and  of  inferior  quality — the 
subsoil  is  of  indurated  clay,  intersperised  with  boulders  and  small  stones,  and  occasionally 
beds  of  gravel.  The  field  was  drained  every  furrow  previous  to  its  being  broken  up  from 
old  lea  in  the  winter  of  1840— ploughed  deep  and  subsoilcd  in  the  autumn  of  1841,  and  ma- 
nured with  farm-yard  dung  in  (he  drill  before  sowing  the  beans  in  the  spring  of  1842.  Owing 
to  the  dryness  of  the  season,  the  beans  were  rather  short  in  the  straw;  (he  specific  manures 
were  applied  after  the  plants  had  attained  some  inches  in  height.  The  sulphate  of  soda  (rhy , 
not  in  crys/als)  blackened  and  destroyed  the  under  leaves,  wherever  it  came  in  contact  with 
them,  but  fresh  shoots  soon  appeared,  and  it  did  not  seem  permanently  to  injure  or  retard  the 
growth  of  the  plants.  They  did  not,  after  the  application,  shew  any  marked  change  of  colour ; 
and  at  no  period  did  they  seem  to  differ  much  from  tlie  rest  of  the  field.  A  few  peas  were 
sown  among  the  beans  :  and  in  dressing  the  grain,  an  attempt,  partially  successful,  was  made 
to  separate  them— each  experiment  underwent  the  same  process  in  the  dres&ing.  Grain 
column  1st  represents  the  produce  in  bean.s — grain  column  2nd  represents  that  in  peas. 
The  separation,  however,  not  being  completely  effected,  there  were  left  peas  among  the  beans, 
and  some  of  the  smaller  and  inferior  beans  among  the  peas.  I  thought  a  distinction  of  this 
kind  worth  making  in  the  Tables,  as  I  observed  that  some  of  the  lots  contained  much  more 
peas  than  others,  and  conceived  that  the  relative  value  of  the  manure,  as  applied  to  either, 
might  thereby  in  soi.ie  measure  be  shown,  as  well  as  tlieir  effects  on  the  beans  alone  more 
truly  exhibited.  The  gross  weights  were  taken,  as  those  of  the  other  experiments,  at  the 
town  of  Haddington's  weighing-machine,  before  thrashing — the  detailed  weights  and  mea- 
surements by  myself.  Wm.   Goodlet. 

The  produce  of  the  undressed  part  amounted  in  the  above  experiment  to  29i 
bushels,  and  it  is  remarkable — 

1°.  That  the  soot  alone  caused  a  sensi«rle  diminution  of  the  gross  produce, 
and  alone  did  not  lessen  the  proportion  of  { ^as. 

2'^.  Although  the  season  was  so  dry  the  s.i.phate  of  soda  gave  a  larger  increase 
than  was  obtained  by  the  addition  of  twice  .ts  own  weight  of  guano, 

3°.  That  an  admixture  of  half  its  weight  ^f  nitrate  with  the  sulphate  of  soda 


No.   VIII.}  EXPERIMENTS  UPOV   EEAt^S.  75 

did  not  increase  the  produce  beyond  that  of  an  equal  weight  of  sulphate  alone. 
This  is  different  from  the  action  of  the  latter  salt  in  the  case  of  the  other  grain 
crops  and  of  potatoes,   • 

4° .  That  1  c wt.  of  sulphate  of  soda  produce  as  great  an  eifect  as  1 6  cwt.  of  rape- 
dust — the  quantity  of  grain  reaped  from  both  applications  being  very  nearly  the 
same. 

Siis'S;estio7i  XL — These  striking  effects  of  the  sulphate  ultimately  took  place, 
although  when  first  applied  to  the  young  plants  it  burned  and  blackened  theii 
leaves.  I  trust  that  these  results  will  also  be  tested  by  repetitions  in  other  years 
— less  droughty,  it  is  to  be  hoped — and  in  other  parts  of  the  country.  For  the 
sulphate  of  soda,  Mr.  Alexander's  experiment  seems  to  say  that  gypsum,  which 
is  still  cheaper,  may  be  economically  substituted. 

5°.  It  will  be  seen  that  guano  v;pon  this  crop,  as  upon  the  wheat  already  noticed 
(p.  68),  was  less  successful  than  some  of  the  other  substances  employed. 

Conclusion. — Upon  the  observations  of  Mr.  Gardiner  in  regard  to  the  effect 
of  the  dressings  of  1841  upon  the  crop  of  1842,  I  have  nothing  to  add  to  the  re- 
marks I  have  already  made  (p.  57)  upon  their  importance,  and  upon  the  good 
that  must  follow  from  continuing  them.  But?  in  concluding  these  observations, 
the  reader  will  please  to  recollect  that  I  have  adverted  to  those  points  only,  in  the 
above  tables  of  results,  which  appeared  to  myself  most  important.  There  are 
many  other  points  to  which  by  a  careful  study  of  the  tables  his  attention  will 
naturally  be  drawn.  He  will  consider  the  observations  themselves  also,  as 
only  so  many  gropings  after  truth.  The  present  state  of  our  experimental  inqui- 
ries can  scarcely  be  supposed  as  yet  to  give  us  more  than  a  glimpse  here  and 
there  of  the  true  light.  Like  a  man  who  finds  himself  in  a  dark  dungeon,  we 
are  peeiing  tlrrough  the  comparative  gloom  of  our  prison-house,  in  the  hope  of 
finding  some  mode  of  escape  into  the  upper  day.  Like  him  we  may  be  long  in 
discovering  the  true  outlet,  and  the  passage  upwards  may  be  narrow  and  in- 
tricate ; — but  the  same  conviction  which  will  give  him  safety,  will  ultimately 
lead  us  also  to  the  light — that  he  who, persists  in  trying — marking  and  recollect- 
ing every  turning  he  has  explored — viay  at  length  escape;  but  that  he  who  sits 
still,  in  indifference,  or  gives  up  his  quest  in  despair,  is  sure  to  die  in  darkness. 


No.  IX. 

ADDITIONAL  EXPERIMENTS  IN  PRACTICAL   AGRICULTURE, 
MADE  IN    1842. 

The  following  experiments  were  made  at  Erskine,  in  Renfrewshire,  upon  the 
Home  Farm  of  Lord  Blantyre : — 

Experiment  I. — Potato  Oats,  after  old  Grass. 

The  soil  was  variable,  chiefly  good  loam,  resting  on  a  subsoil  partly  gravel 
and  partly  sand.  The  field,  having  been  long  in  pasture,  in  many  places  very 
wet,  was  drained  in  November  and  December,  1841 ;  ploughed  soon  after,  and 
sown  with  oats  on  the  8th  of  April.  The  manures  were  applied  on  the  15th 
of  April,  and  harrowed  in  with  a  single  stroke  of  the  harrows.  One-fourth  of 
an  imperial  acre  being  previously  weasured  off  for  each  plot. 

According  to  notes  taken  of  the  appearance  of  the  crop  from  time  to  time — 

May  23. — The  nitrate  of  soda  (No.  1)  looking  darker  in  colour  than  any  of 
the  other  plots;  next  to  it,  in  point  of  colour,  the  foreign  guano  (No.  5)  seems 
best;  then  the  soot  (No.  9);  then  the  sulphate  of  ammonia  (No.  2);  (?annot, 
however,  discern  any  very  decided  difference  in  the  appearance  of  the  othera 


76 


EXPERIMENTS  UPON   OATS    AND   C;5^SS. 


[Appendix^ 


May  30. — There  appears  a  slight  difference  in  favoar  of  all  the  applications 
in  the  order  above  stated,  the  sulphate  of  soda  (No.  3)  pale  in  colour. 

June  28. — Appeai'ance  same  as  on  30th  May. 

The  crop  was  cut  19th  and  20th  of  August,  and  thrashed  from  the  stock  on 
the  7th  of  September ;  the  results  carefully  ascertained,  the  grain  by  weight  and 
measure ;  the  straw  by  weight,  as  it  came  from  the  thrashing-machine ;  no  ac- 
count taken  of  the  chaff. 

RESULTS  OF  EXPERIMENT  I. OATS. 


Increase  + 

or 
Decrease  — . 

Grain.  1  Straw. 

lbs. 
+261 

-18 

lbs. 
+191 
+  53 
+  45 

u 

—49 
+41 
^0 

+  51 

±'^ 

—  73 
+163 

No 


Applications. 


Nitrate  of  Soda,  28  lbs 

Sulphate  of  Ammonia,  28  lbs.. . 

Sulphate  of  Soda,  56  lbs 

Nothing 

Foreign  Guano,  28  lbs 

TurnbuU's  BrilishGuano,56  lbs. 
Turnbull's  Impr'd  Bones,  56  lbs. 
TurnbuU's  Humus,  10  bush.,,. 
Soot,  10  busii. 


PRODUCE. 

Good  grain. 

Light  grain. 

-x: 

o  ;  c 

%:^ 

1! 

& 

as^ 

it 

II 

OQ 

s.  d. 

bsh.  lbs. 

lbs. 

lbs. 

lb.s 

lbs. 

6    3 

12    21 

m 

8 

29i 

908 

5    0 

12    22 

4(1 

10 

770 

3    0 

12    — 

40 

14i 
IO2 
6t 



762 

12    10 

_ 

717 

6    3 

12      4 

11! 



768 

4    0 

12    17i 

IO5 

io| 



788 

3    0 

11       2' 



675 

10    0 

11      8h 

Un 

— 

644 

2  11 

13    30i 

9i 

— 

880 

Experiment  11. — On  Old  Pasture  Grass  to  be  cut  for  Hay. 

The  soil  was  of  medium  quality,  on  stony  clay  subsoil.  The  part  of  the 
field  experimented  on  was  originally  very  wet,  producing  scarcely  any  better 
herbage  than  rushes  and  other  semi-aquatic  plants,  was  drained  in  1835,  has 
been  three  years  pastured  after  a  crop  of  hay  from  young  grass  in  1838 ;  the 
soil  is  of  a  blackish  friable  texture,  the  subsoil  very  retentive.  The  specific 
manures  were  applied  on  15th  April,  with  the  exception  of  the  soot,  which  was 
sown  on  the  plot  in  the  experiment  at  the  same  time  that  the  other  parts  of  the 
field  were  dressed  with  soot,  being  about  the  middle  of  March,  and  by  the 
15th  of  April  were  shewing  a  greener  shade  than  the  portion  left  for  experiment. 

April  25. — Observed  the  ridge  or  plot  No.  5  (sulphate  of  ammonia)  looking 
dark  in  the  shade,  and  that  the  salt  has  burned  the  leaves  of  daisies  and  other 
broad-leaved  plants ;  the  moss  or  fog  seems  also  to  be  burned,  it  looks  black 
and  unhealthy. 

May  7. — The  ridges  or  plots  Nos.  2,  5,  and  7,  look  decidedly  better  than  the 
rest ;  No.  3  also  seems  farther  advanced  than  where  no  applications  were  made. 

May  23. — No.  2  getting  on  Tery  fast,  and  now  looks  as  well  as  No.  1,  which 
has  always  had  the  advantage  (io  appearance)  of  the  other  plots.  The  grass 
on  No.  3  pale  in  colour,  but  taller  than  where  no  manure  was  applied.^ 

The  hay  was  cut  on  the  3d  of  July,  and  the  grass  weighed  soon,  i.  c,  in  a 
few  hours  after  being  cut  down,  but  being  very  sunny  weather  it  was  somewhat 
faded  when  weighed.     The  made  hay  weighed  and  put  into  stack  on . 

Each  plot  consisted  of  onefourth  of  an  imperial  acre. 


RESULTS    OP    EXPERIMENT    II, HAY. 


No. 

Applications. 

Cost  of 
applica- 
tion. 

PRODUCE. 

Increase 
in  Hay. 

Grass. 

lbs. 
2331 
2536i 
1936 
1760 
2516J 
2374 
3024 
2841 

Hay. 

1 
2 
3 
4 
5 
6 
7 
8 

Soot,  10  bushels.... 

8.     d. 
2    11 

\% 

5    'sl 

lbs. 
970 

1026i 
811 
726 
935 
838 

1190 

1044 

lbs. 

188 

111 

153 

408 
262 

Nitrate  of  Soda,  40  lbs 

Sulphate  of  Soda,  80  lbs 

Nothing           

Sulphate  of  Ammonia,  40  lbs. . . . 
Nothing....            

Foreign  Gnano,  40  lbs 

TurnbuU's  British  Guano,  80  lbs. 

No.  IX.]  EXPERIMENTS  UPON   WHEAT   AND   POTATOES.  77 

N.  B. — I  take  the  average  of  the  two  plots  which  had  no  manure,  as  the  sum 
to  deduct  for  finding  the  increased  produce.  The  second  column  from  the 
right  is  made  hay,  the  third  is  green  grass,  weighed  soon  after  being  cut. 

Experiment  III. — Upon  Wlicat. 

Soil,  a  good  strong  loam,  resting  on  a  heavy  subsoil  composed  of  clay  and 
small  stones,  called  till.  The  wheat  was  sown  in  November,  1841,  after  a  crop 
of  potatoes.  The  field  had  been  long  in  grass  previous  to  1840 — when  it  was 
dramed,  and  ploughed  for  oats  in  the  sfiring  of  1840 — was  well  dunged  with 
good  farm-yard  manure,  and  was  also  limed  for  the  potato  crop  of  1841,  so  that 
the  field  was  in  very  good  condition  for  wheat. 

The  manures  were  applied  14th  April,  1842,  and  harrowed  in  with  a  stroke 
of  the  harrows. 

May  10. — The  portion  No.  1  seems  darker  in  shade  than  No.  9  and  No.  8. 

June  28. — A  calm  day,  with  gentle  rain — many  of  the  lots  much  bent  down, 
as  follows: — No.  1  much  bent  down.  No.  2  partly  swirled  and  bent  at  the 
end  next  a  planting.  No.  1  swayed  at  east  e«d  next  the  planting,  not  so  bad  as 
No.  2.  No.  4  less  bent  down  than  No.  3.  No.  5  much  bent  down  and  swirled. 
Nos.  6  and  7  all  standing.  No.  8  partly  laid  down.  No.  9  very  much  swirled 
and  laid.     All  the  laid  wheat  came  up  again  in  a  few  days  after  the  rain. 

The  wheat  was  reaped  with  the  sickle,  and  in  due  course  stacked,  in  good 
condition.     It  was  thrashed  on  the  8th  February,  1843. 

RESULTS    OF    EXPERIMENT    III. WHEAT. 


Applications. 


Soot,  10  bushels 

JTurnbuU's  Humu.s,  10  bushels. , 

Improved  Bones 

TnrnbuU's  British  Guano 

Foreign  Guano 

Nothing 

Sulphate  of  Soda , 

Sulphate  of  Ammonia , 

Nitrate  of  Soda 


Total  Increase  + 
quan- 
tity.   Decrease  — . 


lbs. 
1213 
lO.'JS 
973 
1193 
1(M9 
1008 
1073 
1138 
1159 


+  205 
+  47 
-    35 

+  185 
+    41 

+  65 
+  130 
+  151 


Total 
quantity. 


bush.   lbs. 

13  3:3 
12  48 
11    58 

14  43 
11    34^ 


11 

13  7 

13  38 

13  38 


Weight 

per 
bushel. 


lbs. 


62 

61 

6U 

62 

62 

62 

62 


Increase. 


bush.  lbs. 
2     32 


47 
57 
42' 
3:ii 


2  6 
2  37 
2    37 


Experiment  IV. —  On  Potatoes. 

Soil,  a  medium  loam,  resting  on  gravel  and  sand.  The  field  was  ploughed 
from  old  grass,  and  sown  with  oats  in  1841 ;  was  drained  (where  wet)  and  deep 
ploughed  in  the  autumn  of  1841  ;  prepared  for  potatoes  in  the  spring  of  1842, 
and  well  dunged  at  the  rate  of  about  45  tons  of  very  good  dung  from  Glasgow, 
per  acre.  The  manures  were  applied  in  addition  to  the  dung,  hyping  sprinkled 
ubove  t/te  dung  in  the  drills  before  'placing  tJie  sets,  then  covered  by  reversing  the 
drills,  on  the  21st  and  22d  of  April,  1842. 

During  the  season  could  discover  little  or  no  difference  in  the  appearance  of 
the  portions  dressed  with  the  specific  manures,  from  where  no  applications 
were  made ;  the  crop  was  a  very  equal  good  one  over  all  the  field.  One-fourth 
of  an  imperial  acre  tn  each  plot. 


'  I  can  ill  reconcile  the  great  produce  from  No.  4  with  the  appearances  when  growing, 
and  have  been  suspicious,  that  notwithstanding  every  precaution  being  taken  to  avoid  mix- 
ing, some  sheaves  of  No.  5  plot,  have  been  taken  to  No.  4,  while  the  crop  was  in  stook,  as  it 
was  soinetimes  necessary  (during  the  time  the  stooks  were  in  the  field)  to  have  them  re- 
paired, they  being  blown  down  once  or  twice. 

The  cost  of  the  applications,  as  also  '.he  quantities  applied,  of  the  different  materials,  were 
the  same  as  in  Experiment  No.  I.,  on  Oats.  The  light  grain  is  not  here  taken  into  account, 
as  it  was  too  trifling  in  quantity  and  quality  to  be  of  any  importance,  and  nearly  the  same  in 
every  case. 


78 


EXPERIMENTS   UPON   POTATOES, 


[AppeTidiXf 


RESULTS    OP    EXPERIMENT   IV.- 

—ON    POTATOES. 

1 

1 

i 

Manures. 

Cost.       1           PRODUCE. 

I 
i 

Increase  +  or 
Decrease  — . 

jNo. 

^  Nitrate  of  Soda        14  lbs.  P 

s.     d. 
4    7i 

4    0 

6    3 
4    0 

2  6i 

3  0 

tons.  cwt.  qrs.  lbs. 
3      0      1    24§ 

2  19     0   ai| 

3  0      0      0 
2    19      2    21 
2    15      3    21 
2    19      2    21 
2    18      I    21 
2    19      0      7 

cwt.  qrs.  lbs. 

+  1    1    m 

4-0      0      17i 

+  0      3      21 
4-  0      2      14 
-3      0      14 
+  0      2      14 
-  0      2      14 

2 
3 
4 
5 
6 
7 
8 

j  Sulphate  of  Soda 28  lbs.  \ 

\  Sulphate  of  Soda 28  lbs.  ) 

}  Sulphate  of  Ammonia 14  lbs.  ^ 

TurnbuU's  British  Guano 56  lbs. 

Improved  Bones,  TurnbuU's,  56  lbs. 

Nothin"                 



The  gypsum  used  turned  out  to  be  genuine  on  analysis.* 


REMARKS  UPON  THE  PRECEDING  EXPERIMENTS. 
1°.  Effect  of  the  drought. — It  is  to  be  observed,  in  the  first  place,  that  the 
great  drought  of  the  season  exercised  an  unfavourable  influence  upon  the  re- 
sults of  these  experiments  also.  It  is  necessary,  therefore,  to  suspend  our  judg- 
ment in  some  measure  regarding  them — until  future  experiments  in  other  sea- 
sons shall  confirm  or  modify  them. 

2°.  Inferences  to  be  drawn  frovi  the  colour  of  the  crop. — A  new  feature  in- 
troduced by  Mr.  Wilson  in  the  account  of  these  experiments,  is  the  appearance 
presented  by  the  several  crops  at  different  specified  periods  after  the  dressings 
were  applied. 

It  is  a  common  thing  for  practical  men  to  estimate  the  relative  produce  of 
different  fields  or  parts  of  the  same  field  by  their  appearance,  and  especially  by 
the  colour  of  the  growing  crops.  Yet  that  this  is  not  to  be  depended  upon  in 
a  corn  crop,  is  proved  by  the  observation  that  up  to  the  end  of  June  appearances 
in  the  oat  field  were  most  in  favour  of  the  nitrate  of  soda,  the  guano  being  se- 
cond, and  the  soot  third  in  order.     Yet,  when  reaped,  the — 

Nitrate  gave  an  increase  of  only 2 J  bushels  per  acre. 

Guano 24  lbs.  per  acre. 

Soot 6  bushels  per  acre. 

The  nitrate  did  give  a  little  more  straw  than  either  of  the  other  two,  but  that 
the  colour  is  not  an  unfailing  criterion  even  as  to  the  produce  of  straw  or  of 
nay  is  shewn  by  the  experiments  upon  oats  and  upon  hay.     In  both  of  these 

'  List  of  prices  paid  for  the  manures  used  in  the  foregoing  experiments: — 

1.  Foreign  Guano 25s.  per  cwt. 

2.  TurnbuU's  Guano 8s.      " 

3.  TurnbuU's  Improved  Bones 6s.      " 

4.  TurnbuU's  Humus Is.  per  bushel 

5.  Nitrate  of  Soda  ....  25s.  per  cwt. 

6.  Sulphate  of  Soda  (dry)  6s.      " 

7.  Sulphate  of  Ammonia 20s.      " 

8.  Soot 3id.  per  bushel. 

Nos.  2,  3,  4,  and  7,  were  manufactured  and  furnished  by  TurnbuU  and  Company,  Chem- 
ists, Glasgow.    The  British  (Guano  No.  2)  is  said  to  be  made  up  as  follows  :— 

2  cwt.  of  Sulphate  of  Soda. 
2  cwt.  of  Sulphate  of  Ammonia. 
1  cwt.  of  Common  Carbonate  of  Soda. 
15  cwt.  of  Improved  Bones,  manufactured  by  TurnbuU  «fc  Co. 

20  cwt.,  or  1  ton. 

The  Improved  Bones  are  said  to  be  halT  dissolved  bones  and  half  wood-charcoal.  I  be- 
lieve the  bones  include  animal  matter,  as  \  am  informed  the  carcases  of  old  horses,  Ac, 
are  aU  used  in  the  manufacture.  James  Wilson. 

Freeland,  Erskine,  20th  February,  1843 


No.   IX.]        ,  REMARKS    UPON    PRECEDING   EXPERIMENTS.  79 

crops  the  portions  dressed  with  sulphate  of  soda  are  described  as  pale  in  colour 
and  yet  the  excess  of  produce  over  the  undressed  parts  was  as  follows  : — 
In  the  oats     .     ,     li  cwt.  straw.     } -txri        .u        i   i    .  v  j 

In  the  hay  .  .  2  cwt.  per  acre.  \  ^"^^'^'^  ^^^  ^^^P^^^e  was  applied. 
The  increase  in  neither  case  would  bs  deser-ving  of  much  attention  except 
as  showing  satisfactorily  thaj,  wrong  conclusions  may  be  drawn  in  regard  to 
the  efficacy  of  manures  and  top-dressings  by  those  who  judge  only  by  the  eye 
— and  that  safe  reliaiice  can  be  placed  on  those  comparative  results  oidtj  which  have 
been  tested  by  weight  and  measure.  I  know,  indeed,  that  practical  farmers  who 
have  applied  nitrate  of  soda  to  grass  land,  and  have  been  delighted  by  the  beauti- 
ful green  colour  which  followed,  have  occasionally  been  disappointed  by  find- 
ing that  after  all  this  promise  the  weight  of  hay  obtained  was  no  greater  than 
upon  the  undressed  parts  of  their  fields.  As  to  the  feeding  qualities  of  the  two 
kinds  of  hay  no  experiments  have  yet  been  made,  though  it  is  known  that  cat- 
tle prefer  that  which  has  been  dressed. 

Suggestion  XI. — I  put  down,  therefore,  as  a  distinct  suggestion  for  the  pur- 
pose of  drawing  attention  to  the  subject,  that  this  plan  of  specially  noting  the 
appearance  of  the  crops  at  stated,  say  monthly  periods,  should  be  adopted  in  all 
future  experiments.  This  will  serve,  not  merely  to  show  us  more  clearly  what 
kind  of  appearances  are  to  be  trusted,  and  how  far,  as  indications  of  an  increase 
of  crop — but  may  hereafter  prove  of  further  importance  when  experiments  shall 
begin  to  be  instituted  upon  the  feeding  properties  of  crops  reaped  under  dif- 
ferent circumstances,  and  raised  under  different  kinds  of  management. 

3°.  Importance  of  having  iv;o  or  more  experimental  plots  similarly  treated. — 
The  experiments  upon  hay  above-mentioned  exhibit  another  illustration  of  the 
fact  adverted  to  in  page  59  of  this  Appendix  under  the  head  of  limits  of  error. 
I  there  drew  the  attention  of  experimenters  to  the  difference  in  the  produce  ob- 
tained on  two  equal  patches  of  the  same  field  of  turnips,  to  neither  of  which 
any  dressing  had  been  applied.  At  Erskine  two  equal  plots  of  grass  in  the 
same  field  gave  a  similar  difference  of  produce.  1  pi-esent  both  results  here  for 
the  sake  of  clearness.     The  produce  per  imperial  acre  was — 

Hay  at  Erskine.  Turnips  at  Barochan. 

tons,     cwt  tons,    cwt 

1st  plot 4        5  12      17 

2d  plot 3        3  11        8 

Difference 12  19 

In  my  remarks  upon  the  difference  between  the  two  plots  of  turnips  (Appen- 
dix, p.  50).  I  expressed  an  opinion  that  differences  equally  great,  depending  not 
at  all  upon  the  substance  applied,  might  be  expected  on  equal  portions  of  those 
fields  upon  which  our  different  saline  manures  may  have  been  applied ; — and 
that  very  erroneous  conclusions  might  thence  be  drawn  in  regard  to  the  abso- 
lute and  comparative  effects  of  the  substances  with  which  our  experiments  are 
made  upon  the  crops' to  which  they  are  applied. 

I  have  since  met  with  a  confirmation  of  this  view  in  a  record  of  two  pairs  of 
experiments  made  with  equal  quantities  of  rape  cake  upon  equal  plots  of  red 
whea^,  in  the  same  season,  and  upon  adjoining  parts  of  the  same  field,  ^British 
Husbandry,  I.,  p.  112.)  The  results  of  two  experiments  Vith  different  quem- 
tities  of  rape  dust  were  as  follows : — 

Produce  of  Light 

Rape  dust  applied,  marliet  corn.      Weight  per  bushel.  com. 

stones.  bush.  lbs.  oz.  lbs. 

1st  plot 59i     ...    26    ...    52    10    ...    46 

2nd  plot 59i    ...    21     ...    50      8    ...    67 

1st  plot 86      ...    28    ...    53      4    ...    35 

2nd  plot 86      ...    22    ...    51      2    ...    91 

The  differences  both  in  the  quantity  and  in  the  weight  of  the  grain  reaped,  ir 

30 


80  REMARKS    UPON   PRKCKDINa  EXPERIMENTS.  [Appendix^ 

each  of  these  pairs  of  experiments, are  so  great  that  had  they  been  ohtained  from 
plots  of  ground  dressed  with  different  manures  we  should  readily  have  ascribed 
them  to  the  unlike  action  of  the  substances  we  had  applied.  Doubts  may  natu- 
rally arise,  therefore,  when  we  look  at  the  several  tables  of  results  contained  in 
this  Appendix,  how  far  the  differences  presented  in  them  are  really  due  to  the  un- 
like action  of  the  manures  employed,  and  how  far  to  natural  causes  not  hitherto 
investigated.  Can  all  the  experiments  madedui-ing  these  last  two  years  with  so 
much  care  really  be  vitiated  oy  this  source  of  error'?  The  point  must  be  eluci- 
dated by  further  experiment.  Should  it  prove  that  we  have  here  a  general 
source  of  error,  it  is  satisfactory  at  least  that  we  have  discovered  it  at  the  threshold 
as  it  were  of  our  accurate  experimental  inquiries,  and  that  we  can  devise  means 
of  avoiding  it  in  future. 

I  therefore  repeat  the  Suggestions  I.  and  II.,  which  I  ventured  to  offer  in  page 
60  (Appendix),  that  some  of  my  readers,  of  whom  I  believe  many  are  interested 
in  this  subject,  would  in  the  ensuing  season  ascertain  accurately  the  produce  of 
equal  measured  quantities  of  the  same  field,  under  whatever  crop  it  may  be, 
and  publish  or  transmit  the  result  to  me — and  that  in  all  future  experiments 
made  with  the  view  of  ascertaining  the  effect  of  different  manures  upon  any  crop. 
two  plots  at  least,  and  not  adjoiiiing  to  each  other,  should  be  treated  alike  in  each 
field,  and  the  mean  of  the  several  results  obtained  with  each  substance  taken  as 
the  average  produce  from  which  their  comparative  effects  are  to  be  estimated. 

These  points  appear  to  me  to  be  of  primary  importance,  and  to  lie  at  the 
foundation  of  the  structure  1  hope  we  are  now  beginning  to  rear  with  the  results 
of  inductive  experimental  agriculture. 

4.  Action  of  soot.— In  these  experiments  a  top-dressing  of  soot  increased  con- 
siderably the  produce  of  oats  and  wheatj  while  it  diminished  the  produce  of  po- 
tatoes when  mixed  with  the  manure.  Thus  the  produce  per  acre  on  the  dressed 
and  undressed  parts  was — 

Oats.  Wheat.  Potatoes. 

Undressed  .  .  49  bush.  .  .  44  bush.  .  .  11  tons  10  cwt. 
Dressed  ...  55  bush,  .  .  54  bush.  .  .  11  tons  3  cwt. 
The  unfavourekble  effect  upon  the  potato  crop  may  probably  be  due  to  the 
mode  in  which  it  was  applied,  as  in  other  districts  it  is  veiy  useful  to  potatoes, 
and  gave,  as  we  have  seen,  when  applied  alone  to  turnips,  an  increase  of 4  tons 
per  acre.  (See  Mr.  Fleming's  Experiments,  Appendix,  p.  43:  also,  Lecture 
XVII.  p.  438). 

5.  Comparative  action  of  soot  and  of  nitrate  of  soda. — The  immediate  effect 
of  both  these  substances  is  to  darken  the  colour  and  to  increase  the  growth 
of  hay  and  straw.  In  this  respect  the  advantage  is  rather  on  the  side  of  the  ni- 
trate, while  the  soot  in  some  cases  gives  a  little  more  grain.  Thus  the  increase 
of  produce  per  imperial  acre  of  the  three  crops  of  hay,  wheat,  and  oats,  dressed 
■with  each  of  the  three,  was  nearly  as  follows: — 

Hay.  Wlieat.  Oats. 

Grain.  §traw. 

Soot    ....     7  cwt.     .     .     10    bush.     .     .     6     bush.       6  cwt. 
Nitrate  of  soda .    9  cwt.     .     .     10^  bush.     .     .     6^  bush.       7  cwt. 
In  both  cases,  however,  the  sooted  grass  was  lighter  per  bushel.     Thus  their 
comparative  weights  were — 

Wheat.  Oats. 

Sooted  .  .  ,  58  lbs.  .  .  41  lbs. 
Nitrated  ...  62  lbs.  .  .  42^  lbs. 
Nevertheless,  the  advantage  to  the  practical  man  is  decidedly  on  the  side  of 
the  soot,  since  the  cost  of  40  bushels  of  soot  per  acre  was  only  I2s.,  while  that 
of  1  cwt.  of  nitrate  of  soda  was  25s.  It  is  only  to  be  regretted  that  soot  is  so 
variable  in  its  constitution  that  firm  reliance  cannot  be  placed  upon  the  uniform- 
ity of  its  effects, 

6°.  Actixyn  of  guano. — In  the  text,  p.  460, 1  have  stated  the  apparent  conclusion 
to  which  the  Erskine  experiments,  taken  in  connection  with  all  the  others  Ihav« 


No.  IX.l  HEMAHKS   UPON   PRECEDING    EXPERIMENTS.  81 

yet  met  with,  seem  to  point — that  it  is  more  uniformly  successful  when  applied  to 
root  than  to  grain  crops.  The  increase  of  oats  in  the  present  experiment  did  not 
exceed  half  a  bushel  per  acre — though  that  of  hay  amounted  to  14|  cwt. 

7°.  Action  of  sulphate  of  soda. — I  have  already  noticed  the  effect  which  this 
salt  has  in  paling  the  colour  of  the  crop,  even  when  the  produce  of  grass  or 
straw  is  increased.  In  regard  to  the  grain,  we  see  in  the  experiment  upon  oats 
that  it  reduced  the  crop,  1^  bushels  per  acre — while  the  wheat  crop  was  increased 
10  bushels  by  a  similar  application. 

Is  this  difference  in  its  effects  due  to  the  nature  of  the  soil,  or  to  the  special 
action  of  the  sulphate  upon  the  two  crops  % 

We  have  seen  in  the  experiments  made  in  1842  at  Lennox  Love  (p.  52),  that  the 
sulphate  of  soda  diminished  the  oat  crop  15|  bushels  per  acre — an  effect,  how- 
ever, which  may  be  mainly  ascribed  to  the  great  drought  in  that  locality,  since 
even  nitrate  of  soda  caused  a  diminution  of  12^  bushels.  But  it  also  diminished 
the  wheat  crop  at  the  same  place  to  the  extent  of  9^  bushels  per  acre,  but  upon 
this  crop  also  the  drought  appeared  to  interfere  with  the  natural  action  of  the  sev- 
eral top-dressings  which  were  applied,  so  that  no  trust-worthy  conclusion  can 
be  drawn  from  the  apparent  results  of  their  action. 

Suggestion  XII. — I  have  already  suggested  (p.  72)  an  interesting  experiment 
with  sulphate  of  soda,  in  order  to  test  the  very  curious  observation  of  Mr.  Flem- 
ing, that  when  applied  to  land  sown  with  artificial  grasses,  it  brought  up  a  crop 
consisting  almost  entirely  of  fescue  grasses,  though  none  of  these  had  been 
sown.  1  would  here  suggest  further  that  the  marked  difference  observed  at 
Erskine  between  the  action  of  this  sulphate  upon  wheat  and  oats  should  be 
further  investigated — with  the  view  of  obtaining  a  satisfactory  answer  to  this 
question — Does  sulphate  of  soda  act  less  favourable  upon  wheat  than  upon 
oats  in  the  same  soil  1  Or  does  an  unlike  action  manifest  itself  only  when  the 
soils  are  different  ^  I  fear  the  suggestion  comes  too  late  for  the  present  year, 
unless,  as  I  hope,  there  are'  experiments  already  in  progress  which  will  throw 
light  upon  the  question.  But  the  suggestion  will  not,  I  believe,  be  overlooked 
when  another  year  comes  round. 

It  is  furtiier  worthy  of  remark,  in  regard  to  the  action  of  the  sulphate  of  soda 
upon  the  wheat  crop,  that  the  straw  was  stronger  and  less  laid  than  where  any 
of  the  other  dressings  were  applied. 

8°.  Action  of  siUpkate  of  avinwnia.— The  substance  employed  under  the  name 
of  sulphate  of  ammonia,  as  t  stated  in  a  previous  part  of  this  Appendix  (p.  61,) 
is  not  what  its  name  implies.  The  makers,  the  Messrs.  Turnbull,  of  Glasgow, 
inform  me  that  it  is  prepared  by  adding  sulphuric  acid  to  fermenting  urine,  and 
evtiporating  to  dryness*.  Though  sucli  a  substance  must  vary  in  composition 
with  the  urine  from  which  it  is  prepared,  and  must  contain  more  or  less  am- 
'monia  according  to  the  degree  of  fermentation  which  the  urine  has  undergone, 
yet  good  effects  may  fairly  be  expected  from  it.  I  here  exhibit  the  effect  of  1  to 
li  cwt.  per  acre  applied  to  different  crops — 

Undressed.  Dressed.  Made  at 

Wheat 44    bush.  54j  bush,  Erskine. 

Do 3U  bush.  40    bush.  Gadgirth. 

Oats 49    bush.  50    bush.  Erskine. 

Turnips 12|  tons.  24^  tons.  Barochan. 

Potatoes 12f  tons.  I4j  tons,  do. 

Do 8f  tons.  I3i  tons,  do. 

These  results  not  only  recommend  this  substance  to  the  practical  farmer,  but 
they  also  enforce  the  remarks  I  have  made  in  the  text  upon  the  value  of  urine 
in  general,  upon  the  large  waste  of  manure  annually  incurred  by  the  neglect  of 
it,  and  upon  the  virtual  money-loss  which  is  suffered  by  those  who  allow  it  to 
escape  from  their  farm-yards.     [See  Lecture  XVIII.,  p.  463.] 

9°.  Action  of  Thcr-nbulVs  humus. — This  humus,  is  it  is  called,  is  night-soil 

*  In  the  text  I  have  described  it  under  the  name  of  aulphated  ur»n«.— Bee  p.  461. 


82  REMARKS    UPON   PRECEDINa   EXPERIMENTS.  [AppeTldix, 

and  urine  mixed  with  charcoal  and  gypsum,  and  dried  by  a  gentle  heat.  Its  ef- 
fects upon  the  wheat  crop  are,  in  the  present  experiments,  more  favourable  than 
any  of  those  I  have  yet  placed  upon  record.  The  following  experimental  re- 
sults exhibit  the  nature  of  its  action  in  two  localities,  both  in  the  seune  neigh- 
bourhood : — 

Undressed.  Dressed.  Experiments  made  at 

Wheat      ...    44    bush.  51    bush.  Erskine. 

Oats     ....    49    bush.  45   bush.  do. 

Turnips   .     .     .     12f  tons.  13|  tons.  Barochan. 

Do.         ...     12    tons.  17    tons.  do. 

Potatoes  .     .     .    '  5|  tons.  lOf  tons.  do. 

These  results,  especially  those  upon  the  corn  crops,  are  not  so  beneficial  as 
might  well  be  expected  from  a  prepared  night-soil,  and  they  affoi-d  room  for  the 
suspicion  that  the  mode  of  manufacture  has  been  such  as  to  dissipate  some  of 
the  more  valuable  constituents. 

10°.  Experiments  upon  potatoes. — In  the  experiments  upon  potatoes  the  whole 
crop  averaged  12  tons  per  acre,  and  the  parts  of  the  field  to  which  the  artificial 
manures  were  added  exhibited  no  marked  increase  above  this  general  average. 
Even  the  mixture  of  nitrate  with  sulphate  of  soda,  which  in  so  many  other 
cases  has  proved  beneficial  to  the  potato  crop,  in  this  instance  produced  only  1 
cwt.  of  increase. 

It  may  be  that  the  manure  which  was  added  at  the  rate  of  45  tons  per  acre 
contained  a  sufficient  supply  of  all  those  kinds  of  food  which  were  added  after- 
wards in  the  saline  and  other  substances.  If  so,  a  larger  crop  could  only  have 
been  obtained  by  the  addition  of  some  other  substance  not  tried,  for  a  loam  of 
moderate  quality  ought  to  be  able  to  produce  more  than  12  tons  of  potatoes  per 
acre. 

Or  it  may  be  that  these  same  artificial  manures  would  have  produced  a  larger 
increase  had  they  been  put  on  as  a  top-dressing  after  the  crop  had  come  up,  in- 
stead of  being  spread  upon  the  manure  before  the  potatoes  were  planted  upon 
it.  In  the  experiments  of  Mr.  Fleming  made  with  especial  reference  to  this 
point,  [Appendix,  pp.  49  and  (Jt),]  it  was  found  that  a  lai-ger  propoi'tionate 
iticreose  was  obtained  from  the  same  saline  substances  applied  in  equal  quanti- 
ties to  the  potato  crop  wJien  they  were  spread  upon  the  manure^  than  when  they 
•were  applied  as  a  top-dressing  after  the  crop  had  come  up.  Still  the  experiments 
in  his  case  being  made  in  different  fields,  I  stated  that  the  point  was  not.U)  be 
considei-ed  as  established,  but  was  deserving  of  further  investigation.  This 
opinion  is  strengthened  by  the  results  of  these  experiments  of  Lord  Blantyre : 
I  would  therefore  beg  to  offer  as — 

Suggestion  XIII. — That  the  application  of  saline  manures  to  the  potato 
crop^either  when  the  trial  is  made  for  the  purpose  of  obtaining  practical  infor- 
mation, which  may,  hereafter,  be  valuable  as  a  guide  to  the  operations  of  the 
farmer,  on  the  land  where  his  experiments  are  made,  or  for  that  of  arriving  at 
results  which  may  be  theoretically  useful — that  the  same  proportions  should  be 
applied  to  two  or  more  plots  buried  with  the  manure,  and  to  two  or  more  dusted 
on  as  a  top-dressing.  From  an  accumulation  of  results  obtained  in  both  ways, 
we  shall  be  able  to  extract  something  like  a  principle  by  which  practical  men 
may  be  easily  guided  in  that  direction  which  is  likely  in  the  greatest  number 
of  cases  to  lead  to  the  greatest  amount  of  profit. 

11°.  Water  in  the  potatoes. — I  will  here  add  one  other  observation  upon  the 
potato  experiments.  There  was,  as  we  have  already  remarked,  no  notable  dif- 
ference in  the  weight  of  crop  raised  upon  the  several  patches.  But  the  quality  of 
the  crop — the  weight  of  dry  food  raised  upon  the  several  patches — might  really 
be  different  notwithstanding.  In  my  remarks,  [Appendix,  p.  65],  upon  the  Baro- 
chan experiments  upon  potatoes,  made  in  1842,  I  have  drawn  attenti-on  to  the 
fact  that  potatoes  sometimes  contain  as  much  as  30  per  cent,  of  dry  food,  and  at 
other  times  as  little  as  20  per  cent.,  and  therefore  that  a  ton  of  potatoes  of  one 
kin/i  wiay  contain  6  cwt,,  while  the  same  weight  of  another  contains  only  4 


No.   /X]  REMARKS  UPON  PRECEDING  EXPER'iMENTS.  83 

cwt.  of  dry  nourishment.  It  may  be,  therefore,  that  as  by  growing  in  unlike 
soils  or  with  unequal  degrees  of  rapidity  our  potatoes  may  contain  different  pro- 
ponious  of  water,  so  by  different  kinds  of  dressings  which  act  in  the  same  way 
as  natural  differences  of  soil,  and  cause  the  plants  to  develope  themselves  with 
greater  or  less  rapidity,  the  same  effects  may  be  produced.  One  kind  offline 
substance,  such  as  nitrate  of  soda,  by  hastening  the  growth,  may  give  us  a  crop 
of  potatoes  containing  much  water,  while  another,  such  as  sulphate  of  soda,  by 
retarding  the  growth,  may  give  a  crop  containing  less  water — and  thus,  though 
tnere  may  be  no  difference  in  the  weight  of  the  two  crops,  they  may  be  very 
unlike  in  the  relative  proportions  of  food  they  contain. 

If  such  be  the  case  it  is  of  great  practical  importance  to  determine  the  quantity 
of  water  which  our  several  experimental  potato  crops  contain,  since  without 
this  we  may  draw  very  incorrect  conclusions  as  to  the  value  of  our  experimental 
manures — placing  the  highest  value  upon  that  which  gives  the  greatest  weight 
of  raw  material,  and  esteeming  least,  perhaps,  that  which  produces  the  greatest 
weight  of  dry  food 

1  would  again,  therefore,  draw  the  attention  of  my  readers  to  the  subject  of 
Suggestions  IV.  and  VI.,  [Appendix,  pp.  63  and  65,]  in  reference  to  the  deter- 
mination of  the  quantity  of  water  in  their  experimental  root  crops.  The 
method  of  doing  this  is  very  simple,  and  has  already  been  described,  [Appendix, 
P-  64.]  , 

Each  new  series  of  experimental  results  we  are  called  upon  to  examine  and 
analyse,  will,  I  hope,  more  and  more  satisfy  my  readers,  as  they  do  myself, 
that  this  is  the  true  line  of  procedure,  and  that  though  there  may  be  much  in 
our  results  at  first  which  may  appear  contradictory  and  discouraging,  yet  that 
out  of  these  crude  results,  when  combined,  compared,  and  frequently  repeated, 
the  real  substance  of  a  rational  agriculture  will,  slowly  it  may  be  and  with  dif- 
ficulty, yet  surely  at  last,  be  extracted. 


No.   X. 

RESULTS    OP   EXPERIMENTS    IN    PRACTICAL   AGRICULTURE,    MADE 
AT    B.\ROCHAN    IN    1843. 

Experiment  I. —  Upon  Potatoes. 

Comparative  effects  of  guano,  farm-yard  manure,  gypsum,  &c.,  by  them- 
selves and  in- mixture,  upon  Potatoes  of  different  varieties,  planted  25th,  26th, 
and  27th  April;  lifted,  measured,  and  weighed  from  12th  to  14th  October, 
1843.     On  one-eigJdh  of  an  imperial  acre. 

The  portion  of  the  field  upon  which  these  potatoes  were  grown  contains 
about  five  acres ;  soil — loam  of  medium  texture,  super-incumbent  upon  trap 
rock.  It  was  trenched  with  the  spade  out  of  seven  years  old  lea  in  the  winter 
of  1812  and  1843  to  the  depth  of  16  inches,  the  sward  bein^  turn-spaded  into 
the  bottom  of  the  trench,  and  the  subsoil  a  stiff  yellow  tril  brought  up  to  the 
top,  which  mouldered  down  to  a  fine  mould  during  the  winter.  The  drills  were 
formed  for  the  potato  cuts  with  the  double-moulded  plough,  and  by  the  7th 
June  the  plants  were  all  brairded  in  the  rows,  and  were  worked  in  the  usual 
manner  with  the  plough,  drill,  grubber,  and  hand-hoes.  After  the  drills  were 
formed,  where  the  guano  was  used,  it  was  sown  in  the  drills  by  the  hand,  on 
the  bottom  and  sides  of  the  drills,  the  farm-yard  manure  being  then  put  in  and 
30* 


»4 


EXPERIMENTS    UPON    POTATOES. 


[Appe-ndiXf 


No. 


Manures. 


Guano 

Farmyard  manure 

Guano f. 

Farm-yard  manure 

Farmyard  manure 

Guano  

Farm-yard  manure 

Guano 

Farm-yard  manure 

Gypsum 

Farm-yard  manure 

Gypsum,    powdered    on 

sets 

Farmyard   manure 

Farm-yard   manure 

and  top-dressed  7th  Jaly 

with  Guano 

Guano..  ..• 

Farm  yard   manure 

Guano 

Gaano 

Farm-yard  manure 

Farm-yard  manure 

Guano 


spread  upon  the  top  of  it.  Cut  sets  were  then  laid  on  and  covered  up  with 
aoout  three  inches  of  soil.  Particular  attentioyi  should  be  paid  when  guano  is 
used,  that  it  be  well  mixed  with  the  soil,  as  this  is  of  the  greatest  importance  to  the 
health  of  the  plants  and  the  bulk  of  the  crop,  especially  in  Ike  case  of  potatoes  and 
turnips.  This  conclusion  has  been  arrived  at  after  three  years' extensive  ex- 
perience in  the  use  of  guano  as  a  manure ;  as  it  has  been  found  here  that  the 
more  minutely  it  is  spread  and  worked  into  the  soil  the  crop  is  the  heavier  and 
the  better  matured.  When  it  has  been  used  in  a  body  immediately  under  the 
plant,  it  has  always  been  found  to  induce  a  strong  vigorous  growth  of  stems 
and  leaves,  and,  in  general,  to  ripen  the  plant  prematurely,  and  both  the  potatoes 
and  turnips  were  in  consequence  deficient  in  tubers  and  bulbs.  From  these 
circumstances  it  may  be  inferred — what  is  indeed  known  to  be  the  case — that 
the  guano  does  not  contain  all  the  ingredients  which  are  required  by  the  plants, 
and  that  the  large  proportion  of  ammoniacal  salts  it  contains — when  it  is  laid 
in  a  mass  in  immediate  contact  with  the  roots  of  the  plants — pushes  on  the 

frowth  too  quickly  with  small  stems  and  delicate  leaves.  Numerous  small 
ulbs  are  the  consequence,  and  the  cultivator  being  disappointed  is  led  to  pro- 
nounce the  guano  wortliless,  whilst  his  inferior  crop  may  be  in  a  great  measure 
owing  to  bad  management.  Whatever  may  be  the  reason,  however,  it  has 
been  found  in  using  it  here  that  when  sown  broad-cast  the  crops  of  every  descrip- 
tion have  been  benefitted,  while,  on  the  other  hand,  7vhen  laid  in  a  body  near 
the  roots  the  reverse  has  been  the  case.  In  cutting  the  potato  for  seed,  gypsum 
in  powder  was  strewed  upon  the  sets  when  newly  cut,  and  it  will  be  seen  from 
No.  6  of  the  table,  with  good  effects  in  adding  to  the  produce,  as  where  the  cuts 
were  so  powdered,  as  in  No.  6,  their  superiority  over  No.  7  (which  was  not 
done  so)  m  point  of  strengthand  vigour  was  most  remarkable,  and  when  lifted 
the  produce  was  1  ton  5  cwt.  per  acre  more  than  No.  7.  It  may  also  in  a  certain 
measure  be  a  means  of  preventing  failure  in  the  potato,  as  there  was  no  failure 
in  this  field  where  the  gypsum  was  so  used  on  the  cuts,  while  the  same  seed 
potatoes  failed  upon  another  field  which  was  planted  at  the  same  time,  but 


No.  X.] 


EXPERIMENTS   UPON   POTATOES    AND   HAY. 


85 


where  tw  gypsum  was  poiodered  on  Ike  sets.  At  all  events,  it  is  worthy  of  a  more 
extensive  trial  as  a  preventative,  and  it  will  in  all  soils,  where  it  is  deficient, 
add  to  the  produce.  It  has,  at  the  same  time,  the  merit  of  being  a  cheap  appli- 
cation. 

There  was  no  great  alteration  in  point  of  strength  or  forwardness  till  the  1st 
of  July,  wlien  all  those  patches  upon  which  the  guano  had  been  used  began  to 
take  the  lead  of  those  planted  with  farm-yard  manure  alone.  The  guano  produced 
a  dark  green  colour  and  very  strong  stems  and  leaves,  so  much  so,  that  it  was 
found  when  too  late  that  they  had  been  too  near  planted,  i.  e.,  32  inches  between 
the  drills,  and  12  inches  between  plant  and  plant.  '?here  would  have  been  a 
far  heavier  crop  if  there  had  been  more  space,  as  the  strong  growing  varieties, 
such  as  the  cups  and  blues,  were  nearly  choked  for  want  of  air.  It  will  be 
seen  from  the  tables  that  a  mixture  of  guano  and  farm-yard  manure  gave  a 
greater  crop  than  where  either  of  them  was  used  alone.  The  portion.  No.  8, 
wtis  top-dressed  with  guano  when  the  potatoes  were  set  up  for  the  last  time. 
It  was  sown  broad-cast  between  the  drills,  after  which  the  drill  harrow  was  put 
through  them  and  the  plough  followed,  it  acted  immediately  by  altering  the 
colour  to  a  dax-k  green,  the  plants  putting  out,  at  the  same  time,  new  stems  and 
leaves,  but  owing  to  its  being  applied  so  late  in  the  season,  there  was  a  larger 
proportion  of  small  potatoes  than  at  the  others  when  lifted.  After  many  trials 
it  has  been  found  that  the  best  and  most  economical  way  of  using  guano  for  the 
potato  crop  is  by  adding  2  or  3  cv^L  per  acre  to  half  the  usual  quantity  of  farm- 
yard dtmg,  which  will  be  found  to  give,  at  least,  as  good  a  crop  as  double  the  quan- 
tity of  dung  alone,  whilst  it  is  much  cheaper  in  the  first  cost,  and  saves  much 
cartage,  which  is  of  tlie  greatest  moment  to  the  farmer  in  spring.  From  its 
effects  upon  the  oat  crop  of  this  season,  where  it  was  used  as  a  manure  for  the 
turnip  crop  of  1842,  at  the  rate  of  3  cwt.  per  acre,  it  seems  permanent — as  the 
oats  will  bear  a  comparison  with  those  which  grew  where  the  land  was  manured 
with  40  cubic  yards  of  farm-yard  dung,  and  th6  hay  crop,  at  this  time,  looks 
as  strong  and  forward  as  any  in  the  same  field.  Potatoes  manured  with  guano, 
or  dressed  with  sulphate  and  nitrate  of  soda,  appear  also  to  be  ijnproved  in  /lealth, 
and  the  tubers  so  grown  are  less  apt  to  fail  when  cut  and  planted  the  following 
season. 

Experiment  II. — 0?i  Hay. 

Effect  of  top-dressings  of  various  substances  upon  three  years  old  Grass, 
mostly  Timothy,  cut  for  hay  in  1843  ;  top-dressed  on  the  3d  of  June  ;  cut  on 
the  5th  of  August ;  weighed  when  cut,  and  again  weighed  when  stacked  on  the 
28th  ot  August.  GLuantity  of  ground  under  each  dressing — One-eighth  of  an 
imperial  acre. 


ON  ONK-BIGHTH  OF  AN  IMPERIAL   ACRE. 

PER.  IMP.  ACRE. 

s 

"6 

tU) 

3 

3 

=  13 

ife" 

S- 

0)   0) 

^^ 

.2 

a 

a 

'i 

§■= 

.£3     • 

2  ^ 

^■^ 

No. 

Dressings. 

cd 
1 

o 
s.  d. 

1 
Ihs. 

.a 

c  ^ 
lbs. 

=1 

o  c    . 
St.  lbs. 

III 

m 

O  g 

it 

lbs. 

qrs.  lbs. 

St.  lbs. 

St. 

£.   s.   d. 

1 
2 

Nothing        ........ 

1    14 
5  bush. 

3  10 
2  6 

1344 
4660 

4500 

3316 
3156 

52    11 

91      7 
96      6 

38    10 
43      9 

416 
752 
761 

6    18    8 
12    10    8 

12    13    8 

350 
275 
300 

Guano 

Compost  of   saw-  ) 
dust  and  coal  tar.  ^ 

4 

Muriate  of  ammonia. 

0    20 

30 

3700 

2356 

70      0 

17      3 

560 

9      6    8 

265 

l^ 

Sulphate  of  urine,  ) 

Turnbull's \ 

Nitrate  of  soda 

0    20 

3  0 

3780 

2436 

84      0 

32      0 

672 

11      4    0 

312 

0    20 

09 

2840 

1496 

53      0 

1      0 

424 

7      1    4 

265 

'S 

Muriate  of  ammonia. 
Common  salt 

0  15 

1  0 

2  6    ) 

3760 

2416 

93      8 

41      0 

744 

12      8    0 

375 

«? 

Nitrate  of  soda 

Common  salt 

0    15 

I     1      0 

24   > 
0  4il 

3460|2116 

87    a 

35      0 

696 

11    12    0 

350 

86 


EXPERIMENTS  UPON   HAY    AND    OATS. 


[AppendtZf 


The  part  of  the  field  where  the  above  dressings  were  put  is  a  stiff  clay  loam 
lying  quite  level  upon  a  sandstone  rock,  and  has  a  south  exposure.  The 
dressings  were  late  of  being  put  on,  and  it  was  intended  for  green  cutting  for 
soiUng,  but  owing  to  the  abundance  of  other  feeding,  the  parts  dressed  were 
saved  for  hay.  All  the  dressings  except  No.  3  had  the  eflect  of  altering  the 
colour  to  a  dark  green  in  the  course  of  a  week,  and  they  all  came  away  very 
strong  and  vigorous.  No.  3  (the  compost,  see  note  1°,  p.  88,)  had  the  effect  of  al- 
tering the  coiour  in  about  three  wseks  after  being  appUed,  and  came  away  so 
rapidly  that  it  soon  gained  upon  the  others  in  point  of  strength  and  luxuriance 
of  stems  and  leaves.  It.will  be  seen  from  the  tables  that  xN'os.  4  and  6  gave 
less  hay  from  1000  lbs.  green  cut,  when  used  alone,  than  any  of  the  others  ;  but 
with  the  addition  of  common  salt  1000  lbs.  gave  more  than  any  of  the  other 
dressed  portions.  Sulphated  urine  may  be  considered  a  salt  of  ammonia,  all 
of  which  salts  have  been  found  to  give  greater  bulk  than  almost  any  other  ap- 

EUcation  of  salts  applied  to  green  produce,  but  they  have  invariably  been  found 
ere  to  give  less  dry  hay  when  used  by  themselves.  The  extra  produce  from 
the  sulphated  urine  is  probably  owing  to  its  compound  nature,  it  appears  from 
the  above,  therefore,  that  the  most  profitable  way  of  using  these  salts  is  by 
mixing  them  loith  others,  and  that  the  more  covipound  the  viixiure  is  the  better  will 
be  the  crop* 

Experiment  III. — On  Oats. 
Effects  of  guano    upon  Oats  (potato),   sown  on  the  17th  of  April ;  cut  and 
weighed  on  the  15th  of  September.     Thrashed,  cleaned,  and  weighed  on  the 
S4th  of  October. 


^ 

.5 

11 

IP 

^-'■1 

% 

•i 

U 

»  Sv: 

^?§i    . 

X  JZ 

iC 

<u 

&i) 

No. 

Dressing. 

■a 

O  =  « 

o| 

si 

H 

1 

1 

ll 

c  a 
o  b 

a 

qrs. 

s.  d. 

lbs. 

lbs. 

lbs. 

lbs. 

bush.  lbs. 

bush.    lbs. 

1 
2 

3 

7     6 

3300 
2120 

653 

539 

1015 
749 

40 
42 

15    13 
12    35 

3    20 

Nothing 

Note. — The  above  quantities  were  applied  to  and  reaped  from  one-fourth  of 
an  imperial  acre. 

The  portion  of  the  field  upon  which  tlie  above  oats  were  grown  is  a  deep 
stiff  yellow  clay,  super-incumbent  upon  sandstone  rock.  It  has  been  thoroughly 
drained  for  a  number  of  years.  It  had  been  sown  with  wheat  on  the  20th  of 
January,  1843,  top-dressed  with  guano  at  the  same  time,  which  was  harrowed 
in,  but  owing  to  the  dampness  and  constant  change  from  frost  and  thaw,  the 
greatest  part  of  the  wheat  failed,  and  was  ploughed  up  on  the  15th  of  April,  and 
potato  oats  sown  upon  it  on  the  17th  of  that  montli.  The  oats  brairded  ail 
alike,  showing  no  dilFerencc  in  point  of  earliiiess ;  but  by  the  9th  of  June  a 
most  remarkable  alteration  had  taken  place,  the  portion  which  had  been  dressed 
with  guano  for  the  wheat  taking  the  lead  of  the  undressed  portion,  and  being 
of  a  dark  green  colour  with  broad  leaves,  and  covering  the  ground  well ;  whilst 
that  which  had  no  dressing  was  brown  and  stinted  in  comparison,  and,  the 
ground  not  half  covered.  The  two  portions  continued  throughout  the  season  to 
present  the  same  difference  in  their  appearance,  and  at  the  time  of  cutting, there 
was  more  than  a  foot  in  length  of  straw  in  favour  of  the  dressed  portion.  It 
will  be  seen  from  the  table,  however,  that  although  the  guano  had  the  effect  of 
giving  more  bushels  per  acre,  the  bushels  were  lighter  in  weight  by  2  lbs.  than 
the  grain  from  the  undressed.     It  may  be  remarked,  however,  that  had  common 

'  See  on  this  subject  of  mixtui-es  tK>  fVuthor's  Ehmien/s  of  Agriculhiral  Chemi*try  and 
Geology,  p.  149. 


No.  X.\ 


EXPERIMENTS  UPON  OATS   kVTi   TURNIPS. 


87 


salt  been  mixed  with  the  g:uano,  there  is  reason  to  believe,  from  other  trials, 
that  the  grain  would  not  have  been  deficient  in  weight  per  bushel.  Ammonia- 
cal  salts  should  at  no  time  be  dressed  upon  grain  crops,  without,  at  tlie  same 
time,  adding,  according  to  the  composition  of  the  soil  upon  which  such  crops 
axe  grown,  such  other  inorganic  ingrediej^  as  may  be  required.  Few  soils,  at^ 
least  in  this  part  of  the  country,  appear  ^fp  to  supply  these  in  sufficiency  to  the 
plants — particularly  the  phosphates,  which  seem  always  deficient.  At  least  the 
addition  of  bone-dust  or  animal  charcoal  seems  always  to  improve  the  crops  to 
which  they  are  applied. 

Experiment  IV. — On  Turnips. 
Comparative  eiFects  of  guano,  farm-yard  manure,  bone-dust,  and  animal  char- 
coal, by  themselves  and  in  mixtures,'  on  Turnips  of  different  varieties;  lifted, 
topped,  tailed,  and  weighed,  in  Nov.,  1843. 


Variety  of  turnips  and 
kind  of  manures. 


Time  of 
Sowing. 


ON  AN  EIGHTH  OF  AN  IMPERIAL  ACRE. 


ON  ANIMF.ACRE. 


Quantity  of 
manure 
applied. 


Cost  of 

manures, 

exclusive  of 

cartage. 


Produce. 


Pro- 
duce. 


Value  of 

produce 

at  15s. 

per  ton. 


.SWEDISH. 

Farm-yard  mauure . . . . 

Guano 

Aninial  cliarcoal' 

Farm-yard  manure . . . 

Guano 

Halfincl^i  bones 

Farm-yard  manure.. .. 

Guano 

Half-inch  bones 


June 
5  to  7 


2i  cub.  yds. 

42  lbs. 

70  Iba. 

2^  cub.  yds. 

42  lbs. 

2\  bushels. 

5"  cub.  yds. 

70  lbs. 

5    bushels. 


PURPLE-TOP  YELLOW. 

Guano 

Dung 

Bones 

Farm-yard  manure . . . 

Guano 

Farm- yard  manure... 

Bone-dust 

Farm  yard  manure... 

Guano 

Animal  charcoal 


lbs. 

cub.  yds. 

bushels. 

cub.  yds. 

lbs. 

cub.  yds. 

bushels. 

yds. 

lbs. 

lbs. 


JONES'     YELLOW   TOP. 

Farm-yard  manure . . . , 

Animal  charcoal , 

Farmyard  manure 

Bone-dust , 

Farm-yard  manure 

Sulphate  of  Soda,  as  a 

top-dressing 

Farm-yard  manure 

Guano 

Farm-yard  manure. 

Guanot 

Animal  charcoal.. . 
Compost    of     coal-tar 

and  saw-dust 


3Jy, 

Ih 


29 


ds. 
70  lbs. 
3f  yds. 
l|  bushels. 

3|  yds. 
20  lbs. 

3J  yds. 
70  lbs. 
2^  yds. 
42  lbs. 
\\  cwt. 

8  bushels. 


2  6' 
12  6; 

3  9 
2  6' 

5  0' 

6  3 
10  0 


ts.  cts.  qrs. 
5      6      OJ 

4    19      0 

4  4  2| 
4  1  0 
3      4      1| 


ts.  cts. 
42 


£.  s.   d. 
7    0 


931 


1229  19    3 


33    17 
32 

25    14 


25    7    11 
6    0 


824 


0  5 

1  2 
0  9 
0  12 


4    18      3 


3  10 


36  0 

25  10 

3J  10 

32  0 


14  2 
13  8 
12    0 

18  0 
12  15 


19  15    0 


3    10      0 


5 
5 

2 

13 

12 


3J34 
21 
29 


0    0 
4    6 

0  .0 


1    0  i 
13  6  j 
14  11    0  ' 


The  field  upon  which  the  above  turnips  were  grown  is  a  light  gravelly  loam, 
super-incumbent  upon  a  deep  gravelly  till.  The  greater  part  of  the  field  was 
trenched  with  the  spade,  and  all  drained  with  tiles  and  soles  30  iriches  deep  and 
20  feet  apart,  in  the  winter  of  1841  and  1842,  and  in  the  preparation  for  the  tur- 

•  The  animal  charcoal  here  used  is  the  refuse  of  the  sugar  refiners,  and  contains  about 
ilb.  of  its  weight  o{  bone-earth. 
t  This  part  of  the  field  was  trenched. 


S8  EXPERIMENTS  UPON    TURNIPS.  [AppCTldlXy 

nip  crop  in  1842  and  1843,  what  had  not  been  trenched  .vas  subsoiled.  The 
turnip  crop  was  sown  at  different  times,  as  noticed  in  the  tables.  All  the  parts 
brairded  well  and  healthy,  and  continued  to  grow  without  intermission  through 
the  season.     The  field  contains  about  11  acres  imperial,  and  the  crop  was  most 

flkixuriant,  so  much  so,  that  the  lightest  turnips  in  any  part  of  the  field  would 
have  been  reckoned  good.  The  fieMBras  drilled  for  the  crop  with  the  double 
mould  plough  at  30  inches  apart,  for  swedes  and  purple  top-yclLow,  and  26  and  28 
inches  for  Jones'  yellow,  which  variety  is  remarkable  for  very  small  tops,  and,  in 
consequence,  may  be  drilled  nearer.  The  difference  in  the  appearance  of  the 
turnips,  where  the  various  manures  and  mixtures  had  been  applied,  was  very 
mai-ked.  Wherever  guano  had  been  applied,  the  tops  were  larger  than  any  of 
the  others,  except  No.  3  of  the  table  (^Jones'  yellow),  upon  which  sulphate  of  soda 
was  top-dressed,  after  the  plants  were  thinned.  The  crop  upon  this  portion  was 
remarkable  for  luxuriance  of  tops  and  large  bulbs,  and  gave  a  veiy  good  crop.* 
No,  6  of  the  table  (Jones'  yellow),  was  upon  spade-trenched  land,  and 
is  the  only  lot  where  a  comparison  can  be  made  between  trenching  and  subsoil- 
ing.  Where  bone  dust  was  used  the  tops  were  not  so  large,  and  where  the  ani- 
mal charcoal  had  been  added  the  tops  loere  least  of  all  and  the  bulbs  largest.  Upon 
all  the  varieties  of  soils  in  this  farm,  the  application  of  animal  charcoal  or  bone 
dust  has  been  of  great  benefit  to  all  crops — to  wheat,  barley,  oats,  hay,  and  grass 
— the  crops  being  bulkier  and  of  superior  quality,  especially  upon  soils  superin- 
cumbent on  trap  rock,  giving  an  evidence  that  all  such  soils  upon  this  estate  are 
in  want  of  phosphates.  This  has  also  been  proved  by  the  analysis  of  several — 
none  of  them  giving  more  than  a  trace  of  phosphates,  and  some  of  them  none  at 
all.     Upon  all  these  soils  animal  charcoal  or  bones  seem  to  be  indispensable, 

•  because  the  grain  crops  cannot  be  matured  without  phosphates  of  lime  and 
magnesia.  It  appears  from  the  many  experiments  that  have  been  made  here, 
that  guano  does  not  contain  a  sufficiency  of  the  phosphates  to  supply  the  crops 
to  which  it  is  usually  applied,  and  which,  from  the  greater  luxuriance  of  growth 
its  application  at  all  times  induces,  would  be  required  in  greater  quantity  accord- 
ing to  the  bulk  of  crop.  A  portion  of  the  animal  charcoal  of  the  sugar  refiners 
being  mixed  with  it  at  the  time  of  sowing,  will  supply  the  deficiency,  and  at  all 
places  inland  from  the  sea,  common  salt  will  be  found  a  valuable  addition.  The 
cultivator  who  is  obliged  from  deficiency  of  farm-yard  manure  to  use  guano  will 
find  that  by  taking  one-half  of  his  usual  quantity  of  farm-yard  manure  per  acre, 
and  making  up  for  the  other  half  by  the  addition  of  2  to  4  cwts.  of  guano,  his 
crops  will  be,  at  least,  as  bulky,  and  his  after-crops  as  good,  as  if  he  had  used 
40  cubic  yards  of  good  dung.  Guano,  however,  should  not  be  used  by  itself 
upon  soils  that  do  not  contain  a  certain  amount  of  vegetable  matter  {i.  e.  on  poor 
sharp  soils),  but  it  will  in  all  cases  be  found  an  invaluable  manure  for  thorough- 
drained  moss  soils. 

Notes. — 1^.  The  compost  of  coal-tar  and  saw-dust  used  in  the  preceding  experiments  is 
conaposed  of  saw-dust  or  moss  40  bushels,  coal-tar  20  gallons,  bone-dust  7  bushels,  sulphate 
of  soda  1  cwt.,  sulphate  of  magnesia  1^  cwt,.,  and  common  salt  1§  cwt.,  put  together  in  a 
heap,  with  20  bushels  of  quicklime,  and  allowed  to  ferment  and  heat  for  three  weeks,  when 
it  is  turned,  and  again  allowed  to  ferment,  and  is  then  fit  for  use. 

2°.  In  using  the  nitrate  of  soda  for  the  last  four  years  in  the  garden,  it  has  been  found 
that  top-dressing  the  leeks-  in"  the  month  of  August  or  September  enabled  them  to  resist  the 
effects  of  winter,  whilst  those  tliat  were  not  so  dressed  have  invariably  failed,  and  gone  to 
decay  early  in  the  season  ;  at  the  same  time,  it  increases  their  bulk  in  a  remarkable  man- 
ner. Knowing  this  effect  upon  leeks, — a  crop  that  if  grown  to  a  large  size  has  a  great 
tendency  to  rot  and  fail  in  winter, — might  it  not  have  the  same  effect  upon  autumn  sown 
wheats  if  dressed  with  it  after  they  are  brairded  7  This  hint  is  merely  thrown  out  as  worthy 
of  trial,  as  the  salt  appears  to  have  the  power  of  toughening  the  fibre  or  odierwise  enabling 
the  plants  to  withstand  the  rigours  of  winter,  and  in  this  way  might,  perhaps,  prevent  the 
wheat  crop  from  failing  in  winter,  which  is  often  ilie  case,  to  the  great  loss  and  disappoint- 
ment of  the  farmer 

Wm.  Fleming. 

Barochan,  Feb.,  1844. 

'  Sulphuric  acid  and  the  sulphates  appear  to  exercise  a  marked  action  on  the  turnip  crop.— J. 


No.X.,  REMARKS    UPON   PRECEDING   EXPERIMENTS.'  89 

REMARKS. 

I  submit  these  experiments  to  the  reader  without  any  lengthened  comment. 
The  experiments  with  guano  are  very  seasonable,  and  will  be  of  much  service 
to  the  thousands  of  practical  men  who  are  now  likely  to  try  this  valuable 
manure. 

There  are  three  interesting  general  observations  of  Mr.  Fleming,  to  which 
alone  I  would  direct  especial  attention — 

1°.  That  the  potato  sets  did  not  fail  when  powdered  with  gypsum,  and  that 
the  more  extensive  trials  of  this  substance  which  he  recommends  ought  cer- 
tainly to  be  encouraged. 

2°.  That  potatoes  dressed  with  guano,  or  with  nitrate  and  sulphate  of  soda, 
appear  to  be  improved  in  health,  and  are  less  apt  to  fail  when  cut  and  planted 
the  following  year. 

3°,  That  his  trap  soils  are  supposed  to  be  especially  deficient  in  phosphates, 
and  that  the  use  of  bones,  in  any  form,  always  improved  his  crops  upon  these 
soils. 

These  three  observations  are  very  interesting,  and  a  careful  study  of  the 
tables  of  results  will  lead  the  reader  to  make  other  interesting  observations  and 
deductions  for  himself. 

It  is  very  satisfactory  to  me  to  have  been  able  in  this  Appendix  to  incorpo- 
rate the  results  of  experiments  performed  on  three  successive  years  by  one  so 
skilful  and  zealous  as  Mr.  Fleming, — conducted  every  year  also  with  more 
care,  and  more  likely  therefore  to  lead  to  important  conclusions. 

The  subject  of  agricultural  experiments  has  now  been  taken  up  so  warmly 
and  so  successfnlly  in  almost  every  part  of  the  country,  that  we  may  look  for- 
ward with  confidence  to  the  gradual  accumulation  of  a  body  of  facts,  out  of 
whicii  correct  and  practically  useful  principles  may  gradually  be  elicited.  The 
large  body  of  experimental  results,  which  the  prize  offered  last  year  by  the 
Highland  Society  has  brought  before  the  public,  shows  how  eagerly  the  en- 
lightened practical  farmers  of  the  present  day  will  follow  the  guidance  of  such 
as  are  willing  to  show  them  how  the  art  by  which  they  live  may  be  really  and 
permanently  improved, 


%uh  ^tthlisjiei 


BY 


C.    M.    S  AXT  O  N, 

152  FULTON  STREET,  NEW  YORK, 


SUITABLE   FOR 


SCHOOL,    TOWN,   AGRICULTURAL. 

AND 

PRIVATE     LIBRARIES. 


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more  than  100  engravings.    By  R.  L.  Allen.     Cloth,  $1 ;  mail  edition,  paper,  75  cts. 

American  Poultry  Yard ; 

The  American  Poultry  Yard  ;  comprising  the  Origin,  History  and  Description  of  the  differ- 
ent Breeds  of  Domestic  Poultry,  with  complete  directions  for  their  Breeding,  Crossing, 
Rearing,  Fattening,  and  Preparation  for  Market ;  including  specific  directions  for  Capo- 
nizing  Fowls,  and  for  the  Treatment  of  the  Principal  Diseases  to  which  they  are  sub- 
ject ;  drawn  from  authentic  sources  and  personal  observation.  Illustrated  with  numerous 
engravings      By  D.  J.  Browne.     Cloth  or  sheep,  $1  ;  mail  edition,  paper,  75  cts. 

The  Diseases  of  Domestic  Animals; 

Being  a  History  and  Description  of  the  Horse,  Mule,  Cattle,  Sheep,  Swine,  Poultry, 
and  Farm  Dogs,  with  Directions  for  their  Management,  Breeding,  Crossing,  Rearing, 
Feeding,  and  Preparation  for  a  profitable  Market ;  also,  their  Diseases  and  Remedies ; 
together  with  full  Directions  for  the  Management  of  the  Dairy,  and  the  Comparativ« 
Economy  and  Advantages  of  Working  Animals,  the  Horse,  Mule,  Oxen,  &c.  By 
R.  L.  Allen.     Cloth  or  sheep,  75  cts. ;  mail  edition,  paper,  50  cts. 

American  Bee  Keeper's  Manual; 

Being  a  Practical '  Treatise  on  the  History  and  Domestic  Economy  of  the  Honey  Bee  ; 
embracing  a  full  illustration  of  the  whole  subject,  with  the  most  approved  methods 
of  Managing  this  Insect,  through  every  branch  of  its  Culture,  the  result  of  many  years' 
experience.     Illustrated  with  many  engravings.     By  T.  B.  Miner.    Cloth  or  sheep,  $1. 

The  Modern  Stair  Builder's  Guide  : 

Being  a  Plain,  Practical  System  of  Hand  Railing,  embracing  all  its  necessary  Details, 
and  Geometrically  Illustrated  by  Twenty-two  Steel  Engravings;  together  with  the  Use 
of  the  most  important  Principles  of  Practical  Geometry.  By  Simoii  De  Graff,  Archi- 
tect.    $2. 


Prize  Essay  on  Manures. 


An  Essay  on  IVtanures,  submitted  to  the  Trustees  of  the  Massachusetts  Society  for  Pro. 
moting  Agriotfture,  for  their  Freioium.    By  Samuel  L.  Dana     Paper.    25  cts. 


Books  Published  by  C.  M,  Saxton, 


American  Bird  Fancier. 


Considered  with  reference  to  the  Breeding,  Rearing,  Feeding,  Management,  Ac,  of  CAge 
and  House  Birds.  Illustrated  with  engravings.  By  D.  J.  Browne.  Cloth,  50  cts. ;  mail 
edition,  paper,  25  cts. 

American  Architect. 

The  American  Architect ;  comprising  Original  Designs  of  cheap  Country  and  Village 
Residences,  with  Details,  Specifications,  Plans,  and  Directions,  and  an  estimate  of  th« 
Cost  of  each  Design.  By  John  W.  Ritch,  Architect.  First  and  Second  Series  ouarto, 
bound  in  2  vols.,  sheep,  $6.    Maul  edition,  paper,  $5. 

Domestic  Medicine. 

Gunn's  Domestic  Medicine  ;  or,  Poor  Man's  Friend  in  the  Hours  of  Affliction,  Pain,  and 
Sickness.  Raymond's  new  revised  edition,  improved  and  enlarged  by  John  C.  Gunn, 
8vo.     Sheep.     $3. 

Saxton's  American    Farmer's   Almanac   for    1852. 

Per  100,  $3. 

Family  Kitchen  Gardener. 

Containing  Plain  and  Accurate  Descriptions  of  all  the  Different  Species  and  Varieties  of 
Culinary  Vegetables  ;  with  their  Botanical,  English,  French,  and  German  names, 
alphabetically  arranged,  and  the  best  mode  of  cultivating  them  in  the  garden,  or  under 
glass  ;  also,  Descriptions  and  Character  of  the  most  Select  Fruits,  their  Management, 
Propagation,  &c.  By  Robert  Buist,  author  of  the  American  Flower  Garden  Directory, 
&c.     cloth  or  sheep,  75  cts. ;  mail  edition,  paper,  50  cts 


Practical  Agriculture. 


Being  a  Treatise  on  the  General  Relations  which  Science  bears  to  Agriculture.  Deli- 
vered before  the  New  York  State  Agricultural  Society,  by  James  F.  W.  Johnston, 
F.  R.  S.  S,S.  and  E.,  Professor  of  Agricultural  Chemistry  in  Durham  University,  and 
author  of  Lectures  on  Agricultural  Chemistry,  with  Notes  and  Explanations  by  an 
-American  Farmer.    Cloth,  75  cts. ;  mail  edition;  paper,  50  cts. 

Elements  of  Agricultural  Chemistry  and  Geology. 

By  J.  F.  "W.  Johnston,  M.A.,  F.R.S.     50  cts. 

Youatt  and  Martin  on  Cattle: 

Being  a  Treatise  on  their  Breeds,  Management,  and  Diseases ;  comprising  a  full  History 
of  the  Various  Races  ;  their  Origin,  Breeding,  and  Merits;  their  capacity  for  Beef  and 
Milk.  By  W.  Youatt  and  W.  C.  L.  Martin.  The  whole  forming  a  complete  Guide  for 
the  Farmer,  the  Amateur,  and  the  Veterinary  Surgewi,  with  100  illustrations.  Edited 
by  Ambrose  Stevens.    $1  25. 

Youatt  on  the  Horse. 

Youatt  on  the  Structure  and  Diseases  of  the  Horse,  with  their  Remedies.  Also,  Practi- 
cal Rules  for  Buyers,  Breeders,  BreaJcers,  Smiths,  &c.  Edited  by  W.  C.  Spooner, 
M.R.C.V.S.  With  an  account  of  the  Breeds  in  the  United  States,  by  Henry  S  Ran- 
dall.    $1  25. 

Youatt  on  Sheep : 

Their  Breed,  Management,  and  Diseases,  with  illustrative  engravings  ;  to  which  are 
added  Remarks  on  the  Breeds  and  Management  of  Sheep  in  the  United  States,  and  on 
the  Culture  of  Fine  Wool  in  Silesia.    By  Wm.  Youatt.    75  cts. 


Hoare  on  the  Grape  Vine. 


Practical  Treatise  on  the  Cultivation  of  the  Grape  Vino  on  open  Walls,  with  a  De- 
scriptive Account  of  an  improved  method  of  Planting  and  Managing  the  Roots  of  Grape 
Vines.  By  Clement  Hoare.  With  an  Appendix  on  the  Cultivation  of^e  same  in  Om 
United  States.    50  cts. 


Books  Published  by  C,  M,  Saxton,  3 

The  American  Agriculturist : 

Being  a  Collection  of  Original  Articles  on  the  Various  Subjects  connected  with  the  Farm, 
in  ten  vols.  8vo.,  containing  nearly  four  thousand  pages.     $10. 

Johnston's  Agricukural  Chemistry. 

Lectures  on  the  Application  of  Chemistry  and  Geology  to  Agriculture.  New  edition, 
with  an  Appendix.     $1  25. 

Stephens'  Book  of  the  Farm. 

A  Complete  Guide  to  the  Farmer,  Steward,  Plowman,  Cattleman,  Shepherd,  Field- 
Worker,  and  Dairy  Maid.  By  Henry  Stephens.  With  Four  Hundred  and  Fifty  Illus- 
trations ;  to  which  are  added  Explanatory  Notes,  Remarks.  &c  ,  by  J.  S.  Skinner, 
Really  one  of  the  best  books  for  a  Farmer  to  possess.     Cloth,  $4  ;  leather,  $4  50. 

The  Complete  Farmer  and  American  Gardener, 

Rural  Economist,  and  New  American  Gardener,  containing  a  Compendious  Epitome  of 
the  most    Important  Branches  of  Agricultural  and  Rural  Economy  ;  with  Practical 
Directions  on  the  Cultivation  of  Fruits  and  Vegetables  ;  including  Landscape  and  Orna 
mental  Gardening.    By  Thomas  G.  Fessenden     ^  r-lo.  in  one.     $1  25. 

Chemistry  Made  Easy, 

For  the  Use  of  Farmers.     By  J.  Topham,  M.A.    25  cts. 

Brandy  and  Salt, 

A  Remedy  for  various  Internal  as  well  as  External  Diseases,  Inflammation  and  Local 
Injuries.    By  Rev.  Samuel  Fenton.    12^  cts. 

Southern  Agriculture. 

Comprising  Essays  on  the  Cultivation  of  Corn,  Hemp,  Tobacco,  Wheat,  &c.    $1. 

The  Cottage  and  Farm  Bee  Keeper : 

A  Practical  Work,  by  a  Country  Curate.     50  cts. 

A  Book  for  Every  Boy  in  the  Country. 

Elements  of  Agriculture.  Translated  jfrom  the  French,  and  adapted  to  General  Use, 
by  F.  G.  Skinner.     25  cts. 

Rural  Architecture ; 

Comprising  Farm  Houses,  Cottages,  Carriage  Houses,  Sheep  and  Dove  Cotes,  Pigeries, 
Barns,  &c,  &c.    By  Lewis  F.  Allen.    $1  25. 

The  American  Muck  Book. 

The  American  Muck  Book  ;  treating  of  the  Nature,  Properties,  Sources,  History, 
and  Operations  of  all  the  principal  Fertilizers  and  Manures  in  Common  Use,  with 
Specific  Directions  for  their  Preservation,  and  Application  to  the  Soil  and  to  Crops ; 
drawn  from  Authentic  Sources.  Actual  Experience,  and  Personal  Observation,  as  Com- 
bined with  the  leading  Principle*  of  Practical  and  Scientific  Agriculture.  By  J.  D. 
Browne.     $1. 

ISTouatt  on  the  Pig. 

A  Treatise  on  the  Breeds,  Management,  and  Medical  Treatment  of  Swine  ;  with  direc- 
tion for  Salting  Pork,  Curing  Bacon  and  Hams.  By  Wm.Youatt,  R.S.  Illustrated  with 
engravings  drawn  from  life.     60  cts. 


Youatt  on  the  Dog. 


By  Wm.  Youatt,    Splendidly  illustrated.    Edited,  with  Additions,  by  E.  J.  L«wii,  M.D, 

The  Poultry  Book. 

By  John  0.  Bennett,  M.D.    84  cts. 


^      4  Books  for  Sale  hy  C.  M,  Sax  ton. 

The  American  Poulterer's  Companion, 

With  illustrations.    By  C  N.  Bem«nt.     ^. 

American  Poultry  Book. 

By  Micajah  Cock.    38  ots. 

The  Rose  Culturist. 

A  Practical  Treatise  on  its  Cultivation  and  Management.    38  ct». 

A  Practical  Treatise  on  Honey  Bees, 

Their  Management,  &c.    By  Edward  Townley.    50  ote. 

The  American  Fruit  Book 

By  S.  W.  Cole.    50  cttr.   • 

The  American  Veterinarian. 

By  S.W.Cole.    50  cts. 

The  Gardener's  Text  Book. 

By  Peter  Adam  Schenck.    50  cts. 

The  American  Gardener. 

By  William  Cobbett.    50  cts. 

The  Farmer's  Land  Measurer. 

By  James  Pedder.    50  cts. 

New  England  Fruit  Book. 

By  John  M.  Ives.     56  cts. 

Practical  Treatise  on  Fruits, 

Adapted  to  New  England  Culture.  By  George  Jaques.    60  cts. 

Farmer  and  Emigrant's  Hand  Book. 

A  Guide  to  Clearing  the  Forest  and  Prairie  Land,  &c.,  &c.    By  Josiah  T.  Marshall. 
75  cts. 

Farmer's  Barn  Book. 

By  Youatt,  Clater,  Skinner  and  Mills.     $1  25. 

Hind's  Farriery  and  Stud  Book. 

Edited  by  J.  S.  Skinner.    $1. 

Mason's  Farrier  and  Stud  Book. 

Edited  by  J.  S.  Skinner.    $1  25. 

Stewart's  Stable  Economy. 

A  Treatise  on  the  Management  of  Itorses.     Edited  by  A.  B.  Allen.    $1. 

Sugar  Planter's  Manual. 

By  W.  S.  Evans,  M.D.    $1  25. 

Treatise  on  Hothouses  and  Ventilation. 

By  R  B.  Suckari.    $1  25. 


m     Books  for  Sale  by  C,  M.  Saxton,  5 

Ornamental  and  Domestic  Poultry. 

By  Rev.  Edmund  Saul  Dixon,  A.M.    With  Large  Additions  by  J.  J.  Kerr,  M.D.    With 

illustrations.     $1. 

Canfield  on  Sheep, 

Their  Breeds,  Management,  Structure,  and  Diseases.     With  Illustrative  Engravings  a,x\A 
aij  Appendix.     Edited  by  H.  J.  Canfield.     $1. 

Book  of  Flowers, 

In  which  are  described  the  various  Hardy  Herbaceous  Perennials,  Annuals,  Shrubby 
Plants  and  Evergreen  Trees  desirable  for  Ornamental  Purposes.    By  Jos.  Breck.    75  cts. 

Experimental  Researches  on  the  Food  of  Animals, 

The  Fattening  of  Cattle,  and  Remarks  on   the   Food  of   Man.     By  Robert  Duuda« 
Thompson,  M.D.     75  cts. 

The  American  Flower  Garden  Companion, 

Revised  and  enlarged.    By  Edwajrd  Sayres.    75  cts. 

The  Farmer's  Treasure. 

A  Treatise  on   the  Nature  and  Value  of  Manures,  and  Productive  Farming.    By  F. 
Faulkner  and  Joseph  A.  Smith.     75  cts. 

The  Practical  Farrier. 

By  Richard  Mason.    75  cts. 

The  American  Farrier. 

By  Bamum.    75  cts. 

Principles  of  Practical  Gardening. 

By  Geo.  W.  Johnston,  Esq.     $1  95. 

The  American  Fruit  Garden  Companion. 

A  Treatise  on  the  Propagation  and  Culture  of  Fruit.     By  S.  Sayres.    38  cts 

Spooner  on  the  Grape. 

The  Cultivation  of  American  Grape  Vines,  and  making  of  Wine.    By  Alden  Spoon«f . 
38  cts. 

The  Young  Gardener's  Assistant. 

By  Thomas  Bridgeman.    f  1  50. 

The  Florist's  Guide. 

By  Thos.  Bridgeraan.    50  cts. 

The  Kitchen  Gardener's  Instructor. 

By  Bridgeman.    50  cxs. 

The  Fruit  Cultivator's  Manual. 

By  Bridgeman.    50  cts. 

The  Horse, 

Its  Habits,  Diseases  and  Management,  in  the  Stable  and  or.  the  Road,  &o.    25  ou. 


Books  for  Sale  by  C.  M.  Saxton. 


The  Fruit,  Flo^yer,  and  Kitchen  Garden. 

By  Patrick  Neill,  LL.D.,  F.R.S.,  adapted  to  the  United  States.    |1  25. 

Ladies'  Companion  to  the  Flower  Garden. 

By  Mrs.  Loudon.    Edited  by  A.  J.  Downing.     $1  25. 

The  Fruits  and  Fruit  Trees  of  America. 

By  A.  J.  Downing.    $1  50. 
Do.  do.  do.  do.  colored,    15  00 

Dictionary  of  Modern  Gardening. 

By  Geo.  W.  Johnston.    Edited  by  David  Landreth.     $1  50. 

The  Rose  Fancier's  Manual. 

By  Mrs.  Gore.    $1  50. 

Parsons  on  the  Rose. 

The  Rose  :  its  History,  Poetry,  Culture,  and  Classification.    By  S.  B.  Parsons.    $1  50. 


Hovey's  Fruits  of  America. 


Containing  richly  colored  Figures  and   full  Descriptions  of  all  the  Choicest  Varietiea 
cultivated  in  the  United  States,  in  12  numbers.     $12. 

History,  Treatment  and  Diseases  of  the  Horse, 

With  a  Treatise  on  Draught,  and  Copious  Index.    $2. 

Rural  Economy, 

In  its  Relations  with  Chemistry,  Physics,  and  Meteorology.     By  J.  B.  Boussingault. 
Translated,  &c.,  by  George  Law.     $1. 

Liebig's  Agricultural  Chemistry. 

Edited  by  Lyon  Playfair,  Ph.D  ,  F.G.S.,  and  William  Gregory,  M.D  .  P.R.S.E.    $1. 

The  Modern  System  of  Farriery, 

As  Practised  at  the  Present  Time  at  the  Royal  Veterinary  College,  and  from  Twenty 
Years'  Practice  of  the  Author,  George  Skevington,  M.R.V.C.     $5. 

Ewbank's  Hydrauhcs: 

A  Descriptive  and  Historical  Account  of  Hydraulic  and  other  Machines  for  Raising 
Water,     $2  50. 

The  Fruit  Garden. 

By  p.  Barry.    $1  25. 

The  American  Fruit  Culturist ; 

Containing  Directions  for  the  Culture  of  Fruit  Trees  in  the  Nursery,  Orchard,  and  Gar 
den.     By  John  J.  Thomas.     $1. 

The  Rose  Manual. 

By  Robert  Buist.     75  cts. 

The  Plants  of  Boston  and  Vicinity. 

By  Jacob  Bigelow,  M^.     $1  50. 


Books  for  Sale  by  C.  M.  Saxton,  7 

The  Indian  Meal  Book; 

Comprising  the  best  Receipts  for  the  Preparation  of  that  Article.  By  Miss  Leslie.  25ctB. 

The  Horse's  Foot, 

And  How  to  Keep  it  Sound.     By  'William  Miles.    25  ct». 

Catechism  of  Agricultural  Chemistry  and  Geology. 

By  J.  F.  W.  Johnston.    25  cts. 

Chemistry  AppUed  to  Agriculture. 

By  Le  Count  Chaptal.    50  ct«. 

British  Husbandry. 

Three  Vols,  and  Supplement.    §5. 

Loudon's  Arboretum. 

Eight  Vols.    $25. 

Loudon  on  Gardening. 

Loudon's  Encyclopedia  of  Gardening.     $10. 

Loudon  on  Agriculture. 

Loudon's  Encyclopedia  of  Agriculture,    $10. 

Loudon  on  Trees,  &c. 

Loudon's  Encyclopedia  of  Trees,  Shrubs,  Sea. 

Loudor^on  Plants,  &c. 

Loudon's  Encyclopedia  of  Plants,  &8.        , 

The  Farmer's  Library. 

Two  vols.  8vo.  English.    $5. 

The  Farmer's  Dictionary. 

By  D.  P.  Gardner.    $1  50. 

Practical  Treatise  on  the  Grape  Vine. 

By  J.  Fisk  Allen.     Boards,  $1 ;  paper,  88  ots. 

Practical  Treatise  on  the  Veterinary  Art. 

By  J.  Briddon.     75  cts. 

Sheep  Husbandry. 

By  Henry  S.  Randall.    $1  25. 

Agricultural  Chemistry. 

By  Justus  Liebig.    Cloth,  $1 ;  cheap  edition,  25  cts. 

Animal  Chemistry. 

By  J.  Liebig.    Clotlk,  50  cts. ;  cheap  ed.  paper,  aS  tto. 

Liebig's  Complete  Works, 

In  one  Tol .  8vo.     $1. 


S  Books  for  Sale  by  C,  M,  Saxton. 

Cottage  and  Farm  Houses. 

By  A.  J.  Downing.     $2. 

Country  Houses. 

By  A.  J.  Downing.    $i. 

Sportsman's  Library. 

By  T.  B.  Johnson.     English  edition.    $5. 

Landscape  Gardening. 

By  A.  J.  Downing.    $3  50. 

Cottage  Residences. 

By  A.  J.  Downing.  ^2. 

Chaptal's  Agricultural  Chemistry, 

With  Notes.     $1. 

American  Husbandry. 

By  Gaylord  and  Tucker.     §1. 

Gardener's  Dictionary. 

By  Geo.  Don,  F.L  S.    4  vols,  quarto.    $10. 

Journal  of  Agriculture. 

Edited  by  John  S.  Skinner.    3  vols.    $6. 

Downing's  Horticulturist. 

Half  morocco.    Per  Vol.  yearly  Vols.     $3  75. 

Do.  do.  half  yearly  "  2  GO.  • 

The  Complete  Produce  Reckoner, 

Showing  the  Value  by  Pound  or  Bushel.     By  R.  Bobbins     75  cts. 

The  American  Shepherd. 

By  L.  A.  MorfiU.    $1. 

The  Principles  of  Agriculture. 

By  Albert  D.  Thaer.     $2  50. 

Lectures  to  Farmers  on  Agricultural  Chemistry. 

By  Alexander  Petzholdts.    75  cts. 

The  Complete  Farrier. 

By  John  C.  Know] son.     25  cts. 

The  Complete  Cow  Doctor. 

By  J.  C.  Knowlson.     25  cts. 

Milch  Cows. 

By  Guenon.    38  cts. 

A  Home  for  All ; 

Or  a  New,  Cheap,  and  Superior  mod*  of  B«ilding.    By  0.  S.  Fowler.    SO  tli. 


Books  for  Sale  by  C,  M,  Saxton* 
The  Poultry  Breeder. 

By  George  P.  Burnham.     25  ctt 

The  American  Fowl  Breeder.    25cts. 
The  Farmer's  Companion. 

By  Judge  Buel.     75  cts. 

The  Farmer's  Instructor. 

By  Judge  Buel.    $1. 

European  Agriculture, 

From  Personal  Observation.     By  Henry  Coleman.    2  vols.  $5  00. 

Do.  do.  do.  1vol.  4  50. 

The  Gardener  and  Florist.     25  cts. 
The  Honey  Bee. 

By  Bevan.    31  cts. 

Elements  of  Practical  Agriculture. 

By  John  P.  Norton.    50  cts. 

Rogers'  Scientific  Agriculture.    75  cts. 
Mills'  Sportsman's  Library.    $1. 
Stable  Talk  and  Table  Talk.   $1. 
Hawker  and  Porter  on  Shooting.    $2  is. 
Field  Sports.  ^ 

By  Frank  Forrester.    2  vols.     $4 

Fish  and  Fishing. 

By  Frank  Forrester.     $2  50. 

The  American  Angler's  Guide. 

By  J.  J.  Brown.     $1  50. 

Johnson's  Farmer's  Encyclopedia. 

Edited  by  G.  Emerson,  M.D.     $4. 

Scientific  and  Practical  Agriculture. 

By  Alonzo  Gray.     75  cts. 

Theory  and  Practice  of  Agriculture. 

By  A.  Partridge.    12  cts. 

Armstrong  on  Agriculture.   50cti 


10  Books  for  Sale  by  C.  M.  Saxtcn. 

Hovey's  Magazine  of  Horticulture. 

Published  monthly.    Per  annum  $2. 

Downing'  Horticulturist. 

Published  monthly.    Per  annum  $3. 

Gilpin's  Landscape  Gardening. 

English  edition.     $2  50. 

The  Gardener's  Calendar. 

ByM.  Mahon.     $3  50. 

Agriculture  for  Schools. 

By  Rev.  J.  L.  Blake,  D.D.     $1. 

Text  Book  of  Agriculture. 

By  Davis.     50  cts. 

The  American  Agriculturist  and  Farmer's  Cabinet 

Published  monthly.    Per  annum  $1. 

Weeks  on  the  Honey  Bee. 
Cottages  and  Cotta 

Chemical  Analysis. 

By  Fresinus  and  Bullock.    $1. 

Applied  Chemistry. 

By  A  Parnell.     $1. 

The  Vegetable  Kingdom,    # 

Or  Handbook  of  Plants.    By  L.  D.  Chapin.    $1  35. 

The  Muck  Manual. 

A  new  edition.    By  Samuel  L.  Da.ia.    75  ctt. 

Youatt  on  the  Horse. 

Edited  by  J.  8.  Skinner.     $1  50, 

Clater's  Farrier,    so  cts. 
The  Dog  and  Sportsman. 

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m 


AMERICAN    ARCHITECT, 

omplete  in  24  Nos.,  at  25  cents  each,  or  $5  for  2^ 
Nos.   $6,  bound  in  2  vols. 

PUBLISHED  BY   C.  M.   SAXTON,  NEW-YORK. 


Thb  object  of  this  publication  is  to  introduce  ORIGINAL  DESIGNS  of  Country 
Seats  adapted  to  the  varied  taste  and  circumstances  of  an  American  population  : 
from  the  elegant  Villa  to  the  simple  Cottage  and  plain  Fakm-Housk  ;  from 
Planters'  Mansions  to  Villagk  Domicils.  In  a  word,  every  variety  of  Rural 
Residences  will  be  embraced,  in  order  to  meet  the  views  of  every  person  desiring 
a  Country  House.  In  respect  to  style,  cost,  arrangement,  finish,  &c.,  utility 
will  never  be  sacrificed :  economy  in  the  outlay,  with  an  appropriate  style,  wil 
always  be  kept  in  view.  The  reqjiisite  details,  specifications,  plans,  and  direc 
tions,  with  a  careful  and  reliable  estimate  of  the  cost,  will  accompany  each  design 
These  are  essential  features  of  a  Practical  Work,  and  no  labor  will  be  spared  in 
their  preparation. 

Of  the  diversity  of  human  dwellings,  whether  marked  by  elegance,  convenience, 
or  utility,  or  by  the  want  of  them,  none  can  compare  in  national  importance  and 
philosophical  mterest  with  the  Farm- House— the  Homestead  of  our  species. 

A  triple  value  attaches  to  that  class  of  men  which  feeds  all  others.  With  pri- 
meval farmers,  man's  social  faculties  were  first  unfolded.  With  them  society 
began :  and  among  whatever  people  its  shaft  has  become  polished  and  its  capital 
enriched,  it  still  rests  on  the  cultivators  of  the  soil.  So,  of  tlieir  profession,  agri- 
culture is  the  great  parent  of  the  arts,  while  its  prepared  products  will  forever 
06  the  most  essential  of  all  manufactures.  Then  it  was  in  their  dwellings  that 
Architecture  itself  had  its  birth  ;  it  was  they  who  first  abandoned  the  tent  with 
astoral  life,  and  began  to  devise  and  construct  fixed  and  permanent  abodes. 

The  estimates  we  give  are  based  on  New  York  prices  ;  including  the  best  ma- 
terials, workmanship,  and  finish.  There  is  no  doubt  that  m  many  parts  of  the 
country,  they  may  be  materially  diminished  in  every  one  of  these  respects— eve? 
lo  the  extent  of  one-half. 

The  selection  of  designs  by  those  about  to  build  Country  Residences  is  cora 
aionly  attended  with  embarrassment  and  always  with  expense  When  fumishea 
^y  professional  men,  from  general  ideas  communicated  by  proprietors,  they  are 
Beldom  satisfactory.  The  American  Architect,  by  furnishing  a  collection  of  designs 
adapted  to  ail  tastes'  and  means,  will  remove  every  difficulty  in  the  choice,  and 
Bave  money  expended  on  Plans  of  no  use.  It  will  furnish  twelve  Elevations, 
Plans,  and  Specifications  in  each  year,  at  a  price  hot  exceeding  one-seventh  of 
the  usual  charge  for  one. 

Every  handsome  residence  adds  value  to  the  grounds  attached  to  it ;  hence  the 
iirvportance  of  having  such,  by  those  who  invest  capital  in  this  species  of  property. 

With  regard  to  utility — the  proper  distribution  of  the  apartments  and  theii 
sdlaptation  to  the  purposes  intended  is  the  most  important  point  to  be  attended 
lo,  and  they  are  governed  by  the  Plans. 

From  among  the  great  number  of  notices,  we  select  the  following  :— 

"  The  price  is  only  25  cents  for  each  number,  and  it  is  surely  next  to  impossible 
but  that  such  a  periodical  will  obtain  a  wide  circulation." — Neto  York  Tribune. 

"  This  work  promises  to  supply  a  want  which  has  long  existed,  and  to  bo  ol 
essential  value." — Salem  Register. 

"  This  work  cannot  fail  to  be  useful  and  popular."— LciS/on  Bee. 

"  This  is  a  good  and  beautiful  work,  and  well  adapted  to  eflFect  a  much  desired 
reform  in  American  Architecture." — Boston  Traveller, 

Th<  Cost  of  building  from  the  Plans  given,  will  be  from  f  600  to  $5,000,  wHl 
comp  9te  Specifications  from  a  first-rate  Mason  and  Carpenter,  and  the  pncM 
girea  tut  be  depeixded  upon. 


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UNIVERSITY  OP  CALIFORNIA  LIBRARY 


